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article imageAlaska frogs survive in freezing conditions

By Tim Sandle     Jul 24, 2014 in Science
Anchorage - In subarctic Interior Alaska, wood frogs spend winter in the ground covered by duff and leaf litter in conditions where temperatures can remain below freezing for more than six months with minimum temperatures of minus four (minus 20 Celsius).
Tracking wood frogs to their natural hibernacula researchers wanted to know how cold and how long Alaska's wood frogs could survive in their natural habitat. The study of the frogs under these conditions, and how they adapt their bodies to survive the incredibly low temperature, is the first to take complete readings of the frogs in natural conditions.
The research was led by Don Larson of University of Alaska Fairbanks. In a research brief, Larson explained how the frogs survive the low temperature conditions:
"Imagine what happens when you suck on a freeze pop. After you've sucked out all the sweet stuff, you're left with just ice. That's what happens to cells when they freeze. As ice formation pulls the water out of cells, the cells desiccate or dry out and eventually die."
It appears that the frogscan prevent this freeze-pop effect by packing their cells with glucose, and that this reduces drying and stabilizes cells, a process scientists call cryoprotection. Tests showed that glucose concentrations become 13-fold higher in muscle tissue, 10-fold higher in heart tissue and 3.3-fold higher in liver tissue compared to frogs found in the summer months.
"Concentrating sugar inside the cell helps balance the concentration of salts outside the cell that occurs as ice forms. Less water leaves the cell than if sugar was not present and sugar and other cryoprotectants are thought to "hold" water inside the cell."
The video below expands on the research:
The findings have been published in the Journal of Experimental Biology. The paper is titled "Wood frog adaptations to overwintering in Alaska: new limits to freezing tolerance".
More about Alaska frogs, Frogs, Temperature, Survival
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