 Some frogs
freeze solid
Q: Why do frogs not live in cold places,
like Antarctica-Meg S., Ballston spa, NY
A: Some frogs
do. The Eastern wood frog is found even north of the Arctic Circle, where they
not only survive freezing but do so every winter.
Right: [Janet &
Kenneth Storey, Carleton U] A frozen wood frog
Sixty-seven percent of the frog's
body freezes hard but not inside the cells. As the frog slowly
freezes over several hours, he pumps large amounts of glucose anti-freeze into
his cells. Gradually he stops breathing, his heart stops, his brain activity
ceases but his cells don't freeze. He stays this way for two or three months.
Come spring, when the land thaws,
so does his body. Within an hour or two "the Frog will recover his Summer
Activity, and leap as usual," reported an astounded Captain Francis Smith in his
ship's log, May 1747, near the Canadian Arctic Circle.
Freeze-tolerant frogs, however,
only exist in North America.
Antarctica has no frogs for good
reasons: no place to live, no food to eat, gulls and skuas ready to strike, and
too cold even in the summer for a cold-blooded frog to hop around.
Mites and springtails (small
wingless insects that bound through the air on belly springs) are the largest
land animals in Antarctica and the largest carnivore is smaller across than a
poppy seed, says Julian Paren of the British Antarctica Survey.
The mildest temperatures, found
around the coasts, plunge as low as
-30°C (-22°F)
in the winter.
Even the Eastern wood frog would be out of luck here. He freezes to a body
temperature of -5°C
(23°F)
without a hitch but lower the temperature to -15°C
(5°F) and he dies. No
one knows why.
(Answered by April Holladay, science correspondent, July 11, 2001)
Further Surfing:
Understanding Antarctic biology and wildlife http://www.usatoday.com/news/science/cold-science/indexes/antarctic-understanding-wildlife.htm
Carleton U:
Freeze tolerant vertebrates
British Antarctic Survey: About Antarctica
|
