Adaptation of the andean toad rhinella spinulosa (Anura: Bufonidae) at low temperatures: The role of glucose as cryoprotectant

Abstract

We studied the role of plasma glucose concentration, on individuals of R. spinulosa, in response to the annual temperature variation and freezing temperatures. Measurements and the collection of toads were made every two months for a period of 1 year. To determine if toads exposed to low temperatures in their habitat, we proceeded to the study of operating temperatures (Te). The measures of operating temperature determined by using plaster models placed in the field, simulating the situation where toads are out or in shelters, for which it determined that individuals in the winter season would have exposed to temperatures below zero. Glucose levels measured in field specimens showed an annual variation, but in laboratory specimens exposed to freezing temperatures had higher plasma glucose levels than those obtained from the field toads. Furthermore, the crystallization temperature for the species have recorded, this being - 1.6ºC. The increase in glucose concentration would indicate the possible use as a cryoprotectant before freezing events in this species of frogs, and also in the coldest months is exposed to temperatures below 0ºC.