Common Name: Crown-of-Thorns Starfish

Scientific Name: Acanthaster planci

Kingdom: Animalia

Phylum: Echinodermata

Class: Asteroida

Order: Valvatida

Family: Acanthasteridae

Genus: Acanthaster

Species: A. planci



Acanthaster Planci are red colored echinoderms protected by thorn-like spines. They grow into a diameter up to 40 cm across. They have 12-19 arms extending from their center. These animals do not have a head and are pentamerically symmetrical. Acanthaster planci's have tube feet, or branched tentacles arranged along each arm that function in gas exchange and food gathering. The crown of thorns can grow from the size of a grain of sand to the size of a dinner plate. An exceptionally large crown of thorns can grow to be the size of a car tire. Divers kill these predators by injecting the starfish's own stomach acid into each of their many legs. If even one leg is missed, the sea star can live on.


Before overpopulation, the crown of thorns kept the fast-growing coral from overpowering the slower growing coral. It then proceeds to destroy the coral. Crown-of-thorns starfish are found on coral reefs in the tropics ranging from the Red Sea, the Indian Ocean, and thepacificc all the way to panama. They can live in tropical, saltwater, or marine. In their ecosystem, they do Phenomenally well, but marine biologist are worried about the coral reefs because these starfishes can wipe out an entire reef in just a few weeks. It is possible that crown-of-thorns starfish eggs and larva are preyed upon by economically important reef fish. The decline of these reef fish populations may contribute to population increasing the crown-of-thorns starfish. It eats by climbing onto them, extruding its stomach over them, and then releasing digestive enzymes to absorb the liquefied tissue. They feed alone at night, maintaining a constant distance between themselves and other crown-of-thorn starfishes. During times of food shortage, these creatures can live on their energy reserving for over six months.


Like most starfish, A. planci is separate in sexes. It breeds once each year in midsummer. The female eggs travel through pores located on the surface, and then are released into the water and fertilized to develop into larvae, called bipinnaria. Two stages follow, the brachiolaria and primordium phases. The creature settles to the bottom of the seabed and then the primordium absorbs the brachiolaria, developing into a starfish. These starfish remarkably regenerate lost or broken limbs.


Author: Craig H

Published: 02/2008




Photo Credit: