An Antarctic fish stays liquid in water colder than its freezing point

The sea under the ice is about minus 1.9 degrees. The blood of a notothenioid fish would freeze at a higher temperature than that, except for proteins that bind tiny ice crystals and stop them growing.

Arthur DeVries and colleagues found why Antarctic notothenioids swim in seawater that is colder than the freezing point of ordinary fish blood. Glycoproteins in the circulation adsorb onto the face of an ice crystal and pin it. A crystal that cannot grow cannot freeze the animal. The freezing point of the blood drops below the temperature of the sea. Pull the proteins out and the protection goes with them. The water is still liquid only because the ice is not allowed to use it.

This is not the icefish fact. Icefish, already in the library, have no haemoglobin, and their blood is clear. Many of them also carry antifreeze. The antifreeze claim is older and wider: a whole group of Antarctic fishes, red-blooded and white, live in a sea that would freeze a trout solid. They pay for the protein continuously. There is no season in that water when they can stop. The cold is the climate, and the protein is the rent.