Phylum EchinodermataChapter 28.4Please set up your notebook for Cornell Notes

EchinodermsCharacteristics

Have endoskeleton, water vascular system, spiny skin, 5 part radial symmetry, tube feet and larva are bilaterally symmetricalDeuterostome

Form and FunctionWater vascular system fluid-filled, carries out respiration, circulation and movement

Madreporite opening to water vascular system

Connects to a ring canal that forms a circle around the mouthRing canal branches out to 5 radial canalsTube feet attach to radial canal

Works like a suction cup

FeedingSea urchins use 5 part jaw-like structures to scrape algae from rocks, or eat kelpSea lilies use tube feet to get planktonSea cucumbers scavenge on ocean floorSea stars open shells of mollusks, insert stomach, release digestive enzymes and suck out remains

Respiration and circulationMost respiration takes place using water vascular system

Some have small gillsCirculation takes place using water vascular system

ExcretionDigestive wastes exit anus

Ammonia waste diffused through tube feetResponse

Do not have highly developed nervous systemsSome sensory cellsNerve ring around mouth w/ nerves going down each arm

MovementDetermined by type of endoskeletonMost use tube feet

ReproductionExternalLarva are free-swimming, bilaterally symmetricalAdults live on ocean floor, radially symmetrical

Classes of EchinodermsClass Asteroidea sea stars

Radially symmetrical w/ 5 (or multiples of 5) armsMouth and anus together on ventral sideCan regenerate missing partsMostly carnivorous

Class Crinoidea feather stars, sea liliesRadially symmetrical, body is cup shaped w/ feathery arms projecting from central disk

Arms are called pinnules and are covered in sticky substance that catches passing particles (filter feeders)

Mouth and anus on dorsal side

Class Ophiuroidea brittle starsRadially symmetrical, central body with 5 snake-like armsNo anus, waste eliminated through ventral mouthArms break off to get away from predatorsEat mollusks, worms and crustaceans

Class Echinoidea sea urchins and sand dollars

Radially symmetrical w/ spiny (chitinous) skeletonMouth with teeth located ventrallyAnus on dorsal sideMove using tube feet and spinesMost grazed on algae but some eat sponges

Class Holothuroidea sea cucumbersBilaterally symmetrical, cucumber shaped w/ mouth at one end and anus at the otherEat sand and digest biological particles in it, then poop it outTentacles around mouth are modified tube feetTube feet on bottom move them forwardSome species have separate sexes, some are hermaphrodites