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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
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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.
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“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.
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“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.
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“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.
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