http://www.youtube.com/watch?v=bEUaOfQq4k4&feature=BFa&list=PLED5E234FBC30A8D5

Dissertation

Study of Snail

Objective: Recreate a snail in CG with photo-realistic look, which includes anatomy, behavior, movements and integrate it seamlessly into live action footage.

Team Members

Surabhi Priji Suran - BM0806321 (Modeling and Texturing)

I Apoorva - BM0806328 (Rigging , Skinning and Animation)

Santhosh Menam - BM0809372 (VFX)

R Navya Kavya - BM0806304 (VFX)

CONTENTS

1. HISTORY OF SNAILS

Evolution

Molluscs in Indian tradition and economy

2. MALACOLOGY (study of mollusca)

3. BIOLOGY OF A SNAIL

Anatomy

Life cycle

Life span

Dimensions

Body construction

Organs and organ systems

Shell

4. GENERAL DISCUSSION

Classification of snails

Land snails Fresh water snails Sea snails

Snail Feeding

Diseases

Defence techniques of snails

5. SOCIAL ROLE

Cuisine

Predators

Snails in Popular Culture

6. GIANT AFRICAN SNAIL

Description

General Size, color and life span

Ecology

Habitats Life Cycle Feeding habits

Distribution in the world

Site and Date of Introduction

Ecological Role

Benefits

Parasites

Threats

Control Method

Diseases

Anatomy

Body organs

Systems

Muscular system Respiratory system Sensory organs Circulatory system Digestive system Nervous system

Movements

How it moves

How it breeds

How it eats

How it grows its shell

7.FACTS

Evolution

The first snails were limpet like molluscs that lived in shallow water. They fed on algae and their digestive tract ended at the back end of the body. The mantle cavity had a pair of gills for breathing. During the evolution of snails two important things happened. One is a process called torsion; most of the internal organs were twisted 180 degrees anticlockwise. This meant that the mantle cavity, gills and anus were situated in front of the animal now. This allowed for more room in the shell and the head could be withdrawn first. The other change was that the shell became more conical and then spirally coiled.

The most primitive pulmonates are the Ellobiidae, with genera like Ovatella, Leucophytia and Carychium. The Ellobiidae live in salt marshes and coastal mud-areas.Muddy waters often lack oxygen, so breathing with a lung coming to the surface was probably easier than breathing by a gill. There are only three land genera in the Ellobiidae: Pythia, living in tropical forests along the coast of Australia and Malaya; Carychium and Zospeum. A lot of land molluscs have early ties with estuarine- or freshwaterspecies, and can share the same adaptations. Living in fresh water may lead to preadaptations which makes the route to land life easier than by a direct route from marine conditions. In other words: a limited supply of oxygen can lead to aerial breathing. Tropical Prosobranchs living in stagnant inland water (Pila, Pomacea)have a mantle cavity which has a gill and a lung. Aerial breathing in aquatic snails allows them to aestivate in dry periods. Further adaptations against drying out take place, and a different method of excretion. This finally leads to a life on land. A big group of prosobranchs living on the land and in fresh water are the Neritoidea. The genus Nerita lives on tropical shores. Theodoxus (Neritina)lives in slowly running water. Neritodryas living in the East Indies is almost a land prosobranch.

The family Helicinidae are terrestrial snails living in tropical forests. The Cyclophoroidea have evolved from the Archaeotaenioglossa, just like the Ampullarioidea, which contains the amphibious Applesnails. From the Periwinkles (Littorinacea)the Pomatiasidae are evolved, as are the Valvatidae. They live in slowly running fresh water, and are unique in having a bipectinate ctenidium(gill).

Pulmonate landsnails belong to the order of Stylommatophora(eyes on the top of tentacles),aquatic snails belong to the order of Basommatophora(eyes near the base).The Elobiidae are primitive snails from the latter. Both orders evolved from snails looking like ellobiids. But landsnails from the Endodontidae are known from the Carboniferous which is before the first ellobiid fossils appear.

The earliest Stylommatophora are living in moist conditions, like the Succineidae. A lot of pulmonate snails can live in dry conditions, Helicella species can be found in full sun their shell sealed off.

Hibernation, aestivation and survival of dehydration are features of the higher Stylommatophora. Slugs can lose 58 % of their own bodyweight in a day by loss of water. Terrestrial snails store calcium in the digestive gland which they use for shellbuilding. In most of the pulmonate groups there is an evolution towards complete loss of the shell. For example in the Zonitidae the shell gets thinner in the serie Zonitoides-Retinella-Oxychilus-Vitrea. And in the family Vitrinidae the shell is very thin and sometimes overgrown by the mantle. The slug family Limacidae has evolved from this family,and the Arionidae have evolved from endodontid pulmonates.

Molluscs in Indian tradition and economy

The molluscs constitute a natural resource of sizeable magnitude in many parts of the world. They are an age old group represented among the early fossils, a group of great diversity in size, distribution , habitat and utility. The range of their distribution is as extensive in space as in time for it covers terrestrial, marine and freshwater habitats. They include members from the tiny Estuarine gastropod Bithynia and small garden snails to the Giant Clam Tridacna or the Giant Squid Architeuthis . Their use as ornaments, utility articles and medicine has been widespread from ancient days. Not all molluscs, of course, are so helpful or even harmless. Even as in the humans that exploit them, there is in their midst an effective section that hides behind the goodness of others to indulge in a spot of mischief of their own. The sacredness of the Chank is countered by the sin of the snail-carriers of Schistosoma or by the destructive talents of the ship worms and fouling molluscs. This, in a way, adds to the importance of their study; it does not diminish the positive qualities of the group. Though the recognition of their full potential, including their role as nutritious, even delectable, food is of relatively recent date, it is clear that man has exploited the shell resources to varying extents ever since he started utilizing nature's gifts for his own personal or social needs. In India the molluscs have occupied a marked place in the affairs of man from time immemorial, in his affairs of state and economy, of mind and aesthetic values, of religion and rites of worship. From their pride (3f place in mythology and legend they have inspired countless tales in folklore, caused long-standing customs and traditions, and in more recent times come to occupy prominent positions in heraldry and royal insignia, besides featuring conspicuously in the economy of vast sections of the people. The most renowned of these molluscs, in lore and in literature, is perhaps the pearl oyster, as the very mention of the fabulous pearls strikes a responsive chord rich in associations. History and legend here bring forth such an admixture of fact and fiction, wherein for some historical pearl or other, kingdoms liave fallen, fortunes changed hands or widespread destruction has followed. The pearls have also inspired countless ancient poets to moralise and gush forth lyrical, even if unscientific, accounts of their origin and occurrence.

Molluscs in Ancient India Evidence of long-standing association between man and molluscs in India is afforded by the shell remains disc;overed in human habitations of pre-Vedic Mohenjo-Daro, Harappa, Amri, Nal, Nundara and Rupar. These included not only the cowries (Cypraea) and the Chank (Xancus) but also their products—bangles and cores of shells from which the bangles have been sawn out.

In Vedic times, despite the relative rarity of references to marine life in the Vedas, possibly because of the predominantly agricultural or pastoral nature of Vedic civilization which had very little contact with the sea, the few references that occur relate mainly to the molluscs—the sankha (Chank), sukti (pearl oyster), sambuka, valluka and vodika (generally held to be spiral-shelled gastropods).

But to know the hold of the molluscs over ancient Indian mind, one has to start from the dim ages of mythology and legend.

In mythology The sacred chank, for instance, is so much a symbol of Hindu worship and mythology that it is integrated with almost every aspect of early Indian thought and culture. Vishnu, in his original aspect, has it as one of his four emblems; some of his avatars too are depicted as holding it. Possibly from this close affinity the chank is used in all Hindu temples, irrespective of sects, as an indispensible instrument of worship, as a container for holy water, as an instrument of invocation and call to the devout for worship. The mystic wail of the sacred chank resonant in the fading twilight of daybreak or dusk is part of the spiritual aura that surrounds most Hindu temples. Particularly the sinistral chank, by its very rarity, is held in such esteem that all major temples in India have one or more of these. Such adoration does not appear to be confined to the chank alone, nor to Hinduism alone. The fossil cephalopod Ammonites of the sub-Himalayan region, known to the Vaishnavite devout as salagmm, is held in high veneration as the very abode of Vishnu. And the Buddhist monasteries in Tibet have been known to keep sinistral chanks; the one at the Sakya Monastery, for instance, is believed to have been gifted by the great Kublai Khan himself in late 13th century. In some of the neighbouring countries of India too these shells are preserved as priceless treasures, at some time their value having been assessed at their weight in gold!

In folklore and superstition From its intimate association with the religious and emotional life of the people, the chank gradually slid into man's diverse walks of life. The folklore of different parts of India is replete with tales that have found concrete expression in many social customs as well. The lore relating to the place of chank and chank products in the marriage rites is vast, particularly in Bengal where the wearing of a lacquered chank bangle is part of the traditional ceremony. There is evidence to show that similar customs were prevalent elsewhere too, though non-existent now. Anthropologists refer to agricultural and pastoral communities like the Vellalans and Idaiyans, where the married women wear chank bangles customarily. The lore sometimes links the shell to Shiva who, as the story goes, laughingly chided Parvati at the time of her wedding, as not as charming as she might be, and proceeded to create out of his braided hair a Being who brought chank bangles for the adornment of the bride. Or, as in the story from South India, it is linked with Sri Krishna who, after abducting Rukmini from her marriage with Sishupala, married her himself by placing a chank bangle on her wrist. The influence that the shells exerted on the imagination of the ancient world is also borne out by the wealth of proverbs about the shells in different Indian languages. From religion and folklore it is but a short step to superstition and the shell pervades the superstitious world just as extensively. From innocent, amusing beliefs, such as that sinistral shells blow of their own accord during the nights (a superstition once so entrenched in Tamil areas that even Christian divers felt concerned at this!) to stories of their power to ward off evil, all sorts of superstition, have been reported. Tattooing or branding with heated metal the form of a chank, or burying a chank beneath the first stone laid for the construction of a temple or a house, all were once considered purificatory acts to ward off evil omens.

In social customs and traditions Apart from the uses already mentioned as inspired by folktales and superstitions, shells as traditional personal adornment were in use among many communities. It is quite possible that these were originally worn as amulets or mascots tied round the neck, but their form and use acquired a range in later years from finger rings and necklaces to disc ornaments for hair or head dresses. Rings cut out from Stombus shells were used either as finger rings or strung on a cord and interspersed with coral beads as necklaces. Necklaces were also made with discs cut out of shells or from bisected shells merely strung together. The wearing of these necklaces once a girl had attained a particular age was an obligatory custom in many tribes in the past. The shell discs as ornaments for the ear or as decoration for head-dresses appear to have been popular till recent times among peoples of the northern border—the Bhutanese, the Assamese and the Nagas. Other shells used as ornairents included the ring-cowry Ornamentaria. This cowry and also the money-cowry Monetaria were considered a symbol of wealth and prosperity and found a place in many social functions like marriages, rice-giving ceremonies, sradaha (death anniversaries), etc. Sometimes cowries or chanks were placed with the dead body as part of funereal rites. The cowries were also widely used in gambling and many other indoor games.

In trade and handicrafts Ancient Indians rarely left any records of their commerce or trade, when foreign sources haveoften filled in much information. As one leaves the dim past of myths and legends and comes into years of early history, indications of the commercial importance of molluscs are forthcoming. The accounts of foreign travelers mention the brisk trade that went on in shells from the fishing grounds of the Gulf of Mannar and Kathiawar coasts. The chank bangle trade is referred to in ancient Tamil writings and its prevalence proved by archaeological evidence. The travelling monk Cosmas Indico-Pleustes in the 6th century referred to the export of conch shells from India. The disputes and rivalries that went on between the foreign powers on this score, particularly at the time of the Portuguese and the Dutch, are part of more recent history. Rings, bangles plainly or elaborately carved, and disc ornaments appear to have been the main handicraft products of the past. The "ink" extracted from the cattle fish Sepia was used as a drawing ink till recently and was known to keep the clarity and intensity of colour for long. Similarly the "purple" extracts from some gastropods were also used as dyes and pigments.

As currency The shells, particularly the cowries, constituted the currency among many civilized and uncivilized peoples of the world. The most commonly used were the money-cowries Monetaria.Some ancient Hindu treatises about the 5th century mention the use of cowries as currency. Because of similar use of cowries in many parts of Africa, the trade in cowries flourished. There are records of annual dispatch of cargoes of cowries fished from Laccadive-Maldive waters to Wydah and Lagos, where they were exchanged for Spanish doubloons brought by the slave traders. Many European nations also imported cowries from India and other places for payment to West Africans in exchange for their products. Marco Polo, in the account of his voyage to China, recorded the finding of cowries circulating as currency in Yunnan in the 13th century.

Many Indian hill tribes, including the Nagas, employed it almost until the appearance of the Rupee. Till about a century ago the shells appear to have had a fixed and well-worked-out exchange value among the Nagas. Slaves and cattle were traded in shells. The villages captured during raids paid their ransom in shells as well as in other kind.

As medicine Many molluscs, predominantly the chank, appear to have been extensively used medicinally in ancient India. Chank shells, powdered and mixed with water, were considered an effective salve for ailments ranging from skin diseases to rickets and asthma. Chank ointment was similarly held as cure for eye inflammation or granulation on inner side of yelids, for piles or even for leprosy. Sometimes chank powder was prescribed, mixed with ghee and taken internally, for skin roubles, consumption and such. Another remedy compounded of partially burnt camphor, chank powder and human milk or white of egg was considered a speedy cure for soreness of eyes. The chank powder was, in short, a panacea for iverse illnesses like jaundice, cough, phthisis and general debility. The dried egg capsule of chank, powdered with pepper and coriander in til oil, was considered effective to relieve headache, while the dried visceral mass was thought efficacious for enlarged spleen. Some of the remedies appear scientifically possible of explanation. The use of chank powder as remedy for dyspepsia seems based on the carbonate of lime counteracting the hyperacidity of gastric fluids. Similar may be the case of rickets—an illness characterized by insufficient deposition of lime in bones. In many cases, however, it may be the religious association of the chank and the consequent faith in it that proved responsible for many cures. Other molluscs that were put to medicinal uses included the cowries (Cypraea), the apple snails and the widowpane oysters {Placenta).

Molluscs in Modern India The molluscs in India are playing a living role yet, shedding many of their past associations and reported miraculous properties (the impact, no doubt, of the so-called ungodly present-day generations) but assuming newer and vastly more utilitarian roles.

Surviving customs and traditions However, traditions and habits die hard and superstitions assume modern garb and survive, if only in name. Chanks or other shells tied to the forehead of draft bullocks or around the neck of cows and cow-buffaloes to keep them in milk are still sights not very uncommon. True, they are often put on as mere ornamentation now, their owners having no idea of the origin of this practice. Such is also the case of the shell necklaces that continue to be worn by many tribes even today. The mark of sophistication is not altogether absent, either—the shells that were once used to cut out discs for the ears and the hair, now turn out dress buttons. Even the role of the conch as a clarion call to duty and action, exemplified in ancient days in times of war (when every great warrior had his own individual and renewed conch which he blew lustily while going into action)—even this role appears to have survived in the custom in Bengal of blowing the conches in times of emergencies such as eclipses or

earthquakes. The resounding booms proceeding from almost all houses in a locality is kept up until the calamity is over (or, may be, until the deafened neighbourhood is past caring!).

In heraldry and design

The nobler, more elevated roles of the shells also have survived in part. Apart from the continued use of the chanks in Hindu temples, the heraldic designs of the royal houses as well as the State emblems of both Travancore and Cochin had the sinistral chank as a prominent motif. Perhaps reminiscent of the early use of shells as currency, the chank shell was a symbol on coins issued by many ancient rulers, especially of the Pandyan and Chalukyan dynasties. In more recent times Travancore and Cochin again used them on coins and early stamps. What is perhaps significant here is that in these cases the chank symbol was often used in place of and to the exclusion of the sovereign's head.

In trade and handicraft The trade in shells as raw material for the traditional handicraft products appears to have fallen, with glass and plastics displacing the chank in the bangle and bead-necklace manufacture, to a large extent. The chank bangle industry, however, still survives in Bengal. New forms of handicrafts have evolved in place of old. The old-world infant's drinking-spout fashioned out of chank lingers among some of the poorer classes, while the richer strata are supplied with carved shell ashtrays or Nautilus reading lamps or window-pane oyster lamp shades. A glue made out of the powdered horny operculum of the chank is still in use in some places as an adhesive base in the manufacture of incense sticks.

In industry

The shells are used in modern industry primarily for the manufacture of lime and cement. Especially in this country where in the mortar used in building construction as well as in the whitewash needed for its maintenance lime is an essential commodity, the industry though scattered and so individually on a small scale, is cumulatively a large one. Though mussel and clam shells are usually used for preparing lime, chanks are used for special needs and occasions, as the lime produced by the chank shell is found to be of superior quality. Similarly, though carbonate deposits are widely used in the manufacture of cement, the factory at Kottayam in Central Kerala makes use of the dead and sub fossil shells from the Vembanad Lake as their chief raw material.

As enemy of man This account has so far dealt with some of the useful or at any rate harmless aspects of molluscs in their relationship with man. There is a reverse side to this too. The molluscs can also be agents of large-scale destruction or dreaded carriers of death to livestock or to man himself they cause destruction to property by fouling or by boring. Many bivalves, particularly of the oyster and mussel group, are chief components of fouling communities that encrust submerged objects like piles and boats, causing considerable loss of timber or in case of vessels, reducing their speed and spoiling their streamlined efficiency in water. The wood-borers (like Bankia, Teredo, Martesia, etc.) or ship-worms, even as their latter

popular name suggests, eat away submerged timber and cause extensive damage to wooden hulls of sea-going vessels. These molluscs thus have a significant place in the economy of a marilime people. The importance of molluscs as a hazard to health stems from their close association with many helminth parasites. The well-known Schistosomiasis (Bilharziasis) or snail fever is spread through the agency of amphibian or freshwater snails that are intermediate hosts to these parasites. This dreaded disease is rampant in Africa, Middle East, South-East Asia and tropical South America. But India has so far been free from it though allied helminthes species have been recorded from many common freshwater snails, like Lymnea and Indoplanorbis. These snails are also active in the spread of many serious trematode infections in livestock.

PRESENT RESOURCES:NEED FOR SURVEY AND UTILIZATION

As mentioned earlier the resources of molluscs that can sustain regular and very productive fisheries are abundant in our waters. The primary need is to survey these resources and gather data on the existing level of their exploitation—which is bound to be low. Only the pearl oyster and chank fishing grounds had received some early attention in this regard, and even here a recent cooperative underwater survey conducted by the Central Marine Fisheries Research Institute and the Madras Fisheries Department with the aid of aqualung or SCUBA diving revealed many changes in patterns from that recorded by either surveys done decades ago, and also indicated fresh grounds that could be exploited commercially. Such systematically carried out surveys and preliminary studies should be made for other resources as well. Great as the industrial use of molluscs is, perhaps the significance of molluscs in future would be greater as a potential source for human consumption. Only a few of the mussels, clams and oysters are now generally eaten and even these are more a poor man's food and have not attained their place on the gourmet's table that they could. The need for popularising molluscs as food is great, particularly in a country like ours where provision of nutritious food is a long-standing problem and any means to tackle it should be tried and, if successful, popularized. From the nutritional point of view the molluscs have many advantages such as easy digestibility coupled with high contents of minerals and vitamins. They have approximately 8-10% of proteins (by weight), 4-5% of carbohydrates, 2-3% of minerals with but 1-2% of fat. It has been calculated that a good serving of oysters, for example, would supply more than the needed daily allowance of iron and copper, about half the required amount of iodine, about one-tenth the daily need of protein, calcium, phosphorus, vitamin A, thiamine, riboflavin and nicotinic acid. Thus the role that the molluscs can play, along with fishes, in meeting the country's quest for balanced, nutritious diet has to be more widely recognized.

