A frog freezes and then walks away
The wood frog spends northern winters frozen. Its heart stops, ice forms between its cells, and in spring it thaws and moves.
Established2 min read
Rana sylvatica — Lithobates sylvaticus in the newer name — winters under leaves, not in deep unfrozen water. As the temperature falls, the liver floods the body with glucose. Ice nucleates in the spaces between cells. Up to about two thirds of the body water can freeze. The heart stops. Breathing stops.
Inside the cells, the concentrated sugars limit the ice and limit the shrinkage. When it warms, the heart starts again, in a specific order that has been watched in the lab, and the frog resumes a life. The trick has a floor. Too cold, or ice inside the cells themselves, and it dies like anything else.
Caveats
- Not every frog can do this. The wood frog and a few other northern species are the specialists.
- The ice is extracellular. 'Frozen solid' in the popular sense overstates what the cells themselves undergo.
Sources
- 1Storey K. B., Storey J. M.. Natural freezing survival in animals. Annual Review of Ecology and Systematics 27, 1996.