The slender filefish has evolved the ability to camouflage its body patterns and shape so effectively, it can render itself effectively invisible in a matter of seconds.
At New Scientist, Agata Blaszczak-Boxe describes the findings of Justine Allen and her colleagues at Brown University, who have documented the fish’s disappearing act in the shallow waters of the Cayman Islands, and studied its skin in the lab:
To see an object for what it is, you need to be able to perceive its edges, which mark it out as being separate from the background.
The filefish changes its colouration to create “false edges”. For example, it can make a dark, longitudinal stripe appear on its body that looks like a real edge. The eye sees this false edge, and so can miss the true outline of the fish. And if you don’t see the real outline, you won’t recognise what’s in front of you.
To alter its patterning, the fish gathers visual information from its surroundings, then its brain signals to pigment-containing cells in the skin. Depending on the signal, the pigment can either aggregate at the centre of cells, covering a smaller area of the skin, or disperse to cover a larger area.
More at New Scientist’s Zoologger.