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Crown-of-Thorns Starfish


Snake Sea Stars Toxopneustidae Sea Urchins

There are only two species in the Crown-of-Thorns Starfish family, the Short-Spined Crown-of-Thorns Starfish (Acanthaster brevispinus) and the Common Crown-of-Thorns Starfish (Acanthaster planci), both of which are found in the Indo-Pacific region, but only one of which, the Common Crown-of-Thorns Starfish, is usually found at the dive sites around Koh Lanta.

Crown-of-Thorns Starfish are disc-shaped, multi-armed starfish, starting life with the typical 5 arms, but growing many more as it matures. Members of this family are densely covered in sharp, poisonous spines, have very flexible arms and large stomachs.

Crown-of-Thorns Starfish can be varying shades of blue, purple, red, brown or grey, with variably coloured spines, sometimes with yellow tips or orange.

1 species found on this page.

Common Crown-of-Thorns Sea Star

Acanthaster planci

The Common Crown-of-Thorns Sea Star is a large starfish, variably coloured red to purple, yellow and tan. There are 12 - 19 arms, covered with sharp, poisonous spines which can give a very painful sting.

The Common Crown-of-Thorns Sea Star diet includes coral polyps, and several individuals can consume large areas of coral within a very short period of time. This species can occasionally form very large colonies which can then devastate a coral reef.

Common Crown-of-Thorns Sea Star (Acanthaster planci) @ Koh Bida

Acanthaster planci @ Koh Bida

It is thought that one of the main causes of population explosion is excessive agricultural run-off, flooding areas with nitrates and nutrients. Dangerously large populations which threaten to destroy a coral reef can be controlled by injections of sodium bisulphate.

Common Crown-of-Thorns Sea Star (Acanthaster planci) @ Koh Bida

Common Crown-of-Thorns Sea Star @ Koh Bida

The Common Crown-of-Thorns Sea Star grows to 40 cm and can fully regenerate an individual adult from a severed limb. DNA analysis suggests that the Common Crown-of-Thorns Sea Star comprises 4 subspecies, each with its own distinctive range.

Diving with Crown-of-Thorns Starfish

Spot Crown-of-Thorns Starfish on one of our daily Koh Lanta diving trips. Or if you prefer to keep your adventure on the surface, you can also book one of our Koh Lanta snorkeling trips.

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