for National Geographic News
Scientists have discovered what may be the ideal partner for a game of charades: A long-armed octopus that mimics poisonous creatures of the sea to avoid its predators.
The clever creature is a brown octopus about two feet (60 centimeters) long that slithers along the muddy bottom of shallow, tropical estuaries where rivers spill into the sea. It was discovered so recently that it still doesn't have a scientific name, but scientists are intrigued by its uncanny ability to impersonate lion fish, soles, and banded sea snakes.
Octopuses are thought to be one of the most intelligent invertebrates and can change the color and texture of their skin to blend in with rocks, algae, or coral to avoid predators. But until now, an octopus with the ability to actually assume the appearance of another animal had never been observed.
"Having studied many octopus species in the wild, I am never surprised by the color and shape change capacities of these animals," said Mark Norman of the Melbourne Museum in Australia. "However, this animal stood out as it was the only one we've encountered that goes beyond camouflage to take on the guise of dangerous animals."
Norman and fellow researchers Julian Finn of the University of Tasmania in Australia and Tom Tregenza of the University of Leeds in England describe the octopus mimic in the September 7 issue of Proceedings of the Royal Society of London.
"This," Tregenza said, "is a rather dramatic animal."
Mimicry is a fairly common survival strategy in nature. Certain flies, for example, assume the black and yellow stripes of bees as a warning to potential predators. But the adaptable octopus is the first known species that can assume multiple guises.
Each of the nine specimens that scientists saw during research dives off the coasts of Sulawesi and Bali in Indonesia impersonated more than one toxic species. The creatures they routinely mimicked were:
Sole fish. To take on the appearance of flat and poisonous sole fish abundant in the habitat, the octopus builds up speed through jet propulsion and draws all of its arms together to form a leaf-shaped wedge. It then undulates in the manner of a swimming flat fish.
Lion fish. Just above the seafloor the octopus swims with its arms spread wide and trailing from its body, mimicking the lion fish and its poisonous fins.
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