MALACOLOGY

Malacology is the branch of invertebrate zoology which deals with the study of the Mollusca (mollusks or molluscs), the second-largest phylum of animals in terms of described species after the arthropods. Mollusks include snails and slugs, clams, octopus and squid, and numerous other kinds, many (but by no means all) of which have shells. One division of malacology, conchology, is devoted to the study of mollusc shells.

Fields within malacological research include taxonomy, ecology and evolution. Applied malacology studies medical, veterinary, and agricultural applications, for example mollusks as vectors of disease, as in schistosomiasis. Archaeology employs malacology to understand the evolution of the climate, the biota of the area, and the usage of the site.

In 1681, Filippo Bonanni wrote the first book ever published that was solely about seashells, the shells of marine mollusks. The book was entitled: Ricreatione dell' occhio e dela mente nell oservation' delle Chiociolle, proposta a' curiosi delle opere della natura, &c. In 1868, the German Malacological Society was founded.

Obvious zoological methods are used also in malacological research. Various malacological field methods and laboratory methods (such as collecting, documenting and archiving, mollecular techniques) were summarized by Sturm et al.

GASTROPODA

The Gastropoda or gastropods, more commonly known as snails and slugs, are a large taxonomic class within the phylum Mollusca. The class Gastropoda includes snails and slugs of all kinds and all sizes from microscopic to quite large. There are huge numbers of sea snails and sea slugs, as well as freshwater snails and freshwater limpets, and land snails and land slugs.

The class Gastropoda contains a vast total of named species, second only to the insects in overall number. The fossil history of this class goes all the way back to the Late Cambrian. There are 611 families of gastropods, of which 202 families are extinct, being found only in the fossil record.

Gastropoda (previously known as univalves and sometimes spelled Gasteropoda) are a major part of the phylum Mollusca and are the most highly diversified class in the phylum, with 60,000 to 80,000 living snail and slug species. The anatomy, behavior, feeding and reproductive adaptations of gastropods vary significantly from one clade or group to another. Therefore, it is difficult to state many generalities for all gastropods.

The class Gastropoda has an extraordinary diversification of habitats. Representatives live in gardens, in woodland, in deserts, and on mountains; in small ditches, great rivers and lakes, in estuaries, mudflats, the rocky intertidal, the sandy subtidal, in the abyssal depths of the oceans including the hydrothermal vents, and numerous other ecological niches, including parasitic ones.

Although the name "snail" can be, and often is, applied to all the members of this class, commonly this word means only those species with an external shell large enough that the soft parts can withdraw completely into it. Those gastropods without a shell, and those with only a very reduced or internal shell, are usually known as slugs.

The marine shelled species of gastropod include edible species such as abalone, conches, periwinkles, whelks, and numerous other sea snails that produce seashells which are coiled in the adult stage, even though in some cases the coiling may not be very visible, for example in cowries. There are also a number of families of species such as all the various limpets, where the shell is coiled only in the larval stage, and is a simple conical structure after that.

The word "gastropod" is derived from the Ancient Greek words γαστήρ (gastér, stem: gastr-) "stomach", and πούς (poús, stem: pod-) "foot", hence stomach-foot. This is an anthropomorphic name, based on the fact that to humans it appears as if snails and slugs crawl on their bellies. In reality, snails and slugs have their stomach, the rest of their digestive system and all the rest of their viscera in a hump on the opposite, dorsal side of the body. In most gastropods this visceral hump is covered by, and contained within, the shell.

In the scientific literature, gastropods were described under the vernacular (French) name "gasteropodes" by Georges Cuvier in 1795. The name was later Latinized.

The earlier name univalve means "one valve" or shell, in contrast to bivalve applied to mollusks such as clams and meaning that those animals possess two valves or shells.

Anatomy

The anatomy of a snail is very different from many other animals in the world. Some people find them to be fascinating while others thing they are ugly. When you start to break down all of the parts of the body though, they definitely have an interesting composition to them.

The shell of a snail can be very different in size and shape depending on the type of snail it is. Some of them are round while others are flat. Many of them have a spiral design to them. These shells serve as a way to protect them from the environment and even from predators in some cases. However, many predators are able to bite through the hard shells with powerful teeth and jaws.

The shell of a snail is made up of calcium carbonate. The shell becomes very strong and remains that way as long as the snail consumes a diet that is full of calcium. Without it the shell will start to crack. Since the rest of the body is very soft and slimy, they must have a hard shell if they are going to survive the elements in the world around them.

The parts of the snail are described below

They shell is s safe haven for the snail to reside in. When it senses danger around it, putting the whole body into the shell is the line of defense. You will also find that the snail spends a great deal of time in the shell when they weather is very hot and dry. Otherwise their moist bodies will dry out.

Snails have one or two sets of tentacles that are on top of the head. The number of pairs will depend on the species you are describing. Although most of the time you will find that the eyes are present on the longer set of them if they have two. You may not always see these tentacles though as all land snails have the ability to retract them.

The snail has a very small brain which is known to have four distinct sections to it. They have more of ability for thinking though than most people give them credit for. Most research shows that they do take part in associative thinking which is based on conditioning and experiences that they take part in.

The mouth of a snail is found at the bottom of the head, in close proximity to the tentacles. Snails don’t have lungs but they do need air to breathe. This is achieved through a cavity called the visceral. There are many blood vessels here and the function is the same as what our lungs are able to do for us.

There is a foot on a snail as well that allows it to move forward. There is contracting and expanding in this muscle that allows it to have movement. The mucus that they glide along is produced in a gland in the foot as well. Without this slime under them, the environment would be too hard for their soft bodies to move along without injury.

Around the foot is a protective layer called the mantle. It is also found around the shell to offer it additional protection. Without that they would injure the food and end up not being able to move at all. If you watch how a snail looks before moving you will notice what appear to be spasms through them and then they inch forward. This is the muscles in the foot working. Even though they do move slowly there is a rhythm to it that they will follow over and over again.

Body wall

Some sea slugs are very brightly colored. This serves either as a warning, when they are poisonous or contain stinging cells, or to camouflage them on the brightly-colored hydroids, sponges and seaweeds on which many of the species are found.

Lateral outgrowths on the body of nudibranchs are called cerata. These contain a part of digestive gland, which is called the diverticula.

Life cycle

The reproduction process of the snail is one that has some unusual patterns to it when compared to that of other land animals. In other ways though the process is the same as what you would expect. Learning more about this process will help you to see why there are often concerns about snails and other offspring being able to survive in the future. It takes them about two years to be mature.

Land snails engage in various types of courting rituals to attract mates. They can last for a couple of hours or half a day. They don’t make sounds to call out to each other like many types of animals do. It may surprise you to learn that snails don’t have the ability to hear. So they use touching as a way of courting. They may cover each other in slime that they produce from their bodies before mating.

It is believed this slime also makes it easier for them to engage in the actual mating process. Once they have done so they will go their separate directions. What is interesting is that each snail has both types of reproductive parts. During the mating process both of them will conceive up to 100 eggs. These eggs are extremely small and they will be deposited into the moist soil. It can take up to four weeks for them to emerge.

Many land snails mate on a monthly basis as long as their living conditions are adequate for survival. These eggs will be deposited in moist ground where there is plenty of shade. They are under the top layers of soil but if you dig a bit you will be able to find them.

Even with so many eggs being deposited, only a fraction of these snails make it to maturity. Many of the eggs are washed away by rain and water people use in their yards and gardens. Young snails are often consumed by predators because they are slow and they are plentiful.

When they offspring emerge from their eggs, they immediately need to get calcium into their bodies. They are born with a shell but it is in a fragile state. The calcium will help it to quickly harden up which offers them plenty of protection. The first thing they will instinctively consume after hatching is the shell of the very egg they came from. The shell continues to grow with the snail over the course of its life. The part of the shell it is born will end up in the middle of it when they are fully grown.

Snails grow rings inside of the shell as they grow. This is how scientists and researchers are able to get a good idea of how old they are. For the most part it seems that snails live a life that is slow paced and very basic. You can tell if a snail is full grown or not by looking at the part of the shell that opens up to the rest of the body. If there is a small lip on it then the snail won’t grow anymore. If it is missing then the snail still will continue to get bigger.

A 9-hour-old trochophore of Haliotis asinina

sf - shell field

The main aspects of the life cycle of gastropods include:

Egg laying and the eggs of gastropods The Embryonic development of gastropods The larvae or larval stadium: some gastropods may be trochophore and/or veliger Estivation and hibernation (each of these are present in some gastropods only) The growth of gastropods Courtship of gastropods and mating of gastropods: fertilisation is internal or external

according to the species. External fertilisation is common in marine gastropods.

Lifespan

Balancing selection refers to forms of natural selection which work to maintain genetic polymorphisms (or multiple alleles) within a population. Balancing selection is in contrast to directional selection which favors a single allele. A balanced polymorphism is a situation in which balancing selection within a population is able to maintain stable frequencies of two or more phenotypic forms.The lifespan of snails varies from species to species. In the wild, Achatinidae snails live around 5 to 7 years and Helix snails live about 2 to 3 years. Aquatic Apple Snails live only a year or so.

Dimensions

The most frequently used measurements of a gastropod shell are: the height of the shell, the width of the shell, the height of the aperture and the width of the aperture. The number of whorls is also often used.

In this context, the height (or the length) of a shell is its maximum measurement along the central axis. The width (or breadth, or diameter) is the maximum measurement of the shell at right angles to the central axis. Both terms are only related to the description of the shell and not to the orientation of the shell on the living animal.

The central axis is an imaginary axis along the length of a shell, around which, in a coiled shell, the whorls spiral. The central axis passes through the columella, the central pillar of the shell.

The largest known land snail named Gee Geronimo was a Giant African Snail collected in Sierra Leone in 1976. It weighed about 2lb (900g) and

measured over 15 inches (39.3cm) from snout to tail.

Body Construction

Looking at a snail crawling its way at a proverbial snail's pace, clearly first the difference is seen between the living movable and flexible body, therefore also referred to as the soft body, and the lifeless hard shell.

The soft body

A snail's soft body externally uniform: It is not divided into segments, like in an articulate animal (like an arthropod (Arthropoda) or a segmented worm (Annelida)). All body parts change into each other invisibly.

Brown garden snail

Head and foot

In spite of that, a large part of a snail's body can be seen extended outside of the shell, when the snail is crawling around. This body part is flattened at the belly side (ventrally) to form a flat crawling sole and mainly is used for locomotion. This is why it is consequently called the foot. That snails crawl on their belly has provided them with their scientific name: Gastropoda, the belly-foot animals.

The snail can withdraw its foot into the shell by the aid of a large muscle, the retractor muscle. This muscle is fastened at the shell's so called spindle or columella, which is why it is also called the columellar muscle. While the lifeless shell, strictly speaking, is not a part of the body, by their columellar muscle, snails still always remain connected to their shell, unable to leave it. Empty snail shells found in nature are all that remains of a dead snail.

Snails' tentacles

Locomotion

Snails' locomotion is very different and strongly adapted to their way of life. Terrestrial snails' locomotion at a proverbial snail's pace is well known to us. Waves of the foot sole move from tail to head and so carry the snail slowly forward. In doing this the snail always remains in contact with the ground.

Apart from this crawling motion many terrestrial snails are also able to dig (for example the Roman snail digs a hole into the earth to hibernate or to lay its eggs). Water snails not only crawl their way (pond snails for example also can crawl along hanging from the water surface), but there are also swimming forms.

A pond snail's head

At the foot's frontal end, there is the snail's head. Because both are inseparable externally, so they are also referred to as the cephalopodium or head-foot, a recognising character of all snails. At a snail's head there are tactile organs, the so called tentacles. While most terrestrial snails have four tentacles, which they can withdraw (that is a recognising character of terrestrial pulmonate snails (Stylommatophora)), other terrestrial snails, as well as most water snails only possess two tentacles, which they cannot withdraw.

Especially remarkable are predator snails like the rosy wolf snail (Euglandina rosea), whose lips are extended to form a third tentacle pair. A snail's lips mainly bear sense cells of smell and taste, and wolf snails pursue their prey along its slime thread.

While a terrestrial pulmonate snail's larger tentacles carry one eye each at the tip, in other snails, such as the fresh water pond snail (Lymnaea stagnalis), the eyes are located at the tentacles' base.

The marine opisthobranchs (Opisthobranchia), on the other hand, have a second pair of tentacles at their disposal, which also mainly holds olfactory sense cells and hence is called rhinophores (nose bearers).

The slime layer

Another characteristic attribute is not only important for a snail's locomotion: Snails not only are slow, but also slimy.

A mucus gland produces a slime bed, on which the snail crawls and which it leaves behind as a slime thread. Besides, all of a snail's body is covered in slime.

Simplon door snail

A snail's slime consists of polysaccharides and has astonishing physical properties: Probably the most important of them is hygroscopy: A snail's slime attracts water, because its molecules swell with water. So the slime protects the snail from desiccation. Also, a snail's slime has surprising properties between flexibility and stickiness. For example it reduced friction between the snail's body and the ground, but, together with the sucking action of the foot sole, it also has the snail stick to the ground with surprising force, especially on smooth planes. That explains, how a snail manages to surmount a knife blade, and also, why door snails (Clausiliidae) manage to climb up tree trunks and rocks with their shell giant compared to their foot.

Besides, a snail's slime has still another important protective function: Many snails can foam, when they encounter a predator (such as ants) or if they touch something repulsive. Besides, the slime serves as a protective layer, keeping harmful substances from contact with the body.

Visceral sac and mantle

Apart from the cephalopodium, always outside of the shell when the snail is crawling around, there is a part of the body always remaining inside the shell. This is called the visceral sac, because many of the snails internal organs are in it, though most of them also extend into the foot. The visceral sac is protected by a stout tissue layer covering its entire surface and called the mantle. The mantle is especially sturdy in the shell aperture, where the danger of evaporation is largest.

Egg defences

Apple snail eggs on emerging vegetation

In terrestrial snails and many water snails, in the mantle also the large breathing hole, the pneumostome, can be seen. The respiratory organs of snails can be different, depending on where the snail lives. Basically there are snails with gills, living in the sea and in fresh water, as well as pulmonate snails with lungs, living on land and in fresh water as well. The ability to breathe air and several other adaptations have induced a very large increase in species numbers by adaptive radiation after snails first set foot on dry land.

Pond snails

It is remarkable how visible the egg clutches of many apple snail species are. The pinkish to reddish eggs are attached on the contrasting green vegetation submerging from the water (in the genus Pomacea). This makes them visually inconspicuous from many meters away for predators. This suggests a possible warning function for unpalatability. Field evidence of this unpalatability is provided by the fact that almost all animals foraging in habitats where the apple snails live, ignore these eggs: from fish to birds, they all leave them alone. Also when apple snail eggs are offered to captive predators, they often try to eat them at first, but refuse them after repeated feeding.

Another interesting evidence for the unpalatability is the feeding behaviour of limpkins on apple snails. Limpkins do feed on female apple snail with well-developed albumen (yolk) gland, but they discard this organ before eating the snails. Rejection of the albumen gland is also observed when offering apple snail meat to fish. This suggests that substances in yolk, not in the scale cause the unpalatability of the eggs. Besides their unpalatability, some apple snail species prefer to deposit their eggs on vegetation covered with thorns, making them more difficult catch for a predator. There are also apple snail species that lay greenish eggs like Pomacea glauca, Pomacea pyrum and others, while the apple snail from the genus Pila have white eggs. The green colour is a rather camouflage to render the eggs invisible for predators. The aquatic eggs from the genera Asolene (Asolene), Lanistes and Marisa are protected by a gelatinous slime surrounding the eggs. These eggs are less visible than their aerial cousins because their transparance, and they are deposited on less visible places (between vegetation). A particular interesting way to protect the eggs and the young snails against drought and predators is shown by Pomacea urceus. This snail lays its orange eggs at the inside of the shell near the aperture. The eggs are brooded in this incubation chamber closed of with the mother's operculum (shell-door), while the snail aestivates in the dry mud during the dry season. The young snails hatch inside the mother's shell and crawl around until the rainy season starts.

Organs and Organ Systems

Of all molluscs, the snails have adapted to the most habitats, which has led to their amounting to the by far highest number of mollusc species. Adaptation to so many different habitats only way possibly by optimally adapting organs and organ systems. Alone from external appearance, two gastropod species may sometimes be hard to recognise as two of the same class, Gastropoda.

Respiration

Respiration is one of the characters very different between snail groups. Basically there are pulmonate snails, whose pallial cavity is formed to a simple lung to breathe oxygen from the air. Among those there are most of the terrestrial snails, as well as pulmonate snails living in fresh water.

Other gastropod species have developed the ability to breathe air later. All marine gastropods, as well as some fresh water gastropods, breathe with gills. Snails originally possess the so-called comb-gills (ctenidia), which are also located in the pallial cavity. An exception are the marine nudibranchs (Nudibranchia), whose original gills have been reduced, so the nudibranchs breathe using newly developed feathery dorsal appendages called cerata.

Circulation and Excretion

A snail's circulation basically is open. That means that snails may have some important blood vessels, such as the pulmonary vein, leading from the lung to the heart, and the main artery or aorta, but the blood circulates freely between the organs. There it mixes with the lymphatic fluid, resulting in the so-called haemolymph. A snail's heart has two chambers, one ventricle and one atrium. It is located in the heart bag, the so-called pericardium.The heart bag is also important to the snail's excretion, meaning the disposal of indigestible material usually rich in nitrogen. In the most primordial gastropod species, filtration takes place through the heart bag's wall, the excretion taking place afterwards via an efferent channel, the urethra. Snails' excretion organs originally were derived from the segmented worms' (Annelida) metanephridia. While water snails excrete a very much diluted primary urine, terrestrial pulmonate snails have developed the ability to resorb most of the water. In terrestrial snails, excretion takes place in a kidney, whose interior surface has been increased by many interior walls called septae. Through their walls filtration of blood flowing through takes place. Terrestrial snails usually excrete urea, containing almost no water.

Nutrition

A pond snail grazing the algae on the

water surface

As different as the methods of nutrition may be among snails (there are herbivores, omnivores and carnivores), it can nonetheless be retraced to common organs. To feed, snails use an organ, that is present in most molluscs and unique in the animal kingdom: The radula or a rasp tongue. Basically, it consists of an elastic band running over a gristle core and armed with a large number of chitin teeth. To feed, this rasping band is used like the transportation band of a bucket excavator, food particles rasped of are transported back into the gullet. The bow-shaped jaw is used to cut off food particles.

Similar to other animals' teeth, the radula as well is adapted strongly to the respective methods of nutrition. While plant-eating species, such as the Roman snail, have broad and blunt radula teeth, predatory snails usually have dagger or lance shaped radula teeth, enabling them to hold the prey and also to rip flesh from it (fittingly, a predatory snail from the American Northwest is called the Robust lance tooth - Haplotrema vancouverense).

