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Fast Facts
Type: Invertebrate
Diet: Carnivore
Average lifespan in the wild: Up to 35 years
Size: 4.7 to 9.4 in. Weight: Up to 11 lbs
Did you know? Sea stars have no brains and no blood. Their
nervous system is spread through their arms, and their “blood” is
actually filtered sea water.
Size relative to a tea cup:
Echinoderms
(“spiny-skinned”)
Echinoderms are spiny-skinned invertebrates that live on the
ocean floor. The word echinoderm means "spiny skin." No
echinoderms are found in fresh water. Modern-day echinoderms
have five-fold radial symmetry, having arms or rays in multiples
of five.
Echinoderms are armored animals that have a hard endoskeleton made of
interlocking calcium plates and spines. It is considered an endoskeleton because
the plates are covered with a thin layer of “skin.”
These slow-moving creatures have a water-vascular system, water-filled
channels that go through the body to help with support and movement.
The oldest-known fossil echinoderm is roughly 560 million years old!
Some echinoderms include sea stars (also called starfish), brittle stars, sea
cucumbers, sea urchins, and sand dollars.
Sand Dollar Sea Star
Dollars
Brittle Star Sandare
(Starfish)
Sea stars, Sea Urchin
A bottomechinoderms,
dwelling
A spiny,
disk-shaped another name
marine
spiny-skinned for starfish, globular animal
invertebrate sea bed animals are animals
that lives on
with long, that have 5-part that live on the ocean floor.
the ocean
spiny arms.
radial
floor.
symmetry.
Many echinoderms use their
tube feet to move themselves
alone the ocean floor. Starfish
use their tube feet to open
mollusks, a favorite food.