Supercooling tolerance in the Mexican lizard Barisia imbricata (Squamata: Anguidae).

Environmental temperature impacts the physiological processes of reptiles, determines their hours of activity per day, and may constrain their ability to meet critical ecological requirements. When environmental temperatures reach freezing, a few lizard species exhibit two mechanisms (supercooling and freezing tolerance) to survive freezing, and these two processes depend on cryoprotective molecules, such as glucose. Organisms produce high glucose concentrations to reach lower than normal crystallisation points, and this blood glucose concentration can double after freezing.

Living in the mountains: Thermal ecology and freezing tolerance of the lizard Abronia taeniata (Squamata: Anguidae).

The impact of daily and seasonal variation in environmental temperature on lizards is important, since their physiological processes are body temperature dependent. Lizards that occupy mountainous areas must have been favoured to colonize such habitats through selection on thermal biology traits to thermoregulate effectively. Moreover, mountain lizards may be able to maintain their activity near their minimum critical temperature and even have antifreeze mechanisms.