Invertebrates

A Survey of the various phyla

Cambrian Explosion

• Rapid appearance 530 million years ago years ago of most major phyla.

•Before about 580 million years ago, most organisms were simple, composed of individual cells or small colonies of cells.

• Over 70 or 80 million years the rate of evolution accelerated and the diversity of life began to resemble today’s.

•Charles Darwin saw it as one of the main objections that could be made against his theory of evolution by natural selection.

•What caused such a rapid increase in the number of species?

Strange Cambrian creatures !

Opabinia – an extinct arthropod from the middle Cambrian period

Microdictyon fossil and presumed form when alive

One of the precursors to the Arthropoda (also Onychophora and Tardigrada, is the lobodopian Diania

cactiformis (walking cactus)

A possible restoration of Diania Cactiformis

Phylum Porifera• Examples are the

Sponges.

• Phyla name literally means “pore bearing”

• Asymmetrical symmetry

• Sessile

• No circulatory system

• Heterotrophs, multicellular, lack cell walls, contain few specialized cells.

Porifera body structures

Asconoid Syconoid Leuconoid

Example Sponge

Choanocytes

• Flagellated Structure

• Function in moving water in so the microvilli can filter out food materials from the water.

• Absorbed food is passed on to the amoebocytes which carry the food to the other cells.

• Become sexual cells during times of reproduction.

A large barrel sponge!

Glass Sponge example

Lavender sponges

Touch me not sponges

Sponge Asexual Reproduction

•Sponges have 3 asexual methods of reproduction: fragmentation, budding and producing gemmules.• Fragments of sponges can settle and reorganize as a functional sponge.• Gemmules are survival pods of cells that can survive harsh conditions.• A very few species reproduce by budding.•This picture shows some gemmules of the freshwater sponge spongilla.

Sponge Sexual reproduction

•Most sponges are hermaphrodites• Sperm are produced by choanocytes.• Eggs are formed by transformation of amebocytes, •During spawning, sperm burst out of their cysts and are expelled via the osculum. •If they contact another sponge of the same species, the water flow carries them to choanocytes that engulf them.• The sperm are carried to the eggs and fertilization occurs within the sponge.•A few species release fertilized eggs into the water, but most retain the eggs until they hatch.

Larval Sponges

•There are four types of larvae, but all are balls of cells with an outer layer of cells whose flagellae or cilia enable the larvae to move.• After swimming for a few days the larvae sink and crawl until they find a place to settle.• Most of the cells transform into archeocytes and then into the types appropriate for their locations in a miniature adult sponge.

Freshwater Sponges

• Freshwater Sponges are useful for monitoring pollution

• In addition they produce an antibiotic that may have important biomedical and ecological functions.

Freshwater Sponge

A colony of sponges growing on branches submerged in a Wisconsin Lake.

Cnidarians• Phylum contains over

9,000 species found in mostly marine environments.

• Their bodies consist of mesoglea, a jelly-like substance, sandwiched between two layers of epithelium.

• They have two basic body forms: swimming medusae and sessile polyps.

• Both forms are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes.

• Both forms have a single opening and body cavity that are used for digestion and respiration.

Cnidocysts • These cells function as

harpoons, the barb remains connected to their body by threads.

• 3 types of cnidocytes are known.

• Nematocysts inject venom into prey, and usually have barbs to keep them embedded in the victims.

• Spirocysts entangle prey by means of small sticky hairs on the thread. Only members of the class Anthozoa (sea anemones and corals) have spirocysts.

• Ptychocysts threads are used for building protective tubes in which their owners live.

Form and Function

• Symmetry is Radial• There are two basic forms:

polyp and medusa.• Polyps are mostly sessile,

medusa’s are free swimming.• Two cell layer with a

gelatinous mesoglea.• Gastroderm helps in

digestion.• Prey is caught, placed in

gastrovascular cavity and digested.

• There is no respiratory, circulatory or excretory systems.

