There are so many Sci-Fi movies that include Cryogenics (the study of how matter behaves at very low temperatures), whether people are being shot off into space and are going into a “deep freeze” until they arrive at their destination, or freezing those that are almost dead in order to get them to a hospital or research unit to save them. Sci-Fi is full of it. But is it actually possible to freeze a living thing and expect it to return to life later? And what does this have to do with amphibians?
The 7,000+ amphibian species are all ectotherms (cold-blooded), so their body temperature lowers when the weather gets colder. You may see many amphibians such as frogs or small salamanders during the summer as the heat from the air helps to warm their body up enough to function!
During the cold weather these amphibians have issues because their bodies are too cold to hop around. One of the ways that they deal with the change in temperature is by brumating (similar to hibernating, but is specific to cold-blooded animals). During brumation, unlike hibernation, the animal may wake up on warmer days and move around. There are three different overall places that an amphibian may brumate; the first being the bottoms of ponds or other bodies of relatively deep water.
The deeper the water, the warmer it will actually be as only the very top may actually freeze. Frogs breathe through their skin and through lungs, so when they brumate underwater, they utilize their specialized skin to help absorb the oxygen in the water. The oxygen gets sent to vessels that are located directly beneath the surface of the skin, allowing the frogs to stay underwater for several months. These amphibians don’t have to move around much as they do have fat bodies (who knew that these little critters could be chubby?!) accumulated from eating almost anything that they can fit their mouths around. Amphibians can eat things like slugs, aquatic insects, aquatic plants, snails, spiders, and even other frogs or small mammals like mice! The fat then will be stored in their abdomen to help provide energy for winter survival.
Some amphibians, such as toads and salamanders, are more inclined to stay on land during the winter. Toads are specially adapted to dig below the frost line, which in some cases can be 3ft deep! Salamanders can’t dig so they look for holes made by other animals in previous years to snuggle into for the winter.
The amphibians that don’t want to be underwater or underground just “chill” above the surface (pun intended). Here’s where we get back to the Cryogenics and Science Fiction: there are some frogs that are so specially adapted to the cold that they are actually able to survive being frozen!
The frog’s veins will fill with a sort of anti-freeze mixture that contains glucose and sugar based alcohols that allow the individual cells to continue to function while freezing some of the other less vital organs, like the bladder, and therefore halting metabolic processes. Even brain activity appears to slow to a stop!
Finally, when the warm weather comes again and the frog thaws out or the salamander emerges from its hole, it will be quite alive and ready to go about its fascinating life!
To learn more about the science behind hibernating frogs, click on the links below!