Scientists have discovered an incredible mechanism that some fish use to disguise themselves from predators in the open ocean.
The new findings could help military technologists create more effective methods of ocean camouflage, the University of Texas at Austin reported. The research shows fish use microscopic structures called platelets in their skin cells to reflect polarized light, effectively camouflaging them from hungry predators. Polarized light is composed of light waves that travel on the same plane. Light that travels under the water is usually polarized, and fish can detect variations of this type of light.
"Fish have evolved the means to detect polarized light," said Molly Cummings, professor of integrative biology in the College of Natural Sciences. "Given that, we suggested they've probably evolved the means to hide in polarized light. If we can identify that process, then we can improve upon our own camouflage technology for that environment."
For years, the U.S. Navy has been searching for ways to camouflage in open water. These new findings could provide key insights into how to accomplish this feat.
To make their findings, the researchers built a video polarimeter that can record polarized light in real time. The device allowed them to see polarized light in the same way that fish do. They built an automated rotating platform to hold the fish in place in the water while they took measurements with the polarimeter.
After recording more than 1,500 different angular configurations, the researchers found two fish, the lookdown and the bigeye scad, had better camouflage in polarized light than a mirror. They were also able to camouflage themselves more efficiently than reef fish and surface-skimming fish that do not normally see polarized light. The fish were most efficient at camouflaging at "chase angles," which extend out 45 degrees in all directions from the tail or head, which are the angles at which a predator is most likely to pursue.
The researchers found the key to this incredible disappearing act was the structure of platelets within the skin cells, which work to scatter polarized light differently depending on the angle. The resesarchers hope these novel findings will one day have real-world applications.
"I think it's a great example of how human applications can take advantage of evolutionary solutions and the value of evolutionary biology," Cummings said. "It's important for people to recognize that we take advantage of evolutionary processes and solutions all the time and that even our military does."
The findings were published in a recent edition of the journal Science.
