Scientists have found that fish manipulate the way light reflects off their skin to camouflage themselves in the ocean.
Researchers at the University of Texas, Austin, say that lookdown fish camouflage themselves in the ocean by manipulating the way light reflects off their body. This new discovery overturns the 40 year "mirror" strategy that was previously thought to be state-of-the-art in fish camouflage. Scientists state that fish can hide themselves by a complex manipulation of polarized light.
"The open ocean represents a challenging environment for camouflage," said Molly Cummings, associate professor of integrative biology in the College of Natural Sciences. "There are no objects to hide behind in three-dimensional space, so organisms have to find a way to blend in to the water itself."
For a long time it was believed that open ocean fish hide themselves by reflecting light like mirrors. These fish are known to have mirror like elements in their skin, which helps them in camouflaging. While this technique works well in most lights, it's not very effective with polarized light where individual waves of light align parallel to one another.
"In the polarized light field, there is a lot of structure in the open ocean," said physicist Parrish Brady, a postdoctoral associate in Cummings' lab. "Humans can't see it, but more than 60 different species of fish have some degree of polarization sensitivity. They can perceive the structure in the light."
For the study, Brady and Cummings caught some lookdown fish and put them in a tank in their lab. They then created an environment which imitated the path of the Sun's rays on the ocean through the day and used a custom-built polarimeter to measure how the lookdowns reflected the polarized light. They found that the fish reflected the light far better than a mirror.
"From an evolutionary biologist viewpoint, I am always excited when evolution is one step ahead of humans," said Cummings. "There is this problem out there - how to blend in to this environment, and though we haven't quite solved it yet, an animal has. We can identify these basic biological strategies, and perhaps materials scientists can then translate them into useful products for society."
Authors of this research state that this new discovery can be used in the future to develop camouflage materials that could be used in the ocean.
