1. Endoskeleton made up of interlocking plates embedded within the skin connected by catch connective tissue.
Catch connective tissue allows echinoderms to change their consistency from flexible to *stiff in a matter of seconds.
2. Adults have five-part radial symmetry
Larvae have bilateral symmetry suggesting that echinoderms had bilateral ancestors and radial symmetry is a derived character.
no brain, central ring of nerves with branches expanding into each arm
3. Water-vascular system: *series of water filled canals in each arm
Functions: Movement with tube feet (changes in water pressure extend and retract tube feet), feeding (use suction cups to pull bivalve shells open), gas exchange (walls of tube feet very thin), store water that is used for *circulation.
4. Digestive tract with *consist of: mouth, stomach, small intestine, and anus
*To eat a clam: sea stars use the pressure of their tube feet to pull apart the shell, they push their stomach out of their mouth and into the space between the 2 shells of clam, release digestive juices that dissolve clam body, clam digests in stomach and waste exits out the anus.
5. Can *regenerate limbs
6. Sexual reproduction: fertilization takes place externally, by both males and females releasing their gametes into the environment during the reproductive season
7. Deuterostomes: *first opening of the digestive cavity develops into the anus and the mouth is developed second within the embryo
*same developmental pattern occurs in chordates (phylum all vertebrates belong to)
Annelids, Mollusks and all simpler invertebrates are protostomes (mouth develops first; then the anus)