Breakthrough discoveries about roundfin fish

Scientists have discovered the special properties of roundfin fish, a fish that lives on the bottom near shore in many areas in the northern Atlantic and Arctic Oceans.

If you ask the question, "What color is a roundfin?", you will get many different answers.

This fish changes color over time, and at each age they will have a certain color. Recently, however, scientists believe they have found their true color - fluorescent green.

Roundfin fish are quite funny looking and are often kept on salmon farms because they eat sea lice, helping to clean up the salmon's habitat. (Photo: Reddit/u/NinjaKamihana).

Famous for TikTok

In a study published this month in the scientific journal Journal of Fish Biology, the authors say they found that roundfin fish glow when placed under UV light.

They believe these fish use their biofluorescence radiation to recognize and communicate with each other.

In recent years, researchers have discovered many animals capable of biofluorescence, including cat sharks, koalas, flying squirrels or platypuses. And roundfin fish is the newest name on this list.

The roundfin fish, known as Cyclopterus lumpus, is solitary and spends most of its life on the seabed. They have the ability to attach their abdomens to surfaces such as rocks or seaweed. This body part evolved from the ventral fins and acts like a suction cup.

With a funny face, the roundfin fish is also very popular on the social network TikTok, with thousands of videos of this fish recorded by researchers or fishermen.

"This is a pretty weird fish," said Nathaniel Spada, research assistant at the Woods Hole Oceanographic Institution in Massachusetts. Although he was not involved in the study, Mr. Spada's fin fish videos have been viewed millions of times on TikTok.

"I didn't think they (videos of roundfin fish) would become so popular, but I should have figured it out because they are really interesting fish," Spada added.

Last year, Thomas Juhasz-Dora, a veterinarian working as a doctoral student at the University of Cork in Ireland, became curious when he looked into the bulging eyes of a roundfin fish in the lab. . He suddenly had an idea.

Having witnessed the glow under UV light in some marine species, Mr. Juhasz-Dora wanted to know if roundfin fish possessed this property. He collected 11 fry and photographed them under different lighting conditions.

Under normal light, roundfin fish are blue mixed with green like a sponge. But when exposed to UV rays, their entire body emits a neon blue light.

Roundfin fish give off a strong neon green color when standing under a UV light. (Photo: Thomas Juhasz-Dora).

"I felt like 'Wow'," said Dr. Juhasz-Dora. He was surprised by the strong fluorescence intensity of the roundfin fish. This phenomenon occurs when certain organisms absorb ultraviolet (UV) rays, which are invisible to the naked eye, and re-emit them as a visible color, such as red. , orange or green.

This is different from bioluminescence, where an organism produces its own light through a chemical reaction within its body.

Colorful fish

Many animals have special filters in their corneas that allow them to see biofluorescence without the help of UV light.

Dr Juhasz-Dora hypothesizes that roundfin fish are also equipped with such a filter, allowing them to somehow signal to exchange information with others, while remaining hidden from predators.

According to Elizabeth Fairchild, a researcher and associate professor at the University of New Hampshire with expertise in roundfin fish and other aquatic species, Mr. Juhasz-Dora's hypothesis is completely feasible.

Roundfin fish can also use their biofluorescence to attract prey. But Dr. Fairchild thinks they are more likely to use this tool to communicate.

"Communication is probably the most likely answer. We just don't know what they're communicating," Ms. Fairchild said.

It is also possible that biofluorescence serves no particular purpose. However Dr Fairchild, who was not involved in the study, thinks this is less likely, given the importance of color to roundfin fish.

"Fish have an impressive ability to change colors. When young, they can take on any color of the rainbow. As they grow a bit older, they can change their skin color based on their surroundings, helping hide from predators," explains Ms. Fairchild.

"As an adult, the roundfin fish changes color from light gray to light blue. However, during the breeding season they change color again, the male will turn red-orange and the female will turn blue." , added Dr.

An adult roundfin fish.

How and why bioreflection occurs in roundfin fish is one of many questions raised by Dr. Juhasz-Dora's findings. He and his colleagues are now studying whether the fish have the ability to control their fluorescence, or if it's completely passive.

According to Dr. Juhasz-Dora, his and his colleagues' findings "open the door to new discoveries".

"It allows us to see the world from their (roundfin) perspective, rather than our own," he said.