Unlike icefish and cod, many cold-blooded animals die in subzero temperatures because the water in their blood turns to ice. The ice crystals puncture the cells of the animal's body like millions of tiny razor blades. However, some reptiles and amphibians evolved a sweet way to survive being frozen.
To avoid being stabbed from the inside out, some frogs and lizards increase the amount of glucose, a type of sugar, and glycerol, a sugary alcohol, in their blood. Glucose and glycerol in the blood can help prevent the formation of ice crystals. The European common lizard (Lacerta vivipara) went a step further and developed specialized mitochondria, the energy producing part of the cell, according to a study in the Journal of Experimental Biology. These mitochondria help the lizard continue producing energy without creating harmful byproducts even when half of the lizard's body water freezes.