Species Fact Profile: Crown-of-Thorns Starfish (Acanthaster planci)

Crown-of-Thorns Starfish

Acanthaster planci (Linnaeus, 1758)

Range: Indian and Pacific Oceans
Habitat: Coral Reefs
Diet: Coral, Other Invertebrates, Carrion, Algae
Social Grouping: Asocial, Non-Territorial
Reproduction: Spawns during the summer months (dependent on hemisphere).  Female releases millions of eggs in water, fertilized by sperm from the males.  Not all individuals in population spawn at the same time.  Fertilized eggs are planktonic larva, eventually settling on a hard surface, where it will form into a recognizable starfish
Lifespan: 15-20 Years
Conservation Status: Not Evaluated

• Measures 25-35 centimeters (in some cases up to 70 centimeters) across.  Consists of up to 21 arms radiating around a central disc.  Typically have 5 arms when first forming, growing more with age.  The mouth is on the underside of this disc.  Light-sensitive "eye-spots" are present on the arm tips
• Coloration varies from pale green to reddish-orange to purple, believed to be influenced by the diet.  In some parts of their range they are very brightly colored, possibly a warning to predators
• After settling on the reef, newly-formed adults may migrate for considerable distances, traveling up to 35 centimeters per minute by pulling themselves along.  Juveniles are more exposed to predators because of their migration, and tend to forage at night
• Feeds by inverting its stomach through its mouth and onto its prey, digesting the tissues and absorbing them through the stomach wall before re-inverting
• Some corals house symbiotic crabs, which may drive off the starfish as it attempts to feed
• Predators include giant triton shells, pufferfish, and trigger fish.  Primary defense from predators are the long, stiff venomous spines, for which the animal is named
• If removed from the water, will rapidly deflate, body fluid leaking out.  If placed back in the water before it dies, the starfish will reinflate and recover
• Preferentially feed on young coral, which means that these starfish can pose a challenge in efforts to reestablish coral reefs.  A large starfish may consume over 450 square centimeters (about 70 square inches) of coral a day, feeding more in summer than winter