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 the larva has been virtually transparent, but the posterior section is now opaque with the initial development of a starfish. The late brachiolaria is 1-1.5 mm. It tends to sink to the bottom and test the substrate with its brachiolar arms, including flexing the anterior body to orient the brachiolar arms against the substrate. This description and assessment of optimum rate of development is based on early studies in the laboratory under attempted optimum conditions. However, not unexpectedly, there are large differences in growth rate and survival under various environmental conditions (see Causes of population outbreaks). The late brachiolaria search