Phylum Echinodermata “Spiny – skin”

4 key characteristics Radially symmetrical Endoskeleton Water Vascular System Tube-feet

Key characteristics “Spiny – skin” No head or sign of cephalization “Spines” protrude through skin Calcium carbonate plates Pedicellaria No head or sign of cephalization Oral vs Aboral surface

Development Radially symmetrical (Penta - 5 parts) Except bilaterally symmetrical larvae Bipinnaria Deuterostomes Blastopore develops into anus

Water – vascular system Consists of Tube feet Ampullae (muscular sac) Madreporite (sieve plate)

Water Vascular System Movement Madreporite Stone canal Ring canal Radial canal Ampullae Muscle contraction Water forced into tube feet

Biology of Echinoderms Complete digestive tract and coelom Feeding and Digestion Cardiac stomach (invert into prey) Pyloric stomach (digestive glands) Nutrients transported by coelomic fluid

Biology of Echinoderms Nervous system Little known about nervous system Reminiscent of nerve net Nerve ring and radial nerve Reproduction Separate sexes External fertilization Regeneration

Other body systems No circulatory, excretory, respiratory organ systems Coelomic fluid bathes organs with nutrients and oxygen Gas exchange and excretion of waste diffusion through the tube feet and skin gills

Types of Echinoderms Class Asteriodea (sea stars) Class Ophiuroidea (brittle stars) Class Echinoidea (sea urchins and sand dollars) Class Holothuroidea (sea cucumbers) Class Crinoidea (feather stars and sea lilies)

Class Crinoidea (feather stars and sea lilies) Resemble ancestral echinoderms Mucus covered feet, filter food Sea lilies Sessile and have stalk Feather stars Can swim or crawl as adults

Class Ophiuroidea Brittle stars and basket stars “Snake – like” Long brittle arms for quick movement and filter water Benthic (bottom dwellers)

Class Echinoidea Spine – like Sea urchins and sand dollars Internal organs are enclosed in a test Sea Urchins Move tube feet, feed by scraping algae Long spines Sand dollars Flat, round shape, shallow Tube feet capture food as its passes over them

Class Echinoidea

Class Holothuroidea Sea Cucumbers Armless, benthic Modified tube feet form tentacles around mouth

Class Asteroidea Sea stars or starfish