Phylum Annelida the segmented worms
1st phyla we will talk about and what we will cover in the lab today is the segmented worms Phylum Annelida Annelida from the Latin word annelus meaning little ring All are segmented worms Approximately 15,000 species including earthworms, freshwater worms, leeches, and marine worms Annelida Characteristics
Triploblastic- 3 cell layers Highest level of organization: organs Bilateral Symmetry Cephalization Eucoelomate Body Cavity Eucoelomate
Have a true body cavity that is completely surrounded by mesoderm ectoderm coelom mesoderm Gut endoderm Annelid Characteristics
the coelom is a closed, fluid filled cavity that surrounds the gut the fluid within acts as a circulatory system (blood) tissue membranes (mesenteries) suspend organs in the coelom ectoderm Annelida Characteristics
Metamerism The body is made up of a series of repeating, coordinated segments called metameres that are separated from one another by septa. Each metamere contains sets of repeating organs e.g. gut, blood vessels, nerve cord, excretory organs Metamerism septa Metamerism Annelid Characteristics
Two part head consisting of Prostomium:fleshy lobe that overhangs the mouth Peristomium: first body segment Annuli: circular rings Pygidium: thelast segment;where the anus is Clitellum:reproductivestructure annuli pygidium Annelida Characteristics
Nervous system 2 cerebral ganglia a ventral nerve cord with 2 ganglia per metamere. In some species, sensory organssuch as eyes, palps, and tentacleshave arisen (palps are appendages that may ormay not be covered in cilia that helpthe worm find and pull in food) Annelida Characteristics
Locomotion both longitudinal and circular muscles which allow them to wiggle most have setae (chitonous bristles secreted by the epidermis) that aid in locomotion and burrowing Skeletal System fluid in coelom acts as a hydrostatic skeleton Annelid Characteristics
Gas exchange mainly by diffusion through skin Class Polychaeta often has specialized structures for gas exchange (e.g. parapodia, gills) Annelid Characteristics
Digestive System unidirectional regional specialization (digestive organs) Circulatory System closed circulatory system composed of blood vessels (some of which are contractile and act as hearts) some circulation is also accomplished by the coelomic fluid Annelid Characteristics
Excretion excretion is accomplished by organs called nephridia (singular nephridium) sexual Reproduction Phylum Annelida Class Polychaeta Class Oligochaeta Class Hirudinea Class Polychaeta 1st phyla we will talk about and what we will cover in the lab today is Class Polychaeta All marine
This class contains 2/3 of all known Annelids Common species are clamworms, sandworms, and lugworms have a well developed head with specialized sense organs 1st phyla we will talk about and what we will cover in the lab today is Class Polychaeta Commonly called bristle worms
Have many setae (chitonous bristles secreted by the epidermis) (Poly = many, chaeta= setae) These setae are arranged in bundleson paddle-like appendages called parapodia 1st phyla we will talk about and what we will cover in the lab today is setae Class Polychaeta Parapodium 1st phyla we will talk about and what we will cover in the lab today is setae The parapodia function in gas exchange, locomotion, and feeding. Class Polychaeta Tagmatization (tagmosis)
the fusion and specialization of formerly metameric segments 1st phyla we will talk about and what we will cover in the lab today is Class Polychaeta Many are filter-feeders with specialized structures
1st phyla we will talk about and what we will cover in the lab today is Class Polychaeta Many are predatory with specialized structures
1st phyla we will talk about and what we will cover in the lab today is Class Polychaeta 1st phyla we will talk about and what we will cover in the lab today is Many construct their own homes out of CaCO3 or sand debris and mucous Class Polychaeta Reproduction
Usually dioecious (separate male and female) No permanent sex organs; gametes are shed into coelom where they stay until time for fertilization Fertilization is usually external in water Indirect development trocophore larvae swims around until it grows into adult form by addingsegments 1st phyla we will talk about and what we will cover in the lab today is Ecology Polychaetes often have effective defense strategies:
some have tubes to hide in some have vicious jaws some have modified stinging setae 1st phyla we will talk about and what we will cover in the lab today is a fireworm Ecology Some Polychaetes have a mutualistic relationship with their host for example, many scaleworms are found near, or in the mouth, of brittlestars, starfish, and sea urchins. The scaleworm eats its hosts leftovers and with its vicious jaws, it will attack any predator trying to eat its host. 1st phyla we will talk about and what we will cover in the lab today is Class Oligochaeta 1st phyla we will talk about and what we will cover in the lab today is Class Oligochaeta Habitats: terrestrial, freshwater, and marine
Have few setae (Oligo = few, chaeta = setae) Class Oligochaeta What do earthworms eat? Usually feed on detritus
(decaying organic matter) Depends on habitat, but they can feed on Dead leaves and plant roots Living things such as other worms, bacteria, and fungi Decomposing remains of other animals Class Oligochaeta Do earthworms eat dirt? Yes and No.
Earthworms consume dirt as they burrow, so yes they do swallow it. HOWEVER, they do not get nutrients from the dirt.Their nutrients come from decaying plant and animal remains that are in the dirt. Class Oligochaeta Earthworms have specialized digestive system to obtain the maximum amount of nutrients out of the detritus. Example: pharynx, crop, gizzard, etc. Class Oligochaeta Locomotion Circular muscle contraction
Longitudinal muscle contraction Class Oligochaeta Reproduction Usually monoecious
Still have to have a partner. Cross-fertilize by exchanging sperm clitellum testis Ecology Earthworms are essential soil aerators, meaning they allow air to enter the soil. Mix the soil with their tunnels. Worm feces are great plant food = fertilizer! 1st phyla we will talk about and what we will cover in the lab today is Class Hirudinea 1st phyla we will talk about and what we will cover in the lab today is Class Hirudinea Includes leeches
usually freshwater but there are some marine and terrestrial species no septa between metameres no setae or parapodia have 2 suckers Class Hirudinea have an extendable proboscis for feeding Class Hirudinea usually have a fixed number of segments (34)
each metamere consists of several annuli (think accordion) 1 metamere annuli Class Hirudinea Locomotion
Lack septa between metameres, so they are incapable of moving like Oligochaetes. Instead, they use their anterior and posterior suckers to move. 1st phyla we will talk about and what we will cover in the lab today is Class Hirudinea Reproduction usually monoecious cross-fertilize by
exchanging sperm 1st phyla we will talk about and what we will cover in the lab today is Ecology Although some leeches are parasitic blood suckers (can be temporary or permanent), many are predators. 1st phyla we will talk about and what we will cover in the lab today is Ecology Leeches have been used medicinally since the 19th century.
Currently they are used to increase blood flow following reconstructive surgery Hirudin is a powerful anticoagulant that is found in the salivary glands of leeches 1st phyla we will talk about and what we will cover in the lab today is