How Fish Camouflage in the Open Ocean with Light

Polarized light – light waves all moving in the same plane, like sunlight glare bouncing off water – typically permeates the scenery underwater, and many fish are able to detect variations in it, using a heightened perception of contrast to help them spot prey.

Light-scattering processes in the open ocean create spatially heterogeneous backgrounds. The two are exceptionally well in hiding from ocean predators by simply hiding in the light.

Underwater, however, sunlight becomes polarized. The U.S. Navy funded the study as part of an effort to understand how a few aquatic cranial animals do this, and how it could be an advantage to the navy.

The crew was left with more than 1,500 distinct angular shapes, with two weeks worth of data that was recorded packed into each amount, for five distinct species of fish. Although scientists have long known that a few fish user their luminous scales to camouflage themselves, they did not know exactly how fish did that or to what degree.

One of the co-authors of the study is an integrative biology professor at the Natural Sciences College. The researchers are now trying to identify how the process of the fish’s camouflage works to develop a device or a garment that would mimic the method.

The study suggests that the marine species evolved the means to detect and hide in polarized light.

The team is comprised by researchers from the University of Texas in Austin and has discovered that two species of fish have developed through the evolutionary process the capability of reading and reflecting polarized light. They dropped a video polarimeter to record the polarized light in real time. With an automated rotating platform to hold the fish in place, they measured it with the polarimeter.

Typical light coloring on the ventral side (belly) and dark coloring on the dorsal (top) side of the fish also can help match intensity by differential absorption of light, in addition to reflection matching.

The fish were held against a mirror as video rolled.

The researchers tested and studied more than 1500 angles, according to the Washington Post. They blended in better than three other fish from environments in which polarized light is less of a factor, according to the statement. The fish could camouflage themselves best at “chase angles”, that jut out 45 degrees in all directions from the tail or head.

There are a lot of fish that are silvery. After every revolution researchers would make an adjustment, then restart the apparatus. However, the camouflage effect is only observed when the surrounding water around the fish is uniform. If mirrors were used for camouflage, it can even backfire as it can directly reflect light to the viewer. Each fish was confined to a platform that also had a mirror. These are the angles at which a predator would be pursuing the fish. A study was drafted on the subject and published in the Science journal.

Researchers found that lookdown fish showed the better disguising ability than rest of the fishes and they can scatter polarized light differently depending on the angle. Now, the question at hand is how are these fish capable of blending in their environment? Molly Cummings declared that the study reflects an example where humans can follow the example of nature, and thus take advantage of evolutionary biology.

The researchers’ next line of inquiry will be to see if the fish are able to actively use the ability – perhaps by adjusting the platelets on the fly (or the swim) or by changing to the “correct” swimming angle for hiding whenever predators lurk. It’s possible, but it could take several more years for a definite answer to materialize.