The crown-of-thorns starfish (Acanthaster planci) is a species of starfish found throughout the Indo-Pacific region, occurring from the Red Sea and the coast of East Africa, across the Pacific and Indian Oceans, to the west coast of Central America. This starfish is covered with many thorns, giving it its name
The crown of thorns starfish´s spines are somewhat flexible in life and are used for locomotion and for defense from potential predators. This species is a well-known coral predator, and outbreaks of tens of thousands of individuals have been known to cause serious harm to coral reefs in some areas. These outbreaks may be a result of overfishing of the crown of thorns starfish’s primary predator, the giant triton. These starfish are known to be more successful at preying on large swaths of coral reefs when the corals are already stressed.
During times of coral bleaching or stresses caused by human activities, outbreaks of the crown of thorns starfish may be particularly destructive. These starfish feed by inverting their entire stomach, through the mouth, and digesting the thin layer of soft tissue off of a coral’s skeleton, right in the open environment, and sucking down the available nutrients.
According to Oceana, ¨crown of thorns starfish populations fluctuate between outbreaks with very high densities and times with much fewer individuals. People do not utilize this species, but scientists consider it a species of concern – not because its numbers are too low but because locally high numbers can threaten other species.¨