Echinoderms and their characteristics By Brittanie Sims
Common characteristics • Phylum Echinodermata. • Move by means of hundreds of hydraulic suction cup-tipped appendages. • Have skin covered with tiny, jaw-like pincers. • Found in all the oceans of the world. • All have endoskeletons. • Have radial symmetry. • Water vascular system helps with locomotion. • Only 6,000 species exist today.
Class Ophiuroidea • Brittle stars • Extremely fragile • Parts of its rays will break off, this adaptation helps them survive an attack by a predator. • A new ray will regenerate within weeks • Do not use their feet for locomotion • Propel themselves with the snakelike, slithering motion of their flexible rays. • Use their tube feet to pass particles of food along the rays and into the mouth in the central disk
Class Echinoidea • Sea urchins • Globe or disk shaped animals covered with pointed spines • Have long, slender tube feet, that, along with the spines, aid the animal in locomotion • Spines protect them from predators • In some species, sacs located near the tips of the spines contain a poisonous fluid that can be injected into the attacker
Class Holothuroidea • Sea cucumbers • More flexible than other echinoderms • Pull themselves along the ocean floor using tentacles and tube feet • When threatened, they exhibit a curious behavior. They may expel a tangled, sticky mass of tubes through the anus, or they may rupture, releasing some internal organs that are regenerated in a few weeks. • These actions confuse their predators • May reproduce by shedding eggs and sperm into the water
Class Crinoidea • Sea lilies and feather stars • Resemble plants in some ways • Sea lilies are the only sessile echinoderms • Feather stars are sessile only in larval form • The adult feather star uses its feathery arms to swim from place to place.