Squids may communicate incognito

The squid’s skin is made of a layer of superficially located pigmented chromatophores and underlying iridophores (reflector cells). During camouflage, the squid can cover reflector cells with chromatophores in a fraction of a second. These facing images show the same irid?ophore splotch with yellow chromatophores retracted (left) and expanded to cover polarized iridophores (bottom right). In the Sept. 19 online issue of Biology Letters, Lydia M. Mäthger and Roger T. Hanlon report that they have found that the chromatophores act like a filter by altering the color of light reflected from the underlying iridophores without depolarizing it. This means that squids still may be able to communicate with each other even when camouflaged. The system works because most fish or mammalian predators are not sensitive to differences in polarization. Photos by Lydia M. Mäthger.

Squids, as with other cephalopods, can change color to blend in with their environment. Beneath the camouflaging layer of skin is another layer that the organisms may use to communicate with each other via polarized reflection. Researchers at Marine Biological Laboratory in Woods Hole, Mass., have found evidence that Loligo pealeii, the longfin inshore squid, may be able to communicate even when trying to hide. Courtesy of Roger T. Hanlon.