The Echinoderms (‘spiny skin’)

*Phylum Echinodermata

*pentaradially symmetrical (bilateral in larvae)*Composed of ~6000 living species*Since the skeleton is composed of living

tissue they have an endoskeleton made of ossicles (calcium carbonate plates)*Echinoderms have a water-vascular system:*Fluid-filled hydraulic system (controls all the

tube feet), also used in gas exchange and circulation*Water enters the water-vascular system

through a sieve-like plate called the madreporite

*All systems of an echinoderm radiate from the center*Capable of regeneration

*Gas exchange: through the skin, may have gills*Circulation: open within the coelom (body cavity)*Excretion: through the skin, gills, and anus*Digestion/feeding: complete digestive system, stomach

can be pushed out of body to digest food*Reproduction: sexual, can be hermaphroditic*Response to environment: no advanced eyes but sea

cucumber can release sticky intestines when threatened*Movement: water-vascular system (tube feet)

*Tube foot: used for locomotion*Like a network of plungers and straws combined, working in

concert they move the individual slowly*Individually they are weak but as a team they are very

strong!

*Sea star anatomy:

*Composed of 5 extant classes: Asteroidea, sea stars

*Composed of 5 extant classes: Holothuroidea*Sea cucumbers

*Composed of 5 extant classes: Echinoidea*Urchins and Sand Dollars

*Composed of 5 extant classes: Crinoidea*Feather stars

*Composed of 5 extant classes: Ophiuroidea*Brittle Stars