Mimic octopus

A long-armed sand octopus, mantle to about 6 cm but the arms carrying it to roughly half a metre overall, and no thicker than a pencil at their widest. Small horn-like papillae sit above each eye. The ground colour is brown and cream in high-contrast bands. The animal it is confused with is the wunderpus, which is its closest relative and looks very like it. Four characters separate them reliably. The mimic has a bright white V on the rear of the mantle and a white line along the bases of the suckers; the wunderpus has neither. The mimic’s markings have soft, indistinct edges where the wunderpus’s are crisply defined. The mimic has short eye stalks and a dark area below the eye; the wunderpus has longer stalks and reddish patches that pulse between the eyes. And the mimic is roughly twice the size.

Diurnal, foraging twice a day by pushing its arm tips into holes rather than hunting by sight, and occupying burrows vacated by other animals on silt and fine sand, with a marked preference for river mouths and estuaries. On the mimicry: one form of it is properly documented and the rest is not. Impersonation of a swimming flatfish has been recorded in some five hundred episodes, matching the shape, the swimming action, the speed and the duration, and is deployed specifically when the animal has to cross open sand where camouflage would fail; lab-reared animals do it without having seen it, which suggests it is inherited rather than learned. The often-quoted figure of thirteen or fifteen impersonated species is not a research finding — the paper everyone cites was describing what the animal was reputed to do, in its opening line, and its authors later conceded that the lionfish resemblance is not close. No study has shown that any predator is actually deceived by any of it, which is what mimicry requires. An unrelated Atlantic octopus has independently evolved the same flatfish swimming, which is good evidence that this one behaviour is real.