Mimic packs armful of tricks

October 5, 2001

Eat your heart out, Rory Bremner. Scientists have discovered an Indonesian octopus that can alter the shape and colour of its body to mimic at least three different creatures.

While other species have mastered the art, the Indonesian mimic octopus is the first found to be capable of switching between impersonations to match a given situation.

Tom Tregenza, Natural Environment Research Council fellow at the Centre for Biodiversity and Conservation at Leeds University, said such behaviour was new to science.

"Just being able to use these different forms of mimicry is dramatically more sophisticated than anything we have seen before," Tregenza said. "It is incredible that it can change its body shape and colour like this. It would be really exciting if the octopus could choose when to use a particular form."

Nine individuals of the unnamed species were filmed in action off the coasts of Sulawesi and Bali.

The results have been analysed by a team of scientists from the universities of Leeds, Melbourne and Tasmania, in Australia, and published in the Proceedings of the Royal Society .

While moving through the water, the octopus formed its arms into a leaf-shaped wedge that strongly resembled a type of poisonous sole abundant in the area. It was also seen swimming with its arms tinted electric blue and splayed out to look like a lionfish with its poisonous spines flared.

On four occasions, when attacked by the highly territorial damselfishes, the octopus threaded six arms into a hole and stretched the remaining two out along the seabed, while its colouring switched from its usual brown to strong black and white stripes. This gave it the appearance of a banded sea-snake, which preys on damselfish.

There were also sightings of other possible impersonations of a type of jellyfish, with its arms spread evenly beneath it, and a sea anemone with its arms arranged above its resting place.

Tregenza said the ability could have developed by natural selection as a way to scare off a variety of potential predators.

The octopus has an arm span of 60cm and lives on molluscs and crustacea on the featureless, silty floors of estuaries where there are no coral reefs or rocky outcrops to hide in. Mimicry might provide it with its only refuge from attack.

By mastering such a repertoire of morphological tricks, the octopus may prevent its predators from rumbling a particular ruse.

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