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RE: K/T frogs
On Friday, January 22, 1999 4:07 AM, firstname.lastname@example.org
>It says some Wood frogs burrow in the winter and CAN venture into water
> and be trapped in ice. But they don't die. Their bodies produce sugar
> glycose, a natural antifreeze, inhibits the body tissue from freezing.
These frogs are adapted to withstand dehydration of the cells to a high degree.
As freezing temperatures approach, water leaves the cells by osmosis into the
interstices between the cells. The cell interiors do contain a concentrated
solution that is less likely to freeze than the more dilute solution
(approaching pure water) foud outside the cells. That way, jagged pointy ice
crystals form between the cells, rather than within, so that the cell walls are
not punctured. The sugars are also synthesized at that time, but their
function is more to provide food to get the cells operational again upon
thawing, although it also functions as a cryoprotectant.
> If they could do it, and if other frogs could do it, then Bakkers claim
> that frogs are a good explanation that there wasn't a cooling at the K/T
> boudary is incorrect. Some frogs live just fine in freezing, albet after
> a spirng thaw.
These frogs cannot survive an entire winter in a frozen state. At most they
can survive about two weeks (if memory serves). They could not survive an
extended period such as I assume you are talking about. And if it gets too
cold, even the remaining water within the cells will freeze, and that is always
lethal. Of course, these are extant amphibians. K/T amphibians adapted to live
in a warm climate may very well have been unable to tolerate any freezing at
all, so Bakker could be right..
On Friday, January 22, 1999 12:24 PM, Betty Cunningham
> Toads frequently survive winters by hibernating in a burrow.
> Where do frog workers think frogs and toads diverged? I would think it
> was very very early, pre K/T by a long shot.
The earliest anuran fossils are from the Triassic. Both toads and frogs are
anurans, but more specifically, toads are bufonids, true frogs are ranids.
Bufonid fossils date back to the Pleocene, ranid fossils to the Oligocene.
There are morphological differences other than skin texture.
> What's the difference between regular toad hibernation and
> supersugarcrisp hibernation? (or anyone know a ref?)
Well, the ice formation. Other hibernation processes are common. I can look
up references if you are interested, write privately.
> Would it be possible that salamanders, newts, mud-dogs, and other
> non-frog amphibians could also suparsugarcrisp?
I'm not familiar with any amphibians that tolerate freezing other than anurans,
but I've not done an exhaustive search.
"Nothing in biology makes sense, except in the light of evolution"