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Sea
stars (starfish) are the most common
echinoderms on the Reef and they come
in all shapes and sizes. As their
name suggests, sea stars are commonly
recognised as stars and come in many
different colours, the most common
being yellow, red, orange and pink.
Some are entirely one colour while
others come in many different colours
and each species has a unique design.
Sea stars and all other echinoderms
have three main characteristics including
a symmetrical five-part body plan,
tube feet and a skeleton of plates.
Sea
stars have an amazing water-vascular
system, with water-filled tubes ending
in numerous finger-like projections
(tube feet) that stick out through
the skin. Their tube feet are located
on the underside of their body on
the end of the suckers and are used
for movement.
The water-vascular system works on water pressure, creating a network of tube feet that look like hundreds of tiny, hydraulically operated legs. A sea star's mouth is also found on the bottom of the body. Most sea stars have five arms with an eye at each end. This eye sees only light and darkness. If one of these arms is lost, another one can be grown back.
Some sea stars live on the ocean floor while others live around the coral reefs. Many sea stars are able to reproduce asexually when parts of their bodies break off and grow. In some cases the leg of a sea star will simply 'walk away' from the rest of the body. Some sea stars reproduce by mass spawning. |
