They glide through the water like ghosts: these polar fish glisten in the dark in yellow-green hues. The so-called disk bellies of the species Liparis gibbus grow up to 50 centimeters in size and live in the extreme conditions of the Greenland Arctic Ocean. Researchers from the American Natural History Museum in New York and the City University of New York have now discovered how up to 1,000 animals survive in the cold.

During an expedition to East Greenland in 2019, marine biologists John Sparks and David Gruber discovered the glowing juveniles. Biofluorescence has only rarely been observed in Arctic fish. According to the researchers, the disc bellies are the only species known to glow in the dark.

By examining the animals more closely, the scientists also found out how they survive in water temperatures of -2 degrees Celsius. While some reptile and insect species freeze and survive frost, this is not the case with fish. However, the Greenland disk bellies have special antifreeze proteins that keep them from freezing to death.

“Antifreeze in cars prevents the water in the radiator from freezing at cold temperatures. So it is with some animals. They have developed an impressive machine that protects them from freezing. These include antifreeze proteins, which prevent the formation of ice crystals in the body,” said David Gruber, a biologist at CUNY’S Baruch College.

Disc bellies are perfectly adapted to extreme conditions. They also live in the deep sea. Some species have been observed at depths of more than 8,000 meters. So it’s not surprising that the deepest find of a living fish to date was a disc belly. In 2017, a specimen of the species Pseudoliparis swirei was observed in the Mariana Trench at a depth of 8,178 meters.

Rising temperatures in the Arctic could threaten Greenland’s disk bellies, US researchers say. Because the fish are perfectly adapted to the cold conditions, changes can therefore be life-threatening for these unique fish.
Source: American Museum of Natural History New York