There are many fishes in the sea but not all of them have light-manipulating abilities that enable them to go stealth. Researchers found some fish species' skin cells have microscopic structures that enable them to distribute polarized light underwater. The fish species use this "stealth mode" to escape predators, enabling them to turn invisible.

Through a human's naked eyes, the open ocean may seem like an unchanging environment. But for animals, the ocean is made up of diverse optical surroundings, much like swimming through a kaleidoscope. The marine species' evolution equipped them with camouflage abilities to help evade predators and sustain survival.

A team of scientists led by Molly Cummings and Parrish Brady from the University of Texas had been conducting a study on how fish adjust to the fluctuating polarized lights underwater for five years.

The researchers said that waves of polarized light have vibrations that travel on the same level. However, most light is not polarized and creates vibrations that travel on varying planes. Above waters, sunlight is not polarized. But upon hitting the water's surface, sunlight creates that sparkling shimmer through reflection.

Underwater, however, sunlight becomes polarized. Fish species with skin cells embedded with microscopic structures called platelets can identify and imitate vibrations caused by polarized lights. Fish platelets are composed of small nanoscale crystals, giving their scales a shiny glimmer.

The scientific community have long been aware that shiny scales are somehow connected to the fish species' camouflage skills. Until now, scientists were unable to determine how much the luminous scales contribute to the fish species' survival.

"[The platelets] are organized in a way to scatter reflective light away from the animal and give it its silvery sheen when you look at the fish. They're aligned in a specialized way that we believe in the study gives it its reflective properties," said Brady.

In the tedious experiments involved an analysis of five fish species. The researchers found that the bigeye scad and lookdown performed better when going stealth under polarized light.

Cummings noted that the analysis could lead to human camouflage innovations particularly in military optics. Advancements in this field could help better detect targets under open water.

The research was published in the journal Science on Nov. 20.

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