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Octopus can use its skin to see

The octopus' skin was most sensitive to light on the blue end of the spectrum.

By Brooks Hays
Research shows California's two-spot octopus can see with its skin. Photo by Jerry Kirkhart/Flickr
Research shows California's two-spot octopus can see with its skin. Photo by Jerry Kirkhart/Flickr

SANTA BARBARA, Calif., May 21 (UPI) -- Researchers recently found the same proteins used in human eyes are also present in the skin of the two spot octopus, a species found off the coast of California. The proteins help the octopus sense light, without the help of the eyes or the brain.

All octopi have a remarkable propensity for camouflage, using pigmented organs in their skin called chromatophores to blend in. The same mechanisms allow the octopus to relay messages. Now, researchers have shown that at least one octopus species can manipulate its appearance without use of its central nervous system.

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The chromatophores in the species' skin seem to have coopted the basic seeing ability from the octopus's eyes and brain.

"Octopus skin doesn't sense light in the same amount of detail as the animal does when it uses its eyes and brain," Desmond Ramirez, a doctoral student in ecology and marine biology at the University of California, Santa Barbara, explained in a press release. "But it can sense an increase or change in light. Its skin is not detecting contrast and edge but rather brightness."

Ramirez is the lead author of a new study on the two-spot octopus's unique seeing abilities.

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Researchers found that the cells of the species' chromatophores swelled and shrank in response to different lights, and that the octopus' skin was most sensitive to light on the blue end of the spectrum. Previous research has identified other marine mollusks with seeing skin, but researchers aren't sure how octopi fit into this peculiar genetic lineage.

"Do they all come from the same ancestral source or did they evolve multiple times?" asked Todd Oakley, a marine biology professor and study co-author. "What kind of behaviors do the different groups share and what kind of behaviors does the skin sensing light underlie?"

Oakley, Ramirez and their colleagues will need to conduct further studies to answer those questions.

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