Deep in a Sleepy Hollow

Today’s tale sounds like it comes directly from interstellar travel, or from the 2000-year-old heart of Christianity. Can you die – exhibit no organic activity, suspend the laws of biology, then come back to life as good as new? Our protagonists do. They are hidden now, close by. As Robin Wall Kimmerer writes, “Oblivious to our passage overhead, other stories are unfolding beneath us. But we are moving too fast and we are too far away; all the stories escape us, except our own.”

Though like me, you may already have heard the wood frog’s hibernation story, the depth of winter is a good time to retell it. Reminding ourselves of such a rebirth can inspire us to continue our efforts to help nature itself survive.

Most frogs hibernate underwater, breathing through their skin. Strange enough, but in that environment their body temperature stays safely above freezing. Wood frogs, the same ones you will hear quacking suggestively for mates next spring, turn to ice: so solidly frozen under thin leaf cover near vernal pools that they are for all intents and purposes dead. As winter nears the frogs begin a freeze/thaw cycle along with the falling thermometer. Water flows out of their cells, and when frozen forms a protective layer between those cells, inside the amphibian. Simultaneously they ratchet up their production of glucose and urea and circulate it via bloodstream into the cells. This acts as a ‘cryoprotectant’, a natural anti-freeze. 

Then as permanently low temperatures set in, their heart, lungs, and brain all shut off. 

No heartbeat. No respiration. No brain activity. Up to 60% of the frog becomes ice, nose to toes, and will stay that way for up to 7 months without damage. A few other frog species and one salamander can do this Rip Van Winkle trick. But the reigning world champion in suspended animation must be the Alaskan Wood Frog. The Gates of the Arctic National Park Service site reads “Prospect Creek, just south of the Brooks Range, had the lowest temperature ever recorded in Alaska – minus 80 degrees. Almost certainly, there were hibernating wood frogs near Prospect Creek when that record was set.”

Fish that live above the Arctic Circle have special anti-freeze proteins (AFPs) that lower the freezing point of their blood in winter. Mice can drop their temperature to near freezing and drastically slow heartbeat and breathing. And a hibernating black bear reduces its metabolic rate by 25%, and its body temperature from 96° to 86°. 

We already cool human bodies to 59° to protect the brain when we need to interrupt blood flow to operate. And we freeze human embryos, one for 19 years! Like the wood frog tale, amazing true stories happen to us. In 2001 Erica Nordby, a child, survived 2 hours at minus 11. She was clinically dead with no heartbeat and a body temperature of 61°. And was revived. Sleeping beauty for real.

Paul Simon sang “medicine is magical, and magical is art”. I’d add “biology is science fiction.” Suspended animation already happens. I thought about trying to exhume(?) disinter(?) a wood frog with my brother when he visits at Christmas and get its photo for this blog. Charlie’s reply when I proposed it was “Let sleeping frogs lie.” 

So we will. If you’re like me, you can dream of endless possibilities for humanity to flourish across the Earth, the solar system, and perhaps the universe. But first, we’ll have to wake up from our own sleep…or cast some beams out of our own eyes. Maybe it’ll be spring then.

Next April on a walk when you hear that cheerful quacking, think of how extraordinary Earth’s biology already is.

Happy Holidays!

George Jacobi