Ecinoderm

• •

Kingdom: Animalia Phylum: Enchinoderm

Body Plan

• • • • • • •

Levels of Organization: Specialized Cells, Tissues, and Organs Body Symmetry: Radial (as adults) Germ Layers: Three Body Cavity: True Coelom Embryological Development: Deuterostome Segmentation: Absent Cephalization: Absent

Characteristics

• • •

Regeneration All echinoderms exhibit fivefold radial symmetry in portions of their body at some stage of life Mesodermal skeleton composed of calcareous plates or ossicles

Characteristics

• •

Echinoderms possess a unique water vascular system.

–

a network of fluid-filled canals derived from the coeom Function in:

–

gas exchange

–

feeding

–

sensory reception

–

locomotion

Feeding

• •

Mouth on oral surface (bottom / ventral) Anus on aboral surface (top / dorsal)

http://www.youtube.com/watch?v=HG17TsgV_qI

• •

Respiration, Circulation, Excretion

Circulation - A Echinoderm has water pumped through its body as part of its very simple circulation system.

Respiration - A Echinoderm uses some of the bumps or spines on its surface to take in oxygen. It has a gill structure to take in the oxygen. It has a poorly developed respiratory system.

Response

• •

Water is pushed in and out of the system enabling the echinoderm to move Path of the water:

–

Madreporite



Radial Canal



Stone Canal



Ampulla



Ring Canal Tube Feet



Reproduction

•

Can reproduce asexually through regeneration.

•

Sexually: Fertilization is external

–

Few species are hermaphroditic

–

Starfish have either 2 testes or 2 ovaries per arm

Habitat

•

Marine waters – typically in shallow environments.

Classes

•

The 5 living classes of echinoderms are

–

Asteroidea (sea stars)

–

Crinoidea (sea lillies)

–

Echinoidea (sea urchins and sand dollars)

–

Holothuroidea (sea cucumbers)

–

Ophiuroidea (brittle stars and basket stars)

Class Asteroidea

• • • • Sea Stars Have five arms radiating from a central disc – Mouth (underside) – Anus (topside) – Madreporite (topside) Can regenerate a broken limb or even an entire body – Only if part of the central disc is intact Can take up to a year

Class Ophiuroidea

• Tube feet lack

suckers

and ampulla • 2000 species of brittle stars • Usually

concealed

objects in sand or under • Some live in sponges or other colonial organisms • Only 5 arms that are usually highly

branched

from central disk • Can

crawl/cling

• • Predators, scavengers, or

suspension

feeders

Flexible

arms bear suckerless podia that secrete

mucus

to entrap food and transport it to mouth

Class Crinoidea

• • Most

primitive Feather

feeding like arms used for suspension – Plankton • • Tube feet trap planktonic organism

Cilia

in ambulacral grooves carry food to mouth • Attach to

substrate

with stalk •

Sessile

sea lily • Cup-like body attached to stalk • Can bend stalk and flex/extend arms

Class Echinoidea

• Shell (test) encloses body – Ossicles form plates • • No arms Long spines – Movement –

Venom

• 1000 species of sea urchins/sand dollars • Movable spines and podia surround body; used for

locomotion

•

Herbivorous

,

detrivorous

, suspension feed, a few predators • Unique feeding apparatus called Aristotle’s lantern • Hard plates and muscles just inside mouth • Possesses 5 calcareous

teeth

• Teeth protract to

scrape

algae off rocks or tear chunks of kelp

http://www.youtube.com/watch?v=D3W4OCnHyCs

Class Holothuroidea

•

Soft

body with reduced ossicles • •

Tentacles

near mouth

Respiratory

tree – Breaths through

anus

• 1150 species of sea cucumbers • Mucus-covered oral tentacles

trap

on plankton or ingest sand organic matter • Gut modified to produce respiratory trees used for

gas

exchange • Expel portions of these trees as defense mechanism;

regenerate

http://www.youtube.com/watch?v=wXf_YodWw40