The Crown of Thorns Seastar (Acanthaster planci) is a coral eating Seastar species that is found through the Indian and Pacific Oceans. This is one of the few marine species that feeds on living coral tissue. In small numbers this species is just another part of the coral reef ecosystem however when they occur in great numbers on a coral reef they can have devastating effect causing the coral diversity and abundance to decline. In some parts of the Great Barrier Reef in Australia the Crown of Thorns has decimated coral reefs.
The Crown of Thorns belongs to the seastar family Acanthasteridae and is easily identified by the large numbers of arms it can have (up to 21 arms have been recorded). The body of the species is generally a dull green/brown colour or occasionally the body can be red. Species found in south-east Asia often have a purple/blue coloured body. It gets its common name from the dense coverage of long sharp spines than can be found all over its upper surface. The Crown of Thorns Seastar uses a spawning strategy for reproduction and a single female can produce up to 100 million eggs each year.
This species grows to a maximum diameter of approximately 80 cm.