Arctic fish is filled to the gills with antifreeze, scientists have found

(ORDO NEWS) — In cold sea water, between the turquoise arms of a distant Greenland iceberg, the researchers caught an arctic fish with a body very resistant to low temperatures.

Off the coast of East Greenland, where this young fish was caught, ocean currents regularly drop below 0 degrees Celsius.

These cold temperatures are enough to freeze the blood of fish accustomed to the tropics. But polar fish have their own secret. Many of them have an antifreeze protein in their veins.

When researchers sequenced the RNA of an arctic fish, the variegated snail (Liparis gibbus), they found that the species was loaded with antifreeze proteins to the gills.

“Just as the antifreeze in your car keeps the water in your radiator from freezing at low temperatures, some animals have evolved amazing mechanisms to keep them from freezing, like antifreeze proteins that keep ice crystals from forming,” says urban biologist David Gruber of Gorodskoye. University of New York.

“We already knew that this tiny snailfish, which lives in very cold waters, produces antifreeze proteins, but we didn’t realize how full of these proteins it is and how much effort it goes into producing them.”

The fish in question, L. gibbus, is also known as the polka-dotted snail, so named for the black spatter all over its brown, flabby body.

Outwardly, this is a rather unremarkable sight. But inside it is full of surprises.

In 2019, a variegated snailfish glowing green and red was discovered – the first polar fish ever reported to biofluoresce, and the first example of a single species fluorescing in two colors.

Now RNA sequencing has uncovered another snail secret.

Among the thousands of transcripts sequenced from the arctic species, the researchers found several transcripts encoding antifreeze-like proteins, all of which were highly expressed.

What’s more, one transcript was one of the most highly expressed of all – it was in the top 1 percent.

In the field of genetics, a “transcript” is an RNA copy of a piece of DNA. It gives the cell instructions for the production of certain proteins.

Such a high expression of antifreeze transcripts suggests that snails attach great importance to these proteins. Perhaps they are crucial for survival in freezing temperatures.

Ice-binding antifreeze proteins have been found in many other polar and subpolar fish, as well as some reptiles, insects, and plants.

In fish, these proteins, produced by the liver, are thought to prevent ice grains from growing too large or from accumulating inside cells and body fluids where they can become an obstacle.

The most strongly expressed antifreeze-like protein in snail fish is relatively weak compared to other types of antifreeze-like proteins, but it can still play an important role in maintaining fish biology.

A mixture of weak and strong proteins can work together to give snails the temperature tolerance they need to live in such bitter waters.

For example, while some of the antifreeze proteins may not be powerful enough to keep ice grains in the blood from growing, they can help transport unsaturated lipids that require a certain temperature to move through the vessels.

Thus, the authors say their findings in snails raise the possibility that “weak or combinatorial antifreeze activity may be beneficial” to Arctic fish.

At least it’s beneficial for now.

“Since the mid-20th century, temperatures in the Arctic have risen twice as fast as those in the mid-latitudes, and some studies predict that if Arctic sea ice decline continues at this rate, the Arctic Ocean will be mostly ice-free in summer for the next three decades,” warns study co-author John Sparks, curator at the American Museum of Natural History.

“The Arctic seas are not particularly diverse in fish species, and our study suggests that as ocean temperatures continue to warm, ice-dwelling specialists such as this snailfish may face increased competition from more temperate species that previously could not survive. in these high northern latitudes.”

A lone Greenland iceberg may not exist in all its glory for a long time. Who knows what will happen to the fish swimming in its shadow.

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