A new research conducted by researchers from University of California and published in the Journal of Experimental Biology offers additional information about the unique features of octopuses. It seems that the skin of the octopus contains a particular pigment: opsins or the light-sensitive proteins which make the skin responsive to light.
It is already known that the octopus has the unique ability of changing its pattern, color and even the texture of the skin. It does this not only for camouflage, but also as a way to communicate. Mollusk uses its eyes to send signals to the pigmented organs in the skin known as chromatophores. Afterwards the chromatophores expand contract in order to change the octopus’ appearance. This new study reveals that the skin of the mollusk has a cellular mechanism which detects the light similar to the one which the eyes have.
The lead author of the study Desmond Ramirez of the Department of Ecology, Evolution and Marine Biology (EEMB) explained that the skin of the octopus does not sense light in such a detailed way like the brain and the eyes do. However the skin can sense an increase or decrease in light. It sense brightness rather than edge and contrast.
Desmond Ramirez together with Todd Oakley of University of California (Santa Barbara) used eleven California two-spot Octopus bimaculoides. They removed patches of skin from the octopuses and afterwards mounted the patches on to the Petri dishes. Using light emitting diodes the skin fragments where exposed to light which had different wavelengths.
When the tissues were exposed to light the chromatophores expanded and changed their color. When the light was turned off the skin returned to its original hue because the chromatophores relaxed. According to Ramirez this process indicates that light sensors are linked with the chromatophores and this makes possible a response without input from the eyes or brain. This process was dubbed by the researchers as Light-Activated Chromatophore Expansion (LACE).
Oakley is of the opinion that the discovery of the new components which make up the very complex behavior of camouflage in octopuses is a proof of an evolutionary adaptation. According to him the cellular mechanism in the octopus eye used for light detection was co-opted in the skin of the animals for light sensing and used for LACE. So what LACE does is put parts together in new combinations and ways. Oakley calls cephalopods the invertebrate rock stars.
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