• The skeleton is hydrostatic- water pressure maintains animals shape.

Nerve Net• A Nerve net consist is a series of connected neurons lacking a brain

• This nervous system allows cnidarians to respond to physical contact.

• They may then detect food and other chemicals.

• Although the nerve net allows the animal to respond to its environment, it has trouble telling the animal the direction of the stimulus.

• Simple animals with nerve nets, such as hydra, typically respond in the same way to contact with an object, regardless of where the contact occurs

Reproduction• Sexual reproduction involves a complex life cycle with both polyp and medusa stages.

• In Scyphozoa (jellyfish) and Cubozoa (box jellies) a larva swims until it finds a good site, and then becomes a polyp.

• This grows normally but then absorbs its tentacles and splits horizontally into a series of disks that become juvenile medusae, a process called strobilation.

• The juveniles swim off and slowly grow to maturity.

• The adults have gonads in the gastroderm, and these release ova and sperm into the water in the breeding season

Class Anthozoa

• This class of Cnidarians includes the sea anemones, sea pens and corals.

• The corals are the base for the tremendous diversity amount of life on the coral reef.

There are two types of Coral, Soft and Hard.This is a picture of a type of soft coral. It lacks the hard

calcium carbonate outer covering.

Different types of Coral

Coral Polyp Anatomy

Many species of coral have symbiotic relationship with algae. The algae is incorporated within the polyps bodies.

The algae get protection and the coral get some food.

Cnidarians importance

• Coral Reefs provide food and shelter for thousands of species.

• The diversity of the Coral reef is second only to the rain forest.

• The Great Barrier Reef off the coast of Australia is the largest structure made by animals and can be viewed from space.

A Part of the Great Barrier Reef from Space

The Great Maya ReefThis reef is the 2nd longest barrier reef in the world.

It lies of the the coast of the Yucatan Peninsula

Coral Reef areas of the World

Class Scyphozoa

• Jellyfish can reproduce sexually. The fertilized egg becomes a free swimming larva (planula) that plants on the ocean floor and forms a polyp. Stacks of medusa’s develop on this polyp and break off to become free swimming jellyfish

Jellyfish Anatomy.They lack a brain but can detect light.The digestive system is incomplete.

Jellyfish tank at Monterey Bay Aquarium

Box Jellyfish

• Very poisonous jellyfish found in the South Pacific.

• Symptoms include stinging, redness, burning, swelling of lymph nodes and in severe cases may result in difficulty in breathing and cardiac arrest.

Two Box Jellyfish Sting scars from Boxsafely held by their bells. Jellyfish.

Class Hydrozoa

• Reproduce asexually by budding.

• At low temperatures reproduce sexually. Eggs and Sperm produced from swellings on each animal.

• Fertilized egg grows into a hardened cyst and can survive the winter.

• They can move in a cartwheel like fashion to reattach at some other place.

Hydra Anatomy

Three layer body plan.

Simple diffusion transports food, oxygen and wastes.

Coordination is accomplished via a nerve net.

Hydra Nerve net

A net like system of connected nerve cells.

This allows for coordinated movements.

This nerve net can repair itself.

There is no central area where nerve impulses travel to be interpreted.

Freshwater Jellyfish (these are about 9 mm in dia.)

Freshwater Jellyfish caught in Minnesota (Loon Lake)

Pourtugese Man of War

Portuguese Man of War.

Platyhelminthes – The Flatworms

• This phyla includes tapeworms, flukes and planaria

• These creatures have bilateral symmetry.

• They have a definite head where sense organs and a “brain” are located.

• They have one body opening.

• Flame cells function as primitive kidneys.

• Being thin and flat allows for oxygen to easily diffuse to the cells within.

Planaria Anatomy.Note the presence of a nerve cord.

Planaria

•Note the Nervous system with a definite swelling at the anterior end of the animal.

•Reaction to stimulus will show direction.

•Respiration is through the skin – no system!

•No cirulatory system.

