Echinoderms

Characteristics Kingdom: Animalia Phylum: Echinodermata Means “spiny skinned” Spines are part of the endoskeleton, not the skin! Radially symmetrical as adults All live in marine habitat Eat shellfish, dead plants/animals & algae

The Nervous System Simple nervous system (no brain/ganglia) Nerve ring: circle of nerve fibers around the mouth of an echinoderm Radial Nerve: runs from the nerve ring to the tip of each arm in sea stars, controlling the arm Simple eye: located at the end of each arm, it only senses light The rest of the body is covered with cells that sense changes/chemicals in the water

Nervous System (con’t) Simple Eye

Water Vascular System A system of canals filled with fluid. Uses water pumps to help animal: move, eat, breathe, and sense its environment ** It’s like hydraulics! And only echinoderms have it.

Water Vascular System

Kinds of Echinoderms 5 Classes: Brittle Stars & Basket Stars Sea Urchins & Sand Dollars Sea Lilies & Feather Stars Sea Cucumbers Sea Stars (“starfish”)

Brittle Stars & Basket Stars Look like sea stars, but have long, slim arms Often smaller than sea stars No suckers on their tube feet Move more than other echinoderms

Sea Urchins & Sand Dollars Round Endoskeleton forms a solid, shell-like structure No arms, but use tube feet to move Sea urchins eat algae with special teeth Sand dollars burrow in the mud and eat food they find there Named for their coin-like shape

Sea Lilies & Feather Stars 5-200 feathery arms Arms trap food Sea lilies have a stalk, while feather stars do not Like sea stars, brittle stars & basket stars, feather stars can re-grow lost arms.

Sea Cucumbers No arms Soft, leathery body Long worm-like shape (unique!) Move with tube feet

Starfish 5 planes of symmetry (Radial) Eat by pushing their cardiac stomach out through their mouth, and then retracting it. The food moves into the pyloric stomach where digestive glands secrete enzymes to speed up digestion. Endoskeleton made up of tiny calcium plates called ossicles.

Starfish Anatomy