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Crown of Thorns

  • Wednesday 29th August 2012
  • rockpool

Crown Of Thorns

The Crown of Thorns Sea Star


Probably one of the most infamous of all sea stars, it is easy to tell how the crowns of thorns get their name. Covered in spikes, these are not an animal that would be pleasant to pat, as not only are the spines very sharp, they are also venomous.

Like all sea stars, if the crown of thorns loses an arm, it can quite easily grow it back. Coupled with the fact that they have a lot of arms already, these stars can be found with as many as 21 arms. To match their large number of arms, these sea stars can grow to be massive.

Usually seen around 50cm, some 'monsters' have been spotted at the huge size of 1m. This makes them one of the largest sea stars in the world.

Like all sea stars, to eat, the crown of thorns throws up their stomach out of their mouth, turning it inside-out and onto the food item to digest it. But it's not this surprising feeding method that makes the Crown of thorns so widely known, but rather what they like to eat. This sea star is unusual in that its natural diet consists of corals. If there are small numbers of sea stars the coral reef can survive and recover from the low levels of predation. However, if conditions are present that cause the sea stars numbers to dramatically increase, it can have devastating impacts of the coral reef.

There have been several "outbreaks" of crown of thorns on our Great Barrier Reef, prompting protective control methods to kill and remove the sea stars from the reef to give the coral time to recover. There is continued research and monitoring of the crown of thorns and causes of outbreaks to try to ensure the health of our reefs from this predator.

As well as being good at eating (which they do for about 50% of their time) the crown of thorns is also a very good runner. While you might not think it of a sea star, these critters can move very fast and thought to be able to cover over 20m in an hour.

So, come check out the thorny stars of our new Rocky Shores exhibit, there are two crowns currently on show!


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