Amazing Wood Frog
Freezes Solid in Winter and Comes Alive in Spring
There
are several creatures that possess a certain tolerance to subzero temperatures,
but none as amazing as the Alaskan Wood Frog. This tiny amphibian can
survive being almost completely frozen during winter, only to miraculously come
back to life as soon as spring arrives! For days, even weeks weeks at a
time during its period of winter hibernation, over 60 percent of the frog’s
body freezes;
it
stops breathing and its heart stops beating. Its physical processes like
metabolic activity and waste production come to a halt. “For all intents
and purposes, they are dead,” said Don Larson, a Ph.D. student at Fairbanks,
Alaska. As per his research, wood frogs can survive long winters where
temperatures range between -9C to -18C. In fact, it can go through 10 to
15 freeze/thaw cycles over the course of a single season.
Thanks
to the incredible wood frogs, medical researchers have discovered ways
that living organs and tissues can be frozen and unfrozen without damaging
them, which have had serious implications in areas like organ transplants.
“There’s
an obvious parallel between what these frogs are doing to preserve all of their
tissues simultaneously and our need to be able to cry preserve human organs for
tissue-matching purposes,” Costanzia explained. “If you could freeze human
organs even for a short period of time, that would be a major breakthrough
because then these organs could be shipped around the world, which would
greatly [improve] the donor-matching process.
“The
solutes tend to depress the freezing point,” said Jon Costanzia of the
Department of Zoology at Miami University in Ohio. “It limits the amount of ice
that actually forms in the body at any part.” Costanzia has been researching
wood frogs for the past 25 years – he wanted to understand how the frog could
function on a physiological and chemical level.
Researchers
have discovered that the reason for this the miraculous phenomenon is
the high concentration of cryoprotectants in the wood frog’s tissues.
These are solutes – including glucose and urea – that lower the freezing
temperature of the frog’s cells, helping them survive.
In most animals, exposure to subzero
temperatures for a long time could cause cellular shrinkage. During this
process, water is pulled from the body’s cells to form ice, eventually sucking
them dry and killing the cell. But with wood frogs, cryoprotectants help the
cells resist shrinkage
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