A Roman snail eating a leaf

Maximally adapted to the method of hunting and feeding is the radula of cone shells (Conidae): While elsewhere the radula carries thousands of teeth, cone shells only have one at a time, formed like a harpoon and used to inject the prey with venom. In marine gastropods, the radula is also often used for systematic purposes, which is why the difference is made between beam-tongue gastropods (Docoglossa, among them the limpets - Patellidae) or the venom-tooth gastropods (Toxoglossa, as expected, among others the cone shells-Conidae).

Radula Types

Two salivary gland open into the gullet, which are used to digest food for the first time. In cone shells, they have been transformed into venom glands. A snail's stomach is a simple blind sac, in which the digestion by saliva continues. The main part of digestion takes place in the main digestive gland, a specialised gland taking most of the place in the visceral sac. It is also called a hepatopancreas, being both liver and pancreas. While usually the liver only produces digestive fluids and stores nutrients, in a snail's hepatopancreas also digestion takes place. Also, lime is gained from the food, later transported via the blood stream to the shell-building cells of the mantle.

Nervous system

The nervous system of gastropods is located at the ventral side and can be derived from the segmented worms' (Annelida) rope-ladder nervous system. While in very primordial gastropods, nerve knots (ganglia) are still placed in different parts of the body (the foot ganglion, the visceral ganglion, the pleural ganglion etc.), the nervous system of more advanced gastropod species, especially of terrestrial pulmonate snails, is very much centralised, all ganglia molten to form one common ring around the gullet, called the buccal mass. Especially more advanced gastropod species are capable of rather astonishing neural feats - the marine slug Aplysia, for example, was used to research learning behaviour and conditioning. On the other hand, some water snails, but especially the marine gastropods, reproduce via several larval stages (Trochophora and Veliger larvae), which swim freely or float in the water as part of the plankton.

Mating and Reproduction

The Process of Mating

A Roman snail's mating process takes place in several phases, which go from an attraction phase over an extensive courtship until finally the copulation itself.

In spring, when the Roman snails have been awake from hibernation for some time, it becomes time for mating. Depending on the weather and other environmental conditions, mating time may last until the end of June. Only until then the juveniles will have enough time to prepare for hibernation so they are able to survive winter.

Roman snails, and with them most terrestrial snail species, are hermaphrodites. They have male, as well as female organs in one collective genital apparatus. This organ system not only contains sexual organs in the narrow sense of the word, but also various auxiliary organs, that have respective tasks in different periods during mating.

What advantage does being a hermaphrodite give to a Roman snail? Because of its proverbial slowness the snail needs much time to move in a very small area. So the chances to meet a mating partner are too low to divide them even further by two sexes to choose from. Terrestrial pulmonate snails (Stylommatophora), such as the Roman snail, on the other hand, have double mating chances, because in principle, they can mate with any snail of the right species they encounter. Besides, during copulation, Roman snails do not act as either male or female, but simultaneously as both.

In spring, when the Roman snails are

awake from hibernation,

the mating season begins.

Attraction and Courtship

Attraction and Courtship

Application of a Love Dart

During the courtship possibly a dart may be applied, one snail stinging it into the mate's foot. This dart has been called love dart, as its application obviously is in direct connection with courtship or mating. The pricked snail becomes visibly more excited and active, sometimes it also returns the favour by jabbing a love dart into the mate's body. A Roman snail's love dart can become as long as 7 to 11 mm and consists of a four-edge blade on one and a crown on the other end. In idle state with this crown the dart sits on a papilla in the dart sac. To use the dart, the snail pushes out the interior of the dart sac, thrusting the dart into the mate's body. After separation from the papilla, the dart remains stung in the body. Though it is called a dart, in many languages also an arrow, the Roman snail's love dart is neither thrown nor shot, there is no distance of free flight! Instead it is thrust into the mate's body, more like a dagger, than a dart. Sometimes, though, the love dart also misses its target. Than

Attraction sometimes passes the

borders of species. Helix lu-

corum (left) and pomatia (right)

The encounter of two Roman snails ready for mating is not purely incidental. Like many other terrestrial snails, they as well have a gland located at the head, producing an olfactory sexual attractant. Those attractants are also used by other snail species among the helicid snails, such as banded snails (Cepaea). As a consequence incidentally two snails of entirely different species may feel attracted and try mating. Between snails of different species, that attempt must, of course, remain unsuccessful.

Mating between Roman snails and their relatives, though, are certainly possible, but will not yield any fertile offspring. Bastardization between closely related snail species may, however, lead to the development of new species, as it occurs among the family of door snails (Clausiliidae).

The courtship among Roman snails is a very interesting thing to witness: Both snails begin by raising their heads and putting their flat foot soles against each other. They touch each other with tentacles and lips while they are swaying gently. As a prelude to the actual copulation this courtship process may last as long as twenty hours. The copulation itself will take a much smaller fraction of time.

it may come to rest on the mate's body without penetrating it, but it can also happen that one of the two mates is hurt. It is not in every mating process, that a love dart is applied. To be precise, that is not even possible! Roman snails mate, whenever possible, but the replication of a love dart needs sometimes more time, than remains between two mating encounters. Research has found out, that the application of a love dart does not at all only influence a snail's behaviour. By means of the love dart a secretion is injected, that is produced by the finger shaped glands in the genital apparatus. This secretion contains hormones, that influence certain parts of the genital apparatus and that way improve the reproductive chances of the snail that applied the dart. The exact effects of the hormone secretion transferred by the love dart are described together with the respective organs of the genital apparatus.

Copulation

This is why the two snails remain motionless for a certain time after completing of the copulation: The spermatophore's application in the mate's genital apparatus must be supported; an early interruption of the union may disrupt the spermatophore and thus render useless the hours of toil included in a standard snail courtship.

It so happens that snails are of a very different enthusiasm

during courtship

After the long and extensive courtship there may be several attempts on copulation. It may so happen that the readiness to mate between two snails is very different, so that the copulation attempts may look more like a wrestling match.

When finally both snails managed to find a suitable position, they actually perform copulation. Both penises are entwined and inserted into the mate's vagina. The union successfully completed, both snails stay as they are.

Now, a sperm packet, a so-called spermatophore, is produced in either snail's body and afterwards filled with sperm cells.

This spermatophore is almost 10 cm long and is roughly shaped like a thread. Even after it was positioned in the mate's genital apparatus, the tail still looks out of the snail's genital opening.

It is only now that both snails separate. Only little time later they may meet again with other potential mates. A part of the sperm cells just received, however, will be stored in a special sperm pouch. Those sperm cells may then well manage to fertilize egg cells, though they will have to compete with sperm cells of other mating partners also stored in the same pouch. Fertilisation, though, only happens, when it is time to lay eggs. That finally will happen, provided the environmental conditions are favourable and there is a place where the eggs can be deposited in a special hole in the ground.

Estivation

Snails are usually active in the summer, but if it gets too warm or too dry for them, they enter a period of inactivity known as estivation. They find a safe place—such as a tree trunk, the underside of a leaf, or a stone wall—and suction themselves onto the surface as they retreat into their shell. Thus protected, they wait until the weather becomes more suitable. Occasionally, snails will go into estivation on the ground. There, they go into their shell and a mucous membrane dries over the opening of their shell, leaving just enough space for air to get inside allowing the snail to breath.

Hibernation

In late fall when temperatures drop, snails go into hibernation. They dig a small hole in the ground or find a warm patch, buried in a pile of leaf litter. It is important that a snail finds a suitably protected place to sleep to ensure its survival through the long cold months of winter. They retreat into their shell and seal its opening with a thin layer of white chalk. During hibernation, the snail lives on the fat reserves in its body, built up from a summer of eating vegetation. When spring comes (and with it rain and warmth), the snail wakes and pushes the chalk seal to open the shell once again. If you look closely in spring, you may find a chalky white disc on the forest floor, left behind by a snail that has recently come out of hibernation.

Vision

Shell

Four views of a shell

The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage. In land snails, in some freshwater snails and in intertidal marine snails, the shell is also an essential protection against the sun, and against drying out. Most gastropod shells are spirally coiled. The coiling is usually right-handed, but in some taxa the coiling is left-handed and in a very few species there can be both right-handed and left-handed individuals. The gastropod shell has several layers, and is typically made of calcium carbonate precipitated out into an organic matrix known as conchiolin. The shell is secreted by a part of the molluscan body known as the mantle.

Not all gastropods have a shell, but the majority do. In almost every case the shell consists of one piece, and is typically spirally coiled, although some groups, such as the various different families and genera of limpets, have simple cone-shaped shells as adults.The study of mollusc shells, including gastropod shells, is called conchology.

Vision is not important for apple snails as mechanism to detect predators or other danger. This is supported by the fact that apple snails do not show an alarm response to sudden light changes or moving objects above the water surface. A possible reason why apple snails do not rely on their vision could be the limited ability to form images with their eyes, let alone to distinguish a predator from other objects. If every sudden light change would trigger an alarm response, apple snails would suffer from many 'false' alarms. The combined sensitivity to mechanical disturbance and chemical stimuli appears to be sufficiently adequate for an apple snail to survive.

Chirality in gastropods

Shells of two different species of sea snail:

on the left is the normally sinistral (left-

handed) shell on the right is the normally

dextral (right-handed) shell

Because coiled shells are asymmetrical, they possess a quality called chirality, the "handedness" of an asymmetrical structure. By far the majority (over 90 %) of gastropod species have dextral (right-handed) shells in their coiling, but a small minority of species and genera are virtually always sinistral (left-handed), and a very few species (for example Amphidromus perversus) show an even mixture of dextral and sinistral individuals. In species that are almost always dextral, very rarely a sinistral specimen will be produced, and these oddities are avidly sought after by some shell collectors. If a coiled gastropod shell is held with the spire pointing upwards and the aperture more or less facing the observer, a dextral shell will have the aperture on the right-hand side, and a sinistral shell will have the aperture on the left-hand side. This chirality of gastropods is often overlooked when photographs of coiled gastropods are "flipped" by a non-expert prior to being used in a publication.

This image "flipping" results in a normal dextral gastropod appearing to be a rare and abnormal sinistral one. The chirality in gastropods appears in early cleavage (spiral cleavage) and the gene NODAL is involved.

Mixed coiling populations

In few cases, both left- and right-handed coiling are found in the same population. Sinistral mutants of normally dextral species and dextral mutants of normally sinistral species are rare but well documented occurrences among land snails in general. Populations or species with normally mixed coiling are much rarer, and, so far as is known, are confined, with one exception, to a few genera of arboreal tropical snails. Besides Amphidromus, the Cuban Liguus vittatus (Swainson), Haitian Liguus virgineus (Linnaeus) (family Orthalicidae), some Hawaiian Partulina and many Hawaiian Achatinella (family Achatinellidae), as well as several species of Pacific Island Partula (family Partulidae), are known to have mixed dextral-sinistral populations. The independent appearance of this variation in unrelated groups is probably the result of a simple mutation, whose primary import is with physiological adaptations to arboreal life and not with the direction of coiling. In Partula both dextral and sinistral embryos have been recovered from the same brood pouch, although normally all embryos coil in the same direction. In Amphidromus there is no information on the heredity of this character.

A possible exception may concern some of the European clausiliids of the subfamily Alopiinae. They are obligatory calciphiles living in isolated colonies on limestone outcrops. Several sets of species differ only in the direction of coiling, but the evidence is inconclusive as to whether left- and right-handed shells live together. Soos (1928, pp. 372–385) summarized previous discussions of the problem and concluded that the right- and left-handed populations were distinct species. Others have stated that these populations were not distinct, and the question is far from settled. The Peruvian clausiliid, Nenia callistoglypta Pilsbry (1949, pp. 216–217), also has been described as being an amphidromine species.

The genetics of reverse coiling in a rare dextral mutant of another clausiliid, Alinda biplicata (Montagu), has been studied by Degner (1952). The mechanism is the same as in Radix peregra (Müller), with the direction of coiling determined by a simple Mendelian recessive. Any change in direction caused by cross-fertilization is delayed one generation by an unknown mechanism.

Formation of the shell

Morphology

Gastropod shell morphology is usually quite constant among individuals of a species, and with exceptions, fairly constant among species within each family of gastropoda. Controlling variables are:

The rate of growth per revolution around the coiling axis. High rates give wide-mouthed forms such as the abalone, low rates give highly coiled forms such as Turritella or some of the Planorbidae.

The shape of the generating curve, roughly equivalent to the shape of the aperture. It may be round, for instance in the turban shell, elongate as in the cone shell or have an irregular shape with a siphonal canal extension, as in the Murex.

The rate of translation of the generating curve along the axis of coiling, controlling how high-spired the resulting shell becomes. This may range from zero, a flat planispiral shell, to nearly the diameter of the aperture.

Irregularities or "sculpturing" such as ribs, spines, knobs, and varices made by the snail regularly changing the shape of the generating curve during the course of growth, for instance in the many species of Murex.

Ontologic growth changes as the animal reaches adulthood. Good examples are the flaring lip of the adult conch and the inward-coiled lip of the cowry.

Some of these factors can be modelled mathematically and programs exist to generate extremely realistic images. Early work by David Raup on the analog computer also revealed many possible combinations that were never adapted by any actual gastropod.

Some shell shapes are found more often in certain environments, though there are many exceptions. Wave-washed high-energy environments, such as the rocky intertidal zone, are usually inhabited by snails whose shells have a wide aperture, a relatively low surface area, and a high growth rate per revolution. High-spired and highly sculptured forms become more common in quiet water environments. The shell of burrowing forms, such as the olive and Terebra, are smooth, elongated, and lack elaborate sculpture, in order to decrease resistance when moving through sand. A few gastropods, for instance the Vermetidae, cement the shell to, and grow along, solid surfaces such as rocks, or other shells.

Standard ways of viewing a shell

Description

The shell begins with the minute embryonic whorls of the protoconch, which is often quite distinct from the rest of the shell. From the protoconch, which forms the apex of the spire, the coils or whorls of the shell gradually increase in size. Normally the whorls are circular or elliptical in section, but from compression and other causes a variety of forms can result. The spire can be high or low, broad or slender according to the

Apertural view of shell

Abapertural view of shell

Basal or umbilical view of shell

Dorsal view of its shell

apertural view: this is the most common viewing angle. The shell is shown in its full length with its aperture to the viewer and the apex on top. When the aperture is on the right side, then the shell is called "right-handed"; if the aperture is on the left side, the shell is called "left-handed".

abapertural view: the shell is shown in its full length with its aperture 180° away from the viewer and with the apex on top.

apical view (or dorsal view): the shell is seen in its full width with the apex on top

basal view (or umbilical view): the shell is shown in its full width with the apex below. In most cases, the umbilicus is in clear view.

way the coils of the shell are arranged, and the apical angle of the shell varies accordingly. The whorls sometimes rest loosely upon one another (as in Epitonium scalare). They also can overlap the earlier whorls such that they may be largely or wholly covered by the later ones. When an angulation occurs, the space between it and the suture above it constitutes the area known as the "shoulder" of the shell. The shoulder angle may be simple or keeled, and may sometimes have nodes or spines.The most primitive sculpture of the gastropod shell consists of revolving ridges or spirals, and of transverse folds or ribs. Primary spirals appear in regular succession on either side of the first primary, which generally becomes the shoulder angle if angulation occurs. Secondary spirals appear by intercalation between the primary ones, and generally are absent in the young shell, except in some highly accelerated types. Tertiary spirals are intercalated between the preceding groups in more specialized species. Ribs are regular transverse foldings of the shell, which generally extend from the suture to suture. They are usually spaced uniformly and crossed by the spirals. In specialized types, when a shoulder angle is formed, they become concentrated as nodes upon this angle, disappearing from the shoulder above and the body below. Spines may replace the nodes in later stages. They form as notches in the margin of the shell and are subsequently abandoned, often remaining open in front. Irregular spines may also arise on various parts of the surface of the shell (see Platyceras). When a row of spines is formed at the edge or outer lip of the shell this sometimes remains behind as a varix as in (Murex) and many of the Ranellidae. Varices may also be formed by simple expansion of the outer lip, and a subsequent resumption of growth from the base of the expansion. These simple varices may project from the shell or be reflected backwards.Periodic enlargements of ribs are not considered as varices.The aperture or peristome of the shell may be simple or variously modified. An outer and an inner (columellar) lip are generally recognized. These may be continuous with each other, or may be divided below by an anterior notch. This, in some types (Fusinus, etc.) it is drawn out into an anterior siphonal canal, of greater or lesser length.

In some cases the slit is abandoned and left as a hole (Fissurellidae), or by periodic renewal as a succession of holes (Haliotis). The outer emargination is often only indicated by the reflected course of the lines of growth on the shell.On the inside of the outer lip, various ridges or plications called lirae are sometimes found, and these occasionally may be strong and tooth-like (Nerinea). Similar ridges or columellar plicae or folds are more often found on the inner lip, next to the columella or central spiral twist. These may be oblique or normal to the axis of coiling (horizontal), few or numerous, readily seen, or far within the shell so as to be invisible except in broken shells. When the axis of coiling is hollow (perforate spire) the opening at the base constitutes the umbilicus. The umbilicus varies greatly in size, and may be wholly or in part covered by an expansion or callus of the inner lip (Natica).Many Recent shells, when the animal is alive or the shell is freshly empty, have an uppermost shell layer of horny, smooth, or hairy epidermis or periostracum, a proteinaceous layer which sometimes is thick enough to hide the color markings of the surface of the shell. The periostracum, as well as the coloration, is only rarely preserved in fossil shells.The apertural end of the gastropod shell is the anterior end, nearest to the head of the animal; the apex of the spire is often the posterior end or at least is the dorsal side. Most authors figure the shells with the apex of the spire uppermost. In life, when the soft parts of these snail are retracted, in some groups the aperture of the shell is closed by using a horny or calcareous operculum, a door-like structure which is secreted by, and attached to, the upper surface of the posterior part of the foot. The operculum is of very variable form in the different groups of snails that possess one.

Shape of the shell

The distinction of the shape of the shell may vary, based on the purpose. For example distinguishing into three groups can be based on the height - width ratio:[6]

oblong - the height is much bigger than the width

globose or conical shell - the height and the width of the shell are

Parts of the shell

The terminology used to describe the shells of gastropods includes:

Aperture: the opening of the shell Lip = peristome: the margin of the aperture Apex: the smallest few whorls of the shell Body whorl: the largest whorl in which the main part of the visceral mass of the mollusk

is found Columella: the "little column" at the axis of revolution of the shell Operculum: the "trapdoor" of the shell Parietal callus: a ridge on the inner lip of the aperture in certain gastropods Periostracum: a thin layer of organic "skin" which forms the outer layer of the shell of

many species Peristome: the part of the shell that is right around the aperture Plait: folds on the columella. Protoconch: the nuclear whorls; the larval shell, often remains in position even on an

adult shell Sculpture: ornamentation on the outer surface of a shell Siphonal canal: an extension of the aperture in certain gastropods Spire: the part of the shell above the body whorl. Suture: The junction between whorls of most gastropods Teleoconch : the entire shell without the protoconch; the postnuclear whorls. Umbilicus: in shells where the whorls move apart as they grow, on the underside of the

shell there is a deep depression reaching up towards the spire; this is the umbilicus Varix: on some mollusk shells, spaced raised and thickened vertical ribs mark the end

of a period of rapid growth; these are varices Whorl: each one of the complete rotations of the shell spiral

approximatelly the same depressed - the width is much bigger than the height

The following are the principal modifications of form in the gastropod shell.

