the North American forest frog (Rana sylvatica) has a special ability: it can survive when frozen into ice cubes. Ice crystals break cells, and for most creatures, body freezing is fatal. The forest frog hibernates on the forest floor, and there is nothing to protect it from the wind. In the most extreme cases, the water in the body freezes. At this time, it does not breathe, has no heartbeat, and its metabolism is completely down, just like a piece of glass. The ice in the forest frog is mainly distributed in the less deadly places such as body cavity, hypodermis and lymph, and the brain and internal organs remain intact.

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Frozen forest frogs

Photo: dogonews

Forest frogs are widely distributed, and frogs in different areas have different antifreeze abilities. The forest frog, which lives in Alaska (latitude up to 64 degrees, close to the Arctic Circle), can be said to be the ultimate player among clams. The hibernating time is close to 8 months per year, and it can survive after freezing at a low temperature of-4 ℃ for two months, with a tolerance limit of-16 ℃.

which part of North America has the forest frog not been to?

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there are three main antifreeze tips for forest frogs. The first is glucose. Glucose can increase the concentration of body fluids and reduce the freezing point. The forest frog breaks down the protein of skeletal muscle and the fat of the fat body, converts it into liver glycogen, and stores it in the liver (the liver of the Alaskan forest frog accounts for 22% of the body weight, and the liver of the forest frog living in the warmer Ohio is only 8% of the body weight). Liver glycogen is then converted into glucose and transported to the whole body. It only takes a day or two to "activate" the antifreeze function. The concentration of glucose in the liver of forest frog is the highest, the brain and heart are in the middle, and the skeletal muscle is the least. So the outer tissue freezes quickly, forming an "ice shell".

Frozen condition of forest frog, delicate internal organs remain intact

Photo Source: dogonews

after thawing, the glucose will change back to the form of liver glycogen within a day or two and be saved back to the liver. To supply the energy it uses to reproduce.

third is bound water. The forest frog will convert the free water in the body into the form of bound water. in winter, the water loss of the liver and intestines of the forest frog will reach half, and the water loss of skeletal muscle will reach 23-29%. Turning into "dried frogs" can not only reduce the amount of frozen water, but also increase the concentration of body fluids and reduce the freezing point.

Forest frogs in thawing state

Photo: Wikimedia Commons

scientists are very interested in the antifreeze ability of forest frogs. Mehmet Toner, a biomedical engineering expert at Harvard University, is trying to use trehalose to mimic the antifreeze effect of glucose in forest frogs to protect cells from freezing. He hopes to develop a way to preserve organs at low temperatures for a long time.

this article is reproduced from "the Squirrel Nest of Sex Shrimp". The author can see more species cold knowledge ↓