Fish are cold-blooded animals whose body temperature changes according to the surroundings. So normally at below freezing temperatures of the Arctic, fish should be freezing or they shouldn’t be living there at all! The puzzle has been solved by scientists who have discovered that the fish do possess some anti freeze substance in their blood. The Arctic sculpin, for instance, manufactures an antifreeze protein in its blood named glycoprotein. This depresses the freezing temperature of its plasma sufficiently.
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