Regularly spiral:

Bulloid : bubble-shaped Bulla ampula Coeloconoid : a slightly concave shell in which the incremental angle increases steadily during growth Cone-shaped, obconic. Conus Contabulate, short, with shouldered whorls Convolute ; aperture as long as the shell, nearly or quite concealing the spire. Cypraea Cylindrical, pupiform. Lioplax, Pupa Depressed, lenticular. Ethalia carneolata Discoidal. Elachorbis Ear-shaped. Haliotis Elongated, subulate, elevated. Terebra Few-whorled. Helix pomatia. Fusiform, spindle-shaped. Fusinus Gibbous. Whorls swelled beyond the normal contour of increase (usually on the aperture side ). Streptaxis. Globular. Natica Many-whorled. Millerelix peregrina. Short, bucciniform. Buccinum Trochiform, pyramidal, conical with a flat base. Trochus Turbinated ; conical, with rounded base. Turbo Turrited, turriculated, babylonic ; an elongated shell with the whorls angulated or shouldered on their upper part. Turritella

Scalariform, whorls not impinging. Epitonium Irregularly spiral, evolute. Siliquaria, Vermetus Tubular. Dentalium, or tooth-shell. Shield-shaped. Umbraculum Boat-shaped, slipper-shaped. Crepidula

Conical or limpet-shaped. Patella Biconic : two conical shapes touching their bases and tapering at both ends : Fasciolaria tulipa Multivalve and imbricated. Chiton

The snail shell

The extraordinary diversity in forms, colours and patterns of snail shells has led to them being assembled in collections for centuries. The richest snail shell collections today can be seen in natural history museums, but there are also some very large private collections.

While originally all gastropods have a shell, among slugs it is reduced during embryonic development. The loss of the shell's protection, on the other hand, gives the slug the advantage of better mobility, especially for subterraneous and predatory slugs. The reduction of the shell (the so called vitrinisation) can be seen in recent snail species in very different evolutionary degrees.

In glass snails (Vitrinidae) for example a growing degree shell reduction is visible, until the snail is rendered unable to withdraw into its shell. Keel back slugs (Limacidae) externally are slugs, but they have a tiny shell rest under their mantle shield. The European round back slugs (Arionidae) on the other hand only possess some calcareous grains left under their mantle shield remaining of the shell. Interestingly, in Northwest America there are the so called jumping slugs (Hemphillia), the weird hunchback appearance of which comes from a small shell they still have beyond their mantle shield. Those, too, are classified as Arionidae.

Mountain glass snail

CLASSIFICATION OF SNAILS

Fresh water snails

A freshwater snail is one kind of freshwater mollusc, the other kind being freshwater clams and mussels, i.e. freshwater bivalves. Specifically a freshwater snail is a gastropod that lives in a watery non-marine (freshwater) habitat. The majority of freshwater gastropods have a shell, with very few exceptions. Some groups of snails that live in freshwater respire using gills. Others need to surface to breathe air.According to present classification efforts, there are about 4,000 species of freshwater gastropods (3,795-3,972). At least 33–38 independent lineages of gastropods have successfully colonized freshwater environments. It is not possible to quantify the exact number of these lineages yet, because they have yet to be clarified within the Cerithioidea. From six to eight of these independent lineages occur in North America.

Apple snail

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Ampullarioidea Family : Ampullariidae Scientific name : Ampullariidae

Characteristics : Ampullariidae, common name the apple snails, is a family of large freshwater snails, aquatic gastropod mollusks with a gill and

an operculum. This family is in the superfamily Ampullarioidea and is the type family of that superfamily. The Ampullariidae are unusual because

they have both a gill and a lung, the mantle cavity being divided in order to separate the two types of respiratory structures. This adaptation

allows these snails to be amphibious.

Distribution : Genera Asolene, Felipponea, Marisa, and Pomacea are New World genera (native to South America, Central America, the West

Indies and the Southern U.S.A.). The genera Afropomus, Lanistes, and Saulea are found in Africa. The genus Pila is native to both Africa and

Asia.

Mystery Snail

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Viviparoidea Family : Viviparidae Scientific name : Viviparidae

Characteristics : Viviparidae, sometimes known as the river snails or mystery snails, are a family of large operculate freshwater snails, aquatic

gastropod mollusks.This family is classified in the informal group Architaenioglossa.

Distribution : This family occurs nearly worldwide in temperate and tropical regions, with the exception that they are absent from South

America.There are two genera of Viviparidae in Africa: Bellamya and Neothauma.

Red Rimmed Melania

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Cerithioidea Family : Thiaridae Scientific name : Melanoides tuberculata

Characteristics : The red-rimmed melania, scientific name Melanoides tuberculata, is a species of freshwater snail with an operculum, a parthenogenetic, aquatic gastropod mollusk in the family Thiaridae.The common name comes from the presence of reddish spots on the otherwise greenish-brown shell. It is sometimes spelled Melanoides tuberculatus, but this is incorrect because Melanoides Olivier, 1804 is feminine since it was combined with the feminine specific epithet fasciolata in the original desciption.

Distribution : This species is native to subtropical and tropical northern Africa and southern Asia.

In Africa

Algeria, Burundi, The Democratic Republic of the Congo, Egypt, Eritrea, Ethiopia, Kenya, Libya, Malawi, Morocco, Mozambique, Namibia, Niger

South Africa (Eastern Cape Province, Free State, Gauteng, KwaZulu-Natal, Limpopo Province) Senegal, Sudan, Swaziland, Tanzania, Tunisia, Zimbabwe. in Asia

Bangladesh, China, India (including Andaman Islands), Japan, Laos, Malaysia (Peninsular Malaysia), Nepal, Saudi Arabia, Sri Lanka, Vietnam

Thailand Prehistoric localities include Gobero in Niger in 6200–5200 BCE.

Clea helena

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Buccinoidea Family : Buccinidae Scientific name : Clea helena

Characteristics : Clea helena is a species of freshwater snail with an operculum, an aquatic gastropod mollusk in the family Buccinidae, the true whelks, most of which are marine.

Distribution : This species occurs throughout southeast Asia, especially in Indonesia, Malaysia, and Thailand.

Land snails

A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, (those without shells are known as slugs.) It is not always an easy matter to say which species are terrestrial, because some are more or less amphibious between land and freshwater, and others are relatively amphibious between land and saltwater. The majority of land snails are pulmonates, i.e. they have a lung and breathe air. A minority however belong to much more ancient lineages where their anatomy includes a gill and an operculum. Many of these operculate land snails live in habitats or microhabitats that are sometimes (or often) damp or wet, such as for example in moss. Land snails have a strong muscular foot; they use mucus to enable them to crawl over rough surfaces, and in order to keep their soft bodies from drying out. Like other mollusks, land snails have a mantle and they have one or two pairs of tentacles on their head. Their internal anatomy includes a radula and a primitive brain. In terms of reproduction, the majority of land snails are hermaphrodite (have a full set of organs of both genders) and most lay clutches of eggs in the soil. Tiny snails hatch out of the egg with a small shell in place, and the shell grows spirally as the soft parts gradually increase in size. Most land snails have shells that are right-handed in their coiling. A wide range of different vertebrate and invertebrate animals prey on land snails, and they are used as food by humans in various cultures worldwide, and are even raised on farms as food in some areas.

Garden Snail

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Helicoidea Family : Helicidae Scientific name : Helix aspersa

Characteristics : Helix aspersa, known by the common name garden snail, is a species of land snail, a pulmonate gastropod that is one of the best-known of all terrestrial molluscs. The species has been placed in the genus Helix, in all sources between 1774 and 1988 and in most sources until recently.

Distribution : This species is native to the Mediterranean region (including Egypt) and western Europe, from northwest Africa and

Iberia east to Asia Minor, and north to the British Isles.

Giant African land Snail

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Achatinoidea Family : Achatinidae Scientific name : Achatina fulica

Characteristics : The East African land snail, or giant African land snail, scientific name Achatina fulica, is a species of large, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinidae.

Distribution : While the snail is native to East Africa, it has been widely introduced to other parts of the world through the pet trade

and as a food resource.

Giant West African Snail

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Achatinoidea Family : Achatinidae Scientific name : Archachatina marginata

Characteristics : Archachatina marginata, common name the giant West African snail, is a species of air-breathing tropical land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinidae. They can grow up to 20cm long, and live up to 10 years.

Distribution : This species occurs in Western Africa: Cameroon through Zaire.This species has not yet become established in the

USA, but it is considered to represent a potentially serious threat as a pest, an invasive species which could negatively effect

agriculture, natural ecosystems, human health or commerce. Therefore it has been suggested that this species be given top national

quarantine significance in the USA.

Roman Snail

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Helicoidea Family : Helicidae Scientific name : Helix pomatia

Characteristics : Helix pomatia, common names the Burgundy snail, Roman snail, edible snail or escargot, is a species of large, edible, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Helicidae. It is a European species.

Distribution :

Eastern Europe

Latvia Lithuania Estonia Western Belarus Western Ukraine Moldavia Russia Ukraine

Southern Europe

Italy

South-eastern and central Europe

Germany Austria Czech Republic Poland Slovakia Hungary South-western North and central Balkans Slovenia Republic Of Macedonia

Western Europe

Great Britain Central France Belgium Netherlands Switzerland

Northern Europe

Denmark South Sweden Norway Finland

Sea snails

Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs. (The taxonomic class Gastropoda also includes snails that live in other habitats, i.e. land snails and freshwater snails.) Sea snails are marine gastropods that have shells. Those marine gastropods that have no shells, or have only internal shells, are variously known by other common names, including sea slug, sea hare, nudibranch, etc. Many sea snails are edible and are exploited as food sources by humans. Some well-known kinds of edible sea snails are abalone, conch, limpets, whelks (such as the North American Busycon species and the North Atlantic Buccinum undatum) and periwinkles including Littorina littorea. There is enormous diversity within sea snails; many very different clades of gastropods are either dominated by, or consist exclusively of, sea snails. Because of this great variability, it is not possible to generalize about the feeding, reproduction, habitat and so on of sea snails. Instead it is necessary to look at the articles about individual clades, families, genera or species.

Northern Lacuna

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Littorinoidea Family : Littorinidae Scientific name : Lacuna vincta

Characteristics : The banded chink snail is small, not exceeding 10 x 5 mm. The shell has five whorls. The color is usually light brown with two

to four red-brown bands on the last whorl, although it is not unusual that the bands are absent.The life span of the banded chink shell is no more

than a year. It breads from January to early spring. The ring shaped jelly masses of eggs hatch to planktonic larvae.

Habitat : It is usually seen on algae in the intertidal zone, but has been reported as deep as 40 metres. It tolerates a salinity as low as 20%.

Distribution : It is widespread in the northern parts of the Atlantic as well as the Pacific Ocean. It can be found anywhere along the coast of

Norway

Periwinkle

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Littorinoidea Family : Littorinidae Scientific name : Littorina fabalis

Characteristics : The two species of periwinkles, L. fabalis (previously called L. mariae) and L. obtusata are easily confused. They are best

distinguished by the shape of the penis and the size and shape of the shell. However, studies in the Trondheim Fjord indicate that shell shape

varies so much that even specialists find it difficult to make positive identifications from the shell alone. It is reported from Sweden that the L.

fabalis usually has a yellow body while the color of L. obtusata is often black. Other observations indicate that body color tends to follow the color

of the shell, regardless of species. The most common shell colors are black, olive green, brown and yellow, but even red shells have been

reported. The shell of L. fabalis is more flattened than L. obtusata. The length of the L. fabalis rarely exceeds 12 mm.

Habitat : Both L. obtusata and L. fabalis are common in the intertidal zone, especially on rocky shores, along the entire Norwegian coast. L.

fabalis, tends to live lower on the shore, but this is not a strict rule, they do mix in the same locations.

Distribution : It is distributed from the western Mediterranean to northern Norway, including the British Isles.

Flat Periwinkle

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Littorinoidea Family : Littorinidae Scientific name : Littorina obtusata

Characteristics : The two species of periwinkles, L. fabalis (previously called L. mariae) and L. obtusata are easily confused.They are best distinguished by

the shape of the penis and the size and shape of the shell. However, studies in the Trondheim Fjord indicate that shell shape varies so much that even

specialists find it difficult to make positive identifications from the shell alone. It is reported from Sweden that the L. fabalis usually has a yellow body while the

color of L. obtusata is often black. Other observations indicate that body color tends to follow the color of the shell, regardless of species. The most common

shell colors are black, olive green, brown and yellow, but even red shells have been reported. The shell of L. fabalis is more flattened than L. obtusata. The

length of the L. obtusata may reach 15 mm, this is slightly larger than L. fabalis.

Habitat : Both L. obtusata and L. fabalis are common in the intertidal zone, especially on rocky shores, along the entire Norwegian coast. L. fabalis, tends to

live lower on the shore, but this is not a strict rule, they do mix in the same locations.

Distribution : It is distributed from the western Mediterranean to northern Norway, including the British Isles.

Montagu's Necklace Shell

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Naticoidea Family : Naticidae

Scientific name : Euspira montagui

Characteristics : The diameter of the shell may reach 8 mm. It has six or seven whorls, where last is dominating the total diameter. The spire is flattened.

The color is brown, beige or pale yellow. In contrast to the similar E. pulchella it has no dark band. The most characteristic feature is the large foot, clearly

visible outside the shell.

Habitat : It prefers sandy or muddy substrate and is most frequent on depths between 15 and 200 metres. It can sometimes be seen drilling holes through

the shell of mussels.

Distribution : It is registered in the North-East Atlantic Ocean, from Troms, Norway to the Mediterranean.

Pelican's Foot

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Stromboidea Family : Aporrhaidae Scientific name : Aporrhais pespelecani

Characteristics: The Pelican's foot can only be confused with the less common A. serresianus. The shell opening (aperture) is dominated by an extended

lip, shaped like the webbed foot of a bird. The lip of A. serresianus extends past the tip of the spire (apex), while the lip of A. pespelecani only reachhalf way.

The shell is sand colored on the outside and pearly white on the inside. It can reach a length of 4.5 cm. The body is white with yellow blotches.

Habitat: The Pelican foot lives on mud or muddy sand from the subtidal zone and down to 180 metres.

Distribution: It is registered from the Mediterranean to Norway and Iceland.

Northern Cowrie

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Velutinoidea Family : Triviidae Scientific name : Trivia arctica

Characteristics : The crosswise ridges and the bean-shaped shell are typical features of the cowries. The northern cowrie is a small, the length

rarely exceeds 1 cm. The shell opening (aperture) is long and narrow. The shell itself is reddish brown, beige or almost white. The mantle

wrapped around the shell may have brown blotches. The shell itself does not have any spots, unlike the spotted cowrie.

Habitat : It is often found on rocky locations, from subtidal to 1000 metres depth.

Distribution : It is registered in the North-East Atlantic Ocean, from Norway to the Mediterranean, most frequent in the northern regions.

Sea Snail

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Velutinoidea Family : Velutinidae Scientific name : Velutina plicatilis

Characteristics : This vivid orange, yellow or white snail can reach a body length of 20 mm, from head to tail. The fragile, semitransparent shell

is oval shaped with an oval opening. It is partly covered by a thin skin, periostracum.

Habitat : It is registered on depths from 10 to 375 metres, usually on rocky locations. It is often seen feeding of sea squirts.

Distribution : It is registered in the Arctic and North-East Atlantic Ocean, as far south as northern parts of the North Sea, including Scotland and

the west coast of Sweden.

Smooth Velutina

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Velutinoidea Family : Velutinidae Scientific name : Velutina velutina

Characteristics : The cap-shaped profile is not as pointed as the similar Capulus ungaricus. The shell has hardly more than one whorl. The

oval-shaped aperture covers approximately 90 percent of the shell length.

Habitat : The smooth velutina is often found under rocks on sandy or rocky substrate. It is often seen on sea squirts laying its eggs in them so

they can suck nutrition from the body fluid of its host. It has a wide depth range from the subtidal zone to 1000 metres.

Distribution : It is widespread in the North-East Atlantic Ocean as far south as the Mediterranean, as well as in the northern Pacific Ocean.

Common Whelk

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Buccinoidea Family : Buccinidae Scientific name : Buccinum undatum

Characteristics : Adults can exceed 10 cm from the opening to the cone top. Fine growth lines developed run crosswise the spirals, producing a

pattern of squares. The shell has 7 or 8 whorls, where the last whorl covers more than half the length. The aperture (shell opening) is oval.

Habitat : The common whelk can be found on both soft and hard substrate, on any depth from the subtidal zone and down to 1200 metres.

Distribution : It can be found, and is often abundant, from Iceland and northern Norway to the Bay of Biscay.

Dogwhelk

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Muricoidea Family : Muricidae Scientific name : Nucella lapillus

Characteristics : The shell is oval and conical, the last whorl constitutes 80 % of the total shell length. Spiral ridges, often crossed by fine growth

lines, produce a checked surface. The shell may reach a length of 42 mm. White is common, but it may come in a variety of colors, both

monochrome and striped versions.

Habitat : It is common in the tidal zone, preferably on rocky locations. The dogwhelk is less frequent down to 40 metres depth.

Distribution : It is widespread in the North-East Atlantic Ocean from the Arctic to the Straits of Gibraltar.

Tower Shell

Kingdom : Animalia Phylum : Mollusca Class : Gastropoda Superfamily : Cerithioidea Family : Turritellidae Scientific name : Turritella communis

Characteristics : The tower shell is easily recognized long and slender conical shape and the 16-20 windings. Three distinct ridges can be seen on each winding. The shell can reach a length of 6 cm. The color is grey or brown.

Habitat : Can be found on any depth, from the subtidal zone and down to 220 metres. It thrives on soft substrate.

Distribution : It is widespread along the east coasts of the Atlantic Ocean, from North Africa and the Mediterranean to Lofoten, Norway.

Snail Feeding

Snail moving through bush leaves

Snails tend to feed on a variety of items found in their natural habitat. What they will actually consume depends on where they live and the type of snail that they are. Some common items for their diet include plants, fruits, vegetables, and algae. Plants that are decaying are often a good meal for them. When they can’t find much else to consume they will eat the dirt.They are herbivores which mean they won’t consume meat items. You will likely find snails around your garden as this offers them plenty of fresh fruits and vegetables to eat. If you use herbicides or pesticides on them you may be causing the death of many of them without even realizing it.Snails have to feed on foods that consume large amounts of calcium. This is necessary to keep their shell hard and protective like it should be. When looking for food they use their powerful sense of smell to find their prey. Snails have very poor vision so they can’t see what may be very close to them.

Snails are nocturnal so they will be looking for sources of food during the night or during the very early morning hours. They will consume more food at the colder months ahead come. This is so they can store up fat reserves to live on while they hibernate during the winter.When food sources are very low in the summer or spring months, they may voluntarily put their body into a state of hibernation as well. This allows them to conserve energy and not need to forage for additional food. This is a mechanism that allows them to be able to survive in difficult conditions of drought. They have a tongue that is very rough and the technical term for it is radula. They have rows of very small teeth that they use to scrap against the foods they want to consume. When you have snails as pets you want to pay close attention to their diet. If you feed them anything containing salt or sugar they will die. They are often said to be very noisy eaters. However, the sounds you hear aren’t them consuming the food. Instead it is a part of the body called the radula which is tearing on what has been swallowed so it can find its way to the digestive tract.

