Biologists come to know as to why some species glow

After seeing so many glowing life forms, a biologist at the City University of New York’s Baruch College was keen to know as to why all these species are glowing. Therefore, David Gruber and his colleagues have built a ‘shark-eye’ camera to simulate how fluorescent sharks appear to each other.

The study researchers explained the meaning of bio-fluorescent that they are the molecules in their skin that absorb light of a certain wavelength and bounce it back at a different wavelength. In the ocean, it means that they absorb blue light and transform it into green, red or orange. It is difficult for human eyes to notice it in the dim ocean.

Gruber has found bio-fluorescent effect in so many animals. It led him to wonder what advantage it had on a species. The researchers now know the answer of the question for two bio- fluorescent sharks, which are the Atlantic-dwelling chain catshark and the Pacific-living swell shark.

The researchers did so by looking deep into their eyes in the dissection way. They came to know that though these species are having an excellent low-light vision, they are monochromats. It means that sharks have just one pigment and detects blue-green light. Such is not the case with humans, who build color vision using three types of pigment molecules in the eyes.

Gruber said that the ocean acts like a massive blue filter and it becomes more perfectly blue as one goes deeper. The next question was what parts of shark’s body shine. The researchers studied sharkskin in the lab and used a special camera setup to capture the sharks’ fluorescence in the wild.

The researchers dove at night and found that the sharks’ beige patches were the place from where the fluorescence came. The researchers concluded that the sharks swim deeper in ocean, their fluorescent patterns should stand out more strongly in other sharks’ eyes.

According to a report in Theatlantic by Elizabeth Preston, “David Gruber sees glowing life forms everywhere he looks. He’s found dozens of fluorescent corals in the Great Barrier Reef. In 2014, he reported on more than 180 fish species that fluoresce. Last year, he even stumbled across fluorescent sea turtles.”

Now Gruber, a biologist at the City University of New York’s Baruch College, wants to know why all these species are glowing. He and his colleagues built a “shark-eye” camera to simulate how fluorescent sharks appear to each other, in part so that humans view these creatures a little more kindly.

“These small sharks grow no more than three feet (one meter) long and spend much of their time on the bottom, to a depth around 1,600 to 2,000 feet (500 or 600 meters). They are shy and nocturnal and often hide in crevices,” according to a news report published by NationalGeographic.

“The cool thing about this research is it literally shines a light on animals that are often overlooked,” says David Gruber, the study’s lead author and a National Geographic Emerging Explorer, who is also a researcher at Baruch College, City University of New York and the American Museum of Natural History.

A report published in Phys said, “To further explore this phenomenon, the researchers focused on the visual ability of two different catsharks: chain catsharks (Scyliorhinus retifer) and swellsharks (Cephaloscyllium ventriosum). With the help of Cornell University veterinary expert Ellis Loew, the researchers used a technique called microspectrophotometry to determine how the sharks’ eyes absorb light, discovering that they have long rod pigments that help them see in low-light environments. They used this information to build a special camera filter that simulates how light hits a shark’s eyes.”

“Some sharks’ eyes are 100 times better than ours in low-light conditions,” Gruber said. “They swim many meters below the surface, in areas that are incredibly difficult for a human to see anything. But that’s where they’ve been living for 400 million years, so their eyes have adapted well to that dim, pure-blue environment. Our work enhances the light to bring it to a human perspective.”

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