Crown of Thorns Starfish: Acanthaster planci

A Starfish of Outbreaks

Acanthaster planci is known as the Crown of Thorns Starfish. This sea star is an organism that has caused great concern all over the world, particularly in the south pacific. The Great Barrier Reef has had crown of thorns outbreaks roughly every thirteen years since they were first discovered earlier this century. When the starfish come into a reef ecosystem in these plague proportions, they feed so heavily on corals that they can completely destroy a reef.

Crown of Thorns Starfish Distribution Map

Even today, scientists debate whether these outbreaks are a naturally occuring phenomenon or if they are caused by human influences. There is concern that these outbreaks may be the result of added nutrients to the ocean from terrestrial sources such as agriculture and waste management.

Interesting Facts

The Crown of Thorns is endemic to the Red Sea, Indian Ocean and the Pacific Ocean.
These sea stars are nocternal and prey upon coral polyps.
The spines are venomous.
The Crown of Thorns is the second largest sea star, second only tothe Giant Sunstar.

An Interesting 'MicroDoc' Video from Micronesia

Accounts from the Untamed Science Crew

Rob Nelson: "In 1999, when I was studying marine biology at James Cook University in Queensland Australia I had the opportunity to be a Crown-of-Thorns eradication specialist. Basicaly, I got to go on a giant catamaran full of tourists out to Kelso Reef (50 miles offshore from Townsville), and while I was diving I'd take care of any star fish I saw. The tour company was worried the outbreak would completely destroy their local reef so we worked to control the population. On any one dive we might get 150 or more Crown-of-Thorns. The most humane way of killing a starfish was with sodium bisulphate, injected into 3 spots on the starfish crown. This chemical disrupted their nervous system and they died quickly."

"My main concern with the operation was that now we too were acting as a secondary human influence on something that we did not know was human caused. In understood that the goal on this reef was to save the existing reef community. I would have been sad to see such a beautiful reef destroyed, even if it was a natural process. In anycase, the tour company could not save all the reefs. This was one of many patches of reef in the chain, the rest of which we allowed the starfish to feed upon."