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Cryoprotectant [ krahy-oh-pruh-tek-tuhnt ] (noun): A substance that prevents the freezing of biological tissue, or prevents damage to cells during freezing.
This fun word comes from the ancient greek word “krýos” which means “icy cold, chill, or frost.”
In the colder parts of the world, many insects, fish and amphibians create cryoprotectants (antifreeze compounds and antifreeze proteins) in their bodies to minimize freezing damage during the winter.
The cold season is not usually the time when we think about amphibians, but have you ever stopped to wonder about what these cold-blooded creatures are doing during the colder months of the year?
Some amphibians can stay relatively active all winter long (as long as the body of water they call home doesn't freeze completely solid). Others will hibernate at the bottom of ponds, shallow areas of muddy-bottomed lakes, or in a hibernaculum that they will create by digging deep into the soil, below the frost line.
For terrestrial dwelling amphibians that need to hibernate but don’t have the ability to dig their own hibernaculum, they will find deep cracks in logs and rocks, or they will follow existing underground pathways in the leaf litter. However, these locations are not protected from freezing. So, how does a frog or salamander survive freezing or below-freezing temperatures? With cryoprotectants or antifreeze!
As soon as ice crystals begin forming on the amphibian’s skin, the liver is signaled to start converting glycogen to glucose (sugar), and then floods the blood, carrying the antifreeze to all tissues and organs. This will help keep the cells from dehydrating and shrinking. In turn, the amphibian’s metabolism will slow down, the lungs will stop breathing, and the heart will stop beating. Don’t worry, they’re not dead! They’re only partially frozen. Once the warm of spring arrives, their bodies will slowly thaw out all the glucose in their systems and this will fuel their annual migration from the forest to nearby ponds for breeding.
Wood frogs, spring peepers, dusky salamanders, and red-backed salamanders will all rely on cryoprotectants as part of their winter survival strategy.