Neural control of cephalopod camouflage

Abstract

In Die Another Day, James Bond receives an Aston Martin that can render itself invisible by dynamically reproducing the surroundings on the car's "polymer skin". In what is widely regarded as the worst Bond movie ever, the invisible car scene is cited as the moment the plot plunges into the truly absurd. But what if nature had actually invented such a technology, and did so hundreds of millions of years ago? The coleoid cephalopods - octopus, cuttlefish and squid - are living examples of dynamic camouflage. Their skin is covered with a high-resolution array of 'cellular pixels' (chromatophores) that are controlled by the brain. To disappear into their surroundings, cephalopods recreate an approximation of their environment on their skin by activating different combinations of colored chromatophores. However, unlike the fictional Bond car, whose surface is coated in tiny cameras to detect the environment, cephalopods don't see the world with their skin. Instead, the visual world is detected by the eyes, processed in the brain, and then used to activate motor commands that direct the skin's camouflage pattern. Thus, cephalopod skin patterns are an external manifestation of their internal perception of the world. How do cephalopods approximate the world with their skin? What can this teach us about how brains work? And which neurobiological tools will be needed to uncover the neural basis of camouflage?