An Antarctic fish uses remarkable antifreeze proteins to deal with ice buildup in their bodies, but these proteins may also work against their survival.
In the strange protective process the fish must actually increase their internal ice burden in order to utilize the proteins, the University of Auckland reported.
"What we have found is that antifreeze proteins not only stop ice from growing inside Antarctic fishes, but they also stop it from melting," said Clive Evans, a research scientist in the School of Biological Sciences at the University of Auckland.
The ice inside the fish was found to be "superheated," meaning it remained stable above a melting point. This phenomenon is caused by the binding of antifreeze proteins to the surface of ice crystals.
"This is the first demonstration of the existence of 'superheated ice' inside living organisms, but it presents a significant problem for the fishes since the only known way for them to melt internal ice is through warming of the freezing seawater they inhabit," Evans said.
The researchers looked at a 10 year's-worth of data and discovered seawater in Antarctica's McMurdo Sound never rose to temperatures high enough to melt all of the ice present in the resident fishes.
"Internal ice, protected by antifreeze proteins, seems a permanent burden for most fish in this area and is likely to prove lethal," Evans said.
"What we have here is an evolutionary paradox. The adaptive evolution of fish antifreeze proteins has enabled Antarctic fishes to survive in freezing seawater by stopping internal ice from growing, but at [the] same time by inducing a "superheating" capacity these proteins have reduced the opportunity for melting the ice burden, thus increasing the risk of dying," he concluded.
The study could help researchers gain insight into how fish survive in such a harsh environment, but the temperature records observed could also help scientists look at how aquatic wildlife react to the world's warming waters.
The research was conducted by a multinational research team at the Universities of Auckland, Oregon and Illinois, working out of Scott Base and McMurdo Station.
