The North American wood frog freezes in winter, with its ... | funfact.wiki | funfact.wiki
The North American wood frog freezes in winter, with its heart and breathing stopped, and revives when it thaws. Alaskan wood frogs stayed frozen for about 193 days in a study, and all of them survived.
Glass frogs turn nearly see-through while asleep by packing about 90% of their red blood cells into the liver. In most vertebrates, hiding that much blood would trigger fatal clotting, but glass frogs reverse the process the moment they wake, with no apparent harm.