FROZEN FROG REVIVES! You Won't Believe This Amphibian Can Freeze Solid and Come Back to Life!

The wood frog, a small amphibian found across northern North America, possesses an extraordinary adaptation for surviving frigid winters. Unlike many other frogs that burrow deep underwater to avoid freezing, the wood frog simply hunkers down in the leaf litter on the forest floor, allowing its body to freeze solid. This incredible ability allows it to endure temperatures that would be fatal to most other animals, sometimes remaining frozen (Review) for up to eight months.

When temperatures plummet, specialized proteins in the frog's body trigger ice formation in the extracellular spaces, meaning ice crystals form between the cells and organs, not inside them. Simultaneously, the frog's liver converts stored glycogen into massive amounts of glucose, essentially flooding its cells with a syrupy sugar solution. This glucose, along with urea, acts as a cryoprotectant, preventing the intracellular water from freezing and minimizing cell shrinkage and damage. During this frozen state, the wood frog exhibits no heartbeat, no breathing, and no brain activity, appearing clinically dead.

As spring arrives and temperatures rise, the wood frog begins to thaw, typically from the inside out (Review). The heart is usually the first organ to restart, followed by the activation of the brain and the resumption of muscle movement and breathing. This remarkable process allows the frog to fully revive and quickly resume its normal activities, including breeding, often earlier than other frog species that had to wait for frozen water bodies to melt. Scientists continue to study the intricate biological mechanisms behind this "biological miracle," hoping to gain insights that could have implications for fields like organ cryopreservation.