MarineBiology Chapter7 Echinoderms.ppt

EchinodermsChapter 7

Echinoderms: spiny-skinned animals that lack bodysegmentationgbut have radial symmetryyy ((usuallyy fivepart) and an internal skeleton.Placed in 5 main classes:1. sea stars2 sea urchins and sand dollars2.3. brittle stars4. sea lillies and feather stars5. sea cucumbersRadial symmetry: all similar body parts are regularlyarrangedd aroundd theth centralt l pointi t off an animal’si l’body.

Sea Stars Members of the class Asteroidea Found from the subtidal zone to the deepest parts ofthe ocean Usually have five (or multiples of five) appendages,or arms. Found in clam and/or mussel beds Regarded as pests by the seafood industry

Sun Star – prey on other sea starsor members of their own speciesWestcoastSeaStarAtlanticSeaStarBat Star

When an arm is lost, it can grow a new one but willbe noticeably shorter then the others. SpinesS iare composedd off calciuml icarbonatebt (CaCO(C CO3).)They help support and protect the organism. Spinespare connected to internal skeleton,,endoskeleton. Breathe through their skin and tube feet. Skin gills: small, ciliated, fingerlike projectionslocated on the dorsal surface of the skin. Oxygen diffuses through the thin membrane of thetube feet and skin gills and into the coelom. Coelom is lined with ciliated cells that beat back andforth to circulate oxygenated fluid. Cell waste and carbon dioxide diffuse from thecoelom through tube feet and skin cells.cells

Arms are used for locomotion and obtaining food. Atthe end of each foot is a suction disk for clinging toa surface.Water vascular system: network of fluid-filled canalsthat enables movement.Water enters through a small filter called the sieveplate or madreporite,madreporite located topside near its centercenter.The water then passes down through a short stonecanal, then into a circular ring canal within thecentralt l disk.di k ThenTh watert flowsflthroughthh theth radialdi lcanals.pstructure that resembles the rubber bulb on aAmpulla:medicine dropper. It fills with water from the radialcanal then contracts, forcing water into the tube feet.

Eyespots: tiny light receptors located at the end ofeach arm. Convert light energy into electricalimpulses and coordinate the movements of thearms. Have separate sexes and external fertilizationfertilization. Eacharm carries gonads. Has the ability to regenerate.

Sea Urchins and Sand Dollars Members of class Echinoidea. Movable spines are attached to its internal skeleton,which is formed by bony plates that are fused. Members are characterized by oval or round bodiesthat lack arms. Inhabit the intertidal and subtidal zones.zones Have a unique five-toothed mouth structure called anAristotle’s lantern (because of its resemblance to anancient Greek lantern). Sharp spines can inflict a painful wound and in somespecies contain toxinstoxins. Separate sexes and external fertilization.

Sand dollar: resembles a large coinand has short spines covering itsskin. Use their spines to burrow in thesand where they feed on planktonand organic debris. Have a well developed intestine andanus. When it dies,, its soft partpdecays,y ,the internal skeleton of calciumcarbonate remains.

Eccentric EchinodermsBrittle stars Class Ophiuroidea Nocturnal, bottom-dwelling animals that hide underrocks during the day. Found in the intertidal zone, from the arctic to thetropics.tropics Do not use tube feet for movement. Have muscles intheir arms for quick movement. They eat by either using their arms to gather organicdebris, to capture live invertebrates, to filter-feed, orto capture suspended food bits with their tube feet.feet

Sea Lilies and Feather Stars Members of class Crinoidea Most ancient group of Echinoderms, havingoriginated hundreds of millions of years ago Body is composed of dozens of feathery arms,usually perched atop a jointed stalk Sea lilies are sessile; feather stars crawl slowlyalong coral reefs. Some swim by flapping theirarms. Do not use their tube feet for locomotion

Sea cucumbers: ClassClHHolothuroideal thid Soft, oblong body which lack arms but has five rowsof tube feet Live on sandy and rocky seafloors in intertidal andsubtidal zones Use sticky, branching tentacles to trap microscopicorganisms It can release its digestive organs when disturbed bya predator.It later regenerates lost organs

Sea Urchins and Sand DollarsSea Urchins and Sand Dollars Members of class Echinoidea. Movable spines are attached to its internal skeleton, which is formed by bony plates that are fused. Members are characterized by oval or round bodies that lack arms. Inhabit the intertidal and subtidal zonesInhabit the intertidal and subtidal zones . .