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Antifreeze Allows Antarctic Fish to Survive Ice Crystals in Blood

A unique fish species off the coast of Antarctica has antifreeze proteins in its blood. This adaptation allows the Antarctic fish from freezing in sub 0 temperatures but there seems to be a caveat to this extraordinary evolutionary adaptation.

antarctic fish

An Antarctic fish known as the Notothenioid feature antifreeze proteins in their blood. (Photo: Wikipedia)

The Notothenioid fish species’ blood has to hold onto ice that gets in its blood reports Capital Wire. To prevent the ice crystals from growing to a large size, the antifreeze proteins and mechanisms go into effect. Even after examining the fish in above freezing temperatures, ice was still found in the blood of the Antarctic fish. University of Oregon’s Institute of Ecology and Evolution’s Paul Cziko author of the study stated they found the caveat and trade off. The danger lies in that the waters around the Antarctica region rarely raise enough to melt the ice crystals found in the fish’s blood, so the creatures live their lives with ice crystals in their blood and these crystals could potentially block blood flow.

Cziko noticed that the ice crystals were also found in the fishes’ spleens. This could indicate that there is a system at work to keep the ice from invading the circulatory system. The researchers also collected fish from warmer waters that, unexpectedly, still had these internal ice crystals inside.

Working alongside animal biology professors from the University of Illinois, Arthur DeVries and Chi-Hing Cheng, Cziko found that the antifreeze proteins also serve as “anti-melt” proteins, halting ice crystals from melting.

DeVries was responsible for discovering antifreeze proteins in notothenioid fish during the ‘60’s and went on to describe how the proteins reacted with ice crystals to prevent the creatures from freezing. The protein binds to small ice crystals and inhibits growth and recrystallization of ice; recent literature suggest antifreeze proteins, in certain mammals, also protects cells by binding to their cell membranes.

“This is just one more piece in the puzzle of how notothenioids came to dominate the ocean around Antarctica… It also tells us something about evolution. That is, adaptation is a story of trade-offs and compromise. Every good evolutionary innovation probably comes with some bad, unintended effects,” concludes Cheng.

The study, Antifreeze protein-induced superheating of ice inside Antarctic notothenioid fishes inhibits melting during summer warming, was published in the journal Proceedings of the National Academy of Sciences.

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