Unit V: Marine Biology
Section 3: Echinodermata
I. Echinodermata
A. General Characteristics
1. echinoderm = spiny skin
2. ~ 6,000 species/all marine
3. radial symmetry as adults (bilateral as larvae)
a. pentamerous (5 parts)
4. oral vs aboral sides
5. endoskeleton - calcium carbon units called ossicles in the
form of rods or plates
6. water vascular system - hydraulic system for tube feet
7. Ex: sea stars, sea urchins, sea cucumbers, brittle stars
sea lilies - divided into 5 classes
II. Water vascular system
A. Terms: tube foot, podium, ampulla, radial canal, ring
canal, stone canal, madreporite, ambulacral groove (diagram)
Anatomy of Water Vascular System:
B. Process
1. madreporite (continuous with tube feet) regulates amount of
water in system
2. ampulla above each tube foot acts as a squeeze bulb
3. when ampulla contracts - water is forced into the foot - foot
4. longitudinal muscles of tube foot contract - shortening tube causing suction
5. coordination of tube feet allow for locomotion and feeding
III. Physiology of Echinoderms (Sea stars)
A. Feeding/Digestion
1. predators of bivalves, snails, (slow moving/attached
2. Using tube feet in relays - fatigue clam - evert stomach
- digest food (large digestive glands) - stomach pulled
back in.
B. Circulation
1. nutrients are transported in the fluid (coelomic fluid)
that fills the body cavity (coelom)
C. Respiration
1. outpockets of the epidermis called skin gills carry out
respiration by diffusion
D. Nervous
1. no centralized nervous system
2. nerve ring/radial nerves
3. light sensitive cells clustered at each arm
E. Reproduction
1. external fertilization
2. bipinnaria larvae
IV Significance
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