Echinoderms Section 29.1

Animal Classification Sponges Cnidarians Worms Mollusks Arthropods Enchinoderms Invertebrates Echinoderms Animals Fishes Amphibians Reptiles Ectotherms (cold-blooded) Vertebrates Birds Mammals Endotherms (warm-blooded)

What is an Echinoderm? Echinoderm (Greek word) “echinos” – spiny “derma” – skin Rays – long, tapering arms that are covered with short, rounded spines

What is an Echinoderm? Pedicellariae (PEH dih sih LAHR ee ee) – modified spines into pincerlike appendages Echinoderms have radial symmetry

Water Vascular System Water vascular system – a hydraulic system that operates under water pressure Water enters and leaves the water vascular system of a sea star through the madreporite

Water Vascular System Madreporite (mah druh POHR ite) – a sievelike, disk-shaped opening on the upper surface of an echinoderm’s body

Water Vascular System Tube feet – hollow, thin-walled tubes that end in a suction cup Tube feet look somewhat like miniature droppers

Water Vascular System Ampulla – the round, muscular structure works like the bulb of a dropper Tube feet also function in gas exchange and excretion

Varied Nutrition Sea stars are carnivorous and prey on worms and clams Brittle stars and sea cucumbers feed on dead and decaying matter that drifts down to the ocean floor

Simple Nervous System Echinoderms have no head or brain, but they do have a central nerve ring Each radial nerve branches into a nerve net that provides sensory information to the animal

Simple Nervous System Sea stars have eyespots located at the tip of each arm

Diversity of Echinoderms Sea stars Most species of sea stars have five rays, but some can have up to 40 rays http://www.youtube.com/watch?v=A100m5EpfFI

Diversity of Echinoderms Brittle stars Brittle stars are extremely fragile This adaptation helps the brittle star to distract a predator

Diversity of Echinoderms Sea urchins Globe-shaped Do not have rays Look like pin cushions Sand dollars Disk-shaped Do not have rays A living sand dollar is covered with hair-like spines http://www.youtube.com/watch?v=3uwOURjneWQ

Diversity of Echinoderms Sea cucumbers When threatened, they may expel their organs (intestines) through the anus The organs may rupture and is regenerated in a few weeks http://www.youtube.com/watch?v=wXf_YodWw40