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,
Stichaster striatus these were sessile organisms. It was not found to engage in cannibalism of its own species or to feed on other species of starfish. Many individuals were found to have missing or regenerating arms. This is likely the result of attacks by the dominant predatory starfish in the region "Meyenaster gelatinosus" and "Luidia magellanica". Starfish with missing arms are likely to have a certain minimum size; this is because, if they are too small, they are entirely devoured by the predator which attacked them. Juvenile "S. striatus" are found among the holdfasts of the kelp "Lessonia nigrescens" or hiding in