EchinodermsPhylum Echinodermata

• Include sea stars, sea urchins, sea cucumbers

• Have radial symmetry based on 5 parts (similar parts surrounding central axis) Planktonic larvae has bilateral symmetry

• Considered to have oral/aboral sides, NOT dorsal/ventral

Body StructureHave a water vascular system-

water filled canals• Tube feet-muscular extensions of

these canals usually end in suckers used for attachment & locomotion

• Ampullae-muscular sacs that sometimes fill tube feet with water• Madreporite-connects vascular

system to outside on aboral (top) surface• Also has gonads & digestive system• No heart, brain or eyes

• Complete digestive tract-stomach, digestive gland & anus• Endoskeleton-covered by a thin

layer of tissue• Surface covered with bumps &

spines giving them their name-”spiny skinned” (echinodermata)

Five classes• 1)sea stars–Class: Asteroidea

• 2)brittle stars–Class: Asteroidea

• Subclass:Ophiuroidea

• 3)sea urchins & sand dollars

• Class: Echinoidea

• 4)sea cucumbers• Class:

Holothuroidea

http://www.youtube.com/watch?v=iSA09qg2BMY&feature=related&safety_mode=true&persist_safety_mode=1&safe=active

• 5)feather stars & sea lilies• Crinoidea

Sea stars (starfish)• 5 arms to 50• Most are predatory- bivalves, snails, barnacle, etc.

Sunflower Star http://www.youtube.com/watch?v=ALaMoS_vvNE&safety_mode=true&persist_safety_mode=1&safe=active

Cushion Star

Brittle Stars• Arms very long & flexible-tube feet lack suckers• Eat particles oforganic matter passed from feet to mouth• More species than any other group of echinoderms

Basket Star (Brittle Star)

Brittle Stars

Sea Urchins & Sand Dollars

• Filter feed on drifting plant/animals• Deposit feeders that live on bottoms using tube feet lined with mucus to pick up particles

Sea Urchins

Sand Dollars

Sea Cucumbers• Wormlike, lack spines • Tube feet around mouth reach out and pick up organic material• Escapes by ejecting digestivesystem distracting predators

Sea Cucumberhttp://video.nationalgeographic.com/video/kids/animals-pets-kids/invertebrates-kids/sea-cucumber-kids/

http://www.youtube.com/watch?v=aCxKFc3XtJs&safety_mode=true&persist_safety_mode=1&safe=active

Feather stars & Sea lilies• 5 to 200 arms due to the branching• Mucus helps in catching food• Some attach to bottom, some crawl on surfaces in shallow to deep water

Sea Lilies (with Stalks)

Feather Stars (noStalks

http://www.youtube.com/watch?v=7V_px48dob8&safety_mode=true&persist_safety_mode=1&safe=active

Biology• Sexes are separate in most

echinoderms• External fertilization• Spawning occurs at once to increase

survival

• Echinoderms can use regeneration to replace missing parts• In some sea stars a severed arm

can grow into a complete individual

http://www.youtube.com/watch?v=rE8l-KFQlhY&safety_mode=true&persist_safety_mode=1&safe=active