GENERAL CHARACTERISTICS Ex: sea stars, brittle stars, sand dollars, sea urchins, & sea cucumbers All marine “Spiny-Skinned Animals” Radial Symmetry as adults – 5 parts Regenerate = Autotomy

GENERAL MORPHOLOGY A. INTERNAL SKELETON of Calcareous ossicles (plates) Variations : Brittle / Sea Stars – many small plates that move with one another

Sea Urchin & Sand Dollar – skeleton plates fused into Sea Urchin & Sand Dollar – skeleton plates fused into shell called “test”

Sea Cucumber – degenerated & buried in leathery body

B. Water Vascular System Used in locomotion, food capture, & respiration Network of canals – run throughout body ending w/tube feet Varying internal water pressure can extend or contract tube feet Tube feet end in small suction cups

C. Mouth on oral surface (bottom / ventral) Anus on aboral surface (top / dorsal)

SEA STARS 5 Arms / Rays 4 – 10” Prey on bivalves (clams, mussels) & coral Many eat w/stomach outside body; pop stomach out mouth

Have pedicellariae or tiny, forceps-like structures on aboral surf Have pedicellariae or tiny, forceps-like structures on aboral surf. to pick up & remove dirt

Other Body Systems No circulatory, excretory, or respiratory systems No head or brain Eyespots on the tips of each arm detect light

Reproduction Separate sexes External fertilization Females produce 200,000,000 eggs / season; meroplankton

BRITTLE STARS Most mobile; fast Snake-like movement Disc .4 – 1.2 “; arms 2 – 2.4 “ Scavengers In largest class (with basket stars) Arms break off readily

SEA CUCUMBERS Lack arms & visible spines; elongated Flexible, leathery body Burrowers

5 rows of tube feet run length of body 10-30 modified tube feet form tentacles around mouth Tentacles have sticky ends to trap plankton; or eat detritus Breathes through anus

Sea lilies & feather stars Filter Feeders Can detach & move around

Sea Urchins Spines for protection, moving, trapping food Shell = test Divided into 10 sections 5 Ambulacral w/tube feet 5 Interambulacral without Covered w/muscle & skin to help mobility

Sand Dollars Flattened version of urchin Live in sand along coastlines Food falls between dense spines & carried to mouth by cilia & tube feet          Tiny, moveable spines for burrowing Aristotle’s Lantern

Sea Biscuits Not as flat as dollars Live in sand along coastlines; burrow Tube feet for respiration Pedicellarea Eat detritus in sand    Short dense spines for movement cover test