Copper-accelerated pupation in larvae of the buff-tailed bumble bee

With the expansion of industrial activities, the escalation of pollution by trace metals poses an increasing threat to bees. While the effects of metals on adult bees have been extensively studied in ecotoxicological research, a critical gap persists concerning their impact on bee larvae. Here, we conducted the first study exposing bumble bee larvae to field-realistic concentrations of copper via an in vitro assay, over a span of 25 days. We monitored the duration of their developmental stages, including moments of defecation, pupation, and emergence, alongside their survival rates. Additionally, we recorded their area growth as well as their adult body mass post-emergence. Despite copper exposure exhibiting no discernible influence on the overall duration of development, survival, growth, or adult mass, a significant positive effect was observed on the pupation rate. This outcome is likely attributable to heightened copper-dependent metabolic activities and disturbances in the redox balance. Furthermore, our investigation underscored the pivotal role of initial body size in developmental success, with larger larvae showing elevated emergence and survival rates. Given the efficacy of this assay, we urge regulatory institutions responsible for approving pesticides and other xenobiotics for market use to embrace this experimental approach in future risk assessments.