Antifreeze proteins in Antarctic fishes prevent freezing…and melting
Antarctic fishes that manufacture their own “antifreeze” proteins to survive in the icy Southern Ocean also suffer an unfortunate side effect, researchers report: The protein-bound ice crystals that accumulate inside their bodies resist melting even when temperatures warm.
Five families of notothenioid fishes inhabit the Southern Ocean, the frigid sea that encircles Antarctica. Their ability to live in the icy seawater is so extraordinary that they make up more than 90 percent of the fish biomass of the region.
Aurthur DeVries discovered antifreeze proteins in Antarctic notothenioid fishes in the late 1960s, and was the first to describe how the proteins bind to ice crystals in the blood to prevent the fishes from freezing.
In the new study, DeVries, Paul Cziko, and Chi-Hing “Christina” Cheng investigated whether the antifreeze protein-bound ice crystals inside these fishes would melt as expected when temperatures warmed. When researchers warmed the fishes to temperatures above the expected melting point, some internal ice crystals failed to melt. Ice that doesn’t melt at its normal melting point is referred to as “superheated.”
This discovery may be the first example of ice superheating in nature.
(read more) Science Daily ||| Photo credit: Paul Cziko ||| [paper]