Fluvalinate accumulation in the beehive environment and its effects on semen quality and gene expression of drones under field conditions

This study investigated the accumulation of fluvalinate, a common miticide used in beekeeping, in hive compartments and bee products, as well as its potential harmful effects on detoxifying enzyme expression and sperm quality in drones. Twelve colonies were divided into three groups: a control, a high-dose fluvalinate group (nominal concentration 750 µg/kg diet), and a low-dose fluvalinate group (nominal concentration 75 µg/kg diet). Bees were continuously fed fluvalinate-spikedsugar syrup for 22 days, and a synchronized drone brood was introduced on day 3 to these colonies. After the exposure period, samples of wax, hive stores, drone semen, and intestinal tissues were collected to assess fluvalinate residues, semen quality, and gene expression of antioxidant enzymes. In the high-dose group, fluvalinate residues reached 0.12 mg/kg in carbohydrate stores and 0.196 mg/kg in wax. In the low-dose group, levels were lower but still detectable at 0.017 mg/kg in stores and 0.022 mg/kg in wax. Surprisingly, control samples contained trace residues of fluvalinate, suggesting honeybee drifting among the tested groups. Flow cytometry revealed significantly increased number of dead cells in drone semen from the high-dose group, alongside significantly reduced expression of superoxide dismutase 1 and glutathione S-transferase - key detoxifying enzymes, compared to the control group. These findings indicate that fluvalinate accumulates in hive environments and negatively impacts drone reproductive health and gene expression. This could have broader implications for colony health and the viability of future bee generations.