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 damage includes a major section of the disk together with arms, the number of arms regenerating on the disk may be less than the number lost. Another hypothesis is the "aggregation hypothesis", whereby large aggregations of "A. planci" appear as apparent outbreaks because they have consumed all the adjacent coral. This seems to imply that there is apparently a dense population outbreak when there has already been a more diffuse population outbreak that has been dense enough to comprehensively prey on large areas of hard coral. Female crown-of-thorns starfish are very fecund. Based on the eggs in ovaries, 200, 300