Phylum Echinodermata Introduction

There are ______ characteristics of echinoderms. All echinoderms have: Spiny skin An internal skeleton A five part body A water vascular system Tube feet

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

General Characteristics Adults exhibit pentamerous radial symmetry Radially symmetry is secondary; larvae are bilaterally symmetrical and undergo metamorphosis to become radially symmetrical adults. Echinoderm larva

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

Water Vascular System On the aboral surface is the opening of the water vascular system the madreporite (=sieve plate) Water enters the madreporite and goes through the stone canal canal to the ring canal Water then passes through a radial canal extending into each arm All along the length of these canals are lateral canals that terminate in a bulb-like structures called ampullae equipped with tube feet Tube feet line the grooves on the oral surface - ambulacral grooves

* All echinoderms have __________. Some of them have small hair-like spines, like the starfish. * Some echinoderms have long spines, like the sea urchin.

How the Podia Operate Ampulla contract and force fluid into the podia causing it to become extended Suckers at the tips of the podia come into contact with the substrate and adhere to the surface Then the podia contract, thereby forcing water back into the ampulla, and the body is pulled forward

Class Asteroidea True Starfishes

Asteroidea (“star-like”)  starfish or sea stars belong in this class  found all over coastal shores around the world  prey on oysters, clams, and other sea food that is used by people

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

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

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 –no special organs –across body membranes Nervous System –associated with epidermis –circular oral nerve ring with branches into arms Class Asteroidea Systems

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 Body wall

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 Asteroidea Reproduction

Class Ophiuroidea Brittle Starfishes

Ophiuroidea (“snakelike”)  largest echinoderm class  includes basket stars & brittle stars  primarily reside under stones & in crevices and holes of coral reefs  have thin brittle arms that break off & regenerate themselves quickly  feed by raking food off the ocean floor with their arms and bottom of tube feet  also trap food with mucous strands between their spines.

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 Ophiuroidea Brittle Starfishes and Basket Stars

Class Echinoidea sea urchins, sea bisquits, sand dollars

Echinoidea (“hedgehoglike”)  sand dollars & sea urchins  test: rigid endoskeleton that the internal organs are compacted in  Aristotle’s lantern: complex jaw-like mechanism that is used to grind their food  locomotion: tube feet  protection: barbs on their long spines that are sometimes venomous

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

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 Holothuroidea Sea cucumbers

Class Crinoidea Sea Lillies

Crinoidea (“lilylike”)  They include:  Sea lilies  Feather stars  Crinoidea are sessile  they have long stalks that attach to rocks or to the ocean floor  feather stars eventually detach themselves  Sticky tube feet that are at the end of each arm catch food and serve as a respiratory surface.

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 Class Crinoidea Sea Lillies