Further diversity in the origins of fish antifreeze proteins.

Shifts in environmental conditions can impose strong selection for adaptive traits. During the Cenozoic era, as the oceans cooled, many marine teleost fish species were at risk of freezing. This led to the independent emergence of distinct ice-binding antifreeze proteins (AFPs). The report in this issue by Graham and Davies reveals the development of AFP genes in shorthorn and longhorn sculpin from a copy of the lunapark gene. The predicted sculpin AFP sequences are unrelated to that of lunapark; the coding sequences for the AFPs appear to have arisen from small portions of the lunapark gene by codon frameshifting along with a series of mutations.