Cuttlefish Concealed Communication

Cuttlefish have evolved sensitivity to polarized light as well as cells that reflect incoming polarized light. Usage of polarized light for navigation has evolved in many long distance travelers. Cuttlefish however are not long distance travelers and may have evolved a unique type of concealed communication.

Scientists at the University of Maryland study cuttlefish in order to determine how the animal uses polarized light. The researchers placed the animals in front of mirrors and studied their behavior as they approach a mirror image which either reflects polarized light or does not. Observers who did not know the intentions of the study or the type of mirror being used recorded the reactions of the cuttlefish to their own image. The researchers found that cuttlefish are able to display patterns of reflected polarized light which change with their behavior.

In most cases the polarized reflection could be seen at a maximum of 45 degrees horizontally. When viewed at less than a 20 degrees the pattern is visible up too 100 degrees on each side of the animal. Some reflected patterns like those around the eyes can even be observed from behind the animal. The pattern display is most visible when individuals are hovering around the bottom of tanks. Most cuttlefish retreated when subject to their mirror image reflecting polarized light, it is interesting though that the cuttlefish stayed in place with no response as the polarization component of the reflected light was changed.

Cuttlefish produce a pattern of reflected polarized light which changes with behavior. The cuttlefish’s reaction to their own image is dependent on the absence or presence of this polarization. Cuttlefish may have evolved their own concealed type of communication, invisible to most animals. These displays may have evolved because of the cuttlefish's complex polarized light environment.

Source:
http://jeb.biologists.org/cgi/reprint/199/9/2077.pdf

Posted by SAF (1)