How do fish survive in the icy waters of the polar seas? By using an antifreezing device, just as motorists who want their car engines to work in sub-zero temperatures. Research by Chi-Hing Cheng and Liangbiao Chen of the University of Illinois in Urbana-Champaign, USA, shows that a gene in an Antarctic fish is the missing link which confirms that the natural antifreeze of fish evolved from a digestive protein. Certain Antarctic fish have glycoproteins (AFGPs) in their blood that act as an antifreeze. These proteins bind to ice crystals and stop them from growing inside the fish. Parts of three genes that encode AFGPs resemble the gene for an enzyme found in the intestines of the fish ( Nature , Vol 401, p443).
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