Echinodermata
Spiny Skinned
Echinoderms
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6000 living species 20,000 extinct species
all oceans, all depths
Planktonic larvae - bilateral symmetry
adult - pentamerous radial symmetry
sexual external fertilization
lack a head therefore have oral & aboral surfaces
endoskeleton
water vascular system *** only in echinoderms***
tube feet and ampullae
madreporite
vocabulary
• Water vascular system - network of water
filled canals
• tube feet - muscular sacs that extend outside
the body opposite ampullae. Used for
attachment and locomotion
• madreporite - a porous plate on the aboral
surface, connects water vascular system to
the exterior
The 5 classes of Echinodermata
Phylum
Echinodermata
Class
Asteroidea
Class
Ophiuroidea
Class
Echinoidae
Class
Holothuroidae
Class
Crinoidae
Asteroidea
• Usually 5 arms, up to 50 arms
• Ambulacral groove radiating channels on each
arm, has hundreds of tube
feet
• Pedicellariae - minute pincher
like organs that help keep
surface clean
• What do they eat? Snails,
barnacles, bivalve, etc.
• How do they eat? Project
their stomach into soft body
of prey, partial external
digestion
• EX. Sea Stars or Starfish
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Ophiuroidea
• 2,000 species
• What do they eat?
Organic material
• Arms are long thin and
very flexible.
• Arms lack suckers on tube
feet. They are not used
for locomotion but for
feeding and sensory.
• EX. Basket stars, Brittle
stars and sea serpents
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Echinoidea
• Rigid test with movable
spines and pedicellariae
• Arms moved up to meet at
the top
• Now ambulacral grooves
extend from top to bottom
• What do they eat? Plant
material, encrusting
animals, dead organic
matter
• Aristotle’s lantern - jaws
and muscles
• EX sea urchins and sand
dollars
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Holothuroidea
• Elongated body
symmetry
• Endoskeleton:
microscopic calcareous
spicules throughout
watery skin
• 5 rows of tube feet from
mouth to anus
• Evisceration - sudden
expulsion of gut and
other internal organs
• EX. Sea cucumbers
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Crinoidea
• 600 species
• 5 to 200 arms
• Mouth is located on
the ventral surface
• mucus
• filter feeders
• EX. Sea lilies, Feather
stars
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