Temperature-dependence of metabolic rate in Glossina morsitans morsitans (Diptera, Glossinidae) does not vary with gender, age, feeding, pregnancy or acclimation

While variation in metabolic rate at a single temperature can occur for a variety of reasons and the effect of temperature is well established in insects, within-generation variation of metabolic rate-temperature relationships has been relatively poorly explored. In this study, we investigate the effects of gender, age, feeding and pregnancy, as well as three acclimation temperatures (19, 24, 29°C), on standard metabolic rate and its temperature-dependence within post-developmental (i.e. non-teneral) adult G. morsitans morsitans. Although most of the independent variables influenced metabolic rate at a single test temperature (P<0.001 in most cases), and cold-acclimation resulted in significant up-regulation of metabolic rate at all test temperatures relative to 24 and 29°C acclimation (P<0.0001), mass-independent metabolic rate-temperature relationships were surprisingly invariant over all experimental groups (P>0.05 in all cases). Slopes of log₁₀ metabolic rate (ml CO₂ h^-1) against temperature (°C) ranged from a minimum of 0.03035 (±S.E.=0.003) in young fasted females to a maximum of 0.03834 (±0.004) in mature fasted males. These findings have implications for predicting the metabolic responses of tsetse flies to short-term temperature variation and may also have applications for modelling tsetse population dynamics as a function of temperature.