PDF《Drone exposure to the systemic》

20 days of foraging was determined using GCCMS/MS chemical analysis. However, the values of Fipronil and metabolite concentrations were lower than the limit of detection (LOD?=??0.2?μ? g/kg of honey). Residues in males were not analyzed because we had con- ducted a preliminary assessment of the exposure. This latter assessment was based on the sugar consumption of drones (21C90?mg/drone/day44 ), the sugar concentration in the food (50% w/v), the exposure period (20 days) and the Fipronil concentration in the syrup (0.1?μ?g/L). Thus, in the worst case scenario (i.e., the highest food con- sumption, absence of elimination and complete bioaccumulation of the doses ingested), the cumulative dose of Fipronil ingested per drone during the exposure period was estimated at 360?pg/drone. Considering that drones weigh approximately 196C225?mg45 , this cumulative amount of Fipronil corresponded to 1.84?μ? g of Fipronil per kg of drone for a drone weight of 196?mg;

this amount was less than the LOD of the analytical method (3?μ?g/kg of bees). Despite this low exposure level, Fipronil affecting the development of drones could not be excluded. However, no effects on drone sexual maturity rate or semen volume were observed (Table?1). Because no apparent effects were observed at the individual level, the quality of semen was studied in greater detail by analyzing sperm count and other physiological parameters. Drones achieve spermatogenesis at the larval stage. Thus, number of spermatozoa at emergence is determined early. Therefore, as exposure to Fipronil started at emergence, it could not affect the production of spermatozoa and could only affect seminal fluid production, which occurs during drone's sexual maturation at approximately 15C20 days after emergence. During this period, spermatozoa mature in the seminal vesicles with the head anchored in the secretory epithelium and are released in the seminal gland at sexual maturity46 . In the present study, the semen volume produced per drone was not affected by exposure to Fipronil, which also suggested that Fipronil has no apparent effect on semen quality (Table?1). Nevertheless, exposure to Fipronil induced a decrease in total spermatozoa concentration (median of 8.59?*??106 spermatozoa vs. 10.47?*??106 spermatozoa in controls, P?