Crown-of-Thorns Starfish

Acanthaster planci

The Crown-of-Thorns Starfish is a very large sea star, sporting diameters of up to 20 inches across. They are actually the second largest of all the Sea Stars, beaten only by the massive, nearly meter wide Sunflower Starfish. Crown-of-Thorns Starfish can be found in the Indian and Pacific oceans, as well as in the Red Sea. They are solitary creatures, and live on Coral Reefs.

 Crown-of-Thorns Starfish get their name from the massive spines that grow out of their body. These spines are capable of piercing diving suits, and are full of a neurotoxin that can cause severe pain and swelling in humans. Coral plays a huge part in this Starfish’s life. They are predators that feed off of the Coral Polyps, and their choice of meal can cause huge amounts of damage to the reefs. They pose one of the greatest natural threats to the Great Barrier Reef, for example, because they can feed on Coral faster than the Coral can grow back.

Outbreaks of the Crown-of-Thorns Starfish happen in part because they don’t have too many natural predators, and many of those creatures that do feed on them are overfished. Another reason for the infestations deals with the health of the reefs themselves. Erosion and agricultural runoff has caused reefs to decline in health, which means they aren’t able to consume the Starfish are quickly when they are in their larval phase.

 Efforts have been made to remove and kill Crown-of-Thorns Starfish, but they are tricky to get rid of, since they can regenerate from severed limbs! One method that has had some effectiveness is injecting the Starfish with sodium bisulfate, which is lethal to them but causes no damage to the surrounding reef. Physical removal is also sometimes carried out, but it is more difficult to manage as the Starfish are able to poke through the divers’ wetsuits.

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IUCN Status : Not Listed

Location : Indian and Pacific Oceans

Size : Diameter up to 20in (50cm)

Classification : Phylum : Echinodermata -- Class : Asteroidea -- Order : Valvatida
Family : Acanthasteridae -- Genus : Acanthaster -- Species : A. planci