EchinodermsEchinoderms

Section 38.1Section 38.1

EchinodermsEchinoderms

ExamplesExamples: : sea stars, sand dollars, sea sea stars, sand dollars, sea urchins, & sea cucumbersurchins, & sea cucumbers

Marine environmentsMarine environments Brilliantly coloredBrilliantly colored Radial symmetryRadial symmetry

4 Unique Characteristics:4 Unique Characteristics:

1.1. OssiclesOssicles:: calcium carbonate plates that calcium carbonate plates that make up exoskeletonmake up exoskeleton

2.2. Water-vascular systemWater-vascular system:: network of network of water-filled canals inside bodywater-filled canals inside body

3.3. Tube feetTube feet:: small, movable extension of small, movable extension of w-v system which aid in movement, w-v system which aid in movement, feeding, respiration, & excretionfeeding, respiration, & excretion

4.4. Pentaradial symmetryPentaradial symmetry:: body parts body parts extend from center along 5 spokesextend from center along 5 spokes

ClassificationClassification

6 classes of echinoderms (only 5 6 classes of echinoderms (only 5 discussed in textbook):discussed in textbook):

Class CrinoideaClass Crinoidea Class OphiuroideaClass Ophiuroidea Class EchinoideaClass Echinoidea

Class HolothuroideaClass Holothuroidea Class AsteroideaClass Asteroidea

Class CrinoideaClass Crinoidea

ExamplesExamples: sea lilies, feather stars: sea lilies, feather stars CrinoidCrinoid means means “lily-like”“lily-like” 5 main arms that branch to form up to 200 5 main arms that branch to form up to 200

more armsmore arms Filter feeders Filter feeders Mouth faces upMouth faces up

Class OphiuroideaClass Ophiuroidea

Largest classLargest class with with examplesexamples such assuch as basket stars & brittle starsbasket stars & brittle stars

OphiuroideaOphiuroidea means means “snake-tail”“snake-tail” Live on bottom of oceanLive on bottom of ocean Regeneration of broken armsRegeneration of broken arms Long, narrow arms allow for quick Long, narrow arms allow for quick

movementmovement

Class EchinoideaClass Echinoidea

ExamplesExamples: sea urchins & sand dollars: sea urchins & sand dollars EchinoideaEchinoidea means means “spinelike”“spinelike” Test: compact, rigid endoskeleton that Test: compact, rigid endoskeleton that

surrounds internal organssurrounds internal organs Spines can have barbs or venomSpines can have barbs or venom

Class HolothuroideaClass Holothuroidea

ExampleExample: sea cucumber: sea cucumber HolothuroideaHolothuroidea means means “water polyp”“water polyp” ArmlessArmless Ossicles are not connected thus soft Ossicles are not connected thus soft

bodiesbodies Tentacles around mouth to capture preyTentacles around mouth to capture prey

Class AsteroideaClass Asteroidea

ExampleExample: sea star (starfish): sea star (starfish) AsteroideaAsteroidea means means “starlike”“starlike” Variety of sizes, shapes, and colorsVariety of sizes, shapes, and colors Compete with humans for oysters, clams, Compete with humans for oysters, clams,

etcetc

Sea StarsSea Stars

Section 38.1 continuedSection 38.1 continued

External StructureExternal Structure

Several arms extending from central Several arms extending from central regionregion

Two rows of tube feet on underneath side Two rows of tube feet on underneath side of each armof each arm

Oral surface:Oral surface: side where mouth is located side where mouth is located Starfish = undersideStarfish = underside

Aboral surface:Aboral surface: side opposite of mouth side opposite of mouth

Rough texture due to short spinesRough texture due to short spines Pedicellariae:Pedicellariae: tiny pinchers surrounding of tiny pinchers surrounding of

each spine that keep body free of foreign each spine that keep body free of foreign objectsobjects

Water-Vascular SystemWater-Vascular System

Network of water-filled canals that are Network of water-filled canals that are connected to the tube feetconnected to the tube feet

Water movement:Water movement: Madreporite Madreporite (sievelike plate on aboral (sievelike plate on aboral

surface) surface) stone canalstone canal ring canalring canal (encircles mouth) (encircles mouth) radial canalradial canal (extends to (extends to each arm) each arm) tube feettube feet

AmpullaAmpulla: bulblike sac at end of tube feet : bulblike sac at end of tube feet that allows for movement and suctionthat allows for movement and suction

Feeding & DigestionFeeding & Digestion

Prey: mollusks, worms, clamsPrey: mollusks, worms, clams Cardiac stomachCardiac stomach: can be turned inside out : can be turned inside out

through mouth during feedingthrough mouth during feeding

Digestive pathway:Digestive pathway: Mouth Mouth cardiac stomach cardiac stomach pyloric stomach pyloric stomach

digestive glands in each arm digestive glands in each arm anus anus

Other Body StructuresOther Body Structures

No circulatory, excretory, or respiratory No circulatory, excretory, or respiratory systems!systems!

Skin gills:Skin gills: thin walls of tube feet that allow thin walls of tube feet that allow gas exchangegas exchange

Nervous systemNervous system = = nerve ringnerve ring (around (around mouth), mouth), radial nervesradial nerves (length of each arm), (length of each arm), eyespotseyespots (end of each arm), (end of each arm), tentaclestentacles

Reproduction & DevelopmentReproduction & Development

Separate sexesSeparate sexes – each arm has sex – each arm has sex organsorgans

External fertilizationExternal fertilization After 2 months of swimming they settle to After 2 months of swimming they settle to

bottom of ocean and metamorphous into adultbottom of ocean and metamorphous into adult

Regeneration (asexual)Regeneration (asexual) As long as part of the central region stays in As long as part of the central region stays in

tacttact