Home Ice bergs Greenland fish survive sub-zero temperatures by being “full” of antifreeze

Greenland fish survive sub-zero temperatures by being “full” of antifreeze

0

Life, as they say, finds a way. To find a way to survive in the cold waters of Greenland, the animals resort to all sorts of tactics. Some are developing antifreeze proteins, and this has already been described. But according to a new study, some snails are packed with antifreeze protein, the highest levels ever seen.

In 2020, John Sparks and David Gruber, two biologists associated with the American Museum of Natural History, were on an expedition to Greenland, examining the prevalence of biofluorescence in the Arctic. In a makeshift laboratory with fresh water straight from the glacier, the pair set out to explore Greenland’s icy ecosystem.

Far from a desolate landscape, the two biologists turned explorers discovered an ecosystem teeming with life under the waves.

“There is so much kelp! Kelp with huge fronds, and there were few fish swimming, or lots of shrimp swimming on the kelp, it was very beautiful underwater,” Sparks recalled in a video about the expedition.

Diving from an isolated cove, they explored the ecosystem in depth.

“We did dives in several different habitats, we looked in fjords, we looked in kelp forests, and on several dives we actually looked for specimens in the ice, among the icebergs,” adds Gruber.

The huts in which the researchers slept and worked during their expedition. Image credits: American Museum of Natural History.

What is interesting with these icebergs is that they are a kind of refuge for many small creatures. Crustaceans move in and out of the ice, and even some fish head for these icebergs. But the problem, as the two biologists would learn on their own, is that the cold is not easy to manage. Because ocean water contains salt, it can drop below zero degrees Celsius (or 32 F) without freezing — so you have to endure freezing temperatures one way or another. When they finished their initial research on bioluminescence, they returned to the problem of cold.

Some animals refer to a familiar substance to help them fight the cold – not a substance we know from biology, but rather something we know from cars: antifreeze.

“Similar to how the antifreeze in your car keeps the water in your radiator from freezing in cold weather, some animals have developed amazing machines that keep them from freezing, like antifreeze proteins, which prevent the formation of crystals of ice,” said David Gruber, a research associate at the Museum and a distinguished professor of biology at Baruch College at CUNY. “We already knew that this little snailfish, which lives in extremely cold waters, produced antifreeze proteins, but we didn’t realize just how full of these proteins it is and how much effort it goes to. make these proteins.”

A still image under the waves. Image credits: American Museum of Natural History.

Some species (especially some reptiles and insects) can survive if their body fluids partially freeze, but the same cannot be said for fish. Fish need to keep their body fluids liquid, so they depend on antifreeze proteins. They make these proteins in the liver, and just like car antifreeze, the proteins work by lowering the freezing temperature of the liquid.

The ability of some fish to produce antifreeze was discovered about 50 years ago, but when researchers analyzed antifreeze levels in snail samples obtained on this expedition, they were surprised: snail genes have the highest antifreeze protein expression levels ever observed. This highlights how important it is for these fish to adapt to freezing temperatures around Greenland, and it also raises a red flag for their survival.

As temperatures continue to rise due to global warming, this adaptation will be less helpful and may actually pose a threat to their survival.

“Since the mid-twentieth century, temperatures have risen twice as fast in the Arctic as at mid-latitudes and some studies predict that if Arctic sea ice decline continues at this current rate, the Arctic Ocean will be in largely ice-free in the summer within the next three decades,” Sparks said. “Arctic seas do not support a high diversity of fish species, and our study hypothesizes that with ocean temperatures over in warmer conditions, ice specialists such as this snail may encounter increased competition from more temperate species that were previously unable to survive in these higher northern areas. latitudes”.

The Arctic is warming much faster than other regions. While temperatures on Earth have risen by an average of one degree since 1990, temperatures in the Arctic have risen at least four times that much. If temperatures continue to rise, this whole brilliantly adapted ecosystem may not be able to adapt.

The study was published in the journal Evolutionary bioinformatics.