AIMS Crown-of-Thorns Starfish

Crown-of-thorns starfish Questions & Answers

AIMS home

About AIMS

Research

Facilities

News

Site map

Site index

Topics index

APPEARANCE

7. What does a crown-of-thorns starfish look like?

The crown-of-thorns starfish is somewhat sinister in appearance as it is covered by a large number of long, very sharp spines (4-5 cm in length) which can inflict a painful wound. Photographs of the upper (aboral) and lower (oral) surfaces of this starfish are shown in Figures 1 and 2. The crown-of-thorns starfish is multi-coloured and ranges in colour from purplish-blue with red tipped spines to green with yellow-tipped spines. Those on the Great Barrier Reef are normally brown or reddish grey with red-tipped spines while those in Thailand are a brilliant purple. Their colour may change somewhat depending on diet and the degree to which hair-like projections (papulae) extend from the skin.

Figure 1
The upper (aboral) surface of the crown-of-thorns starfish (Acanthaster planci). Notice the many spines and arms. The white patch on the left has been recently eaten by the starfish. It is termed a feeding scar.

Figure 2
The lower (oral) surface of a crown-of-thorns starfish showing the mouth and the lines of tube feet radiating out along each arm.

Adult starfish on the Great Barrier Reef have different numbers of arms (generally 14-18) as they may shed them when stressed (see 30) or lose them to predators (see 19). Given sufficient time (about 5-6 months) they are able to regrow these lost appendages.

Although crown-of-thorns starfish normally range in size from 25-35 cm in diameter, individuals as large as 80 cm have been found. We don't know how old these large individuals are since it is not possible to determine the age of crown-of-thorns starfish from their size. Like most echinoderms size is determined by what they eat, availability of food and number of starfish in the population. Starfish grown in aquaria for 2 years on a diet of encrusting algae may be up to 20 times smaller than those fed on corals (see 21 and 22).

AIMS home page