More fish in the sea dating
The water vascular system of the starfish is a hydraulic system made up of a network of fluid-filled canals and is concerned with locomotion, adhesion, food manipulation and gas exchange.
Water enters the system through the madreporite, a porous, often conspicuous, sieve-like ossicle on the aboral surface.
With their appealing symmetrical shape, starfish have played a part in literature, legend, design and popular culture.
They are sometimes collected as curios, used in design or as logos, and in some cultures, despite possible toxicity, they are eaten.
They are found from the intertidal zone down to abyssal depths, 6,000 m (20,000 ft) below the surface. They typically have a central disc and five arms, though some species have a larger number of arms.The fossil record for starfish is ancient, dating back to the Ordovician around 450 million years ago, but it is rather poor, as starfish tend to disintegrate after death.Only the ossicles and spines of the animal are likely to be preserved, making remains hard to locate.Luidia ciliaris has seven arms, members of the Solasteridae have ten to fifteen while the Antarctic Labidiaster annulatus can have up to fifty.It is not unusual in species that typically have five arms for some individuals to possess six or more through abnormal development.