Antifreeze Proteins: An Arctic Fish Secret to Braving Below-Zero Waters

An Arctic fish that has been caught by researchers has a body that is very impervious to freezing temperatures. Its ability to brave the waters even in below-freezing temperatures is due to a body stuffed with antifreeze proteins.

The fish was caught off the coast of East Greenland where ocean currents frequently drop below 0 degrees Celsius.

The blood of fish used in the tropics will freeze in these arctic conditions. Polar fish, however, is hiding something. Many people's veins are filled with antifreeze proteins.

Variegated Snailfish, Polka-Dot Snailfish

The RNA of the Arctic fish, a variegated snailfish (Liparis gibbus), was sequenced, and the researchers discovered that the species was stuffed with antifreeze proteins.

David Gruber, a biologist from the City University of New York, says that Similar to how antifreeze in a car prevents the water in its radiator from freezing in cooler temperatures, some animals have developed incredible machinery that prevents them from freezing, like antifreeze proteins that stop ice crystals from forming.

He continued by saying that although it was previously unknown how many antifreeze proteins were produced by the tiny snailfish, which dwells in the coldest waters, as well as how much work was involved.

The concerned fish, L. The gibbus, also called a polka-dot snailfish, gets its name from the black spots that can be seen all over its flabby, brown body.

It appears to be a fairly ordinary species. But there are many surprises inside.

Greenland Iceberg

The first polar fish to biofluoresce was discovered in 2019 and it was a variegated snailfish, the first instance of a single species fluorescing in two colors.

RNA sequencing has now revealed a further snailfish secret.

Researchers discovered a few transcripts that specify antifreeze-like proteins among the multitudes of transcripts sequenced within the body of the Arctic species, and all of these transcripts were highly expressed.

One transcript was one of the best expressed out of the group, ranking in the top 1%.

A "transcript" in the study of genetics is an RNA copy of a piece of DNA. It instructs a cell on how to make specific proteins.

The fact that antifreeze transcripts are expressed so frequently suggests that snailfish value these proteins highly. They are likely essential for surviving in below-freezing temperatures.

Many other polar and subpolar fish as well as some insects, reptiles, and plants have antifreeze proteins that cope with ice.

Antifreeze Protein in Fish

These liver-produced proteins in fish are thought to prevent ice grains from accumulating inside cells and bodily fluids where they might become obstructive or grow too large.

Despite being relatively weak in comparison to other antifreeze protein types, the snailfish antifreeze-like protein that is most highly expressed may still be crucial for maintaining fish biology.

The combination of stronger and weaker proteins may help snailfish maintain the necessary temperature tolerance to survive in such abrasive waters.

For instance, while some antifreeze proteins may not always be strong enough to prevent the growth of ice grains in the blood, they might aid in the transportation of unsaturated lipids, which must travel through vessels at particular temperatures.

Accordingly, the authors claim that their discoveries in snailfish suggest that Arctic fish may benefit from weak or combinational antifreeze activity but at least it helps right now.

Read also: 6 Animals That Can Freeze Themselves and Come Back to Life! 

Arctic Sea Decline

John Sparks, a curator from the American Museum of Natural History, warned that Since the middle of the 20th century, temperatures in the Arctic have risen twice as quickly as those in mid-latitudes. According to some studies, if Arctic sea ice continues to disappear at the current rate, the Arctic Ocean will mostly be ice-free in the summer sometime in the next three decades. Sparks is also a co-author of the study.

The Arctic seas, he continued, do not harbor a wide variety of fish species. According to their research, more temperate species that previously couldn't survive at any of these higher northern latitudes may become more competitive with ice-dwelling specialists like this snailfish as ocean temperatures continue to warm, Science Alert reports.

Related article: Natural 'Antifreeze' Found in Antarctic Fish Also Prevents Melting