Snail eating leaves

Snail Food List

Spinach Peeled Seedless Grapes Cucumbers Squash Romaine Lettuce and other soft lettuces Celery Green beans Zucchini spears Frozen/freeze-dried bloodworms Sinking fish foods Frozen snow pea pods Canned iguana food Turtle, reptile, goldfish, shrimp, or betta pellets Algae Wafers, Spirulina Sinking Pellets, or Bottom Feeders' Sinking Wafers Baby Carrots Snail biscuits Dandelions Pear Apple Kiwi Watermelon Aquarium plants Parsley Banana Collard greens Brocolli Cauliflower Baby shrimp Flake food Tomatoes

Diseases

Schistosomiasis

Schistosomiasis (also known as bilharzia, bilharziosis or snail fever) is a parasitic disease caused by several species of trematodes (platyhelminth infection, or "flukes"), a parasitic worm of the genus Schistosoma.

Although it has a low mortality rate, schistosomiasis often is a chronic illness that can damage internal organs and, in children, impair growth and cognitive development. The urinary form of schistosomiasis is associated with increased risks for bladder cancer in adults. Schistosomiasis is the second most socioeconomically devastating parasitic disease after malaria.

This disease is most commonly found in Asia, Africa, and South America, especially in areas where the water contains numerous freshwater snails, which may carry the parasite.

The disease affects many people in developing countries, particularly children who may acquire the disease by swimming or playing in infected water.

Classification

Species of Schistosoma that can infect humans:

Schistosoma mansoni (ICD-10 B65.1) and Schistosoma intercalatum (B65.8) cause intestinal schistosomiasis Schistosoma haematobium (B65.0) causes urinary schistosomiasis Schistosoma japonicum (B65.2) and Schistosoma mekongi (B65.8) cause Asian intestinal schistosomiasis

Avian schistosomiasis species cause swimmer's itch and clam digger itch

Species of Schistosoma that can infect other animals:

S. bovis normally infects cattle, sheep and goats in Africa, parts of Southern Europe and the Middle East S. mattheei :normally infects cattle, sheep and goats in Central and Southern Africa S. margrebowiei : normally infects antelope, buffalo and waterbuck in Southern and Central Africa S. curassoni :normally infects domestic ruminants in West Africa S. Rodhaini: normally infects rodents and carnivores in parts of Central Africa

Signs and symptoms

Above all, schistosomiasis is a chronic disease. Many infections are subclinically symptomatic, with mild anemia and malnutrition being common in endemic areas. Acute schistosomiasis (Katayama's fever) may occur weeks after the initial infection, especially by S. mansoni and S. japonicum. Manifestations include:

Abdominal pain Cough Diarrhea Eosinophilia :extremely high eosinophil granulocyte (white blood cell) count. Fever Fatigue Hepatosplenomegaly :the enlargement of both the liver and the spleen. Genital sores: lesions that increase vulnerability to HIV infection. Lesions caused by schistosomiasis may continue to be a problem after

control of the schistosomiasis infection itself. Early treatment, especially of children, which is relatively inexpensive, prevents formation of the sores.

Skin symptoms: At the start of infection, mild itching and a papular dermatitis of the feet and other parts after swimming in polluted streams containing cercariae.

Occasionally central nervous system lesions occur :cerebral granulomatous disease may be caused by ectopic S. japonicum eggs in the brain, and granulomatous lesions around ectopic eggs in the spinal cord from S. mansoni and S. haematobium infections may result in a transverse myelitis with flaccid paraplegia.

Continuing infection may cause granulomatous reactions and fibrosis in the affected organs, which may result in manifestations that include:

Colonic polyposis with bloody diarrhea (Schistosoma mansoni mostly); Portal hypertension with hematemesis and splenomegaly (S. mansoni, S. japonicum); Cystitis and ureteritis (S. haematobium) with hematuria, which can progress to bladder cancer; Pulmonary hypertension (S. mansoni, S. japonicum, more rarely S. haematobium); Glomerulonephritis; and central nervous system lesions.

Bladder cancer diagnosis and mortality are generally elevated in affected areas.

Pathophysiology

Life cycle

Schistosoma life cycle. Source: CDC

Schistosomes have a typical trematode vertebrate-invertebrate lifecycle, with humans being the definitive host.

Snails

The life cycles of all five human schistosomes are broadly similar: parasite eggs are released into the environment from infected individuals, hatching on contact with fresh water to release the free-swimming miracidium. Miracidia infect fresh-water snails by penetrating the snail's foot. After infection, close to the site of penetration, the miracidium transforms into a primary (mother) sporocyst. Germ cells within the primary sporocyst will then begin dividing to produce secondary (daughter) sporocysts, which migrate to the snail's hepatopancreas. Once at the hepatopancreas, germ cells within the secondary sporocyst begin to divide again, this time producing thousands of new parasites, known as cercariae, which are the larvae capable of infecting mammals.

Cercariae emerge daily from the snail host in a circadian rhythm, dependent on ambient temperature and light. Young cercariae are highly mobile, alternating between vigorous upward movement and sinking to maintain their position in the water. Cercarial activity is particularly stimulated by water turbulence, by shadows and by chemicals found on human skin.

Humans

Penetration of the human skin occurs after the cercaria have attached to and explored the skin. The parasite secretes enzymes that break down the skin's protein to enable penetration of the cercarial head through the skin. As the cercaria penetrates the skin it transforms into a migrating schistosomulum stage. The newly transformed schistosomulum may remain in the skin for 2 days before locating a post-capillary venule; from here the schistosomulum travels to the lungs where it undergoes further developmental changes necessary for subsequent migration to the liver. Eight to ten days after penetration of the skin, the parasite migrates to the liver sinusoids. S. japonicum migrates more quickly than S. mansoni, and usually reaches the liver within 8 days of penetration. Juvenile S. mansoni and S. japonicum worms develop an oral sucker after arriving at the liver, and it is during this period that the parasite begins to feed on red blood cells. The nearly-mature worms pair, with the longer female worm residing in the gynaecophoric channel of the shorter male. Adult worms are about 10 mm long. Worm pairs of S. mansoni and S. japonicum relocate to the mesenteric or rectal veins. S. haematobium schistosomula ultimately migrate from the liver to the perivesical venous plexus of the bladder, ureters, and kidneys through the hemorrhoidal plexus.

Photomicrography of bladder in S. hematobium infection, showing clusters of the parasite eggs with intense eosinophilia,

Source: CDC

Parasites reach maturity in six to eight weeks, at which time they begin to produce eggs. Adult S. mansoni pairs residing in the mesenteric vessels may produce up to 300 eggs per day during their reproductive lives. S. japonicum may produce up to 3000 eggs per day. Many of the eggs pass through the walls of the blood vessels, and through the intestinal wall, to be passed out of the body in feces. S. haematobium eggs pass through the ureteral or bladder wall and into the urine. Only mature eggs are capable of crossing into the digestive tract, possibly through the release of proteolytic enzymes, but also as a function of host immune response, which fosters local tissue ulceration. Up to half the eggs released by the worm pairs become trapped in the mesenteric veins, or will be washed back into the liver, where they will become lodged. Worm pairs can live in the body for an average of four and a half years, but may persist up to 20 years.

Trapped eggs mature normally, secreting antigens that elicit a vigorous immune response. The eggs themselves do not damage the body. Rather it is the cellular infiltration resultant from the immune response that causes the pathology classically associated with schistosomiasis.

Diagnosis

High powered detailed micrograph of Schistosoma parasite eggs in

human bladder tissue

S. japonicum eggs in hepatic portal tract

Microscopic identification of eggs in stool or urine is the most practical method for diagnosis. The stool exam is the more common of the two. For the measurement of eggs in the feces of presenting patients the scientific unit used is eggs per gram (epg). Stool examination should be performed when infection with S. mansoni or S. japonicum is suspected, and urine examination should be performed if S. haematobium is suspected.

Eggs can be present in the stool in infections with all Schistosoma species. The examination can be performed on a simple smear (1 to 2 mg of fecal material). Since eggs may be passed intermittently or in small amounts, their detection will be enhanced by repeated examinations and/or

concentration procedures (such as the formalin-ethyl acetate technique). In addition, for field surveys and investigational purposes, the egg output can be quantified by using the Kato-Katz technique (20 to 50 mg of fecal material) or the Ritchie technique.

Eggs can be found in the urine in infections with S. japonicum and with S. intercalatum (recommended time for collection: between noon and 3 PM). Detection will be enhanced by centrifugation and examination of the sediment. Quantification is possible by using filtration through a nucleopore membrane of a standard volume of urine followed by egg counts on the membrane. Investigation of S. haematobium should also include a pelvic x-ray as bladder wall calcificaition is highly characteristic of chronic infection.

Recently a field evaluation of a novel handheld microscope was undertaken in Uganda for the diagnosis of intestinal schistosomiasis by a team led by Dr. Russell Stothard from the Natural History Museum of London, working with the Schistosomiasis Control Initiative, London.

Tissue biopsy (rectal biopsy for all species and biopsy of the bladder for S. haematobium) may demonstrate eggs when stool or urine examinations are negative.

The eggs of S. haematobium are ellipsoidal with a terminal spine, S. mansoni eggs are also ellipsoidal but with a lateral spine, S. japonicum eggs are spheroidal with a small knob.

Antibody detection can be useful in both clinical management and for epidemiologic surveys.

Prevention

Eliminating or avoiding the snails

Prevention is best accomplished by eliminating the water-dwelling snails that are the natural reservoir of the disease. Acrolein, copper sulfate, and niclosamide can be used for this purpose. Recent studies have suggested that snail populations can be controlled by the introduction of, or augmentation of existing, crayfish populations,as with all ecological interventions, however, this technique must be approached with caution.

In 1989, Aklilu Lemma and Legesse Wolde-Yohannes received the Right Livelihood Award for their research on the sarcoca plant, as a preventative measure for the disease by controlling the snail. Concurrently, Dr Chidzere of Zimbabwe researched the similar gopo berry during the 1980s and found that it could be used in the control of infected freshwater snails. In 1989 he drew attention to his concerns that big chemical companies denigrated the gopo berry alternative for snail control. Gopo berries from hotter Ethiopia climates reputedly yield the best results. Later studies were conducted between 1993 and 1995 by the Danish Research Network for international health. For many years from the 1950s

onwards, civil engineers built vast dam and irrigation schemes, oblivious to the fact that they would cause a massive rise in water-borne infections from schistosomiasis. The detailed specifications laid out in various UN documents since the 1950s could have minimized this problem. Irrigation schemes can be designed to make it hard for the snails to colonize the water, and to reduce the contact with the local population. This has been cited as a classic case of the relevance paradox because guidelines on how to design these schemes to minimise the spread of the disease had been published years before, but the designers were unaware of them.

Treatment

Schistosomiasis is readily treated using a single oral dose of the drug praziquantel annually. As with other major parasitic diseases, there is ongoing and extensive research into developing a schistosomiasis vaccine that will prevent the parasite from completing its life cycle in humans. In 2009, Eurogentec Biologics developed a vaccine against bilharziosis in partnership with INSERM and researchers from the Pasteur Institute.

The World Health Organization has developed guidelines for community treatment of schistosomiasis based on the impact the disease has on children in endemic villages:

When a village reports more than 50 percent of children have blood in their urine, everyone in the village receives treatment. When 20 to 50 percent of children have bloody urine, only school-age children are treated. When less than 20 percent of children have symptoms, mass treatment is not implemented.

The Bill & Melinda Gates Foundation has recently funded an operational research program:the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) to answer strategic questions about how to move forward with schistosomiasis control and elimination. The focus of SCORE is on development of tools and evaluation of strategies for use in mass drug administration campaigns.

Antimony has been used in the past to treat the disease. In low doses, this toxic metalloid bonds to sulfur atoms in enzymes used by the parasite and kills it without harming the host. This treatment is not referred to in present-day peer-review scholarship; praziquantel is universally used. Outside of the U.S., there is a drug available exclusively for treating Schistosoma mansoni (oxamniquine) and one exclusively for treating S.hematobium (metrifonate). While metrifonate has been discontinued for use by the British National Health Service, a Cochrane review found it equally effective in treating urinary schistosomiasis as the leading drug, praziquantel.

Mirazid, an Egyptian drug made from myrrh, was under investigation for oral treatment of the disease up until 2005. The efficacy of praziquantel was proven to be about 8 times than that of Mirazid and therefore Mirazid was not recommended as a suitable agent to control schistosomiasis.

Epidemiology

The disease is found in tropical countries in Africa, the Caribbean, eastern South America, Southeast Asia and in the Middle East. Schistosoma mansoni is found in parts of South America and the Caribbean, Africa, and the Middle East; S. haematobium in Africa and the Middle East; and S. japonicum in the Far East. S. mekongi and S. intercalatum are found locally in Southeast Asia and central West Africa, respectively.

Among human parasitic diseases, schistosomiasis (sometimes called bilharziasis) ranks second behind malaria in terms of socio-economic and public health importance in tropical and subtropical areas. The disease is endemic in 74-76 developing countries, infecting more than 200 million people, half of whom live in Africa. They live in rural agricultural and peri-urban areas, and placing more than 600 million people at risk. Of the infected patients, 20 million suffer severe consequences from the disease. Some estimate that there are approximately 20,000 deaths related to schistosomiasis yearly. In many areas, schistosomiasis infects a large proportion of children under 14 years of age. An estimated 600 million people worldwide are at risk from the disease.A few countries have eradicated the disease, and many more are working toward it. The World Health Organization is promoting these efforts. In some cases, urbanization, pollution, and/or consequent destruction of snail habitat has reduced exposure, with a subsequent decrease in new infections. The most common way of getting schistosomiasis in developing countries is by wading or swimming in lakes, ponds and other bodies of water that are infested with the snails (usually of the genera Biomphalaria, Bulinus, or Oncomelania) that are the natural reservoirs of the Schistosoma pathogen.

Disability-adjusted life year for schistosomiasis per 100,000 inhabitants. no data less than 50 50-75 75-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 450-500 more than 500

Defense Technique of Snails

One of the basic defence mechanisms of apple snails is to avoid detection by possible predators. This technique consists of camouflage: the

shell colour (green to brown) resembles the vegetation and the banding pattern breaks the shell in smaller parts, less visible between branches

and stems of vegetation. The yellow variety of apple snails available in the aquarium trade is much less common in the wild as snail-eating

animals easily spot these snails. Protection against small predators like insects (for example water bugs) and small fish consists of retracting the

body into the shell and closing the shell with the operculum (shell door). Apple snails also adopt their behaviour to cope with predators that eat

their tentacles, as many fish tend to do by keeping their head and tentacles under their shell. They also wiggle their shell from side to side to

remove insects and other possibly dangerous animals from their shell. Apple snails, however, do not very often use this wiggling method, it is

common in pond snails.

The defence techniques described above are effective against a great number of predators. Once spotted by a larger predator these techniques

are ineffective though and the snails (from the genus Pomacea) rely on their main defence behaviour: drop-off and burial. In other words: once

the apple snail is alarmed, they loosen their grip and drop to the bottom, where they bury on the spot or crawl until they contact a object like a

stone or some twigs and bury close to this. Burial against an object may be advantageous as it makes the snail more difficult to grasp. The burial

itself achieved by alternating extension of the foot with pulling the shell down into the substrate and within 5 to 10 minutes the snail can bury

themselves completely. The stimuli at which apple snails exhibit this drop-off and burial alarm response is triggered mechanical and/or chemical.

Mechanical disturbance involves sudden water flow and vibrations. The sensitivity for apple snails to respond to this stimuli varies amongst the

species. Pomacea paludosa is for example far less sensitive than Pomacea glauca. Also the age and size of the apple snail determines its

reaction to a mechanical disturbance: young and little snails are less reactive compared with their older counterparts. Once little snails are

triggered, they often react with drop-off without burial after it. Chemical stimuli that invoke an alarm response (drop-off and burial) consist of the

juice of crushed apple snails of the same (intraspecific) or a close related (interspecific) species and the odour of predators like turtles. The alarm

response to snail juice is a remarkable feature in apple snails that enables them to detect actively foraging predators in close distance and react

to it by a drop-off and burial before being detected. Of course this detection mechanism only works when the predator crushes its victims and it is

not effective when the predator swallows them whole or takes them out the water like some birds do. The opposite occurs as well: the juice of

another snail invokes feeding behaviour, mainly in younger snails. In such case the snails are rather attracted instead of alarmed. The

mechanical disturbances of predator activity, however, still invokes an alarm response.

The alarm response to odours of predators is a fascinating adaptation against predation shown in apple snails. It appears to be specific to certain

predators that inhabit the same area as the apple snail and is identical in form shown to (intraspecific) snail juice: drop-off and burial. The

sensitivity to the odour of certain predators appears to be well developed before the snails hatch from the eggs and is possibly further enhances

due conditioning at a later stage. In the never-ending battle between predator and prey, apple snails have fine-tuned their response to specific

odours. For example Pomacea paludosa snails only react to the odour of the musk turtle (sternotherus minor) when they are young and once the

snails have grown to a weight of 3 grams, they don't show a alarm response to this turtle. At this weight they are too big to be eaten by the musk

turtle. This weight related reactivity to certain odours is not shown with the odour of the snapping turtle (Chelydra serpentina), which is able to eat

a larger snails as well. This observation supports the highly specific development of defence mechanisms against predators. Predators like fish

and frogs do not cause a drop-off and burial response by odour, possibly because they simply do not produce enough odours. Another example

of refined alarm response is illustrated by light depend alarm response to odours (burial at day, no alarm response at night). Many predators

depend on their vision to locate apple snails, so only during daylight a reaction is necessairly. No evidence has been reported for a snail-snail

alarm response in which apple snails alarm each other by releasing alarm messages. This would be ineffective, as such release of alarm

messages would cause a whole cascade of alarm messages throughout the environment, alarming all snails, even those far away from the

predator.

Cuisine

Edible land snails range in size from about one millimeter long to the giant African snails, which occasionally grow up to 312mm (1 foot) in length.

In French, snails are called escargot, limaçon or limace. Whereas "escargot" usually means a snail, especially an edible one, limaçon means an inedible snail and limace a slug.

Different snail species are traded as escargots. Basically many of them belong among the family of Helicid snails (Helicidae) and among those especially to the Roman snail's relatives (Helix and related genera). On the other hand also the Achatinidae family of giant African land snails is important as edible snails. In Europe and North America, the main part of edible snails consists of Helicid snails. Achatinid snails, in contrary, are mainly consumed on the African continent. Piecemeal or in conserves, they may also be found in the European and American cultural area.

Among edible Helicid snails, there are, on the other hand, also species like the noodle snail (Eobania vermiculata), which, in contrary to Roman snails, are not cultivated in snail farms, but collected from nature.

This snail's scientific name also has got an interesting culinary history: It goes back to the Danish malacologist Otto Friedrich Müller who first described the species and thus earned the right to name it. The species' shell pattern reminded him of Italian Vermicelli noodles, which is why he named the species vermiculata – noodle snail. That is the reason why, until today, the complete scientific name of this species is Eobania vermiculata

Although mainly considered a French dish, escargot (snails) have been eaten for many thousands of years. Large quantities of empty shells have been found in the caves of prehistoric man, indicating that in various parts of the world they were a common part of the diet at that time. With the rise of civilization, various cultures (including the Greeks and Romans) have continued to eat snails, often considering them a delicacy.

Today there are over 100 different types of edible snails (with 116 different types being the most quoted number). In France, only two types are commonly eaten: the 'Petit-Gris' (which is French for 'Little-Gray', and is scientifically known as Helix Asperse) and the 'Escargot de Bourgogne' (which is French for 'Burgundy Snail ', and is scientifically known as Helix Pomatia). It is possible to collect snails from the wild and eat them; provided you know which ones are edible and where to find them. In France there is a hunting season for edible snails, and they can only be

collected during this time. Although restricting snail collection to this hunting period is intended to protect the wild snail population, here and elsewhere in the world the population has been reduced through over-collecting.

