Carl Zimmer in the New York Times:
Octopuses, squid and cuttlefish — a group of mollusks known as cephalopods — are the ocean’schampions of camouflage.
Octopuses can mimic the color and texture of a rock or a piece of coral. Squid can give their skin a glittering sheen to match the water they are swimming in. Cuttlefish will even cloak themselves in black and white squares should a devious scientist put a checkerboard in their aquarium.
Cephalopods can perform these spectacles thanks to a dense fabric of specialized cells in their skin. But before a cephalopod can take on a new disguise, it needs to perceive the background that it is going to blend into.
Cephalopods have large, powerful eyes to take in their surroundings. But two new studies in The Journal Experimental Biology suggest that they have another way to perceive light: their skin.
It’s possible that these animals have, in effect, evolved a body-wide eye.