Research suggests that the skin of the octopus is sensitive to light

The Guardian reports, 20th May 2015: “Octopus skin contains a light-sensitive pigment found in eyes, suggesting that these clever cephalopods can “see” without using their eyes.

Octopuses are well known for changing the colour, patterning, and texture of their skin to blend into their surroundings and send signals to each other, an ability that makes them both the envy of, and inspiration for, army engineers trying to develop cloaking devices.

As if that wasn’t already impressive enough, research published in the Journal of Experimental Biology shows that octopus skin contains the pigment proteins found in eyes, making it responsive to light.

These clever cephalopods can change colour thanks to specialised cells called chromatophores, which are packed in their thousands just beneath the skin surface. Each of these cells contains an elastic sac of pigmented granules surrounded by a ring of muscle, which relax or contract when commanded by nerves extending directly from the brain, making the colour inside more or less visible.

Octopuses are thought to rely mainly on vision to bring about these colour changes. Despite apparently being colour blind, they use their eyes to detect the colour of their surroundings, then relax or contract their chromatophores appropriately, which assume one of three basic pattern templates to camouflage them, all within a fraction of a second.

The researchers also noted that the chromatophores in their skin preparations expanded in response to light touch as well as to light. It’s still not entirely clear whether octopus chromatophores act as light sensors, mechanical receptors, or both, but Ramirez and Oakley are planning to find out, in a series of new experiments designed to determine what kind of behaviours they are involved in.

Source: The Guardian, 20th May 2015. For the full text, see
Reference: Ramirez, M. D. & Oakley, T. H. (2015). Eye-independent, light-activated chromatophore expansion (LACE) and expression of phototransduction genesgene A string of the DNA (deoxyribonucleic acid) molecule that is the fundamental unit of inheritance, so it is variations in the make up of this molecule in the gene that controls variations in an organism's appearance and behaviour. Genes are found in the nucleus of the organism's cells. in the skin of Octopus bimaculoides. J. Exp. Biol. doi: 10.1242/jeb.110908.

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