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Biological Miracle – Wood Frog

(www.nps.gov)
503 points thunderbong | 4 comments | 15 Nov 24 18:16 UTC | HN request time: 0.657s | source
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abound ◴[16 Nov 24 04:12 UTC] No.42154107[source]▶
> Nobody yet understands what starts the wood frog’s heart after being frozen and inert for the entire northern winter.

To me, that's the most fascinating part of the (already quite fascinating) story. Frog is frozen solid, there is no (to our knowledge) heartbeat or brain activity. It thaws and something happens that gets it going again.

I have trouble imagining what that mechanism could even look like. Tiny portion of brain responsible for keeping track of frozen-ness? Some chemical signaling from within the body cavity?

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m463 ◴[16 Nov 24 07:05 UTC] No.42154971[source]▶
What puzzles me is... it is not just the heart but the entire circulatory system.

Maybe it is that thawing happens in reverse with the extremities, then the rest of the system thawing, with the heart being last. Would be a biological advantage in this case for the heart to be centrally located.

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1. Someone ◴[16 Nov 24 08:13 UTC] No.42155213[source]▶
> Maybe it is that thawing happens in reverse with the extremities, then the rest of the system thawing, with the heart being last

FTA: In spring, the wood frog thaws from the inside outward. First the heart starts beating. Then the brain activates. Finally, the legs move.

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2. cmrx64 ◴[16 Nov 24 11:07 UTC] No.42155813[source]▶
The article says that, but it can’t be the normal meaning of thaw. Thermodynamically, onbiously the innermost portion of the volume is going to warm last. But in terms of the frog’s system restart order, that order makes sense.
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3. ethbr1 ◴[16 Nov 24 15:58 UTC] No.42157011[source]▶
The inside of the frog isn't actually frozen, because it's glucose-flushed.

So the sequence is more:

   1. Outside of frog thaws
   2. ??
   3. Heart starts beating
4. Someone ◴[16 Nov 24 16:34 UTC] No.42157245[source]▶
This frog is alive. It could detect that long-term thaw is imminent (say from sensors on its skin) and start some processes that produce heat around its heart.