Biofluorescent snailfish brave Arctic waters with built-in antifreeze

Penicillin, gunpowder, and the microwave are three of the most important scientific discoveries that were made by accident. Now, natural antifreeze can be added to the list by a team of scientists looking at how some animals survive in the bitter Arctic. According to a recent study that was just published in the journal Evolutionary Bioinformatics, a tiny snailfish species that lives in Greenland has extremely high amounts of antifreeze proteins that enable it to survive in extremely cold temperatures.

In 2019, study coauthor David Gruber, a renowned biology professor at CUNY's Baruch College and a research associate at the American Museum of Natural History in New York, went on an excursion to eastern Greenland to seek for creatures that shone in the dark beneath the ice. This part of Greenland, which is located in the Arctic Circle, experiences nearly uninterrupted summertime sunlight but is completely dark during the winter. The team's objective was to comprehend how light affects marine organisms that live in habitats that experience such extreme seasonal cycles of never-ending and very little sunlight. They discovered a young biofluorescent snailfish, a little fish with a tadpole-like body that is generally found in waters that are much below freezing, at 28.4 degrees Fahrenheit, as a result of their search. A rare phenomenon among Arctic fish that spend the majority of their lives in darkness is biofluorescence, which occurs when an animal absorbs blue light and emits either green, red, or yellow light.

Snailfish imaged at the bottom with white and fluorescent light, displaying dazzling green glowing light

The biology team looked at every gene being produced by the snailfish in order to better understand how it produces light. They were startled to discover that antifreeze proteins were one of the most often produced proteins in the body. According to a news statement from Gruber, "Some creatures have evolved incredible machinery that prevents them from freezing, such as antifreeze proteins, which prevent ice crystals from forming," similar to how antifreeze in your automobile stops the water in your radiator from freezing in cold weather.

Antifreeze proteins had previously been discovered 50 years prior by marine biologists. Antifreeze proteins have been documented to have evolved in a variety of species, including bacteria, insects, fish, and reptiles, in order to survive in icy conditions. The liver of snailfish produces antifreeze protein, which stops big ice grains from accumulating inside of cells and bodily fluids. The blood of snailfish would freeze solid without antifreeze protein.

Since the first discovery, researchers have learned that five separate gene families produce antifreeze proteins. However, marine biologists were unaware of the amount of energy snailfish expended to produce antifreeze proteins. In retrospect, Gruber said, "It makes sense; of course a young fish living on an iceberg is producing tons of proteins that keep it from freezing." The team's genomic investigation revealed two gene families, known as Type I and LS-12-like proteins, that encode two different antifreeze protein types. These genes, which made up the top 1% of expressed genes in snailfish, were highly expressed.

According to the study's authors, these antifreeze proteins must be expressed at high levels in order to survive in the freezing waters. However, several marine biologists have expressed some skepticism regarding how significant of a conclusion to make from these findings. C.-H. LS-12-like proteins, which are also found in the Northwest Atlantic longhorn sculpin but were not involved in the study, did not significantly aid in keeping fish from freezing to death, according to Christina Cheng, an evolutionary biologist at the University of Illinois Urbana-Champaign. She argues that the snailfish may be producing this protein for a different developmental purpose. Additionally, compared to other Type I proteins from the same species, the snailfish's Type I antifreeze protein has a unique expression.

Cheng claimed that by further examining antifreeze protein activity in the blood plasma, these differences may be clarified. "The plasma antifreeze activity would be significant if all these identified transcripts are actually converted into functional antifreeze proteins," she says. It is doubtful that these transcripts are converted into active antifreeze proteins if the plasma antifreeze activity is minimal.

The new research does, however, emphasize the significance of antifreeze proteins in the survival of Arctic snailfish—a region that is particularly sensitive to rising global temperatures. The Arctic has warmed four times as quickly as the rest of the earth over the previous century, and forecasts indicate that the Arctic ocean will be completely ice-free in 30 years.

Ice-dwelling fish will be forced to adapt to warmer climates or face extinction when the region experiences major changes. In an Arctic without icebergs, Gruber said, "this juvenile snailfish's superpower of generating gobs of antifreeze proteins will no longer be a superpower." The situation may worsen as a result of the introduction of more fish species that typically live in temperate regions, which would increase competition for food and shelter.

Future research by Gruber and his group will focus on the subtleties of antifreeze in snailfish and other species that inhabit these frigid conditions. According to him, "Snailfishes are an unusual family as they contain members that dwell at the ocean's surface and at depths of more than 8,000 meters." The capacity of snailfish to tolerate extremely cold and extremely high pressure settings is something we are interested in looking into.