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,
Crown-of-thorns starfish starfish larvae in experimental studies gave support for a mechanism for starfish outbreaks: increased terrestrial runoff → increased nutrients denser phytoplankton↑→ better larval survival → increased starfish populations There have been further conformations of these connections, however research by Olson (1987), Kaufmann (2002), and Byrne (2016) suggests terrestrial runoff has little or no impact on larval survival. The conflicting data describing the negligible role of terrestrial agricultural runoff has been described as "an inconvenient study". There is also a flow-on effect in that where there are large starfish populations producing large numbers of larvae, there is likely to be heavy