Phylum Echinodermata Starfish, sea urchins, sand dollars, sea cucumbers, brittle stars, basket stars, sea lilies, feather stars

Phylum Echinodermata “Spiny skin” 5800 species Most exhibit radial symmetry Most have an endoskeleton of plates call ossicles Unique water vascular system

Starfish 5 or more arms tapering gradually from a central disc.

Water Vascular System Series of canals and tubules for locomotion and food capture Opens at the sieve plate on the dorsal surface Controls water pressure in the tube feet

Tube Feet Found in deep groves along the lower surface of the echinoderms rays Joined by water canal that extends along the starfish rays to the ring canal within the central disc Uses suction to grip onto things

Nutrition and Digestion Uses tube feet to grab and pry open clams and oysters Can extrude its stomach through its mouth which is located in the center of the ventral side and begin digestion externally.

Repiration/Circulation and Excretion Skin gills, which are projections of the coelom, allow oxygen to be exchanged through the skin and waste to diffuse out. Amoebocytes move through the fluid filled coelom and pick up waste. Amoebocytes leave through the skin gills carrying the waste with them.

Reproduction Separate sexes Sexual reproduction through external fertilization Regeneration Regenerates lost rays A ray can grow into a whole new starfish as long as it contains a small portion of the central disc Ciliated larvae has bilateral symmetry

Nervous System No brain or head, but does contain a nerve ring and nerve net, coordinates movement and transmits information from light sensitive eyespots at the end of each arm

Ecological Impact Hard to control Can destroy a commercial shellfish bed in a short time Some species eat coral polyps http://www.youtube.com/watch?v=D3W4OCnHyCs http://www.youtube.com/watch?v=HG17TsgV_qI