If collecting snails from the wild, considerations include:

Some snails are protected (due to population decline) and cannot be legally taken. Others may have a hunting season, which is the only time they can be collected.

Not all snails are edible. Some have an unpleasant taste, while other are poisonous. If collecting wild snails, take local advice to avoid a disappointing meal (or worse).

The taste of wild snails is affected by what they eat. If they happen to have eaten poisonous plants, they will also become poisonous until the poison has been purged from them (see the above section on Preparation).

The increasing scarcity of wild snails (and associated costs of collection) has promoted the creation and growth of snail farms, which now grow a proportion of the snails for public consumption. Breeding of edible snails has focused almost entirely on the 'Petit-Gris' rather than the 'Escargot de Bourgogne’. For more information (and pictures on snail breeding) click on Escargot Breeding. The technical term for farming snails is heliciculture.

Early man all over the world consumed what they could for survival, and that often included the snail. In parts of the world including Rome snails were eaten on a very large scale. In fact, they were harvested so that there would be a huge supply of them all the time to meet the demand.That desire to consume then hasn’t stopped there. They continue to be a huge industry for the restaurant business. Offering snails is a common offering for wedding receptions and other elaborate affairs. If you haven’t tried them the idea may not be very appealing to you. However, you may find that your taste buds are really impressed by them.

It is no secret that many people find snails to be delicious as an appetizer or as a main course. There are plenty of well known recipes out there for making them and many people do so at home. Such dishes are common in many types of restaurants as well. For thousands of years this practice has been going on all over the world. You will find that these types of recipes for the dishes vary by country too. Without a doubt though the snail is widely distributed which means it is also widely consumed.

For example in France they are often cooked in oil with garlic added for seasoning. They are very expensive in France though due to the fact that they consume them in such large volumes and the demand is often greater than what they can get their hands on. In Greece and Italy they are often consumed in sauces and poured over various types of pasta. The largest number of recipes are found in the United States where people create a variety of dishes. Many of them are spin offs from what is cooked in these other countries as well.

Snail meat is high in protein (37-51%) compared to that of guinea pig (20.3%), Poultry (18.3%), Fish (18%), Cattle (17.5%), Sheep (16.4%) and Swine (14.5%). Iron content (45-59mg/kg), low in fat (0.05-0.08%) and contains almost all the amino acids needed for human nutrition. In addition to the nutritional value of snail meat, recent studies indicated that the glandular substances from edible snails cause agglutination of certain bacteria, which could be of value against a variety of ailments including whooping cough. In folk medicine, the bluish liquid obtained when the meat has been removed from the shell is believed to be good for infant's development. It is believed in some quarters that snail meat contains pharmacological properties of value in counteracting high blood pressure.

Snail meat was thought to contain aphrodisiac properties and was often served to visiting dignitaries in the late evening. The high Iron content of

snail meat is considered important in the treatment of anaemia and in the past the meat was recommended as a means of combating ulcers and

asthma.

As a note of caution it is important to mention that you need to properly cook snails before you consume them. The failure to do so can result in parasites entering the body which have been linked to the development of meningitis. The failure to cook them properly can result in people becoming very ill with a type of food poisoning as well. When you buy snails to cook you need to keep them very cook so that bacteria won’t grow on them.

Predators

All creatures need a source of energy to stay alive. Plants get their energy from the sun and animals get energy from eating plants or other

animals.

A food chain shows what eats what in a habitat. This is a simple food chain for a garden.

A simple food chain in a garden

There may be lots of food chains in a habitat, because lots of animals eat grass, other animals eat snails and birds get eaten too.

A food web shows how all the living things in a habitat can be connected.

Here are a few more living things that you might find in a garden, connected together as a food web.

Predators and the techniques used by apple snails to avoid them

As apple snail are a popular food source for various animals like birds, turtles, fishes, insects and crocodiles, it is not surprising that they have

developed several techniques to avoid predation. The most important enemy of the apple snail is man. They are collected to be used as a food

source and by collectors for their interesting shell. Amongst the naterual enemies are the snail kite and Limpkins. These birds are found in range

from Florida through the Antilles and South America. Besides birds other animals feed on apple snails. The caiman lizard even feeds exclusively

on these snails and has specialised teeth to crush the shell. Other animals like fishes, insects and mammals occasionally predate on apple

snails. In area's where small rodents like rats feed on apple snails, the danger of infection with the rat lungworm (Angiostrongylus cantonensis)

exists.

This nematode parasite needs both the apple snail and rodents to complete it's life cycle. The snail serves as intermediate host, while rodent is

the main host. Ingestion of raw, infected snails can cause serious illness in man. To give an idea of which animals are enemies for the apple

snails, a number of know predators is listed below.

List of Apple snail predators

Fishes

Lepomis macrochirus (sunfish)

Botia sp. (clown loaches)

Tetraodon sp. (puffers)

Bunocephalus sp. and

Leiocassis sp. (catfish)

various cichlids

(Pseudotropheus sp.,

Melanochromis sp.,

Cichlasoma sp., Aequidens sp.

and others)

various Gourami's

(Osphronemus sp.,

Trichogaster sp. and others)

some Betta splendens (Betta

Fish)

Mylopharyngodon piceus

(Chinese carp)

Reptiles

Dracaena guianensis (Caiman

lizard)

Snakes

Natrix sp.

other snakes

Insects

Sciomyzidae sp.

Odonata sp.

Belostomidae sp. (water bugs)

Dysticidae sp. (dragonflies)

Lampyridae sp. (fire flies)

Hydrophilidae sp.

Solenopsis geminata

Crocodilians

Alligator sp.

Crocodylus sp.

Paleosuchus sp.

Caiman sp.

Turtles

Sternotherus sp.

Kinosternon sp.

Pseudemys sp.

Trionyx sp.

Podocnemis sp.

Malaclemys sp.

Gopherus sp.

Crayfishes

Procambarus sp.

other crustacea

Mammals

Oryzomys palustris (rice rat)

Neofiber alleni (water rat)

Birds

Rostrhamus sociabilis

(everglade kite)

Aramus guarauna (limpkins)

Lassidic mexicanus (boat-tailed

grackles)

Anastomus lamelligenus

(open-bill stork)

Snails in Popular Culture

Snails don’t seem to have a good stigma to them in many cultures due to the fact that they are slow. Most people associate that nature with being lazy and not good for much. The fact that the snail isn’t a lovely animal either means that it gets overlooked when it comes to art and other types of cultural remnants.

Snails are more intelligent though than many people realize. There are stories that depict them as being very strong and self reliant. Those are traits that most people would love to have. The moral of such stories is to explain even though the snail is slow it has a purpose just like every other creature out there. Yet the fact that they aren’t mystical or beautiful has lead to more stories and cultures viewing them as something bad or evil.

In fact, with many early cultures the movements of the snail were viewed as being unclean and they often even marked people with it as a sign of punishment. Yet you will find some great early writings about the snails. For example the Greeks believed that when the snails could be seen climbing the stalks it was time for the harvest to begin. This was a signal to them that it was time to reap the rewards of the foods the gods had allowed them to grow and to live from.

The Aztec believed that the snail was the moon god and that the shell was his protection. They also felt that the appearing of the snail at times and then not at others had to do with the meaning of the rebirth of the moon. Of course we now know that this has to do with them being nocturnal and searching for food at night instead of during the daylight hours.

Most of us are familiar with the works of psychologist Carl Jung. He often talked about interpreting thoughts and dreams. The analogy he refers to with snails is that the shell is the conscious thought process and then the soft part of a snail is the unconscious thought process. Not everyone buys this theory though but the analogy is one that many professors continue to use in their educational lessons today.

There are quite a few references in our language today that refer to snails, but they aren’t in good light. They are meant to mean a very slow process. For example saying someone moves as the pace of a snail or that they are as slow as a snail. The other is called snail mail which refers to mailing something through the post office. We get used to e-mail which allows us instant access so we then become impatient with what takes longer to receive.Sometimes you will notice snails in books or movies with characteristics that are quite charming. The Disney productions are great at doing this and the charm they put into them helps people to enjoy these animals more. However, they still don’t seem to get the attention or the accreditation in society as so many others.

Description

The East African land snail, or giant African land snail, scientific name Achatina fulica, is a species of large, air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinidae.

This mollusc is now listed as one of the top 100 invasive species in the world. In recent times, the land snails have been kept as pets; however, they are illegal to possess in some countries including the United States.

Kingdom : Animalia

Phylum : Mollusca

Class : Gastropoda

Family : Achatinidae

Scientific name : Achatina fulica

Size, color and life span

The adult snails have a height of around 7 centimetres (2.8 in), and their length can reach 20 centimetres (7.9 in) or more. The shell has a conical shape, being about twice as high as it is broad. Either clockwise (sinistral) or counter-clockwise (dextral) directions can be observed in the coiling of the shell, although the right-handed (dextral) cone is the more common. Shell colouration is highly variable, and dependent on diet. Typically, brown is the predominant colour and the shell is banded.

Full grown Achatina fulica reach up to 20 cm in length and 12 cm in maximum diameter. The dark and light brown (sometimes more of a cream color) swirls wrap around its cone like shell. Its convex body allows for about 7 to 9 whorls. The outlines of the whorls fluctuate from narrow to broad even within the same colony. An adult Achatina Fulica’s lip opening is generally very thin and sharp. The shell itself is thick and strong if healthy (needs a high calcium diet). The rest of the body resembles a slug like appearance with a variance in color.

The snail is brown red and yellow in color and it has a very hard outer shell.It weighs about 250 to 450grams and has a life span of 3 to 10 years.

Habitat

The East African land snail is native to East Africa, especially Kenya and Tanzania. Its habitat includes most regions of the humid tropics, including many Pacific islands, southern and eastern Asia, and the Caribbean. It is a highly invasive species, and colonies can be formed from a single gravid individual. The species has established itself in temperate climates also, and in many places release into the wild is illegal. The giant snail can now be found in agricultural areas, coastland, natural forest, planted forests, riparian zones, scrub/shrublands, urban areas, and wetlands.

Life cycle

The Giant East African Snail is a simultaneous hermaphrodite; each individual has both testes and ovaries and is capable of producing both sperm and ova. Instances of self fertilisation are rare, occurring only in small populations. Although both snails in a mating pair can simultaneously transfer gametes to each other (bilateral mating), this is dependent on the size difference between the partners. Snails of similar size will reproduce in this way. Two snails of differing sizes will mate unilaterally (one way), with the larger individual acting as a female. This is due to the comparative resource investment associated with the different genders.

Like other land snails, these have intriguing mating behaviour, including petting their heads and front parts against each other. Courtship can last up to half an hour, and the actual transfer of gametes can last for two hours. Transferred sperm can be stored within the body for up to two years. The number of eggs per clutch averages around 200. A snail may lay 5-6 clutches per year with a hatching viability of about 90%.

Adult size is reached in about six months; after which growth slows but does not ever cease. Life expectancy is commonly five or six years in captivity, but the snails may live for up to ten years. They are active at night and spend the day buried underground.

fresh eggs

hatching from eggs

a juvenile snail

Feeding habits

The giant East African snail is a macrophytophagous herbivore. It eats a wide range of plant material, fruit and vegetables. It will sometimes eat sand, very small stones, bones from carcasses and even concrete as calcium sources for its shell. In rare instances the snails will consume each other.

In captivity, this species can be fed on grain products such as bread, digestive biscuits and chicken feed. Fruits and vegetables must be washed diligently as the snail is very sensitive to any lingering pesticides. In captivity, snails need cuttlebone to aid the growth and strength for their shells. As with all molluscs, they enjoy the yeast in beer, which serves as a growth stimulus.

Achatina fulica require about 18.28 % of crude protein in its diet during the growth.

Distribution

This snail is native to East Africa, however the species has been widely introduced to Asia, the Pacific and Indian Ocean islands, and to the West Indies.

Distribution include:

Tanzania This species has been found in China since 1931. Its initial point of distribution in China was Xiamen. Pratas Islands, Taiwan

The species has recently been observed in Bhutan(Gyelposhing,Mongar), where it is regarded as an invasive species. It has begun to attack agricultural fields and flower gardens. It is believed that dogs which have consumed the snail died as a result. Where the snail is seen as a pest, it has been intercepted widely by quarantine officials and incipient invasions have been successfully eradicated, for instance in the mainland

USA. This species is already established in the USA, and is considered to represent a potentially serious threat as a pest, an invasive species which could negatively effect agriculture, natural ecosystems, human health or commerce. Therefore it has been suggested that this species be given top national quarantine significance in the USA.

Site and Date of Introduction

These snails spread throughout East Africa into Ethiopa, Somalia, Mozambique, and Madagasar. Interestingly, they were not sighted in northern Africa until the late 1980’s. The first occurrence of these snails outside of Africa was Bengal, India in 1847. Since then, the Giant African Snail has been transported mistakenly and purposefully throughout the countries listed in the above section. Giant African Snails were first spotted in the US in the late 1940’s around San Pedro, California.Many of these snails were affixed to cargo imported to the US. Over 50 interceptions occurred within a ten year span (from 1948-1958) in the California ports.In 1958, a young boy stashed Giant African Snails into his suitcase from his travels in Hawaii returning to California and driving to Arizona. Once the snails were discovered in his belongings, they family released them to the outdoors. Another very similar incident occurred in 1966, where another young boy visiting Hawaii decided to take a few Giant African Snails home to Miami, Florida to keep as pets and were released into the family’s garden. The Florida State eradication process took 10 years costing over one million dollars.These snails continue to enter the US through illegal trade or in shipping containers and in plant shipments from the Hawaiian Islands, Guam and other Pacific Islands. Inspectors fairly easily identify these snails, intercept them and eradicate them. In the early 2000’s the introduction of Giant African Snails have also occurred in Wisconsin, Michigan and Ohio due to pet store trade and educational institutions’ requests.

Ecological Role Achatina fulica forage on over 500 different plant species. During less favorable conditions (dry, cool), they nest in lose soil for during their period of hibernation. One may postulate that this behavior promotes health in the soil as the soil is churned and as matter from the snail settles into the soil. However, with over population, the snails destroy and pollute their surroundings, including the soil.

Benefits Giant African Snails contribute to the degradation of animal matter. In addition, the Giant African Snail provides nutrients to the India glowworm Beetle; specifically to the larvae (male larvae consume 20 to 40 Achatinas; female larvae eat 40 to 60 Achatinas during their development). Other beetle species consume the Achatina fulica, such as the lampyriad and the coprine beetle.

The hermit crab is one of the most dangerous predators to the Achatina fulica and has been known to use the shell as its home. The coconut crab also views the Achatina fulica as a delicacy. The domesticated duck along with a vast variety of other bird species forage on Giant African Snails. Other mammals such as the wild pig prey on Achatina fulica.

Parasites

Parasites of Achatina fulica include:

Aelurostrongylus abstrusus Angiostrongylus cantonensis - causes eosinophilic meningoencephalitis Angiostrongylus costaricensis - causes abdominal angiostrongyliasis Schistosoma mansoni - causes schistosomiasis, detected in faeces Trichuris spp. - detected in faeces Hymenolepis spp. - detected in faeces Strongyloides spp. - detected in faeces and in mucous secretion

Threats The Giant African Snails’ greatest lethal threat to humans is eosinophilic meningitis. This condition is caused by the rat lungworm parasite, angiostrongylus cantonesnsis. Most often this parasite is transferred by eating the snail, as some humans consider snails a delicacy. In addition the Giant African Snail can carry the gram-negative bacterium, aeromonas hydrophila, causing a wide variety of symptoms, especially in persons with a weak immune system.

Giant African Snails cause great economic peril to farmers due to their propensity in consuming large amounts of crops/plants. Their diet consists of over 500 different plant species. A wide variety of horticulture and medicinal plants are known to be attacked by this snail. Not

only does this decrease the income for agricultural producers, but it also impacts their living conditions (often requiring relocation) and decreases food and medical resources for humans, animals and other species.

The economic consequences persist in eradicating these creatures, sometimes costing millions of dollars. Another economic penalty involves the decrease in tourism. As noted earlier, Giant African Snails thrive in warm, tropical conditions – often tourist destinations.

Control Method

Molluscicides have been designated as one of the most effective means to eradicate the Giant African Snail. The most widely used active ingredient is the metaldehyde. The downside is that most molluscicides negatively impact the soil, plants and other beneficial organisms (such as ground beetles and earthworms).

Iron phosphate is becoming more popular in use for killing snails with less negative consequences to other beneficial organisms.

Education provides great opportunity to decrease and eventually stop the illegal trading and importation of the Achatina fulica. Educational institutions would prohibit such introductions of this snail if the lethal consequences were known. The same would be true for pet trade stores selling these creatures as pets.

The above measures are the most effective in controlling across large areas of land. Other methods, such as creating frigid temperatures or saturating the snails in ethanol, are also effective in controlling the Giant African Snail.

Muscular System

Unlike vertebrates the muscles in moluscs are not distinguished as voluntary and involuntary. However there is a clear physiological distinction

and they can be identified as somatic and visceral muscles comparable to some extent respectively to the voluntary and involuntary muscles of

the vertebrates.

The entire columellar muscle complex comprises somatic muscles. In addition; somatic muscles are also present in the foot, visceral stalk,

tentacles, labial palps, buccal mass, penis, vas deferens and oviduct. The visceral muscles are present only in the mantle, alimentary tract and

other visceral organs. In Achantina both types of muscle fibres are non-striped.

The columellar muscle complex lies to the left of the hind gut hence it is designated as the left columellar muscle. It is divided into two large

muscles: the pedal retractor and the free retractor muscle. These lie side by side and are attached to the columella close to the junction of the

body whorl and the penultimate whorl.

From the two later dorsal and poster dorsal surfaces of the foot, ventral to the neck, projects the pedal retractor muscle backward and after

gradually tapering for about 30mm,it becomes spirally twisted and completes one full turn. This portion is attached to the columella and its spiral

shape corresponds to the shape of the columella. The function of this muscle is to anchor the body of the snail to the shell. It also seems to help

in the contraction of the foot, but its role in this regard appears to be very small.The free retractor is proximally attached to the columella beyond

the origin of the pedal retractor. In this region the muscle is ribbon like. Distally it divides into right and left retractors.

The right free retractor muscle has five branches running anteriorly to the buccal mass, snout, vas deferens and the anterior part of the foot.

These are:

The penial retractor

The right pedal retractor

The right ocular retractor

The right dorsolateral retractor

The right dorsomedio buccal retractor

The main trunk becomes membranous and divides into two branches

The right dorsomedial retractor is a large median branch and ends diatally on the right dorsal wall of the snout,It is membranous on the

medial side and uniting with its fellow of the other side, forms a complete dorsal covering over the buccal mass.Anteriorly it ends on the tip

of the snout and is connected posteriorly with the cerebral ganglia and adjacent nerves.it helpsin the retraction of the snout along with the

nerve ganglia.

The median branch of the right tentacular retractor ends ont the dorsolateral wall of the snout at its tip and the lateral branch on the right

ventral tentacle.

The left free retractor is stouter than the right one and has the following branches:

The ventrobuccal retractor

The left pedal retractors

The left ocular retractor

The left anteropedal retractor

The main trunk of the left free retractor becomes membranous.Its subsequent branches and their course are very similar to those of the

corresponding branches of the right one.

