Effects of Glyphosate and High-Temperature Stress on Queen Larvae of the Honey Bee ( Apis cerana cerana )

Against the backdrop of agricultural intensification and climate change, bee colonies are increasingly exposed to both agrochemical residues and extreme temperatures, posing a growing threat to their survival. Glyphosate (GLY), one of the most widely used herbicides worldwide, and high temperature are two major environmental stressors associated with pollinator decline. However, their combined effects on queen larvae remain poorly understood. In this study, we examined the individual and combined effects of sublethal GLY exposure and 40 °C heat stress on queen larvae of the honey bee Apis cerana cerana, with a focus on development, hormone levels, detoxification enzyme activities, and related gene expression. The results showed that both GLY and high temperature significantly reduced the larval capping, emergence, and eclosion rates, and decreased the body weight and abdominal weight of newly emerged queens. Under combined exposure, emergence weight, abdominal weight, juvenile hormone (JH) levels, glutathione S-transferase (GST) and the expression of heat-shock protein83 (HSP83) and Nuclear Factor YC(NF-YC) transcription factor-related genes showed significant effects. In addition, co-exposure to GLY and high temperature significantly increased ecdysteroid (Ecd) levels and markedly altered the expression patterns of detoxification- and antioxidant-related genes. These results indicate that GLY and high temperature jointly disrupt endocrine regulation, detoxification metabolism, and key molecular responses in queen larvae, leading to more severe developmental impairment than either stressor alone.