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,
Common starfish a point at their tips, which are often turned up slightly. There is a line of short white spines running along the centre of the aboral (upper) surface of the arms with low, soft mounds called papulae on either side. The oral (lower) surfaces of the arms have rows of small tube feet, used in locomotion and feeding. The starfish is usually orange or brick red on the aboral surface and paler on the oral surface but can also be purple or pale brown. Individuals from deep water are usually paler. It grows to a maximum diameter of about but