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

Zonation | Intertidal Pools | Collection Etiquette

Kelp & Algae | Fungi | Porifera | Cnidaria

Mollusca | Echinodermata | Osteichthyes

Tides | References