Antarctic fish have adapted themselves magnificently to the extreme environment. Antarctic fishes have natural antifreeze proteins in their system which prevents them from freezing. However this anti-freeze is a double edged sword which can have detrimental effect on the animal.
The fishes also known as Notothenioid (ice-loving) fish can make a special kind of protein which are able to attach to the ice crystals in the blood and prevent it from clustering. The downside is that these crystals stay solid even at normal temperatures.
Paul Cziko, a doctoral student at the University of Oregon and co-leader of the study, said, “We discovered what appears to be an undesirable consequence of the evolution of antifreeze proteins in Antarctic notothenioid [ice-loving] fishes. What we found is that the antifreeze proteins also stop internal ice crystals from melting. That is, they are anti-melt proteins as well.”
The process by which the ice crystals did not melt at normal temperatures is known as superheated ice. Researchers who investigated the cause of the crystals not melting even at room temperature and found that the tiny crystals stayed together even when the temperatures became normal. The process of superheated ice was not seen in nature before.
Notothenioid fish are abundant in the Southern Ocean surrounding Antarctica. The Southern Ocean is home to more than five families of notothenioid fish, which make up over 90 percent of the fish biomass in the waterway.
The study envisaged placing under water thermometer was placed at McMurdo Sound in the ocean, where it measured temperatures for 11 years. This is more than the life of the animals. The researchers found that the water never grew warm enough during those years to melt ice in the bloodstreams of these fishes. Researchers have opined that the ice particles could cause blockage of blood vessels in the fish much akin to what the clots do in humans.
Cziko stated “Since much of the ice accumulates in the fishes’ spleens, we think there may be a mechanism to clear the ice from the circulation.”