•One body opening.

•Note the presence of an excretory system.

•Planarians are hermaphroditic.

Planaria body cross section

Planaria regeneration

Various regeneration experimental results

Class Trematoda

• Blood flukes and liver flukes are flatworm parasites of other animals including human.

• Blood flukes are the 2nd most important tropical disease after malaria. (Schistosomiasis)

• Parasitic organisms usually have a very simple digestive system since the food is coming to them predigested.

• Parasitic organisms often have a complex life cycle with at least one intermediate host for the young.

Blood Fluke life cycle

Blood Fluke taken from circulatory system

Class Cestoda

• Commonly called tapeworms.

• Composed of a head (scolex) and many body sections (proglottids).

• At least two hosts for life cycle.

• Human tapeworm involves infected cow muscles.

Nematodes• This phyla is called the round worms and includes trichina, hookworms, heart worms and nematodes.

• Bilateral symmetry

• 2 body openings (a mouth and an anus)

• Hydrostatic skeleton system

• A pseudocoelom or a body cavity incompletely lined with mesoderm is present.

Nematodes cont.

• Have a digestive system with a mouth and an anus.

• Respiration, circulation and excretion is through the skin.

• 4 nerves run the length of the body with an anterior ring that serves as a brain.

• Bilateral symmetry of the body.

• They reproduce sexually with male and female worms.

• C. elegens, a free living nematode is important in research because it is transparent, easy to breed and easy to use in genetic research.

Trichina

• This photo shows trichina worms which have formed cysts in muscle tissue

• A human eating undercooked meat with these cysts would most likely catch this disease.

Filarial Worms• Filarial worms and their

larvae are parasitic thread-like round nematodes that cause a group of tropical infectious diseases called Filariasis.

• The larvae are transmitted to humans through a mosquito bite.

• Filariasis is characterized by fever, chills, headache, and skin lesions in the early stages.

• If untreated, one type can progress to include gross enlargement of the limbs and genitalia in a condition called elephantiasis.

A person suffering from elephantiasis.

Dracunculus medinensis• Another filarial disease is caused

by the Guinea worm.• It infects people through the

crustacean cyclops.• Larvae from the cyclops, a

freshwater crustacean, are released when this creature is unknowingly swallowed while drinking water.

• Larvae develop in the intestinal wall and when mature (up to 120 cm long) the female moves under the skin to the persons leg.

• A blister develops here as the female releases her eggs.

• One of the most effective treatments is to curl the worm slowly up on a stick.

Ascaris

• Common parasite of humans. Enters the mouth via contaminated food, water or hands.

• Live in the small intestine.

Hookworm• This is a parasitic nematode that lives in the small intestine of its host, which may be a mammal such as a dog, cat, or human.

• It thrives in warm earth where temperatures are over 18°C.

• They exist primarily in sandy or loamy soil and cannot live in clay or muck.

• Rainfall averages must be more than 1000 mm (40 inches) a year.

• Infection of the host is by the larvae, not the eggs.

• the usual method of infection is through the skin; this is commonly caused by walking barefoot through areas contaminated with fecal matter

Hookworm cont.

• The larvae are able to penetrate the skin of the foot.

• Once inside the body, they migrate through the vascular system to the lungs.

• From there they move up the trachea, and are swallowed.

• They then pass down the esophagus and enter the digestive system, finishing their journey in the intestine, where the larvae mature into adult worms.[

A world wide problem

• The most significant risk of hookworm infection is anemia.

• The worms suck blood voraciously and damage the mucosa.

• However, the blood loss in the stools is not visibly apparent.

• Hookworm is a leading cause of maternal and child morbidity in the developing countries of the tropics and subtropics.

• It is estimated that between 576-740 million individuals are infected with hookworm today.

Annelids (latin – “little ring”)

• Since their larva are very similar to clams and snails annelids are probably more closer related to mollusks.

• Annelids are worms with segmented bodies.

