Notothenioid fish in the seas around Antarctica have a tough life. Surviving sub-freezing temperatures isn’t easy, but the fish have evolved natural antifreeze proteins.

A study published in the Proceedings of the National Academy of Sciences found something surprising, though. While the antifreeze proteins keep the ice from growing, it also prevents it from melting. Even when temperatures are warm.

“We discovered what appears to be an undesirable consequence of the evolution of antifreeze proteins in Antarctic notothenioid fishes,” said Paul Cziko, lead on the study.

“What we found is that the antifreeze proteins also stop internal ice crystals from melting. That is, they are anti-melt proteins as well.”

Ice becomes ‘superheated’ ice when it fails to melt at its normal melting point.

“Our discovery may be the first example of ice superheating in nature,” said Chi-Hing Cheng, a University of Illinois animal biology professor who worked alongside Cziko.

The inability to melt the ice may have physiological consequences. But, Cziko did notice that a lot of the ice was located in the fishes’ spleens and “may be a mechanism to clear the ice from the circulation.

This study was mainly looking at how evolution led to the notothenioids dominance of the Antarctic seas. “It also tells us something about evolution,” says Cziko.

“That is, adaption is a story of trade-offs and compromise. Every good evolutionary innovation probably comes with some bad, unintended effects.”

Hey, if it worked right the first time, it wouldn’t be called evolution.

Image credits: Paul Cziko, Elliot DeVries

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