Frogs that Freeze - Journals

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Frogs that Freeze
Oct 9, 2009 at 3:27 PM
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Nature has more tricks than we could ever know! I love these little guys, and we can learn ALOT about their amazing abilities to freeze (solid???) and "come back to life".

The wood frog, otherwise kown as rana sylvatica, are the only frogs found near north of the Arctic Circle! in additio, they are found throughout most of the northeastern United States, so it is possible you have seen some of these cute frogs. The picture below is from the University of Wisconsin. Note there is a wide range of normal color variation. All the basic frog-info is available on the website maintained by the University of Michigan's Museum of Zoology. There you can read about morphology, habitat, predation and development.

The special thing about these frogs is their ability to freeze and then return to normal activity once thawed, which is a major factor contributing to their ability to live so far to the north. In the winter almost half the frog's body water will freeze and develop ice crystals, including under the skin and between organs. This is a special trait that is not held by most other species, including humans. If the water in our bodies starts to freeze and form ice crystals, the crystals cause alot of cellular damage that will kill us. So how does the frog freeze without dying?

The secret is in the glucose and other specialized proteins that act as an intracellular antifreeze. This means the frog can freeze up to 65% of the water in its blood and tissues without every cell being frozen and damaged. The frog gets ready for freezing by increasing the protein production as well as increasing the blood glucose level. When ice from the habitat touches the frog, it initiates the freezing, which ends with the frog being a hard, cold lump of frozen tissue. If you come across a frozen frog, you would likely think it was dead! Want to see the thawing of this frog in action? Dr. Jon P. Castanzo (credited with the picture above) from the University of Miami has a video on his website. In addition, he studies freezing of other vertebrates as well as invertabrates.

Understanding how the frog accomplishes this remarkable freeze-thaw can help us perfect the methods to suspend human life in cryonic storage. It could also help us understand how blood sugar levels are related to temperature maintainance, particularly in populations that live in colder climates.

Tonya

AKA sunmoonstars

The Science Spot

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