The mimic octopus (Thaumoctopus mimicus) has some interesting ways to keep from being eaten. The brown-and-white stripes on its arms resemble the patterning on venomous sea snakes and the coloring of spiny lionfish. And it can vary its shape and positioning to look like a variety of different underwater creatures. For example, when the octopus swims, it can arrange all of its long arms behind its body and impersonate a toxic flatfish, such as a zebra sole. These aren't perfect impersonations, but they may startle a predator enough that the octopus has time to flee.

In a new study in the Biological Journal of the Linnean Society, biologists examined DNA sequences of the mimic octopus and 35 of its relatives to create a family tree and determine when each of the mimic's distinctive traits evolved. They found that the octopus began to swim like a flatfish around the same time that it evolved very long arms. The conspicuous body patterning came later.

That coloring may not all be mimicry, though. The mimic octopus wasn't discovered until 1998, so scientists are still learning basic characteristics. The bright pattern may be a warning that the octopus isn't tasty, though it's not been confirmed that it's unpalatable to fish or anyone else. However, scientists have witnessed at least one case in which a flounder spit a mimic out after trying to eat it.

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