Crown-of-thorns starfish occurs where coral reefs or hard coral communities occur in this region. The body form of the crown-of-thorns starfish is fundamentally the same as that of a typical starfish, with a central disk and radiating arms. Its special traits, however, include being disc-shaped, multiple-armed, flexible, prehensile, and heavily spined, and having a large ratio of stomach surface to body mass. Its prehensile ability arises from the two rows of numerous tube feet that extend to the tip of each arm. In being multiple-armed, it has lost the five-fold symmetry (pentamerism) typical of starfish, although it begins its life cycle with
Crown-of-thorns starfish hypotheses focused on changes in the survival of juvenile and adult starfish - the "predator removal hypothesis": Many of the reports of fish preying on "Acanthaster" are single observations or presumed predation from the nature of the fish. For example, the humphead wrasse may prey on the starfish amongst its more usual diet. Individual puffer fish and trigger-fish have been observed to feed crown-of-thorns starfish in the Red Sea, but there is no evidence that they are a significant factor in population control. A study, however, based on the stomach contents of large carnivorous fish that are potential predators of