Abstract:
Amphibians, with their unique physiology and habitat requirements, are especially
vulnerable to changes in environmental temperatures. While the activation of the
physiological stress response can help to mitigate the impact of such habitat alteration,
chronic production of elevated glucocorticoid levels can be deleterious in nature. There
is no empirical evidence indicating the physiological response of African amphibians
to temperature changes, where individuals are unable to emigrate away from potential
stressors. To rectify this, we used the edible bullfrog (Pyxicephalus edulis) as a model
species to determine the effect of elevated temperature on the adrenocortical response
of the species using a recently established matrix. While a control group was kept at
a constant temperature (25 ◦C) throughout the study period, an experimental group
was exposed to control (25 ◦C) and elevated temperatures (30 ◦C). Mucous swabs
were collected throughout the study period to determine dermal glucocorticoid (dGC)
concentrations, as a proxy for physiological stress. In addition to this, individual body
mass measurements were collected. The results showed that individuals within the
experimental group who experienced increased temperatures had significantly elevated
dGC levels compared to the control animals. Furthermore, there was a significant
difference in the percentage mass change between experimental and control animals .
These findings indicate the physiological sensitivity of the edible bullfrog to a thermal
stressor in captivity. While this study shows the importance of proper amphibian
management within the captive environment, it also highlights the coming danger of
global climate change to this and similar amphibian species.
