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EveryFish

Antifreeze proteins

Molecules in the blood of polar fish that stop ice crystals from growing, letting them live in water below zero.

Also: antifreeze glycoproteins

Sea water freezes at about minus 1.9 degrees Celsius, colder than fresh water, and polar fish live at that edge. Antarctic notothenioids, such as the toothfish and icefish, and some Arctic cods have proteins in their blood that bind to tiny ice crystals and stop them growing. Antarctic icefish go further: they have no red blood cells and no haemoglobin, so their blood is nearly colourless and carries oxygen dissolved in plasma, which works in very cold water rich in oxygen.

See also

Cold-blooded Polar fish Warm-bodied fish

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