Coelomates: Protostomes and DeuterostomesProtostomes have spiral cleavage, the blastopore becomes themouth, mosaic development - mollusks, annelids, arthropodsDeuterostomes have radial cleavage, the blastopore becomes theanus, regulative development - echinoderms, chordates

spiral cleavage

radial cleavage

Protostomes

Deuterostomes

Phylum Echinodermata - Echinodermsincludes starfish, sea urchins,

sand dollars, sea cucumbers

Name means “spiny skin” - havehard endoskeleton, often with spinesbelow thin skin

Endoskeleton is made of calcium carbonate plates that form internallyPossess a unique water vascular system - a hydraulic system to aid

movement and circulationMouth opens ventrally in most - anus is dorsal

Adults have no head orbrain

Nervous system composed of circularnerve ring and radialbranches

Sexes are separateFertilization is externalGonads (ovaries and

testes) found in arms

Echinoderms exhibit radial symmetry as adults - but have a bilaterally symmetric larva

Transform to pentaradial symmetry as they mature

Radial symmetry works well for sessile organisms - primitive echinoderms (likesea lilies) are sessile

Bilateral larva thought to indicate that they originatedfrom a bilaterally symmetricancestor - original ancestor is uncertain

The Water Vascular SystemFive radial canals extend from a ring canal around the esophagusWater enters through madreporite, a sieve-like plateFlows to ring canal through the tubular stone canalRadial canals have lateral canals to tube-feetEach tube-foot has a muscular fluid-filled ampulla at its base

Operation of the water vascular systemAmpulla contracts, one way valve causes fluid to be forced into

tube-foot - results in extensionFoot can attach to substrate, sometimes with suction-cup tipLongitudinal muscles contract and shorten tube-footWater forced back into ampullaRepeated movement results in locomotion or manipulation of objects

Have large coelom, lined with ciliaHelps provide for circulation and

respirationIn most, respiration and waste removal

occur through skin gills (papulae) that project through skin

Endoskeleton composed of ossiclesMovable or fixed plates under skinTube feet extend through perforations

Reproduction - many species capable of extensive regenerationmay shed body parts when attacked -some reproduce asexually by splitting into parts

Sexual reproduction and fertilization is externalSexes are separate, have free-swimming bilaterally symmetric larva

There are Six Living Classes of EchinodermsCrinoidea - sea lilies and feather starsAsteroidea - sea starsOphiuroidea - brittle starsEchinoidea - sea urchins and sand dollarsHolothuroidea - sea cucumbersConcentricycloidea - sea daisies - recently discovered

Class Crinoidea: The Sea Lilies and Feather StarsSessile, sedentary animalsMouth and anus located on upper surface of an open diskMany highly branched arms located around central disk - 5 to 200

arms - smaller pinnules branch from each armfood collected by mucus on pinnules - transported by tube-feetFossils abundant, many more extinct forms than living species

Sea lilieshave a stalk

Found inwater deeperthan 100 m

Class Asteroidea - Sea Starsthe familiar "starfish"Active, important marine predatorsAbundant in shallow and deep watersArms merge gradually with diskArms in multiples of five, usually fiveBody flattened, flexible, covered with

pigmented epidermis

Often feed on bivalves

Grasp shell with tube feetto wrench open

Extrude stomach into shellSecretes enzymes, digests

soft parts of bivalve

Many are scavengers

Class Ophiuroidea - Brittle StarsLargest class of echinodermsCalled “brittle” because they shed their

arms readilyFound in shallow water and one of

most abundant animals in the deep-sea

Slender arms set off sharply from central disk

Actively move arms for locomotionArms may be covered with spinesSome use arms to swimTube feet are important sensory organsTube feet capture small food particles

and move food to mouth

Class Echinoidea - Sea Urchins and Sand DollarsLack distinct arms, but still have five-part body planFive rows of tube feet protrude from plates of skeletonEndoskeleton is made of fused platesSea urchins are globular with large spinesSand dollars are flattened

Walk with tube feet ormovement of spines

Feed on algaescraped off thesurfaces bytriangular teeth orfeed on food itemsfound on or in thesubstrate

Class Holothuroidea - Sea CucumbersSoft, sluglike organisms with tough, leathery skinBilaterally symmetric externally, with five-part internal body planMouth is located on one end, anus on otherMouth surrounded by tube feet modified into tentaclesTentacles secrete mucus to trap food particles

Endoskeleton reduced to widely separated,microscopic plates

Respiration by respiratory tree that originates at anus

Have tube feet on bodyMove by tube feet or flexing of entire bodyMost are sluggishMay eject digestive system or respiratory

tree when threatened by a predator