Echinoderms

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Echinoderms
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Phylum Echindermata

• Share common features with chordates
• Radial Cleavage
• Deuterostomes (Blastopore becomes anus)
• Development of true coeloem
• Usually slow moving or sessile
• Usually are radially symmetrical
• Body parts usually radiate from center
  (frequently as 5 spokes)
• Possess a thick calcium plate endoskeleton
  surrounded by a thin skin layer
• Possess a unique Water Vascular System, which
  continues throughout animal and extends into
  extensions called Tube Feet.
• Functions for locomotion, feeding, gas
  exchange.
• Reproduce sexually or through regeneration.

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Class Asteroidea

• Include sea stars
• Usually have 5 (or multiple of 5) arms radiating
  from central disk
• Tube feet located underneath each arm used for
  locomotion grasping prey. Operate by hydraulic
  principles.

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Anatomy of a Sea Star
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Feeding

• Feed on mollusks by pulling shells apart and
  extending stomach outside the mouth into the
  bivalve. The bivalve is digested within it's
  shell. The sea star than re-ingests its stomach

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Reproduction

• Can reproduce sexually by releasing sperm and
  egg.
• Can reproduce by regeneration

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Sea Stars
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Class Ophiuroidea

• Include Brittle Stars
• Distinct central disks with long tube-like arms
• Lack suckers
• Move by serpentine motion of their arms

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Brittle Star
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Class Echinoidea

• Include Sea urchins sand dollars
• Lack arms, but possess tube feet
• Many species of urchins possess poisonous spines
  used for defense

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Echinoideans
Sand Dollar
Sea Urchin
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Class Holothuroidea

• Include Sea cucumbers
• Are elongated along oral-anal axis
• Lack spines and have reduced endoskeleton.
• Do possess tube feet and water vascular system

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Sea Cucumber
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Class Crinoidia

• Ancient class of animals
• Include sea lilies
• Filter feeders with arms radiating from mouth
• Most are sessile, but some can move

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Crinoids