Class Asteroidea Pedicellariae Tiny pincher-like organs on the aboral side keep the surface clean Most sea stars are predators of bivalves, snails, or other attached or slow moving animals

Class Ophiuroidea Includes: Brittle Stars Legs proportionally longer and thinner than sea stars Allows for better movement Organs in central disc Tube feet lack suckers

Class Ophiuroidea Eat organic matter and small animals they find on the bottom

Class Echinoidea Includes: Sea Urchins & Sand Dollars Body structure forms a round, rigid body with movable spines and pedicellariae Locomotion achieved by movable spines

Class Echinoidea Body plan of sea stars repeated by moving arms upward and connecting them at the tips Mouth is on the bottom, anus on the top Spines: sharp, hollow and sometime contain venom

Plates: 10 plates Alternating abulacral (have openings for tube feet) and interambulacral (bumps for spines)

Class Echinoidea The mouth has an intricate system of jaws and muscles called Aristotle’s Lantern Used to bite off algae and other bits of food from the bottom

Class Echinoidea Heart Urchins and Sand Dollars are adapted for the soft bottom of the ocean Flat bodies and short spines

Class Holothuroidea Sea Cucumbers Similar body plan to a sea urchin, just stretched out from mouth to anus Lies on sides, oral and aboral surfaces are at the ends

Class Holothuroidea Most have five rows of tube foot that run mouth to anus Some excrete toxic substance as defense mechanism Some expulse gut and other internal organs out of the mouth or anus, called evisceration Believe that they grow the organs back