 Approximately 6,000 species.  Moves by means of hundreds of hydraulic, suction cup-tipped appendages and have skin covered with tiny, jaw-like pinchers.  Echinoderms are found in all the oceans of the world.  They have endoskeletons.  They have long, tapering arms that are called rays.  They are also radial symmetrical.  Also have a simple nervous system.  They have no head or brain, but do have a central nerve ring that surrounds the mouth.  They have cells that detect light and touch, but most do not have sensory oragns.  Echinoderms have a water vascular system that enables them to: › Move › Exchange Gases › Capture food › Excrete Wastes

 More than 1/3 of the 6,000 species of Echinoderms belong to this phylum.  Sea stars belong to this class.  Endoskeleton  Pedicellariae  Madreporite  Tube Feet  Anus  Stomach  Tube Feet  Eyespots  Most have 5 rays, but some have more. › Some even have more than 40 rays.

 “Brittle Stars”  They are extremely fragile.  Brittle Stars do not use their tube feet for locomotion, but instead they use them to propel themselves with the snakelike, slithering motion.  Their body parts break easily but grow back with regeneration.  They also use them to pass particles of food along rays and into the mouth in the central disk. › This adaptation is an advantage because it helps them survive attacks by keeping the predator busy with the broken piece.

 “Sea Lilies & Feather Stars”  They resemble plants in some ways.  Sea Lilies are the only sessile echinoderms.  Feather stars are sessile only in larval form.  They use their feathery rays to capture downward drifting organic particles.

 “Sea Cucumber”  Vegetable-like appearance!  They reproduce by shedding eggs and sperm into the water, where fertilization occurs!  They have a leathery covering that allows them to be more flexible than others.  When harmed they may: expel a tangled, sticky mass of tubes through the anus, or release some internal organs that are regenerated in a few weeks.  These really confuse their predators so therefore they can make a quick escape. They trap organic particles by sweeping their mucus-covered tentacles over the ocean bottom.

 “Sea Urchins & Sand Dollars”  Globe- or disk-shaped animals covered pointed spines.  Its spine protects it from predators.  They have long, slender tube feet that, along with the spines, aid the animal in locomotion.  The spines also aid in locomotion and in burrowing.  Sea Urchins often burrow into rocks to protect themselves from predators and rough water.  Sand dollars burrow into the sandy ocean bottom.  They feed on tiny organic particles found in the sand.