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The star fish is without any doubt one of
the most beautiful marine creatures. Some of the most met star
fish are the Common starfish, the Blue sea star, the
Eleven-armed sea star, the Comb sea star, the Japanese sea star,
the Crown of thorns sea star, the Pincushion sea star and the
Carpet sea star. The star fish are marine invertebrates with
five or more arms and a radial symmetry, which means that they
have only bottom and top sides, without left or right sides.
They also have an indistinct disk from which the arms radiate.
In the larval pluteus form, the star fish shows remnants of
their body's bilateral symmetry. The star fish have a protective
skeleton but not a movable one to help them in locomotion.
Instead of such a jointed skeleton, the star fish have a
hydraulic water vascular system which supports them in
locomotion. The water vascular system numerous projections are
situated on the star fish arms (more exactly, on the arm's
ventral face). These projections are called the tube feet and
have functions of feeding and locomotion. The most of the star
fish are not able to move fast but some species, such as the
Luidia or the Astropecten can move very fast. This thing is
possible due to the pointed tube feet that are owned by these
species and which are adapted for the sand excavation. The
star fish have two stomachs, one used for digestion and the
other one for digestion the “extra” prey, so the star fish can
hunt the preys that are much bigger than their mouth is. Their
diet is made in general from clams and oysters. Another
interesting detail about the star fish is that they can
regenerate a lost arm. |
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