Echinoderms

• Sea stars, sea urchins, and sea cucumbers belong to phylum Echinodermata (“spiny skin”, “hedgehog skin”)

• Exclusively marine• Adult echinoderms possess pentamerous

symmetry; in which the body is arranged in five parts around a central axis– No dorsal, ventral, anterior or posterior end; oral

and aboral ends only

Phylum Echinodermata

• Echinoderms have an internal skeleton, or endoskeleton covered by a bumpy, sometimes spiny, tissue layer

• Echinoderms have a network of water-filled canals connected to muscular tube feet, which extend when filled with water

• The vascular system connects to the outside environment via the madreporite on the aboral surface

Phylum Echinodermata

Types of EchinodermsSea stars can regenerate missing body parts

Brittle stars have long, flexible arms; most abundant group of Echinoderms

Sea urchins have a round, rigid test

Sea Urchin (class Echinoidea)

Types of Echinoderms

Sea cucumbers are worm-like; elongated along the oral-aboral axis, as if pulled/stretched from the mouth and anus

Crinoids use outstretched, feathery arms to capture food

particles from the water; includes feather stars and sea lilies