The lizard abides: cold hardiness of Liolaemus pictus argentinus in Patagonia, Argentina

CECCHETTO, NICOLAS; MARLIN MEDINA; TAUSSIG, SERGIO; IBARGÜENGOYTÍA, NORA

PHYSIOLOGICAL AND BIOCHEMICAL ZOOLOGY

UNIV CHICAGO PRESS

Lugar: Chicago; Año: 2019

1522-2152

In environments where the temperature periodically drops below zero throughout the year, lizards can either migrate to a warmer location or endure. Their survival depends on behavioral mechanisms, physiological mechanisms, or both. Physiologically, lizards can alter their biochemical balance to tolerate freezing or avoid it by supercooling (a metastable state where body fluids reach temperatures below the equilibrium freezing point and don?t freeze). We analyzed the cold hardiness of a population of Liolaemus pictus argentinus located at high altitude (1400 masl) in the mountains of Esquel (Chubut) during autumn, before brumation period. In the experiments, a group of lizards was exposed to temperatures that gradually went below 0°C, while a control group stayed at room temperature in the same conditions. Biochemical variables present in the liver and the heart that could act as cryoprotectants (urea, glucose, total proteins, and albumin) were analyzed. Even after reaching temperatures as low as -5°C, lizards continued unfrozen (absence of an exothermic reaction) and were able to react shortly after being taken out of the cold, suggesting that the most likely cold hardiness mechanism that L. pictus argentinus uses is supercooling. There was a decrease in the glucose level by the end of the cooling experiment in control individuals, and an increase in cooled down individuals, which supports the contribution of glucose in a fast response to cold in L. pictus argentinus.