Phylum Echinodermata – “spiny skin” sea stars, sea urchins, sea cucumbers a return to radial symmetry; larvae are bilateral most have arms and/or body parts in multiples of 5 have endoskeleton (test) water vascular system; tube feet are an extension of this system some are predatory (sea stars); some algae feeders (sea urchins); some deposit feeders (sea cucumbers); suspension feeders (feather and basket stars)

Class Asteroidea – sea stars  - most have 5 broad arms radiating from a central disc  - hundreds of tube feet radiate from ambulacral grooves  - some spines are modified into pedicellariae, pincer- like organs keeping surface clean  - predatory on bivales, snails, or other sessile and slow moving animals

Figure 14_08

Class Ophiuroidea – brittle stars and basket stars  - arms sharply demarcated from central disk  - arms used for movement; tube feet for feeding  - feed primarily on detritus; move food particles from foot to foot towards mouth  - often well hid under rocks, corals, or in sand/mud

Class Echinoidea – sea urchins - endoskeleton forms round shell-like test with moveable spines - most are grazers feeding on algae - have specialized mouth parts called Aristotle’s lantern for scraping algae - sea biscuits (heart urchins) and sand dollars are more flattened, living on and within soft sediments

Class Holothuroidea – sea cucumbers - elongated and worm-like with 5 rows of tube feet on bottom - deposit feeders; tube feet around mouth modified to collect particles of food - defense includes toxins, release of sticky filaments or evisceration

Class Crinoidea – feather stars, sea lilies - suspension feeders using feathery, outstretched arms - feather stars crawl and perch on hard surfaces for feeding - Sea lilies are sessile usually in deep water