Crown-of-thorns starfish substrates with their arms and, when offered a choice of substrates, tend to settle on coralline algae, which they will subsequently feed on. In the classic pattern for echinoderms, the bilaterally symmetrical larva is replaced by a pentamerously symmetrical stage at metamorphosis, with the latter's body axis bearing no relationship to that of the larva. Thus the newly metamorphosed starfish are five-armed and are 0.4–1 mm diameter. (Note the size of the tube feet relative to the size of the animal.) They feed on the thin coating layers of hard encrusting algae (coralline algae) on the undersides of dead coral
Crown-of-thorns starfish the starfish found no evidence of the starfish in the fish's guts. These carnivorous fish were caught commercially on the coral reefs on the Gulf of Oman and examined at local fish markets. One problem with the concept of predators of large juvenile and adult starfish causing total mortality is that the starfish have good regenerative powers and they wouldn't keep still while being eaten. Also, they would need to be consumed completely or almost completely to die. 17–60% of starfish in various populations had missing or regenerating arms. Clearly the starfish experience various levels of sublethal predation. When the