• They have a true coelom that is lined with tissue derived from mesoderm.

• They have a tube –within–a-tube digestive tract.

• Three classes:• Oligochaetes – earthwoms• Leeches• Polychaetes – marine

annelids

Form and FunctionFeeding and Digestion

• The range from filter feeders to predators.

• In earthworms the pharynx pumps food and soil into a tube called the esophagus.

• The food then moves through the crop, where it can be stored.

• Next the gizzard grinds the food into smaller pieces.

• The food is absorbed in the intestine.

• Wastes pass out the anus.

Form and FunctionCirculation

• Closed circulatory system; Blood is within vessels.

• Two main vessels – dorsal moves blood to the head, ventral moves blood to the tail.

• Dorsal blood vessel functions like a heart.

• Oxygen is absorbed through the skin.

• Aquatic annelids have gills.

Form and FunctionExcretion

• Like other animals annelids produce 2 kinds of waste.

• Digestive wastes pass out the anus.

• Cellular waste is eliminated by nephridia.

• Nephridia filter the the fluid in the coelom

Form and FunctionNervous system

• Annelids have a well developed nervous system with a brain and several nerve cords.

• Sense organs are best developed in free-living marine annelids.

• Many of the marine worms have sensory tentacles, chemical receptors, statocysts or eyes.

Form and FunctionMovement• Annelids have two major

groups of muscles.• Longitudinal muscles –

run the length of the animal and can make it shorter and fatter.

• Circular muscles wrap around each segment and make the worm thinner and longer.

• The alternating use of these muscles allows the earthworm, with the help of the setae, to move through the soil.

Form and functionReproduction• Most annelids

reproduce sexually.• Some use external

fertilization and have separate sexes.

• Others are hermaphrodites.

• Earthworms are hermaphrodites.

• When eggs are ready for fertilization a clitellum secrtetes a mucus ring into which the eggs and sperm are released.

• Fertilization takes place within this ring.

Giatn gippsland earthworm of Australia

Class Hirudinea

• Leeches are annelids that are ectoparasites of other animals.

• They have been used for hundreds of years in medicine to allow a wound to not coagulate too quickly.

Terrestrial LeechesThis species feeds on earthworms.

Land LeechesLive in jungle areas of Asia and Australia

Will attach themselves to people as they walk through the jungle.

Class polychaeta

• Largest and oldest class of annelids.

• Include fan (C) and feather (B) worms and the birstle worm (A) seen in this slide.

• Touching the bristle worm causes the bristles to break off creating painful wounds.

Ecology of Annelids• Aerate and mix the soil

to a depth of 2 m or more.

• Tunnels provide passageways for roots and water.

• Allow the growth of beneficial oxygen requiring bacteria.

• They pull plant material down into the soil which helps it decompose.

• They bring minerals up from below and their castings are rich in nitrogen.

• The are an important part of the diet of many animals.

Mollusks• Soft body, often with an internal or external shell.

• Gastropods, Cephalapods and Pelecypods (Bivalves)

• Octopus probably has largest and most complex brain of any invertebrate.

• Giant Squid (Architeuthis dux, 1878 - 55 ft.long - 4,400 lbs.

• Colossal Squid (Mesonychoteuthis hamiltoni larger but not longer and more rare.

MollusksForm and Function

• Largest marine phylum

• All have a mantle with a cavity used for breathing and excretion.

• The mantle in many mollusks secretes the shell. (CaCO3)

• All have at least two pairs of nerve cords.

• Most have a muscular foot.

• All mollusks have the same trochophore larva

Zebra Mussels• Originally native to

Russia• Introduced to the US in

ballast water in large cargo ships.

• With no native predators has caused lots of problems by literally covering all hard structures.

• Poses a threat to native mussels, intake pipes, boats and any other hard structure in the water.

• No known way to control the population.

Body Plan• Foot – muscular organ. In snails secretes mucus to aid movement. In clams is adapted for burrowing. In cephalopods it is used for jet propulsion and is the origin of the tentacles.

