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