U. S.: Octopus Sees with Skin Through Light Sensors

The California two-spot octopus, and most likely, other octopuses, can do something that no other animal can; it sees with skin and can both detect and react to the light without the signal having to go through its brain or its eyes as it makes its travel in the ocean. This was recently discovered by biologists at the University of California at Santa Barbara.

Even though the California two-spot octopus sees with skin, the information it perceives isn’t as detailed as if it was using its eyes because the skin can only perceive the variations in the brightness of light that the two-spot octopus detects on its skin as it makes its travel through its ocean territory.


Proteins in Skin React to Light, So Octopus Sees with Skin

The study shows that the reason the California two-spot octopus sees with skin is due to proteins called rhodopisines. The proteins are able to react to changes in light and they are abundant in the skin of this kind of octopus. Researchers used samples of the octopus skin and subjected it to different types of light to see if there was a reaction. In darkness, the skin stayed normal colored, but when light was turned on, the skin changed color.
The rhodopisines proteins normally are found in the eyes of vertebrates or creatures with backbones, not in the skin. The pigments are found in the rods of the eyes inside the retina, and they work to convert the electronic signal from light and turn it into nerve impulses to the brain.

Octopus Have Ability to Camouflage Their Special Skin

Octopus are cephalopods, which mean they are in the same family as creatures like squid and cuttlefish that travel around the ocean. All cephalopods can use camouflage to hide themselves or sneak up on prey. They have to be able to perceive light in different ways than most creatures, so they can alter the way they look to match their environment.

Data from the Journal of Experimental Biology shows this is part of why the octopus sees with skin, as their actual eyes are colorblind. This comes from millions of years of evolution to help the two-spot octopus survive in its environment. It is like having eyes all over its body, which even if they are not actual eyeballs, it contains the same kinds of proteins that react to light and help the octopus “see.”


Experiments Prove Two-Spot Octopus Skin Very Sensitive to Colors

Other tests by the scientists showed that the two-spot octopus was the most sensitive to blue lights and reacted the quickest when this was used. Now, the scientists want to find out exactly what part of the skin actually sees with skin and if there is any kind of relationship with the octopus’ kind of skin and other animal’s skin.