Due to contraction of the powerful colmellar muscles,the anterior tentacles, ocular tentacles, snout ant the anterior part of the foot are

retractable.The retraction begins at the tip of the snout and gradually runs backwards.With the contraction of the columellar muscles,the intrinsic

muscles of the foot also contract and the foot becomes shortened and wavy in cutline.The visceral stalk contracts due to the contraction of its

longitudinal muscles.By coordination of the columellar muscles and the muscles of the visceral stalk and the foot, the snail, is able to withdraw

itself rapidly into its shell.

The Respiratory System

Like other pulmonates, Achatina also is an air breather. In pulmonates havimg an outer protective shell like Achatina, the edge of the mantle is

fused to the snail's neck expect for a small opening on the right side. This opening is known as pneumostone which is contractile. Like other

pulmonates, in Achatina also, gills are absent. The mantle cavity is tranformed into a pulmonary sac which acts as a respiratory chamber. This

chamber is highly ramified with blood vessels on the inner surface of the roof. It is filled with air by the snail's rising to the surface and opening of

the pneumostome. It is by this opening that the snail communicates with the external medium.

In A. fulica, during aestivation/hibernation also, when the aperture of its shell is closed by a thin, fragile epiphragm has a small slit over the

pneumostome to allow reduced respiration.

The Sensory Organs

The sensory organs comprise of (a) organs of sight, (b) olfactory orangs, (c) oragans of equilibrium and (d) tactile organs.

(a) Organs of Sight

Eyes of A. fulica are lodged slightly dorsally at the tip of two ocular (posterior) tentacles and look-like round black dots.

The eye-stalk is bound externally by a homogenous lamina covering a columnar epithelium. The lamina and the epithelium are continous over

the eye to form the outer cornea which is supported below by a very thin layer of fibrous connective tissue. A narrow posterior strip of the fibrous

layer runs posterolaterally and medially to form a capsule or the eye vesicle. The nner cornea lies below the fibrous layer and is restricted to the

anterior part of the eye in the region of the outer cornea only. At the base of the eye is the retinal layer which is lined internally by a very thin

membrane and a large number of closely-placed cone shaped structures. The optic nerve piercces the eye vesicle posteriorly and forms a nerve

layer inside the capsule, the nerves finally ending in the retinal cells. The round space enclosed by the layer of cones is filled up with a

homogenous, structureless lens.

(b) Olfactory Organs

There are four olfactory organs each lodged in an anterior and posterior tentacles. Each olfactory organ consists of a club-shaped olfactory

ganglion in the center of which are scattered nerve cells, whereas the periphery of the ganglion is crowded with nerve cells. From the anterior

and anterolateral sides of the ganglion, slender processes arise and ramify on the covering epithelium of the tentacles. Ganglion of the ocular

tentacle is relatively larger.

The ocular tentacles with the eyes and olfactory organs and the anterior tentacles with the olfactory organs if cut, are capable of complete

regeneration. The time taken in regeneration depends upon factors like age of the snail and the season. tentacles in younger snails, during

favourable season regenerate comparatively more quickly. Also if the antenna is cut from near the base.

The olfactory system of the snail is functionally capable and structurally complex. The morphology of the olfactory epithelium and the glomeruli

are similar to analogous structures in vertebrates. However, the snail system differs markedly from the vertebrate system in its lack of a mucus

secretion and the apparent absence of spatial patterning. Such similarities and differences teach us about the limitations and options governing

the evolution of olfactory systems. The comparative approach leads to the following conclusions, or ‘lessons’: (1) Death and replacement is

normal for olfactory receptors. (2) Olfaction requires large numbers of receptors and other neurons. (3) Glomerular structures in the olfactory

neuropil aid sensory processing. (4) Local interactions are important in the early stages of olfactory processing. (5) The role of mucus in olfaction

is peculiar to the vertebrate nose. (6) The spatial patterning of odor responses is not necessary for effective odor processing.

(c) Organs of Equilibrium

In the snail, the organs of equilibrium are the statocysts which enable it to know its positin in space. These are two in number. Each is situated on

the pedal ganglion dorsolaterally, slightly posterior to its middle. The statocyst is a round sac bound externally by a thin layer of fibrous tissue

enclosing a cavity. The cavity is full of a fluid containing about 50 elliptical statoliths (statoconia). The statocyst is supplied by a nerve from the

cerebral ganglion of the side.

(d) Tactile Organs

All the four tentacles of the snail also act as tactile organs. In addition, the anterior ends of the foot and snout also are sensitive to touch.

The Circulatory System

Generally the cirulatory system of pulmonates is comparatively less open than in other

gastropods.

The pericardium and the heart: The pericardial chamber is a closed sac except for the

reno-pericardial aperture lies transversally in the left side of the mantel cavity in its anterior

part parallel to the kidney. it is elongate-oval and there is a narrow space between the

auricular part of the chamber and the kidney. The ventricular part is in contact with the wedge-

shaped forward process of the kidney. Dorsally, the pericardium is fused with the mantle but

ventrally it is free.

The chamber is narrower at the ventricular end where it is fused with the apex of the

ventricle and the base of the aortic ampulla. It is broader and somewhat rounded at the

auricular end is fused with the narrow end of the auricle and the base of the pulmmonary vein.

The pericardium is a tough membrane, traversed by numerous lacunae. It is bound on the both sides by one cell thick epithelium of flat cell. A

thin sheet of longitudinal muscle underlies the epithelium and encloses a thick, compact muscular layer of interwoven fibers.

The pericardial cavity is in direct communication with the lumen of the kidney through the ciliated reno-pericardial passage. The flow of the

fluid from kidney into the pericardial chamber is prevented due to the one-way movement of the cilia of the reno-pericardial passage.

The auricle is wine-glass-shaped and thin-walled. its apex is narrower and continuous with the pulmonary vein. The broad concave base

receives the convex base round the auriculo-ventricular orifice. The thin wall of the auricle is strengthened with longitudinal, transverse, and

oblique muscular strands attached to its inner surface and also running through the cavity. These strands are branched, and often fused at the

points of thier intersections, forming a network, and occupying a considerable portion of the auricular cavity; the size of the cavity is consequently

reduced.

The ventricle is a conical structure, with a broad base and a narrow apx. The thick and spongy wall of the ventricle is further strengthened by

variously-oriented muscles, arranged in trabeculae and forming prominent ridges on the inner surface. Branches of muscular starnds like those

of the auricle are also present and being numerous and thicker, they greatly reduce the size of the cavity of the ventricle.

The myocardium constitues the walls of both auricle and ventricle and is formed by closely-packed non-striated, ramified muscle fibres,

running in various directions. Externally, it is bound by a thin epicardium made of a single layer of flattened syncitial cells without distinct

separating membranes. The inner surface of the wall is continuous with the muscular strands running in the cavities of the chambers. areolar

tissue, capillaries, and lacunae are present in the interstices of the cardiac tissue but the auricle is characterised by more areolar tissue.

The pulmo-auricular orifice is fairly large and not garded by valves, but the wall around it is thick and muscular and acts as a sphincter,

closing the aperture during auricular contraction.

A large auriculo-ventricular orifice connects the auricular and ventricular cavities. The orifice is guarded by two large, muscular semi-lunar

valves, broader at the base and slightly narrower at the apex. they are formed by the inpushing of the ventricular wall and are connected with

each other at their broad bases. Each valve is made of several narrow strands of longitudinal muscle fibers sending branches in different

directions and these fibers occupy the intervening spaces between the strands. During ventricular systole, the valves come in close apposition

and the auriculo-ventricular orifice is closed.

The auricle is connected with the pulmonary vein and the ventricle with an aortic ampulla which gives rise to arotae.The aortic ampulla is a

small slightly elongated chamber, formed by the union of the bases of the aortae. A thick ring-like muscular band serving as a sphincter muscle

is present at the junction of the ventricular and the ampulla and prevents the backflow of blood from the ampulla during its contraction. The

visceral and the cephalic (also often called anterior cephalic) aortae arise from the side and apex of the ampulla respectively.

Ciculation of blood through heart: The pulmonary vein receives oxygenated blood from the lung through efferent sinuses and a small

amount of de-oxygenated blood comes directly from the anterior border and ventral surface of the kidney.

The contraction starts at the junction of the aortae and the ampulla and is propagated to the ventricular and finally to the auricle through

the junctional tissue between auricle and ventricle. There is no pause between the contraction of auricle ventricle and the wave of contraction

passes so rapidly that different components of the heart appear to contract simultaneously . Transmission of contraction by peristalsis is entirely

absent. The back-flow of blood from the auricle to the pulmonary vein and the aortic ampulla to the ventricle is prevented by the closure of the

pulmo-auricular and ventriculo-ampullar orifice respectively brought about by the contraction of thier mucular walls. The auriculo-ventricular

valves stop back flow the ventricle in driving blood to the aortae with greater force.

The heart beats rhythmically. In an average-sized specimen the rate of heart beat is approximately 25 to 30 per minute. It may come down

to 9 to 10 per minute during aestivation and increases considerably when the animal is under mechanical, chemica; and electrical stress.

In pulmonate gastropods to which A. fulica also belongs, generally the arterial blood vessela are well-defined arteries which finally

terminate into capillaries. Network of capillaries occur on the surface or in the interior of all the organs. Probably the capillaries open into into

transitional channels through contractile openings; these transitional channels discharge blood into the large venous sinuses. In pulmonates, like

other gastropods, the interior spaces are just blood sinuses and not coelomes; true coelmes are only the cavities of the pericardial sac and

around the ovotesis .

The pulmonate veinous blood vessels are the centrally-placed cephalic and visceral sinues, right and left marginal sinues, rectal sinus along

the rectum and one median and paired lateral pedal sinues in the foot. Finally the entire veinous blood reaches a circular channel, the veinous

circle along the edge of the pulmonary sac including a ring around the pneumostome. A large number of efferent pulmonary arteries from the

veinous circle branch into capillaries which form a network in the roof of the pulmonary sac in which the blood is aerated. numerous efferent

pulmonary veins join a main pulmonary vein which opens into the adjacent auricle. it seems that in the pulmonary net, there is no direct passage

from the arterial capullaries to the venious capillaries. Efferent capillaries adjacent to the nephridium, end in the nephridial sinues and are then

gathered together to enter the pulmonary vein before it discharge into the auricle. Thus, it is evident that the heart carries only arterial blood

some of which has also been made free from excretary matter.

Digestive system

The digestive system is remarkably simple and consists of

The alimentary canal

The salivary glands

The digestive gland

The Alimentary Canal

It is divisible into

Mouth

Buccal mass

Oesophagus

Crop

Stomach

Intestine

Rectum

The Mouth: It is a semi circular opening located at the anterior end of the body with a plicate and enclosing a small vestibule posteriorly. A pair

of liable palps project laterally arising slightly dorsally from each corner of the mouth.

The Buccal Mass: It is thick and highly muscular in structure,narrower anteriorly and broader posteriorly.The anterior border is bound dorsally by

the jaw and ventrally by the sphincter muscle.It can be produced forward by the contraction of the protractor muscles and retracted partly by the

relaxtion of the protractor muscles and partly by the contraction of the retractor muscles.

The jaw is a semilunar, homogeneous cartilage, about 6.25mm long. The anterior surface is capped with a thick layer of brownish plicate cutivle

whereas the posterior surface is deeply concave. The sphincter muscle is attached at the concavity.The vertical height of the jaw is greater than

its thickness. The cartilage continues posteriorly from the entral border and gradually becomes thicker.

The buccal cartilage is a thick, horse shoe shaped structure with a broad body and the limbs gradually coming closer and nearly touching each

other at their ends.The deeply concave face of the body is directed posterodorsally while the convex face is anteroventral. The limbs are long,

broad, concavo-convex and slightly thickened towards their free ends. The anterior end of the radula is placed on the anterior convex surface of

the cartilage. The elastic membrane, the radualr and subradular retractors meet the buccal cartilage at the free ends of its arms, while the

sphincter muscle is inserted into the side of the arms.

The radula is elongated and has a narrow anterior and a blunt posterior end. The anterior end is recurved and lies against the anterior convex

face of the buccal cartilage. Its sides at the posterior end become folded to enclose the subradular collostyle.

In Stylommatophora the rows of radular teeth and the number of teeth per row is often large. Thus in the slug Arion empiricorum there are

160 rows with 100 teeth per row in the European garden snail Helix pomatia there are 170 rows of radular teeth each row having 140 to 150

teeth . In the adult gaint African snail, has reported 140 rows each row having 129 teeth.

The buccal cavity is divisible into an anterior tubular and a posterior arched, dorsoventrally compressed spacious chamber. Asmall

subradular cavity is present at the junction of the two and below the anterior end of the odontophore. The odontophore occupies the major

portion of the posterior chamber, while the jaw cartilage forming the root, extends up to about half of it. Posteriorly, the buccal cavity narrows

down and ends in the oesophagus.

Numerous tubular and racemose salivary glands are embedded in the muscle forming the floor of the buccal cavity, specially towards its

anterior end. Small multi-cellular, scattered glands are present in the posterolateral walls of the cavity. The ducts of the salivary glands open at

the junction of the buccal cavity and the oesophagus.

The oesophagus: It is about 36 mm long, narrow, thick-walled tube with several internal longitudinal folds. It runs backwards and downwards

from the buccal mass and posteriorly ends in the crop at the junction of the anterior and median haemocoelomic chambers.

The crop: It is about 50 mm long, thin-walled sac. The junction of the oesophagus and the crop is distinct because of the large chambers by a

constriction at the junction of the two chambers. The anterior chamber is longer than the posterior one being about 37 mm long and broadest

near its anterior end while posteriorly it narrows, become thick-walled and the constriction acts as a spinctor to check free flow of substances

from the anterior to the posterior chamber. The posterior chamber opens in the stomach on the right side by a round aperture. A short and broad

duct from the anterior lobe of the digestive gland opens in the posterior chamber of the crop, a little before its opening in the stomach.

The stomach: It lies embedded in the mass of digestive gland. It is more or less heart-shaped with its round posterior end shifted slightly

towards the right. Ventrally, the anterior border is almost straight but dorsally it is depressed in the the middle and bears two round forward

prolongations. A large duct from the posterior lobe of the digestive gland opens on the vetral surface of the stomach.

The intestine: It is a 75 mm long, thin-walled tubular structure arising from the left anterior boarder of the stomach. Anteriorly, the intestine runs

straight for a very short distance, then turning to left , it forms an arch and proceeds along the posterior end of the kidney. It then takes a trun

slightly to the right and dorsally gets completely embedded in the mass of the digestive gland. Later running anterolaterally along the left boarder

of the visceral mass, it ends in he rectum.

The rectum: It is a very thin walled tube about 68 mm long running along the posterior boarder of the mantel cavity. The wall of the posterior part

for about 6 mm has strong longitudinal folds which obliterate its lumen and act as a spincter. The rectum opens to the outside through the anus.

The Salivary Glands

These are cream-white, paried, multilobed structures, each being about 27 mm in length. These lie dorsolaterally on the posterion end of

oesophagus and dorsally on the anterior part of the crop. The glands are narrow anteriorly and relatively broader posteriorly. A long salivary duct

measuring about 25 mm arises fron the anterior end of each gland and opens in the buccal cavity.

Each lobe of the gland is sub-divided into a number of lobbules; each lobule is enclosed in a thin capsule and is made of a large number of

alveoli; from each alveolus, emerges a narrow duct, and all the ducts of the alvoeli unite to form as a single large duct. However, the ducts

emerging from different lobules open "either directly in the main duct" of the gland or "unite with ducts coming from other lobules".

The Digestive Gland

It is a dull, blackish-brown, large, thick, boiled, spirally-twisted structure. Posteriorly, it narrows and occupies nearly the whole of the apical

visccral mass. The anterior lobe is short, broad , thick and extends about half way to the stomach. The posterior lobe is maore or less conical,

broad and thick anteriorly and narrower and spirally-twisted posteriorly. The gland is made up of a large number of lobules of varying thickness

and several of these unite to form interlobular ducts which unite with each other and move forward. The lobules are full of dull-brown secretion

produced from the gland cells.

The Nervous System

The nervous system consists of several pairs of nerve ganglia and

nerves emerging from these. The main ganglia are cerebral, buccal,

pleural, parietal, abdominal and pedal. The abdominal ganglion is

single, all others are paired. The buccal and pleural pairs remain

seperate while the rst of the pairs get fused during development,

each pair forming a single ganglionic mass.

The cerebral ganglia are paired, almost spherical structures, broader

towards their outer and narrower towards the inner ends. The

cerebral ganglia are "chiefly sensory". They are fused towards their

inner ends to form a ganglionic mass which lies dorsal to the

oesophagus, about 18 mm behind the buccal mass. The cerebral

ganglia supply nerves to the head and anterior region of the visceral

stalk and the organs lodged there. From each ganglion arise a

number of nerves which can be arranged according to their origin

into : (a) Dorsal antero-median nerves and (b) Ventral antero-lateral

nerves.

(a)Dorsal antero-median nerves

The following nerves arise from the dorsal and antero-median aspects of each cerebral ganglion:

Ocular nerve: It is slender and innermost in origin, it runs anterolaterally to join the ocular retractor muscle.

Ommatophoral nerve: It is stoutest of the group and arises anterolaterally to the ocular nerve, runs anterolaterally and making a broad

arch, becomes inserted into the ocular retractor muscle in front of the ocular nerve. Slightly posterior to the tip of the ocular tentacle the

nerve bifurcates; the slender dorsal branch ends in the eye, while the stout ventral branch swells to form a club-shaped ganglion sending

processes to the tip of the ocular tentacle.

Superior frontal nerve: It is anterior and slightly ventral to the ommatophoral in origin, runs anterolaterally and dorsally to end in the snout

at the base of the ocular tentacle.

Inferior frontal nerve: It is a slender nerve, anteroventral to the superior frontal and runs almost parallel to it to end in the dorsal and

dorsolateral wall of the snout.

(b) Ventral Antero-lateral Nerves

The following nerves arise from the ventral and antero-lateral side of each cerebral ganglion:

Posterior oesophagal nerve: It is a small and slender nerve which arises from the ventral surface of the outer and antero-lateral border of

the ganglion and runs posteromedially to end in the oesophagus.

Cerebrp-buccal connective: It is a medium sized nerve and is medial to the posterior oesophagal nerve in origin and runs anteriorly to join

the buccal ganglion of the side.

Nuchal nerve: It is a slender nerve being anteomedial to the cerebro-buccal connective and runs anteroventrally and slightly laterally to

inervate the anteroventral wall of the snout and the ventral surface of the anterior end of the buccal mass.Another nerve, the nuchal nerve

proper originates close to the nuchal nerve and runs anterodorsally and very slightly laterally to end in the wall of the snout, anteroventral

to the anterior tentacle of the side.

Labio-tentacular nerve: It is the innermost nerve of the series parallel to the nuchal nerve proper and innervates the wall of the snout

around the base of the anterior tentacle and sends some branches up to its tip.One of these branches is stout and centrally placed and

swells to form a club-shaped olfactory ganglion, sending processes to the tip of the anterior tentacle.

How it moves?

The snail moves by creeping on a flat "foot" underneath the body. The band of muscles in the foot contract and expand and this create a kind of rippling movement that pushes the snail forward. The "foot" has a special gland that produces a slimy mucus to make a slippery track. You can often see these silvery tracks in the garden. The slime comes out from the front and hardens when it comes into contact with air. The snail is able to move on very sharp pointed needles, knife, razors and vines without being injured because the mucus-like secretion helps to protect its body. New evidence suggests that the key to locomotion in snails stems from the animal's complex muscle movements, and not from its mucus, as had been previously thought. This finding could open the door to the construction of robots which could imitate this form of propulsion.

