Echinoderms

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.

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.

Anatomy of a Sea Star

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

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

Sea Stars

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

Brittle Star

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

Echinoideans Sand Dollar Sea Urchin

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

Sea Cucumber

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

Crinoids