Impact of Acute Thermal Stress in Male Drosophila melanogaster on Climbing Performance, Oxidative stress and Brain Histology

Climate change-induced heat waves pose significant physiological challenges to organisms, yet the sublethal effects of acute heat stress on living organism’s health remain poorly understood. This study investigated the effects of acute heat stress (5 and 10 minutes at an elevated temperature of 40oC) on oxidative stress markers, locomotor function and brain sections in male Drosophila melanogaster within a duration of 2 days. Oxidative stress was assessed by measuring malondialdehyde (MDA), superoxide dismutase (SOD), and reduced glutathione (GSH) levels, while climbing performance was evaluated using the Rapid Iterative Negative Geotaxis (RING) assay. Brain morphology was also examined histologically. Results showed decreases in MDA and SOD levels across both heat-exposed groups that was not significant (p >0.05), while GSH levels decreased after 5 minutes but increased after 10 minutes, these changes were also not significant. However, the RING assay revealed a significant decline in climbing performance following 10 minutes of heat exposure (p < 0.05 for the control; p < 0.01 for the 5-minute group), despite the absence of significant changes in biochemical markers. Brain micrographs from the 10-minute group showed pronounced vacuolation and neuropil disruption in the optic lobes and central brain, correlating with the observed motor deficits. The findings of this study demonstrate that acute heat exposure causes a decline in motor performance and alters brain histological architecture in Drosophila melanogaster. However, no significant changes were detected in the oxidative stress biomarkers.

Key Words: Drosophila melanogaster, Heat stress, RING assay, Oxidative stress, Brain histology