The mucus is highly adhesive, which offers some advantages such as walking on walls and moving on the ceiling. When snails move, they do not use force over specific points, as animals with legs do, but rather they distribute a relatively low force over a relatively large area. What also happens is that it is difficult to move over glue without exerting quite a bit of force while dragging fluid along. Snails, after millions of years of evolution, have succeeded in being able to move on a highly adhesive surface, avoiding these inconveniences which is without a doubt of interest and worthy of study.

Foot The muscular foot is used for locomotion and consists of several muscular layers. There are two types of walking in apple snails: with creeping locomotion and with a small wave locomotion. The creeping locomotion is consists of an extention-contraction (elongation-shortening) movement of the foot. Snails that use this rather rare technique do not move at a constant speed . At least one apple snail species uses this walking method, although not all the time: Asolene spixi.Other species use this movement tecnhique when theu burry in the substrate. A much more common locomotion is used by the majority of the apple snails and is achived by contraction waves on the sole of the foot. The result is a smooth walk with a constant velocity.

Because the apple snail has a lung the animal doesn't have to bear all it's weight when moving under water: the animal partly floats on the air in the lung. This declares why such rather big snails can 'walk' fairly elegant across the bottom. Besides it locomotion function, the foot is also used to collect food from the surface (film-feeding or ciliary feeding). Forming a funnel with the foot in which particles from the surface can be trapped does this. To attract the floating food pieces, the snail makes the same movement with its foot as it does to walk, but only with the front part of the foot and the middle part, forming the funnel. With the tail of the foot, the snail stays attached to the side or an object near the surface. Once the funnel is filled with food, the snail brings its mouth in the funnel and starts with its meal.

When the snail retracts in it's shell, the sole of the foot is transversely folded and the shell opening is closed of with the operculum, which is firmly attached at the back of the foot.

How it breeds?

Most Giant African land snails species are fairly easy to breed. The snails lay two batches of eggs (one for each parent). Eggs are usually laid within a month of mating. For Achatina snails, there are usually 100-200 eggs in each batch. These eggs are relatively small - Achatina fulica eggs are about 6mm in length. Archachatina snails lay 6-15 eggs in each batch. These are large - Archachatina marginata eggs are about 20mm in length.

If you want to breed your snails, make sure the soil is at least 5cm deep for the eggs to go in. Achatina fulica reaches sexual maturity at about 80mm in shell height, and if you have two or more snails this big, and they are well looked-after, it will not be long before you are presented with some eggs. Eggs must be kept warm and moist. A temperature of 25-29°C will have good results. You can leave the eggs where they are, move the snails that are in the tank elsewhere to stop them disturbing them, or move the eggs out - put them in a plastic tub (with air holes) containing soil, moss or Vermiculite. Put the tub somewhere warm, e.g. an airing cupboard. Make sure to spray the eggs regularly. When the eggs hatch, the babies must be left in the soil to eat their eggshell. They stay under the soil for about a week and then come to the surface. Having adult snails in the tank with them is not a good idea, the babies should be in a tank of their own. Gestation time is very variable. Achatina eggs can hatch in a few days, or take up to three weeks. Archachatina eggs take a long time to hatch, usually 30-40 days, depending on temperature. Archachatina eggs are much more difficult to hatch than Achatina eggs; they should be disturbed as little as possible and made sure to be very warm and moist. If you don't want babies, the best thing to do is remove the eggs and put them in a freezer for several hours (or crush them). If you want to breed Achatina fulica, only hatch as many babies as you want to keep yourself as they're so common it's difficult to find homes for any unwanted babies.

Posting snails

To package a large snail (30mm+) place it in a plastic tub the snail can fit comfortably into. Fill the tub with moss (some people use damp kitchen roll) so the snail will not move around while in there. Then wrap the tub in bubble wrap or pad it with crumpled newspaper and place it into a box,

which is sealed tight with tape. The tub must not be able to move around inside the box. For smaller snails (20mm or less), you can put them in the tubs for photograph films. Place the snail inside the tub with moss packed around it, then put the tub in a padded envelope. Don't post snails when if it's winter and too cold. Snails can be sent across the world and still be okay, although they probably shouldn't be in the post longer than 8-10 days. The snails must have access to air, so the inner and outer packaging must have airholes. When you recieve the snail, put it straight on some food.

How it eats?

Giant African land snails are very easy to feed. They eat a wide variety of fruits, vegetables, greens and more. Achatina fulica, for example, is known to eat over 500 types of vegetation. Experiment with a variety of food to see what your snails like best. Most snails love lettuce, especially the Romaine variety (they prefer the greener leaves). Other favourites of Giant African land snails include cucumber, banana, aubergine, sweet potato, apple, carrot, mushroom, sweetcorn and dandelion leaves. The cucumber should be cut in half lengthways and layed down so the snails can eat the juicy middle. Snails usually like the inner parts of fruit and vegetables so cut or peel them. With sweetcorn, they don't seem to eat the outer layer of the corn kernel, so it's best to remove that. Snails also like oats and other seeds such as sunflower and hemp, which should be soaked first, and the hard seeds ground up. The oats can be mixed with other ingredients such as grated apple, mashed banana and the ground up seeds. Experiment with your own food mixes. Some more unusual foods can be given to snails as well, such as tortoise food, dog biscuits and raw meat. Foods with salt in and pasta should never be given to them. Snails should be fed every day, or at least every other day. You must experiment to find out how much your snails will eat daily.

Snails need calcium for their shell growth, it's very important. Without it the snail's shell will be thin and may grow in a strange way. Even if the snail is fully grown it should still have a calcium source. This is most convieniently provided in the form of a cuttlefish bone (above), these are cheap and available from most pet shops (they're given to birds as well). Other calcium sources include egg shells (remove the inside skin), calcium powder, powdered oyster shell, natural chalk and wood-ash. Some of these are not easy to obtain. Powdered oyster shell is the best source of calcium.All food/calcium must be washed before being given to the snails, especially if it is non-organic.Snails will get their food, food plates and calcium dirty by dragging their substrate over it. Cuttlefish can be cleaned with a toothbrush and water. Food plates must be cleaned whenever new food is added to them. Wash any dirty but otherwise okay food with water.

How Does a Snail Make Its Shell?

Nearly all mollusks have shells. Most mollusks also have organs called mantles. The mantle is thin and a bit like skin. In a snail, it lines the shell. A snail, like most other mollusks, uses its mantle to make its shell.

To make a shell, the mantle releases a liquid made up of shell materials. Gradually the liquid hardens and forms the shell. Over time, the mantle releases more of this liquid. This in turn adds to the size of the shell.

Snail shells come in many different shapes and sizes. Most snails have spiraled shells, like this tree snail. Some sea snails have shells that coil into cones. Other snails even have shells that are shaped like macaroni.

Facts

Snails take about two years to be mature for reproduction.

Snails are considered to be one of the slowest creatures though on the entire Earth.

Snails will die if they consume either salt or sugar.

The largest land snail recorded weighed only 2 pounds and was 15 inches long.

They scrape up their food by moving back and forth on an edible surface. You can picture this when you recall seeing a snail attached to

a leaf. Later you see the leaf is full of holes.

Snails include the kind served in restaurants, as well as clams, and the snails in your garden that destroy your plants.

They are triploblastic protostomes. This means that their bodies are made up of a mass of material that holds the organs, a foot that holds the muscle enabling them to attach to a surface, and the head. Some, but not all, have eyes and tentacles.

The snail's body has a sheet or mantel, which forms a shell from secretions. They scrape up their food by moving back and forth on an edible surface. You can picture this when you recall seeing a snail attached to

a leaf. Later you see the leaf is full of holes. Snails do not have segmented bodies, like most all land animals. They are believed to be related to the annelids. Annelids are animals that do have segmented bodies. They are not male or female - they are hermaphrodites. They can produce both sperm and eggs. The snail has no sense of hearing, they use their sense of smell and feeling to maneuver about the earth. A snail is not in the insect family. There are more snails than insects on earth. The trail of slime that they leave as they move allows them to move on any type of surface in any terrain without being injured. Think of

being able to walk on glass, sharp rocks etc. without hurting your feet. That’s how they are. Snails in nature live 15 years on average, up to 25 years. In captivity, they live longer because they are protected from predators. Larger snails eat smaller snails. Snails are also on the menu for birds, frogs, dogs and cats (sometimes they just kill them and don’t eat

them). They can seek protection by withdrawing into their shells but predators often break the shells. Snails don’t carry disease like cockroaches do, contrary to common belief. They are not dangerous to touch. To be safe though, you

should wash after handling them. They are safe to eat only if they are prepared correctly. If you are planning to try a recipe for snails, use an established cook book and

follow directions exactly as written. It is generally accepted that they have been on earth for month that 600 million years.

Snails do not have any hearing which is why their second pair of tentacles carry out such an important job.

Snails are very active at night. They are nocturnal. Land snails can walk up stalks, sticks and walls and can even go up sharp corners without getting hurt all because it is protected by slime. World's largest snail is the Australian trumpet (Syrinx aruanus), a sea species from the shores of northern and western Australia which

can grow up to 77.2 cm (30 inches) in shell length, while the flesh weighs upto 18 kg. The snail slime was found by American researchers to be an excellent scaring factor. Snail slime is also used in some beauty products. Garden snails have up to 14,175 teeth. They are all located on their tongue (radula). Most ground snails are peaceful veggies (well, not exactly all), but the marine species can be top predators of the sea. They are armed

with a harpoon like weapon (named toxoglossan radula, snails modified "tongue") injecting a deadly venom into their victims. In some areas, like New Guinea, the shells of sea snails were used for long as currency. Some sea snail produce sulfuric acid which they use for dissolving the shells of the clams on which they feed. French researchers discovered that the digestive secretions of the garden snail are effective against stomach ulcer. 10 mg of this powder

led to a decrease by 42 % of the human stomach acidity. The product was also effective against chronic bronchitis.

StoryBoard

Reference Images

Modeling

Work in progress:

Head of the Snail Body

I started the model with a cube and extruded the eye and tentacles out of it. The tip of the eyes and tentacles are spheres attached to the

extrusions. The next task was to get the flappy shape of the mouth with proper looping.

Body :

The snail being an invertibrate does not require any strong muscular looping. The body of the Snail was easy to model, but the looping had to

be done differently in the mouth area as its mouth was like a flap.

Looping was also done in the edges of the body specifically to get a wavy kind of depth on the body. I used lattice to get the shape of the body.

Shell

To model the shell i used a helix and extracted a curve from it. Then i created evenly spaced curves around the extracted curve and applied

birail. Using transform component i created roundness of the shell. Since the major part of the shell is hollow i had to manually model it in order

to get the depth in it.

Final model with wire-frame

Unwrap

Body Shell

Unwrapping of the model was done using Uvlayout software and then the .obj file was imported to maya.

Texturing

Sculpt details

Color details

The scale details of the snail is one of its most important

features. To obtain these details i had to first create

different types of stencils where each scale in the stencil

had a gradient from black to white in order to get the

bulge of the scales. Using stencil, displacement on the

snail was sculpted and smoothened each scale.

After sculpting, a base colour was given and each scale

was manually coloured for the required depth on the

scale.

Textured Snail

Body:To make the scales, a stencil was created in photoshop. As it was difficult to get the depth for the scales using the

stencil i had to smoothen the each scale and after a couple of attempts i got it right. I had to make different kinds of

stencils for different areas of the body and in order to merge them they needed to be placed appropriately. More stencils

needed to be made for another layer of smaller scales on the body. After displacement, i started working on the color

map with a dark base color. In a new layer each scale was painted individually. The maps were extracted and applied on

the shader. The issue in this process was the seam being seen which had to be corrected in the vector displacement

map.

Sculpt Details

Color Details

Shell: The displacement map on the shell had subtle grooves that had to be drawn manually. Then a little noise was added using a

stencil. Initially a color map was created for the shell. As there were too many colors on this map i had blend the colors to get the

desired output. A layer of scratches had to be applied on the shell to get its worn out realistic look. 4k resolution maps were extracted

for a better output.

Snail Textured

Blendshapes

Creating blendshapes for the snail was a major problem during this project. Correctives had to be made for the eyes and the tentecles in order to

send them into the body. The entire body of the snail had to be sent into the shell as we had to show it coming out of the shell. I tried various

methods and finally lattice deformer was used on the blends for the required output

Snail Texture Maps

Color map Vector Displacement map Normal map

Shell Texture Maps

Normal map Color map

Rigging

Rigging the snail was a difficult task as the snail as such is an invertebrate and has no joints. It is a very flexible character and it was difficult to

get the required flexibility using a rig. The character had to be rigged a number of times for the required output. Ultimately with the help of the

rigging faculty the final output of the snail’s joint structure and rig was obtained. It had to have attributes for the eyes and tentacles to go into the

body in order to use them in the correctives. Also additional controls were given for the side waves of the snail for minute movements.

Joint structure joint structure with curves

The rig of the snail comprises of a spine ik structure with basic parent constraints for the sides. The eyes and tentacles were sent in using simple

attributes and set driven key. The shell of the snail was connected to the body with a joint as if it was kept separate the geometry cache of the

shell could not be obtained after animation.

Snail into the shell trial

The next major problem faced after rigging was to be able to send the snail into the shell. I tried doing it with the rig entirely but since it was

not possible to do so using only the rig we had to use blend shapes for the desired output.

Skinning

Skinning had to be done using the interactive option of bind skin in order to get the weights up to 1 in total. This option had given lot of problems

because if the weight was exceeding 1 then the weights would automatically get adjusted to the nearby joints. After a few trials I understood how

to rectify the problem and evenly distribute the skin weights. Thus the required skinning output was obtained. The shell was skinned to its joint

with a value of 1 as it was a solid object.

Skinning of the edge

Skinning of the head

Skinning of the shell

Animation

Animating the snail required a lot of observation on its movement and flexibility. The snail glides along surfaces and this action had to be shown

without making it look like the snail was skidding. All the more the snail takes a lot of time for moving from one point to another and a lot of

frames were required to show this slow movement of the snail. The eyes and tentacles had to be moved randomly without looking clumsy.

The character for animation was referenced from the rig and I had to create two reference files of the rig, one with the snail going into the shell

and one with the proper rig for the animation, in order to use them in the required shots.

Once the snail was referenced into the shot the size of the snail had to be set according to the environment. This had to be done by scaling the

pftrack data group. The snail could not be scaled as the textures would not sit properly on the mesh if it was scaled. I had to make sure that the

size of the snail did not change in each shot.

Once the animation was done the geometry cache was taken of the animation and it was given for compositing.

The shooting started with the making of HDRI, which was useful for image based lighting in Maya to light the scene without creating lights.

Shooting Techniques

According to the script we had nine shots that later got divided into 16 shots. All the shots were taken according to the storyboard. The

camera used for the footage was Canon 5d mark II. A portable dolly was used for the shooting of certain pan shots.

A Nikon camera was used to take photographs of the HDRI (High Dynamic Range Image).

Problems faced after shooting

The focal length was not noted while shooting and major depth of field was required to focus the subject which later resulted in difficulty to track

the camera.

The above shot has a lot of de-focus which made it difficult to track the footage. So I used manual and geometry tracking for shots like above.

Note:

Note the set data for every shot because they will be useful when we work with the shots in the software.

Avoid maximum shake of the camera to track the camera perfectly later in CG.

Segregation of shots and naming sequence is very important for the backup we take.

Finalize the shots required and put them separately to use them for any purpose required.

Tracking & Match move

In this dissertation every shot has maximum amount of depth of field so the shots are tough to track in auto mode tracking. Hence I used

geometry tracking and manual tracking for this project.

For geometry track we need a minimum piece of geometry made from the scene that was shot which consists of a maximum number of vertex

points so that the track could be done using the contrast matter in the footage.

I created 2 stones in CG using Autodesk catch through live referencing photographs.

Maximum number of vertices act as track points in texture tracking or geometry tracking.

Problems faced in tracking

Tracking is very difficult in shots which are shaky, defocused and have depth of field.

Pan & still shots were easy to track but frame by frame tracking failed many times because of blur footages.

I was not able to estimate the focal length in most of the cases because set data was not available.

All the shots in my project have geometry tracking and manual tracking.

Match move :

Finally I managed to track the shots accurately and match the object accordingly to the stones in the footage.

PFtrack 5.0 is used.

Rotoscoping

In some shots grass was a foreground of the subject. When a CG element was composed in the footage, the grass was behind the cg element.

Hence through Rotoscoping the footage,the required result was obtained.

Following are the steps of Rotoscoping

Footage

Footage with CG-Element

Grass cut matte

Final output

ROTO-Spline soft edge – 0.01 (grass defocus value )

Shading the snail

The Snail’s body was a slimy substance material with a large amount of specular in it.The shell is a hard n blond shiny object.The body was

planned with a subsurface scatter material.In Maya its officially called Maya simple skin.

It has three layers involved in making the scatter substance, namely:

sub dermal scatter

epidermal

back scatter

Variation of shading

Lambert(color map) with base color final scatter material (SSS)

Color shade with base color blin material

The Scatter material involves three maps

Color map

Details map

Base color

Problems in shading

A number of values were set to get the correct shader output but

none of them matched the reference.

It was a time consuming task and I had never used the scatter

material before .After several attempts and with the values used

below the required output was obtained .

Lighting

HDRI is used for image based lighting to light the basic fill of the scene.

HDRI stitched

Image base Lighting setup (IBL)

Additionally 3 point lighting was used to set the scene so that it matches the live footage.

A directional light was used as the key light and 2 spot lights were used for fill and rim simultaneously.

3 point lighting

light composed = without light + light pass

The light information is rendered through a light pass.

Rendering

After finalizing all the camera work, shading ,texturing and animation, rendering is done to compose the sequences together.A rendering rig

(reference from internet) was made which extracted all the linked passes with master beauty.There are 10 passes involved in rendering.All are

used in compositing for a better result.40,096 files were rendered including all the 10 passes in 14 shots (2 shots deduced).

This rendering network is assigned with fixed texture maps and displacement .

This render rig renders one master beauty and extracts the remaining passed in the same master render time. Here time was saved as

rendering all other passes was not required.

I used DEADLINE RENDER MANAGEMENT SYSTEM to render all the batch sequences.

Rendered Passes

Color pass Master Beauty

Indirect pass (finalgather) Light (direct) pass

Reflectivity pass Specular pass Fresnel pass

RGB Matte SSS (scatter)

All the passes composed together

The software used for compositing was Fusion6.3

After all the passes were rendered, I segregated them in an assigned folder to start compositing.

All the naming and frame padding had to be perfect to get the sequence correctly.

Process:

Light information passes – Occlusion light (direct pass) & indirect (final gather)

1. Multiplying occlusion and indirect pass

X =

indirect depth info

2. Multiplying indirect depth information & Light pass

X =

Light information

Compositing

3. Scatter information

Connect scatter pass to both foreground and background

- =

4. Add Light information on scatter information & multiply with scatter again

+ X =

Now all the scatter and light information is ready.

5. Now multiply color pass & scatter and light information

X =

complete color information

6. Reflection specular & Fresnel information

After screening the reflection and specular pass we get

/ =

reflection information

7. Screen reflection information and Fresnel pass

/ =

complete reflection information

8. Merge complete color information and reflection information

/ =

final composition

Basic connections of the fusion nodes

This is just a sample of the compositing style

9. Finally RENDER the sequence in the required format

RGB matte is used to control the segregated objects through bitmap

Footage

Composed image with all rendered passes