ORIGINAL ABSTRACT

Insecticides and herbicides are utilized worldwide in agricultural practices, and these hazardous materials retained in the environment impose potential threats to pollinators, including bumblebees. However, whether and how short-term exposure to sublethal concentrations of insecticide/herbicide induces lasting toxicity effects in newly emerged gynes remain uncharacterized. In this study, we comprehensively investigated the long-term consequences of short-term exposure to sublethal imidacloprid (IMI) and glyphosate (GLY) (singly or combined) on bumblebee (Bombus terrestris) gynes under different exposure regimens through integrated physiological and transcriptomic analyses. Short-term exposure of gynes to IMI alone and IMI + GLY mixtures not only impacted survival, tissue development, nutrient reserves, mating, diapause energy metabolism, and reproduction of queens but also caused transgenerational toxicity affecting offspring development and performance. In contrast, GLY exposure alone adversely affected tissue development, nutrient reserves, diapause energy metabolism, and offspring development of queens. Notably, compared to direct exposure, starvation exacerbated the adverse effects of IMI exposure on queens' diapause survival and energy metabolism and aggravated the impacts of GLY exposure on gynes' ovarian development and lipid reserves. For combined IMI + GLY exposure, starvation mainly amplified physiological disturbances related to queens' diapause survival, energy metabolism, and offspring development and performance. The observed defects in short-term IMI- and IMI + GLY-exposed gynes may result from altered nutrient metabolic pathways. Collectively, our research unveils the lasting toxicity of short-term mixed insecticide/herbicide exposure on gynes/queens and their offspring from physiological and molecular perspectives, underscoring the urgent need for regulatory consideration of combined pesticide risks in bumblebee conservation.