• Mantle – dorsal part of the body wall. Secretes shell and forms the mantle cavity.

• Shell – secreted from mantle, composed of chitin hardened with CaCO3

• Visceral mass – area below the mantle that contains the digestive, nervous and excretory organs

Feeding

• Clams – Filter feeders with incurrent and excurrent siphons.

• Snails- have a chitinous radula that is used to rasp bits of algae off of hard surfaces.

• Cephalopods – have a chitinous parrot like beak used to tear into prey.

Respiration, Circulation, Nervous, Movement

• Respiration is through gills except for terrestrial mollusks.

• Circulation – cephalopods closed, gastropods and bivalves open system.

• Nervous – ganglion/brain with a ventral nerve cord

• Movement – snails and clams via the foot, cephalopods incurrent and excurrent siphon.

Reproduction

• Gastropods – hemaphroditic, but exchange sex cells

• Bivalves – mostly separate sexes

• Cephalopods – separate sexes

• All except cephalopods have a trocophore larval stage.

Gastropods

Flamingo tongue snail Sea Slug

Bivalves

Scallop Giant Clam

Cephalopods

Northern Giant Octopus Humboldt Squid

The Giant Squid Architeuthis dux

• This is a picture of an adult female Giant Squid that washed ashore on the coast of Tasmania in July 2002.

• She weighed 550 lbs. And total tentacle length was estimated at 50 feet

Colossal Squid Mesonychoteuthis hamiltoni

• Very rare. This picture is of a subadult accidentally caught on a long line in antarctic waters

• Suckers on tentacles are enhanced by strong hooks.

• Suspected to grow to 50 feet or more.

Colossal Squid

• This picture is of the animals beak which is exceptionally large and strong.

• 6 specimens are known excluding this one, with five coming from sperm whale stomachs.

Colossal Squid tentacles

• Another look at the hooked tentacles of the Colossal Squid.

Hypothetical sizes(note Sperm Whale should be increased

to 25 meters)

Mollusks (Squid, octopi, and nautaloids)

• North Pacific Octopus is the largest.

• 23 ft radial spread and 118 lbs.

Cephalopods have separate sexes

Mollusks - Gastropods

• Literally means stomach footed. This class includes snails, conchs and slugs.

• This picture shows a conch which is a species of marine snail. They are such a popular food that in many areas they have to be protected.

Mollusks Bivalves

• This class includes animals with two shells. (Clams, mussels, scallops,etc.)

• The Giant Clam can weigh over 500 lbs. And be more than 3.5 feet long.

• It is grown as a food crop in the South Pacific.

Ecology of Mollusks

• Clams, as filter feeders, help to clean up the water.

• Others assist in eating and disposing of detritus.

• Many species are important sources of food for people.

• Are hosts to parasites or are parasites themselves.

Arthropods – “jointed feet”• Examples include crabs,

shrimp, spiders, scorpions, butterflies and daphnia!

• 750,000 species.• More than 3X the number

of all the others combined!

• Like annelids, arthropods are composed of body segments.

• Evolution of arthropods has led to fewer body segments and specialized appendages for feeding, movement and defense.

• Cambrian arthropods include trilobites.

Form and Function Feeding and Feeding

• Mouthparts have evolved to enable different species to eat almost any food imaginable.

• Include pincers, fangs, sickle shaped jaw and proboscis of various shapes.

• The army ant, pictured here, uses its jaws for defense!

Form and FunctionRespiration and

Circulation

• Terrestrial species breathe through a net work of branching tracheal tubes.

• Aquatic species use gills.

• Spiders use book lungs to breathe.

• They have an open circulatory system.

• A well developed heart pumps blood through arteries that branch and enter tissues.

• The blood recollects in a large sinus near the heart.

Spider anatomy – book lungs

Crayfish gills

Form and FunctionExcretion

• Terrestrial arthropods use malpighian tubules to filter nitrogenous wastes from the blood.

