A fish with its own 'natural' antifreeze in its veins was discovered in Greenland

Scientists who were drilling deep in an iceberg in Greenland have discovered a fish with glowing green antifreeze in its veins.

The juvenile variegated snailfish (Liparis gibbus) contained the "highest expression levels" of antifreeze proteins ever reported, a new study found.

According to LiveScience, this new species, which works like antifreeze to keep the engines from freezing in cars, seems to be alive to protect itself from the cold like the many other species in Greenland.

"Antifreeze proteins stick to the surface of smaller ice crystals and slow or prevent them from growing into larger, and more dangerous, crystals," study co-author David Gruber, a research associate at the American Museum of Natural History (AMNH) and a distinguished biology professor at City University of New York's Baruch College. "Fish from both the North and South Poles independently evolved these proteins."

Some cold-blooded reptiles and insect species can survive when their bodily fluids freeze, but fish cannot. This situation may cause grains of ice to form inside their cells.

"The fact that these different antifreeze proteins have evolved independently in a number of different — and not closely related — fish lineages show[s] how critical they are to the survival of these organisms in these extreme habitats," told John Sparks to Live Science, a curator in the AMNH's Department of Ichthyology and co-author of the study.

Snailfish produce antifreeze proteins "like any other protein and then excrete them into their bloodstream," Gruber said. However, snailfish appear to be "making antifreeze proteins in the top 1% of all other fish genes."

A biofluorescent snailfish was discovered before

In 2019, scientists also discovered the tiny tadpole-like biofluorescent snailfish glowing brilliant green and red in the icy habitat off the coast of Greenland. During the trip — part of the Constantine S. Niarchos Expedition, a series of science-based expeditions led by the AMNH.

"The snailfish was one of the few species of fish living among the icebergs, in the crevices," Gruber said. "It was surprising that such a tiny fish could live in such an extremely cold environment without freezing."

It's rare for Arctic fishes to exhibit biofluorescence. Normally this characteristic is found in fish swimming in warmer waters.

The scientists further examined the biofluorescent properties of the snailfish and found "two different types of gene families encoding for antifreeze proteins," according to a separate statement, an adaptation that essentially helps them avoid turning into frozen fish sticks.

Study abstract

Polar fishes have evolved antifreeze proteins (AFPs) that allow them to survive in subzero temperatures. We performed deep transcriptomic sequencing on a postlarval/juvenile variegated snailfish, Liparis gibbus (Actinopterygii: Scorpaeniformes: Cottoidei: Liparidae), living in an iceberg habitat (−2°C) in Eastern Greenland and report the detection of highly expressed transcripts that code for putative AFPs from 2 gene families, Type I and LS-12-like proteins (putative Type IV AFPs). The transcripts encoding both proteins have expression levels among the top <1% of expressed genes in the fish. The Type I AFP sequence is different from a reported Type I AFP from the same species, possibly expressed from a different genetic locus. While prior findings from related adult sculpins suggest that LS-12-like/Type IV AFPs may not have a role in antifreeze protection, our finding of very high relative gene expression of the LS-12-like gene suggests that highly active transcription of the gene is important to the fish in the iceberg habitat and raises the possibility that weak or combinatorial antifreeze activity could be beneficial. These findings highlight the physiological importance of antifreeze proteins to the survival of fishes living in polar habitats.