Seasonal Changes in the thermal tolerances of Odontophrynus occidentalis (Berg, 1896) (Anura: Cycloramphidae)

Abstract

We studied the thermal tolerances of Odontophrynus occidentalis during the dry and wet seasons of the Monte Desert in San Juan Province, Argentina. This toad had differences in CTmax between dry and wet seasons, with CTmax values being greater in the wet season (Austral summer). Operative temperature, body temperature, and environmental maximal temperature were related to CTmax suggesting seasonal acclimatization in O. occidentalis. Additionally, the CTmax recorded for O. occidentalis was 36.1ºC, and the maximum ambient temperature measured during the toads’ activity time was 37ºC. The CTmin of O. occidentalis was 4.1ºC while the minimum environmental temperature recorded was 7.2 ºC. The wide tolerance range observed and the relationship between tolerance limits and the environmental extremes indicate that seasonal acclimatization is an effective mechanism by which toads can raise their thermal tolerance. This is a highly relevant adaptation allowing them to survive in the challenging conditions of the Monte Desert.