Advanced Life Science Rainier Jr/Sr High School Mr. Taylor Echinoderms Advanced Life Science Rainier Jr/Sr High School Mr. Taylor

Echinoderms Kingdom Animalia Literally “spiny skinned”. Phylum Echinodermata Literally “spiny skinned”. Have calcium projections from their endoskeleton Juveniles exhibit bilateral symmetry; adults have radial symmetry

Echinoderms Most common organisms are the sea stars Sometimes called starfish but they are NOT fish. Most have 5 arms, but can have as many as 50. Arm is hollow with digestive and reproductive organs inside Have rows of tube feet extending from the ventral side.

Sea stars: digestive system Mouth is on ventral side under central disc with stomach lying dorsal to it. Stomach is able to evert inside of clams, corals, and other echinoderms. Once inside the shell of the prey item, the stomach releases digestive enzymes and absorbs the digested materials for final processing in the arms of the sea star.

Sea stars: nervous system Sea stars have no brain but do have a central nerve ring used to coordinate movements Most have photoreceptors (non-image-forming) on ends of the arms

Sea stars: respiration and regeneration Sea stars exchange O2 and CO2 using skin gills These are protected by the spiny extensions of the endoskeleton. Many species can regenerate body parts (arms) if the central disc is not involved. A few species will regenerate a new organism from the fragments.

Sea stars: Water vascular system Water enters through the madreporite (“mother opening”) This opening is on the dorsal surface, centrally-located in the central disc.

Sea stars: Water vascular system Water then enters the ring canal and is distributed to the radial canals down each arm.

Sea stars: Water vascular system The radial canals connect with hundreds of tiny tube feet composed of a sucker and a muscular ampulla. By alternately filling and emptying the foot, the sea star is able to attach to a surface (or prey item) and pull itself along.

Other Echinoderms: Sand dollars Also exhibit radial symmetry and move using a water vascular system (tube feet) Have 5 rows of tube feet and 5 “lobes” on dorsal surface.

Other Echinoderms: Sea urchins Same echinoderm characteristics Long spines serve a protective function. Use tube feet for locomotion.

Other Echinoderms: Brittle Stars Name is derived from their ability to lose arms easily and re-grow them.

Other Echinoderms: Sea cucumbers Don’t look like an echinoderm, but do possess all the characteristics. They do have 5 rows of tube feet and radial symmetry.