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Biological Miracle – Wood Frog

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501 points thunderbong | 2 comments | 15 Nov 24 18:16 UTC | HN request time: 0.42s | 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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1. abainbridge ◴[16 Nov 24 08:49 UTC] No.42155333[source]▶
I skimmed https://en.wikipedia.org/wiki/Sinoatrial_node#Function. Here's my guess at what is going on:

In humans (and I guess many animals), the thing that controls the heart beat is a structure in the heart called the Sinoatrial node. Each cell in the SA node has an ability to generate its own rhythmic electrical impulse. I imagine that when one of these cells thaws out in a Wood frog, it immediately starts producing its rhythmic pulse. It has to get in sync with the rest of the cells in the Sinoatrial node before the heart will beat correctly, so the cells have a mechanism to communicate their rhythm with their neighbours. I guess each cycle, each cell adjusts its phase a little towards the average phase of its neighbours and thus a consensus will be reached.

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2. mock-possum ◴[16 Nov 24 10:21 UTC] No.42155652[source]▶
Fireflies eventually manage to more or less sync up and they’re completely separate organisms - tiny cells with physical connections inside the body should be able to make it work.