• In aquatic species diffusion moves these wastes from the body to the water.

Form and FunctionResponse/Nervous

• Well developed nervous system with a brain and a ventral nerve cord.

• Along the nerve cord are several ganglia which help to coordinate the movements of individual legs and wings.

• Most have sophisticated sense organs such as compound eyes.

Form and Functionmovement /

exoskeletons, chitin

• Arthropods have well developed muscle tissue that pull across the joints of the exoskeleton.

• The muscles are grouped in opposing pairs so one group can undo (flex) what the other group does extend)!

• The exoskeleton is made up of the polysaacharide chitin.

Reproduction

• Terrestrial species have internal fertilization.

• The male either deposits the sperm in the females body or leaves it in a packet to be picked up by her.

• Aquatic species have internal and external fertilization.

Growth and Development

• Exoskeletons do not grow.

• As the arthropod grows it will molt (shed its skin) and manufactures a larger one to take its place.

• Molting is controlled by the endocrine system which uses hormones.

• Skin glands digest the old exoskeleton.

• The new one can take several hours to develop and harden.

Complete metamorphosis

• Process of growth and development where the larval form looks nothing like the adult.

• Usually there is a resting state in a pupa, chrysalis or cocoon.

• Bees, moths, butterflies, ants, and beetles undergo complete metamophosis.

Incomplete metamorphosis

• This process proceeds from an egg to nymph to adult.

• Grasshoppers, crickets and boxelder bugs undergo this process.

• There may be several nymph stages.

Class Crustacea

Two body regions, cephalothorax and abdomen.

At least one pair of mandibles

Swimmerets - specialized appendages used for swimming.

Includes crayfish, crabs, lobsters, shrimp, barnacles, copepods, daphnia and sow bugs

Crayfish external anatomyPhylum – Arthropoda subphylum - crustacea

Crayfish internal anatomy – this view is below the gills.

6 species of Crayfish live in Minnesota with one species, the Rusty Crayfish, being an introduced invasive pest. The northern or Virile

crayfish, listed below is common in Minnesota and attains a length up to 145 mm (14.5 cm or nearly 6 in. long)

Pillbugs

• Pillbugs are land crustaceans with a rounder back and deeper body than sowbugs.

• When disturbed they can roll into a tight ball like an armadillo

• They have gills which need constant moisture so they live in moist, humid areas

• They are nocturnal, eating decaying plant material

Sowbugs

• Sowbugs are land crustaceans which look a lot like pillbugs.

• They have 7 pairs of legs and reach a length of 15 mm.

• They also have gills and feed on decaying plants and young plant shoots.

Class Arachnida• Includes spiders, scorpions, mites and ticks.

• Two body segments, fangs and pedipalps, book lungs and Malphigian tubules.

• Two general groups, wolf spiders and orb weavers.

• All have a poisonous bite, but few actually bite.

• In the US the black widow and the brown recluse are the most dangerous.

Wolf Spiders

• Minnesota Fishing Spider or Dock Spider is the largest spider in the state with a body length of 1 inch and a leg span of 3 inches

• Very active hunters patrolling rocks and docks near the waters edge.

• They have been seen running across the water to catch minnows, frogs and tadpoles.

• They will give a painful bite if handled roughly.

Orb Weavers

• Spin a web and wait for prey to become entangled.

• Poisonous bite paralyzes prey.

• Male usually much smaller.

• Black widow is most poisonous in US and will venture into garages and basements in the southern US

Brown Recluse Spider

• Very shy with a violin shaped marking on the back.

• Body 1/4 to 1/2 inch long, legs and body cover an area the size of a quarter.

• Most poisonous spider in MN

Class Arachnida sub-class solfugae (Sun Spiders)

Sun spider chelicerae

Class Insecta• 3/4 of all known species.

• 3 body regions, head, thorax and abdomen.

• Three pairs of legs attached to the thorax.

