Other fish in the sea online dating
Most can regenerate damaged parts or lost arms and they can shed arms as a means of defence.
The Asteroidea occupy several significant ecological roles.
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.
These are honeycombed structures composed of calcite microcrystals arranged in a lattice.
They vary in form, with some bearing external granules, tubercles and spines, but most are tabular plates that fit neatly together in a tessellated manner and form the main covering of the aboral surface.
About 1,500 species of starfish occur on the seabed in all the world's oceans, from the tropics to frigid polar waters.
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.
They are opportunistic feeders and are mostly predators on benthic invertebrates.
Pedicellariae are compound ossicles with forceps-like jaws.
They remove debris from the body surface and wave around on flexible stalks in response to physical or chemical stimuli while continually making biting movements. Paxillae are umbrella-like structures found on starfish that live buried in sediment.
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.