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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 Stone Canal Ring Canal
Radial Canal Ampulla 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 in sand or under
objects
• 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 like arms used for suspension
feeding
– 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