Phylum Echinodermata
Sea stars, brittle stars, sea urchins, sea cucumbers,
sand dollars
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Echinodermata means “spiny skin”
About 7000 species – all marine
Planktonic larvae are bilateral
Adults are radially symmetrical
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Pentamerous – symmetry based on 5 parts
They have an oral (mouth) side and an
aboral side
Have an endoskeleton
Possess a water vascular system
Tube feet usually have suckers and are
used for attachment, locomotion, and
receiving chemical and mechanical
stimuli
Echinodermata
The Basics
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Most species have 5 arms that radiate
around a central disk
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Hundreds of tube feet cover the oral
surface
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Can move in any direction by reaching out their
tube feet and pulling themselves along
Endoskeleton consists of interconnected
calcium carbonate plates that form a
relatively flexible framework
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Some species can have up to 50 arms
Allows their arms to be somewhat flexible
Aboral surface is often covered with spines
Feed on bivalves, snails, barnacles, and
any other attached or slow moving animal
Echinodermata
The Types – Sea Stars
Ochre Sea Star
Spiny Sea Star
Goose Foot Sea Star
Crown of Thorns
Sun Star
Common Sea Star
Sand Star
Echinodermata – Sea Stars
Cushion Sea Star
Northern Pacific Sea Star
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Have 5 arms that are long, very
flexible, and sharply defined from the
central disk
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The snake-like arms are used in
locomotion
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The tube feet (lacking suckers) are
used for feeding
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Most eat detritus and small animals
they pick up from the bottom
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Largest group of echinoderms as well
as the most widely distributed
Echinodermata
The Types – Brittle Stars
Banded Brittle Star
Green Brittle Star
Millipede Brittle Star
Heart Brittle Star
Ruby Brittle Star
Echinodermata – Brittle Stars
Blunt Spined Brittle Star
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Endoskeleton forms a round, rigid, shelllike test with movable spines
Locomotion is achieved by the movable
spines, jointed to sockets in the test, and
the sucker-tipped tube feet
Graze on seaweeds and seagrasses, but
will also ingest detritus
Mouth has an intricate system of jaws and
muscles called Aristotle’s Lantern
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Used to bite off algae and other bits of food
from the bottom
Found worldwide on rocky shores
Echinodermata
The Types – Sea Urchins
Black Hatpin Urchin
Boring Urchin
Pencil Urchin
Crown Urchin
Fire Urchin
Echinodermata – Sea Urchins
Long Spined Urchin
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Sand dollars and heart urchins are
closely related to urchins
 Flattened
bodies with shortened spines,
deposit feeders
Echinodermata
The Types – Sea Urchins
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The animal lies on one side, where the 5 rows of
tube feet are concentrated
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The oral and aboral surfaces are at the ends
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Endoskeleton consists of microscopic, calcareous
spicules scattered through the warty, often
tough, skin
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Deposit feeders
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Tube feet around the mouth are modified into
tentacles that are used to scoop food into mouth
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Lack spines so they have other defense
mechanisms: secretion of toxic substances,
expulsion of internal organs
Echinodermata
The Types – Sea Cucumbers
Beaded Sea Cucumber
Sea Apple Sea Cucumber
Pink Warty Sea Cucumber
Echinodermata – Sea Cucumbers
Chocolate Chip Sea Cucumber
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Suspension feeders that use outstretched,
feathery arms to obtain food from the
water
Includes feather stars and sea lilies
Capable of swimming
Body plan is best described as an upsidedown brittle star with the mouth directed
upward
Some only have 5 arms, while others may
have up to 200 arms (because of
branching of the initial 5 arms)
Tiny tube feet secrete a mucus to aid in
catching food particles
Echinodermata
The Types - Crinoids
Echinodermata - Crinoids
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Sea stars are carnivorous and extend
their stomach inside out through the
mouth to envelop the food
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Sea urchins and sea cucumbers have
long and coiled guts
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urchins need the long gut in order to
digest plant material
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cucumbers need the long gut in order
to process large amounts of sediments to
obtain enough organic matter for survival
Echinodermata
Digestion and Feeding
Echinodermata
Sea Star with expelled stomach
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Have a water vascular system, which is
a system of internal tubes filled with
fluid
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water, nutrients, gases, and wastes
throughout the body
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Tube feet are the main surface for
respiration (gas exchange)
Echinodermata
Respiration and Circulation
Echinodermata
Water Vascular System
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Digestive wastes are released as feces
through the anus
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Nitrogen-containing cellular wastes are
excreted in the form of ammonia
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waste is passed into surround water
through the tube feet and skin
Echinodermata
Excretion
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Very simple
Have a nerve ring that surrounds the
mouth and radial nerves that connect the
ring with the body parts
Do not have a brain
Coordinates movements of tube feet and
spines
Most have scattered sensory cells that
detect light, gravity, and chemicals
released by potential prey
Many have the ability to turn their bodies
over after being flipped
Sea urchins have also been known to
camouflage their bodies with debris
Echinodermata
Nervous System
Echinodermata
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Most species have separate sexes
Mostly external fertilization through
spawning
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Some sea stars, brittle stars, and sea
cucumbers regularly reproduce asexually
by the separation of the central disk/body
into two pieces
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Developing larvae become part of the plankton
Each piece then grows into a complete
individual
Regeneration – the ability to regrow lost
arms and damaged body parts
Echinodermata
Reproduction
Echinodermata
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http://www.shapeoflife.org/video/ech
inoderms-ultimate-animal
Echinodermata
Echinoderms: the ultimate animal
Video 14 min