K.B. and Storey, J. M. (2011) Hibernation: Poikilotherms.
In: Encyclopedia of Life Science 2011, John Wiley & Sons, Ltd:
Kenneth B. Storey and Janet M. Storey
Poikilothermic, or cold-blooded animals face a risk of death due to cold or freezing over the winter and have evolved multiple strategies for survival. Some are unique options include migration by some butterfly and dragonfly species whereas honeybees heat their hive by shivering. Many animals are insulated from deep cold by hibernating underground or under water. For lung breathing turtles and frogs, under water hibernation requires novel adaptations: skin breathing by frogs and biochemical adaptations to survive without oxygen by turtles. Other poikilotherms manage to endure temperatures below 0°C. Many insects can prevent themselves from freezing with the use of antifreeze proteins and high concentrations of sugar alcohols that keep their body fluids liquid down to -40°C or lower. Other insects as well as some intertidal mollusks, and some frogs, turtles and lizards endure whole body freezing with adaptations that regulate ice formation in extracellular spaces, protect the intracellular environment and ensure the reactivation of heart beat, breathing and other vital functions after thawing.