Tiny Frogs' No. 1 Option: Hold in Pee All Winter

Behold the wood frog, which literally freezes to 'death' and comes back to life
By Newser Editors and Wire Services
Posted May 2, 2018 9:20 AM CDT
This April 24, 2018, photo shows a wood frog in Ohio.   (Clara do Amaral, Mount St. Joseph University via AP)

(Newser) – If you've ever been unable to find a bathroom in a moment of need, you know the gotta-go feeling. That's nothing compared to the wood frog, which doesn't urinate all winter; in Alaska, that's eight months without peeing, reports the AP. Scientists have figured out how they do it, or rather how they survive without doing it. Recycling urea—the main waste in urine—into useful nitrogen keeps the frogs alive as they hibernate and freeze. Urea protects cells and tissues, even as the critters' hearts, brains, and bloodstreams stop. The frogs can do it because special microbes in their guts recycle the urea, according to a study in Tuesday's Proceedings of the Royal Society B. Some call the frog pee a type of antifreeze, but study co-author Jon Costanzo, a Miami University zoologist, bristles at that. "Their eyes are white. Their skin is frosty. They're like little rocks. They're frozen," Costanzo says.

Costanzo's team captured wood frogs during active times, then turned them into frog-sicles under controlled conditions. Costanzo and colleagues looked at the bacteria that live in frog guts. One type of bacteria, Pseudomonas, soars in the winter but can't be seen in active frogs. If the frogs were human, they would be called dead, Costanzo notes; some Alaskan wood frogs get as cold as zero degrees. But once the temperatures warm, they come back to life. Other animals don't urinate when they hibernate, but mammals don't do the big freeze quite like wood frogs, which wake up in still-cold February to mate. "This is stress that would definitely kill any mammal," Costanzo says. "People are fascinated by bear hibernation, but in my book any animal that allows itself to freeze solid and is able to ... go about its business like nothing happened, to me that's about as cool as it gets."

(Read more frogs stories.)

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