• Wings are made of chitin as well as the exoskeleton.

• Have mouthparts designed for their food.

• Can communicate with sounds or pheromones.

Red Admiral• Wingspan 2.0 -2.3 in.• Hibernates in MN• Caterpillar feeds on

Nettles, Hops and baby tears.

• They use a few strands of silk to draw the leaf together in a tube.

• Adults feed on the nectar of lilacs, butterflybush and other flowers.

Mosquito

• Adult female feeds on blood to help nourish developing eggs in her body. Males feed on flower nectar.

• Eggs are laid in water and larva hatch and eat algae in water, breathing through a tube which extends to surface of water.

Termites

• Social insects with different forms having specific jobs in the colony.

• Can eat wood, because of microbe in the gut.

• One of the chief producers of methane gas on the planet.

Hornets (Yellowjackets)

• These are not bees!!• They can sting several

times, since stinger is not barbed.

• Eat nectar and decaying plant and animal material. Become aggressive and persistent towards the end of summer.

Chilopoda

• Can have up to 100 pairs of legs.

• One pair of legs for each body segment.

• Their spiracles do not close and their exoskeleton is not water proof.

• They tend to live in warm, moist areas.

• Claws located near the head are often poisonous.

Diplopoda – the millipedes

• Each segment has two pairs of legs.

• Tend to be vegetarians.

• Will roll up in a ball when disturbed.

• Some species protect themselves by secreting unpleasant chemicals.

• Harmless vegetarians for the most part.

Echinoderms

• Spiny skinned animals, internal skeleton, water vascular system and tube feet.

• Most have 5 part symmetry.

• Include Starfish, Brittle Stars, Sea Cucumbers, Sea Urchins, Crinoids and Sand Dollars

• Largest phylum to not include any freshwater or terrestrial representatives.

• Radial symmetry

• Tube feet

• Nerve ring and chords in arms.

• Largest 54 inch diameter and 13 lbs.

Starfish

• Usually has 5 arms.

• Mouth and anus on ventral side close to each other.

• Pedicallaria, tiny pincer-like structures keep the arms free of algae.

• They are carnivorous eating sponges, bryozoans, ascidians and molluscs.

Echinoderms – Form and Function

• Respiration through tube feet.

• Digestive wastes through anus.

• Ammonia released through tube feet.

• Nerve ring with nerve cords down the arms.

• Scattered cells that are sensitive to light, chemicals and gravity.

• External Fertilization. • Swimming larva settles to

bottom and grows into adult.• Larva have bilateral

symmetry!

Sea Lillys• Cup shaped body with

feather like arms protruding from a central disk.

• Mouth and anus on the upper side of disk

• Usually anchored to bottom, they can crawl, swim, roll or walk to new areas.

• They feed on planktonic animals that they catch with their feathery arms.

Sea Cucumbers

• Bilateral symmetry with a mouth at one end and an anus at the other.

• Flexible muscular body, with numerous modified tube feet around the mouth which function in food gathering.

• Most of them crawl over the bottom ingesting sand and digesting organic material from the sand.

• When attacked they excrete a thread like material that is part of their digestive system. This tissue is very toxic and usually discourages the attacker.

A few different sea cucumbers

Crown of Thorns Starfish

• This starfish eats coral polyps.

• It has damaged extensive areas of the Great Barrier Reef.

• It seems as if there numbers have decreased lately.

Sea Urchins

• Radial symmetry with a ventral mouth containing a jaw and horny teeth.

• Anus is on the upper surface.

• Movable spines are attached to the body and some are poisonous

• Movement is by tube feet.• They eat algae, detritus,

sponges and ascidians

Sand Dollars

• Sand Dollars are specialized Sea urchins that bury themselves in sand and eat decaying organic material that they find there.

Brittle Stars

• Close relatives of Starfish, they have no anus, wastes are eliminated through the ventral mouth.

• They feed on small invertebrates, plankton and organic material they find on other animals.