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 Echinodermata
The Phylum Echinodermata has six classes:
- Class Crinoidea - sea lillies and feather stars
- Class Concentricycloidea - sea daisies
- Class Holothuroidea - sea cucumbers
- Class Ophiuroidea - brittle stars
and basket stars
- Class Asteroidea - sea stars
- Class Echinoidea - sea urchins and
sand dollars
There are approximately 7,000 species and all but a rare
few are marine.
Characterists include:
- Spiny endoskeleton (internal skeleton) composed of ossicles
or plates
- Radial symmetry in adults - can meet the environment 360
degrees
- Bilateral symmetry in larvae
- Pedicellaria - microscopic pincher like arms on aboral side
- No cephalization (no head)
- Gonochoristic (sexes are separate)
- Some species are hermaphroditic (both sexes)
- Mass Spawning (chemical que in water to trigger others to
spawn - advantage less energy - disadvantage goes directly into
water not as good of chance of fertilization)
- Almost all are benthic (don't swim or float)
- Water Vascular system (consisting of stone canal, madreporite,
radial canal, ring canal and tube feet)
- Most are capable of regeneration
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