Decode the disguise of fish

American scientists have deciphered the disappearance of many fish in front of enemies in the ocean, a discovery that can create breakthroughs in camouflage.

Learn about the camouflage ability of fish

In a study published Nov. 20 in the journal Science, a team at the University of Texas Austin said that some fish species use microstructures on their skin cells to reflect polarized light , giving their magic seems to disappear from the enemy's view.

Polarized light is made up of light waves that propagate in the same plane, such as when you see sunlight reflected on the water surface. Under the surface of water, light tends to be polarized. Many types of fish are able to detect changes in such polarized light.

Scientists found that fish that live in the ocean, like Fish Lookdown, can reflect polarized light from their bodies in a special way, making them seem to disappear in the eyes of the enemy.(Photo: The University of Texas).

" Fish has evolved to detect polarized light , " said Molly Cummings, a professor of biology at Texas Austin University of Science for Phys Org.

"We think they have changed themselves to be able to hide in polarized light. If we can determine that process, we can improve the underwater camouflage technology."

"Whether a predator chasing a fish or a satellite looking for an object, light helps detect targets in the ocean in three ways: through brightness contrast, contrast. contrasting colors and polarity contrast, in which polarity contrast is considered to be the most effective way in the ocean. "

The US Navy took years to learn how to camouflage in water and sponsor Cummings' research team. In a previous laboratory-scale study, scientists found that the Lookdown fish could use light polarization to benefit them. New research conducted in the ocean shows that Lookdown fish and other fish also disguise themselves in this way.

Parrish Brady, a partner of Cummings and the lead author of the study, built a polarimeter that enables film capture and polarized light recording in real time, helping researchers to observe light. Polarized light like fish.

The study results show that two types of ocean fish, Lookdown fish and bigeye tuna can best disguise in polarized light. Notably, ocean fishes can best camouflage at a certain angle of view, called "hunting angle", which can be up to 45 degrees in all directions from the tail or the fish head. These are the directions from which a predator will chase the fish, or from there the fish will pursue their prey.

Many fish in the oceans are silver, allowing them to reflect light like a mirror . For many years, experts say this is the main vehicle for camouflage among fishes. But this camouflage approach only works well when the surrounding water environment is homogeneous, as for the human eye.

Scientists are examining how ocean fish use polarized light to camouflage.(Photo: The University of Texas).

Polarized light is an important component of underwater light fields, which are heterogeneous but vary greatly. Using silver skin to camouflage in such an environment can be counterproductive and make it easier to stand out in the ocean.

As for the real cause of fish camouflage, Cummings' team thinks that microstructures in fish skin cells play a decisive role. They scatter polarized light differently depending on the angle. Researchers will continue to study whether fish can actively use this ability, perhaps by changing the angle at which they swim or somehow adjusting the microstructures on their skin.

"I think it's a great example of taking advantage of the biological values ​​of evolution to develop into applications for people , " Cummings said.