Echinoderms

• Echinoderms


  Radially symmetrical organisms, like cnidarians and comb jellies
• Echinoderms


  • Radial symmetry is only a secondary development
  • Lack a head
  • Have a complete digestive tract, a well-developed coelom, and an internal skeleton
  • Have a unique water vascular system and tube feet
• Types of Echinoderms


  • Sea Stars (class Asteroidea)
  • Brittle stars (class Ophiuroidea)
  • Sea Urchins (class Echinoidea)
  • Sea Cucumbers (class Holothuroidea)
  • Crinoids (class Crinoidea)
• Sea Stars


  • Clearly display the distinctive echinoderm body plan
• Brittle Stars


  • Have a star shaped body architecture with long, very flexible, and sharply demarcated arms from the central disk
• Sea Urchins


  • Have an endoskeleton that forms a round, rigid, shell-like test with movable spines and pedicellariae
• Sea Cucumbers


  • Are superficially worm-like, do not have spines, and lack an obvious radial symmetry
• Crinoids


  • Are suspension feeders that use outstretched, feathery arms to obtain food from the water
• Feeding and Digestion in Echinoderms

  Most sea stars are carnivorous and feed by everting part of their stomach to envelop the food
• Nervous System and Behavior of Echinoderms

  • Have a nerve net that coordinates movements of tube feet and spines in the absence of a brain
• Reproduction and Life History of Echinoderms

  Sexes are separate, gonads shed sperm or eggs directly into the water, gametes do not survive long so individuals spawn all at once
• Echinoderms have a high ability to regenerate lost or damaged body parts