An Octopus Impersonates a Cast of Species

A sea creature known as "mimic" has shown researchers it's an octopus of many talents.

Biologists have observed this eight-limbed, 24-inch-long invertebrate impersonating a cast of other marine creatures.

The octopus, which lives on muddy ocean bottoms off the coasts of Bali and Indonesia, has never been observed before, so it isn't yet named. But already, the cephalopod has created quite a stir among zoologists.

"There's really no other animal that mimics more than one organism or that can switch between impersonations," says Tom Tregenza, a zoologist at the University of Leeds in the U.K. "This is quite a unique ability."

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Some of the octopus' repertoire includes:

The sea snake — a highly poisonous reptile that attacks fish. To "become" a sea snake, the octopus changes its coloring to match the yellow and black banding of the snake. It tucks its body and all but two of its limbs into a small hole in the ocean floor. Then, like a puppet master behind a screen, it waves its two exposed tentacles in opposite directions, mimicking the motion of two individual snakes.

The sole fish — a flat, oval-shaped, fish that is often poisonous. After building up speed using jet propulsion, the octopus draws all eight appendages into a leaf-shaped wedge and undulates, moving much the way a sole fish swims. It changes its color to match the drab banded brown coloring of the sole.

And the lion-fish — a nocturnal fish with an array of feather-like poisonous fins. To match this gaudy species, the octopus turns a bright blue and swims with its eight legs flared in the same way a lion fish's fins are splayed.

In a report in the September issue of Proceedings of the Royal Society of London B., Tregenza and his coauthors, Mark Norman of the Melbourne Museum in Australia and Julian Finn, of Australia's University of Tasmania noted that the octopus appears to imitate other sea creatures as well, but these three were the most distinctive.

All of the animals the octopus mimics are venomous creatures and scientists believe the octopus eludes attacks from large fish by using its various disguises. It may even alter its appearance, based on the predator that's near.

Damsel fish are aggressively territorial fish that often attack and bite octopuses — and they are preyed upon by sea snakes. Researchers observed when a damsel fish approached the octopus, it immediately adopted its sea snake guise.

"That behavior suggests it may be able to impersonate a specific animal on cue," says Tregenza.

A Different Kind of Smarts

But scientists aren't sure whether the octopus changes characters consciously, or if it has evolved the ability to do so on instinct. Other observations have shown that octopuses are quite capable of learning. When presented with mazes, species of Octopus vulgaris have made their way through and then improved their times during subsequent tests.

And, according to Jim Cosgrove, an octopus expert at the Royal British Columbia Museum in Victoria, British Columbia, the animals have learned to uncork bottles and unscrew jar lids to get to food.

But Cosgrove points out it's hard to rate the 'intelligence' of an octopus since their nervous system is so different from our own.

"Fifty percent of their nervous system is in their arms and suckers," he says. "They don't have a reasoning center as one would think of as a brain. So we have no understanding of the animal in terms of its own biology."

It's possible, says Tregenza, that the "mimic octopus" might simply cycle through its imitations randomly. That way, it would be difficult for predators to catch on that it's all a hoax. On several occasions the researchers observed the octopus shifting between impersonations as it scuttled across the ocean floor.

"These animals are the intellectuals of the marine world," says Tregena. "Having a repertoire of several imitations gives predators less chance to learn that a slightly dodgy looking lion fish may not be a lion fish at all."