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Marine Animal Encyclopedia

Crown-of-thorns Starfish Acanthaster planci

Occasional plagues of the crown-of-thorns starfish, which is large and destructive, have killed extensive areas of coral on the Great Barrier Reef of Australia and the western Pacific reefs. There has been much debate on whether such plagues are natural or are caused by over-fishing of the few mollusks and fish that can eat this starfish, such as the giant triton, Charonia tritonis. With up to 20 arms and a formidable covering of long spines, the crown-of-thorns starfish has few predators. The spines are mildly venomous and may inflict a painful wound if the starfish is picked up with bare hands. Crown-of-thorns starfish feed on corals by turning their stomach out through their mouth and digesting the coral’s living tissue. Pure white coral skeletons indicate that this starfish has been feeding recently in the area. In popular diving tourism areas, attempts are sometimes made to kill the starfish by injecting them with poison or removing them by hand, but with only limited success.

Crown-of-thorns Starfishzoom image
  • Class Asteroidea
  • Diameter Up to 20 in (50 cm)
  • Depth 3–65 ft (1–20 m)
  • Habitat Coral reefs
  • Distribution Tropical waters of Indian and Pacific oceans
Crown-of-thorns Starfish habitat mapzoom image