Phylum Echinodermata Introduction

Echinodermata About 6000 species, all marine

Echinodermata Major characteristics secondary pentamerous radial symmetry internal skeleton water vascular system

Water Vascular System Madreporite stone canal ring canal radial canal lateral canals Ampulae tube feet

CLASSIFICATION OF ECHINODERMATA Class Asteroidea Class Ophiuroidea Class Echinoidea Class Holothuroidea Class Crinoidea

Class Asteroidea True Starfishes

Class Asteroidea True Starfishes arms not sharply delineated from central disc tube feet with suckers; used for Locomotion obtaining food madreporite and anus aborally located some have pedicellariae - jawlike appendages of epidermis

Class Asteroidea True Starfishes Feeding Mouth cardiac stomach- can be extruded pyloric stomach pyloric caecae Anus feed primarily on sessile organisms

Class Asteroidea Systems Circulation poorly developed with fluid filled chambers; no heart; coelom ciliated for fluid movement Excretion no special organs general diffusion across body surfaces like tube feet Respiration across body membranes Nervous System associated with epidermis circular oral nerve ring with branches into arms

Asteroidea Body wall Epidermis- outer surface; includes mucous cells epithelium Pedicellariae- jawlike appendages of the epidermis can open and close used to clean body of debris or put debris on body Dermis- includes nerve cells connective tissue Skeleton- below dermis made of ossicles lattice like connections Calcium carbonate with spines and tubercles Muscle layer- below dermis Peritoneum that lines coelom

Asteroidea Reproduction are dioecious; external fertilization usually 10 gonads; 2 in each arm have fissiparity- division of central disc into two animals

Asteroidea Reproduction free living larvae bipinnaria- first larval form develops into brachiolaria - shows development of arms

Class Ophiuroidea Brittle Starfishes

Class Ophiuroidea Brittle Starfishes and Basket Stars 5 arms usually central disc well marked off, no branches of gut in arms

Class Ophiuroidea Brittle Starfishes and Basket Stars no anus, no ambulacral groove madreporite on oral surface no suckers on tube feet, no ampullae (have a valve to control pressure) no pedicellariae able to move quickly and snake like hence their class name

Class Echinoidea sea urchins, sea bisquits, sand dollars

Class Echinoidea no arms skeleton is fused into a solid test tube feet have suckers covered with moveable spines and pedicellariae

Class Echinoidea specialized mouth structures - Aristotle's Lantern

Class Holothuroidea Sea cucumbers

Class Holothuroidea Sea cucumbers body elongated in oral-aboral axis skeletal system reduced or absent no spines or pedicellariae mouth and anus at opposite ends of body

Class Holothuroidea Sea cucumbers no external madreporite tube feet with suckers respiration through anal respiratory tree dioecious; single gonad suspension or detritus feeders commensal relationship with pearl fish

Class Crinoidea Sea Lillies

Class Crinoidea Sea Lillies most are extinct most primative all sessile, with stalk that attaches to substrate have branched arms for filter feeding no suckers on tube feet no madreporite no pedicellariae