How an octopus can “see” with its skin

We already know how awesome the octopus can be, and now scientists from UCSB have discovered something else awesome – the skin of the California two-spot octopus contains a type of light-sensitive protein that allows the skin to “see” light.

The proteins, known as rhodopsins, are the same cellar mechanism used in its eyes for detecting light – and in the skin, the opsins can sense light even without input from the octopus’ central nervous system.

Other marine mollusks have been known to sense light via the skin, but this is the first time scientists have seen it in cephalopods. The findings were published in the Journal of Experimental Biology.

A California two-spot octopus hatchling.
Credit: UCSB

“Octopus skin doesn’t sense light in the same amount of detail as the animal does when it uses its eyes and brain,” said lead author Desmond Ramirez, a doctoral student in the Department of Ecology, Evolution and Marine Biology (EEMB). “But it can sense and increase or change in light. Its skin is not detecting contrast and edge but rather brightness.” 

Ramirez and his co-author, Todd Oakley, an EEMB professor, tested the skin’s sensitivity by exposing it to different wavelengths of light, a process they called Light Activated Chromatophore Expansion (or LACE). They then ran molecular experiments to establish what proteins were involved in the process and discovered that rhodopsin was present in the sensory neurons on the skin’s surface.

The researchers suggest it could be an evolutionary adaptation of the octopus’ complex camouflage. They will be running new experiments to see if the skins of marine mollusks also contain these light-sensitive proteins.

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