Little fish have antifreeze to survive in Greenland, study finds

A little fish that lives in the frigid waters off the coast of Greenland may be diminutive in size, but it’s a giant for science.

One type of snailfish, a member of the Liparidae family, is full of naturally occurring antifreeze proteins at levels never seen before and help it survive in sub-zero waters, according to new research.

Named Liparis gibbus, the snailfish is also distinguished by its biofluorescence, which makes it glow green and red.

Researchers David Gruber and John Sparks, both from the American Museum of Natural History in New York, were part of the Constantine S. Niarchos Scientific Expedition in 2019 when they noticed a snailfish glowing off the east coast of Greenland.

Biofluorescence occurs when animals have the ability to convert blue light into green, red or yellow light. It’s an incredibly rare trait in arctic fish, which live in long periods of darkness. So far, the snailfish variety is the only known polar fish to have this glow.

Gruber and Sparks collected a young snailfish just 1.9 centimeters long, smaller than a fingernail. For comparison, an adult of the same species reaches 11.5 centimeters.

Scientists wanted to learn more about the species’ biofluorescent properties when they came across another surprise in its genetics: the highest levels of antifreeze protein expression ever observed.

“Just as the antifreeze in the car prevents the water in the radiator from freezing at low temperatures, some animals have evolved fantastic machines that prevent freezing, such as antifreeze proteins, which prevent ice crystals from forming,” said Gruber, a contributor Research Fellow at the American Museum of Natural History and Distinguished Professor of Biology at Baruch College, City University of New York.

The scientific journal “Evolutionary Bioinformatics” published the results on Tuesday (16).

“We already knew that this tiny snailfish that lives in extremely cold waters produced antifreeze proteins, but we didn’t realize how full of proteins it is and the amount of effort it takes to produce such proteins.”

As Arctic waters remain warm due to the climate crisis, however, the future of this type of snailfish, with its remarkable adaptation to the cold, is uncertain.

That’s the view of study co-author John Burns, a senior research scientist at the Bigelow Laboratory for Ocean Sciences in East Boothbay, Maine.

The polar oceans are extreme environments for marine life and only creatures that have adapted to live within the frigid temperatures can live there.

Some insect and reptile species can survive if they experience partial freezing of their body fluids, but fish cannot.

Therefore, they need antifreeze proteins, largely produced in the liver, which prevent large ice grains from forming in their cells and body fluids.

Scientists first discovered antifreeze proteins in fish nearly 50 years ago. They are present in five different genetic families.

The snailfish is particularly intriguing because it has two different types of gene families that code for antifreeze proteins: type I and type IV.

“The genes that encode type I antifreeze proteins are likely recent additions to the fish genome and may be actively expanding into additional copies,” Burns said. “It’s like discovering an evolution in action.”

By capturing a young fish, scientists were able to uncover many genetic details over the course of development.

“We noticed that in addition to growth, this fish also works very hard to protect itself from freezing,” Burns said. “The amount of RNA that the fish creates to avoid freezing is equivalent to what it invests in the fundamental cellular machinery, that is, the material that forms the cells.”

So far, scientists do not know whether there is a link between biofluorescence and antifreeze proteins.

But warming temperatures in the Arctic could pose a threat to the same creatures that have adapted to survive there — meaning all the energy they put into frost protection is wasted effort, says Burns.

Some scientists predict that if the region’s sea ice continues to decline at its current rate, the Arctic will be ice-free for the next three decades.

“Arctic seas do not have a great diversity of fish species, and our study hypothesizes that, with increasingly warmer ocean temperatures, species living in ice habitats, such as this snailfish, may suffer greater competition with more temperate species that previously could not survive in the higher northern latitudes,” explained Sparks, curator of the ichthyology department and professor at the American Museum of Natural History at the museum’s Richard Gilder Graduate School.

For Burns, understanding more about antifreeze proteins could help scientists translate the results into biotech uses, such as protecting crops from frost or improving the freezing properties of meat.