echinoderms. sea star sea cucumber brittle star

Echinoderms

Sea Star

Sea Cucumber

Brittle Star

Urchin

Sand Dollar (Keyhole Urchin)

Video Clip from Blue Planet

https://www.youtube.com/watch?v=r4cX2EPt2zE

Finger of Death

Phylum Echinodermata

“Spiny skin”Radial symmetry – 5 parts or multiples of 5Water vascular system – hydraulic pressure system for movement

Water Vascular System

WVS Operation

Water enters through madreporiteThrough tube system to ampullae of feetMuscle contracts - water ejected onto foot – suctionMuscle relaxes – water back into ampullae – no suction

Skeletons

Plates under skin (some fused) or spicules (endoskeleton)Ca(CO3) – like mollusks

Projections

Sea Stars

Flexible – plates of skeleton with musclesAmbulacral groove with tube feetMouth and anusEyespots sense light

Sea Star Feeding

Diet – mollusks, coralOpens shells with tube feetExtrudes stomachLiquefies mollusk

Brittle Stars

Distinct central diskTube feet have no suction – send food to mouthArms for locomotionMouths with teethNo anus

Regeneration

Need 1/5 of central disk and 1 arm to regenerate

Sea Urchins

TestMouth and anusBall and socket spinesSpines and tube feet for movement

Sea Urchins

Algae-eaters and scavengersMouth with teeth (Aristotle’s Lantern)

Sand Dollars

Flat sea urchinsShort spines

Sea Cucumber

Elongated bodySmall skeletal fragmentsModified tube feet for tentacles on oral end