Effects of temperature on plasma corticosterone in a native lizard

Area of Science:

• Zoology
• Physiology
• Ecology

Background:

• The glucocorticoid stress response is a key indicator of vertebrate environmental adaptation.
• Body temperature is known to influence glucocorticoid levels, particularly in ectothermic species.

Purpose of the Study:

• To investigate the impact of body temperature on plasma corticosterone concentrations in eastern fence lizards (Sceloporus undulatus).
• To determine if laboratory findings on temperature effects on stress hormones are applicable to field conditions.

Main Methods:

• Laboratory acclimation of lizards to different temperatures (22°C, 29°C, 33°C, 36°C) with baseline and stress-induced corticosterone measurements.
• Exposure of lizards acclimated to 22°C or 29°C to a standardized restraint stressor.
• Measurement of plasma corticosterone in field-caught lizards to assess correlation with body temperature.

Main Results:

• Both baseline and stress-induced plasma corticosterone concentrations were lower in lizards at lower body temperatures.
• Lizards acclimated to 29°C exhibited a significant corticosterone increase upon stress, unlike those at 22°C.
• No correlation was found between body temperature and baseline plasma corticosterone in field-caught lizards.

Conclusions:

• Body temperature substantially affects plasma corticosterone levels in reptiles.
• Laboratory studies on glucocorticoid stress responses may not accurately reflect field conditions due to temperature differences.
• Reptile stress hormone research must account for body temperature to ensure ecological relevance.