Cephalopods are masters of disguise. Pigmented skin cells (called cromatophores) enable them to change their color instantaneously, remaining undetected by prey or predator.

Squid and cuttles also produce polarized skin patterns by changing the iridescence of their skin, possibly creating a "hidden communication channel", visible only to animals which perceive polarized light.

Researchers Lydia Mäthger and Roger Hanlon presented evidence that the polarized aspect of the skin of the longfin inshore squid, Loligo pealeii, is preserved after passing through the pigment cells responsible for camouflage.

There are some already known animals producing polarization signals and using them in communication.

Mäthger and Hanlon's findings present the first anatomical evidence for a "hidden communication channel" that can remain masked by normal camouflage patterns.

This means that it is possible for squids to send hidden polarized signals to one another while keeping camouflaged to vertebrate predators, most of which do not posses polarization vision.

Mäthger notes that these messages could also contain territorial or diverse kinds of information.

"Whether signals could also contain information regarding the presence of predators (i.e., a warning signal) is speculation, but it may be possible," she adds.

Investigation of the masked polarization signaling system in cephalopods in natural environment would provide new knowledge about animal camouflage mechanisms.

It is possible that many other species use this type of communication.