Brittle stars are echinoderms that are closely
related to starfish.
They typically have five very flexible arms
that they use for locomotion.
They can move quite rapidly by wriggling their
arms.
The arms are joined at a central disk that
contains their vital internal organs.
The arms are typically covered in delicate
spines.
Their spines may be so dense that they give
their arms a fuzzy appearance.
Brittle stars can voluntarily detach their
arms if attacked by a predator.
The missing arms can regenerate.
Their mouth is located on the underside of
their disk.
Their body is supported by an internal skeleton
of calcium carbonate plates.
There are over 2000 different species of brittle
stars.
The largest have arms that can reach 24 in
long (60 cm) long.
They inhabit all oceans, in both deep and
shallow waters.
The majority of species are bottom dwellers.
Brittle stars may hide under rocks, in crevices
or on other organisms like coral and sponges.
They may also bury themselves in sediment.
They are common in tidepools and reef flats.
Feeding tactics vary by species.
Some feed by extending their arms to snatch
nutritious particles out of water column.
Their tube feet help gather the food particles
and transfer them to their mouth.
Some are scavengers and some are predators
that prey on small animals like crustaceans
and mollusks.
Any undigested material that they eat must
pass back out of their mouth.
Brittle stars are sensitive to light and will
typically scurry for cover when exposed.
Research on some species has shown that their
body is covered with tiny transparent calcite
crystals that act to focus light onto their
light-sensitive tissues underneath.
This forms an array that functions as a single
eye.
They have chromatophores that can be used
to change color by expanding and contracting.
They usually become lighter in color at night.
The nerve endings in their skin can sense
chemicals in the water and touch.
They usually become sexually mature at about
2 years old.
Many species are broadcast spawners that release
their eggs into the water.
Others may brood their eggs.
Some species can reproduce asexually by fission.
They accomplish this by splitting their disc
in two and regenerating the half that was
split.
They generally live up to 5 years.
Some brittle stars have been observed exhibiting
bioluminescence.
They may use this ability to glow to deter
predators.
For more marine facts, click the SUBSCRIBE
button!!
