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

Phylum Echinodermata Characteristics Adults have pentaradial ( 5 part) symmetry Capable of extensive regeneration

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

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

Sea Cucumber – degenerated & buried in leathery body

B. Water Vascular System 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 Used in locomotion, food capture, & respiration

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

ECHINODERM TYPES

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

Body Plan 2 – 4 rows of tube feet on each ray extend from ambulacral groove

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

Water Vascular System Water enters madreporite on aboral surface into a short, straight stone canal Stone canal connects to circular canal around the mouth = ring canal. Enters five radial canals extending down each arm

Water Vascular System Radial canals carry water to hundreds of paired tube feet. Bulb-like sacs or ampulla on tube feet contract & create suction

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 (their larval stage is planktonic)

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

BRITTLE STAR LARVA

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

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

Eject internal organs to scare predators (evisceration) ; regenerate in days Symbiosis with Pearl Fish which lives in its anus. Feed on gonads by day

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

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

Tube feet – moving, capturing food Pedicellarea – cleaning & defense Aristotle’s Lantern – 5 teeth together like bird’s beak; to scrape algae from rocks

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