MadSci Network: General Biology

Re: If you put a frog in the freezer, would it live on it's fat bodies?

Date: Tue Jun 22 19:54:42 1999
Posted By: Rob Campbell, Oceanography, University of British Columbia
Area of science: General Biology
ID: 927248185.Gb

Hi James-

I got in touch with a friend of mine who works on frogs at Dalhousie University (in Nova Scotia, Canada) named Kerri Oseen, and asked her your question. Her answer follows (with a little editing by me):

"There are only certain species of frogs which can survive freezing - one of these is the wood frog. Not all frogs can freeze - lots of them will burrow down below the frost line so that they don't get cold enough to freeze [as well, frogs in tropical areas don't have to worry about freezing- Rob]. Wood frogs actually freeze solid, and they do this by changing the metabolic pathways in their bodies (temperature dependent pathways) such that the liver starts producing large quantities of glycogen (read: sugar!). This is pumped into the bloodstream, making the blood hypotonic, which makes the fluid in the cells come out into the blood. So, all the cells essentially desiccate. When the frog freezes, it's metabolism goes down to zero, so it's not using energy at all. It doesn't need to live off of it's "fat bodies". Over time, the cells will sustain some damage due to ice crystals forming, so a frog can't be frozen indefinitely."

You should also know that a freezer is a little different from nature- for starters, it's a lot colder than a frog might normally experience, and they tend not to survive when placed in the type of freezer found in kitchens- it's so cold that the frog's cells are completely dessicated and cannot recover (click here to go to a great article at The Exploritorium about the biology of freezing wood frogs, including an explanation about what happens when they're exposed to excessively cold temperatures). I don't know if you had an experiment in mind, but I'd strongly suggest against freezing any frogs - frog populations are declining pretty much world wide and it would be a terrible waste to needlessly kill one by sticking it in a freezer.

Rob Campbell, MAD Scientist

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