A new analysis by biologists at the University of California has found that octopuses don't require their eyes to detect light and the changes in its intensity, and can do so through their skin. The researchers had tested the theory on two-spot octopuses and found that the skin of the animal has color organs called chromatophores, which are activated by the light.
"Octopus skin doesn't sense light in the same amount of detail as the animal does when it uses its eyes and brain," researcher Desmond Ramirez, said, The Mirror reported Thursday, adding: "But it can sense an increase or change in light. Its skin is not detecting contrast and edge, but rather brightness."
The scientists discovered that the octopuses have opsins in their skin, just like a cuttlefish. Opsins are photoreceptor molecules found in the retina of animals and help them to detect light. But instead of producing the opsins in their chromatophores, the octopuses produce them in the form of nerve-like endings in the skin. The researchers, who had cut pieces of octopus' skin to see the reaction to light, said that the skin remained pale when the lights were off. However, as soon as the lights were switched on, the chromatophores expanded at a fast pace, turning the skin dark, in just seconds.
“We didn’t expect to see such a fast reaction,” Todd H. Oakley, a biologist at the University of California and a researcher in the analysis, said, according to the New York Times. He suspects that when the light hits the skin opsins of the octopus’ skin, the neurons get stimulated and pass on the information to other chromatophores.
The researchers also said, according to the Times, that blue light triggers the fastest reaction.
Roger T. Hanlon, a biologist at the Marine Biological Laboratory in Woods Hole, Massachusetts, and his colleagues had concluded in 2010 that cuttlefish and squids can make opsins in their skin, which had triggered the possibility of animals sensing light through their skin. However, Hanlon and his team had taken pieces of animal skin to see if it can perceive light and color, but were unable to get a response.
“I’m very happy that they’ve succeeded,” Hanlon, said, according to the Times, referring to the research by Oakley and Ramirez, adding: “And a little bit envious.”