Starfish Starfish Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or "basket stars". 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, below the surface. Starfish are marine invertebrates. They typically have a central disc and five arms, though some species have a larger number of arms. The aboral or upper surface may be smooth,
Starfish into juveniles. Some species of starfish are able to reproduce asexually as adults either by fission of their central discs or by autotomy of one or more of their arms. Which of these processes occurs depends on the genus. Among starfish that are able to regenerate their whole body from a single arm, some can do so even from fragments just long. Single arms that regenerate a whole individual are called comet forms. The division of the starfish, either across its disc or at the base of the arm, is usually accompanied by a weakness in the structure that provides