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Correction to This Article
A Dec. 12 Metro article about animals that freeze solid incorrectly said that spring peepers and gray tree frogs lose their ability to freeze as they age. The animals keep that ability into adulthood.
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Trying to Crack An Icy Mystery

"You can see that it's quite solidly frozen," Layne said. "They kind of turn bluish."

The frogs can survive this process, in which as much as 65 percent of their body water freezes, because their cells are protected by a kind of natural antifreeze.



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Frozen Frog Time-Lapse Video

Scientists say that, before winter comes, the frogs eat ravenously, storing a starch in their livers. A freeze triggers their bodies to convert the starch into other compounds, most often glucose, or blood sugar. The frogs become, in essence, extremely diabetic.

The glucose lowers the freezing temperature of water inside the frogs' cells, and because of this, the cells stay liquid, even as ice fills the space around them. This is crucial: If the water inside the cells froze, scientists say, the jagged ice crystals would destroy everything inside, killing the frog.

It's very hard to find frogs frozen like this in the wild, because they're hidden underground. At the Patuxent Research Refuge, a 12,750-acre forest near Laurel, wildlife biologist Robin E. Jung of the U.S. Geological Survey, said she occasionally gets lucky and finds wood frogs hunkered down for winter.

"Just like" -- she stiffened like she'd been shot with a super-villain's ice ray -- "freezing."

In this area, cold snaps usually aren't long enough to keep the frogs frozen for more than a few days. But wood frogs live as far north as Canada and Alaska, and in those places they can freeze for months, scientists said.

Medical researchers say they hope to copy these long-term freezing abilities to add hours or even days to the time that human organs can be preserved.

Now, after organs are removed from a donor, they are packed in a special solution and kept on ice. But they can't be frozen because of the damage that ice crystals would do to the cells. Without freezing, the shelf life of these organs can be as much as 48 hours for a kidney and as little as four hours for a heart.

If organs could be preserved longer, it would allow more time for locating an organ recipient and setting up the transplant operation, said Jimmy A. Light, head of transplantation at Washington Hospital Center.

"It would allow you to have a more prepared patient," Light said. "Now, it's kind of like a fire drill. The bell rings, the clock ticks and you've got to get going."

In one experiment, University of California professor Boris Rubinsky removed a rat's liver and filled it with glycerol, hoping the chemical would act as glucose does in wood frogs.

The experiment worked: The liver was frozen, then thawed and transplanted successfully into another rat, Rubinsky said.

Other researchers have turned to arctic fish, which manufacture special chemicals to keep from freezing even as the water around them falls below 32 degrees.


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