Phylum Echinodermata
- 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.
- Include sea stars
- Usually have 5 arms radiating from central disk
- Tube feet located underneath each arm used for locomotion & grasping prey
- Feed on mollusks by pulling shells apart and extending stomach outside the mouth into the bivalve. The bivalve is digested within it's shell.
Internal anatomy of a seastar
Feeding
nSeastars 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
Reproduction
nCan reproduce sexually by releasing sperm and egg.
nCan reproduce by regeneration
Class Ophiuroidea
- Include Brittle Stars
- Distinct central disks with long tube-like arms
- Lack suckers
- Move by serpentine motion of their arms
- Are usually deep ocean scavengers
Class Echinoidea
- Include Sea urchins & sand dollars
- Lack arms, but possess tube feet
- Many species of urchins possess poisonous spines used for defense
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
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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