PHYLUM ECHINODERMATA (means spiny skinned) ex: seastars, sea urchins, sand dollars, sea cucumbers, sea lilies Seastars Characteristics: 1. Radial (pentamerous) symmetry 2. Internal skeleton (endoskeleton) 3. Complete digestive system 4. Water vascular system with tube feet (hold or sense) 5. Highly regenerative - can eviscerate 6. Separate sexes; external fertilization

PHYLUM ECHINODERMATA (means spiny skin) ex: seastars, sea urchins, sand dollars, sea cucumbers, sea lilies Why are they considered advanced? 1. endoskeleton of calcium carbonate plates 2. bilaterally symmetric larvae 3. water vascular system instead of muscles is a big advantage in predatory situations 4. highly regenerative - can regrow lost or damaged body parts 5. separate sexes; external fertilization

Why are they considered simple? 1. Light-sensitive eyes located at the end of each ray do not provide vision because there is no brain nor head. 2. They have reduced internal organs - no respiratory, circulatory, excretory. No nervous system. 3. Nerve net (no nervous system) – exhibit complex behavior 4. Adults have pentamerous (5-fold) radial symmetry (associated with sedentary lifestyle) 5. Respiration is by diffusion through the skin.

SEA STARS – ASTEROIDEA Seastars are predators and eat a variety of organisms. Sunflower Sea Star The seastar can open a clam shell a few millimeters wide. Then by everting its stomach into the shell, the clam is digested and absorbed. Sestar Eating Seastar Eating a Clam Missing parts from injuries or evisceration are quickly replaced. Any portion of the central disk will regenerate a new seastar - a fact that oyster fishermen learned too late!

BRITTLESTARS - OPHIUROIDEA Brittle stars have long flexible arms extending from a central disk Brittle stars eat particulate organic matter Gray Brittle Stars (Ophiura luetkenii) on the move

SEA URCHINS- ECHINOIDEA Sea urchins use tube feet and spines to move Sea urchins graze on seaweeds, seagrasses and algae Mouth has complex system of jaws & muscles – Aristotle’s Lantern Time Lapse of a Sand Dollar at Pismo Beach California Army of Sea Urchins - Planet Earth - BBC Wildlife

SEA CUCUMBERS - HOLOTHUROIDEA Sea cucumbers are deposit feeders -The Adventures of Sea Cucumber Sea Cucumber Sea Cucumber Fights with Guts (Literally) Some secrete toxic substances Some expel their gut and other internal organs - evisceration Missing parts from evisceration are quickly replaced

FEATHER STARS OR SEA LILIES- CRINOIDEA Crinoids are suspension feeders Sea lilies are deep water Feather stars perch and crawl on hard bottom shallow to deep water Upside down brittle star Feather Stars and Sea Lilies Crinoid - Feather Star Feeding

SEASTAR DISSECTION Seastar Dissection Seastar External Anatomy Seastar Anatomy Internal