The Cold Hardiness of Phrynocephalus erythrurus, the Lizard Living at Highest Altitude in the World.

BACKGROUND: Phrynocephalus erythrurus living at Qinghai-Tibet Plateau, is believed to be the highest lizard in the world, but we know little about how these lizards cope with very low temperatures in winter. OBJECTIVE: The aim of this study was to find the difference of the lizards before and after cold acclimatization. MATERIALS AND METHODS: In this study the limit of supercooling and inoculative freezing, the concentration of four organic osmolytes, and the activity of lactate dehydrogenase in the plasma were measured in samples shortly after capture and in other samples after 7-8 weeks of acclimatization at 2-4 C. RESULTS- Animals acquired an ability to undergo deeper supercooling and inoculative freezing through the course of acclimatization. We find no regular changes of the four organic osmolytes after the acclimatization. CONCLUSION: We think that this species of lizard is partly freeze-tolerant and conclude that it uses supercooling to survive in winter.