This frog freezes solid through winter, its heart stops, then it thaws out alive
Wood frogs survive sub-zero North American winters by letting up to roughly 65 percent of their body water freeze into ice, during which breathing and heartbeat stop entirely. They survive by flooding their cells beforehand with glucose, produced rapidly from stored liver glycogen, which acts as a cryoprotectant that keeps the cells themselves from being damaged by ice crystals. Come spring, the frog thaws from the outside in and its heart restarts on its own.