Detecting light away from eyes can trigger animals’ color changes
Octopus skin can detect light and respond to it — no eyes or brain required.
Tests of fresh skin samples from California two-spot octopuses (Octopus bimaculoides) show this ability clearly for the first time in any cephalopod, says Todd Oakley of the University of California, Santa Barbara. White or blue light prompts the pale skin’s tiny quick-change color organs, or chromatophores, to expand, creating waves of yellows and browns.
The octopus tests, along with another research team’s new studies of two kinds of cuttlefishes and a squid, feed discussion about whether light detection in places other than eyes plays some role in cephalopods’ changing color displays. All four species studied have light-sensing compounds in tissues beyond their eyes, the two teams report May 15 in the Journal of Experimental Biology.