Echinoderms

Phylum Echinodermata

• triploblastic eucoelomate

  • complete digestive system

• all marine

• dioecious

• larvae bilateral, adults pentaradial

• dermal exoskeleton

  • calcium carbonate

characteristics of echinodermata

• water vascular system

• pedicellariae

• lack definite head & decentralized nervous system

• ring with radiating nerves; regeneration

water vascular system

locomotion & food acquisition

• canals connected to tube feet

• ampullae: muscular sacs attached to tube feet that use hydraulic pressure

pedicellariae

pincher-like spines that are used to remove debris from the outer surface

what are the 6 classes

1. Crinoidea

2. Asteroidea

3. Ophiuroidea

4. Echinoidea

5. Holothuroidea

6. Concentricycloidea

Class Asteroidea

sea stars

Class Asteroidea characteristics

• body

  • central disk

  • 5-20 arms

• oral surface: mouth or underside of the body

• aboral surface: madreporite on top of the body

• pushes stomach out of mouth & into body

• gas exchange via dermal gills

• dioecious

madreporite

the water entry point into the water vascular system

Class Crinoidea

sea lilies & feather stars

Class Ophiuroidea

brittle stars & basket stars

Class Echinoidea

sea urchins, sea biscuits, & sand dollars

Class Holothuroidea

sea cucumbers

Class Holothuroidea

sea cucumbers

Class Holothuroidea characteristics

• modified tube feet form

• gas exchange via respiratory trees (in the anus)

• defense mechanisms

  • shooting sticky tubules from the anus

• eviscerate themselves when stressed/threatened

Phylum Chordata

• bilateral

• triploblastic eucoelomate

• terrestrial & aquatic