PDF《Drone exposure to the systemic》

and early supersedure or queenless colonies14,18 .

1 INRA, UR

406 Abeilles & Environnement, Toxicologie Environnementale, Avignon, 84914, France.

2 SUPAGRO, Laboratoire de Pathologies de l'Abeille, Montpellier, 34090, France.

3 INAT, Laboratoire de Zoologie et d'Apiculture, Tunis, 1082,Tunisie.

4 INRA, UR

546 Biostatistiques & Processus Spatiaux,Avignon, 84914, France. Correspondence and requests for materials should be addressed to J.-L.B. (email: [email protected]) received:

26 January

2016 accepted:

26 July

2016 Published: 23August

2016 OPEN

2 These symptoms may be due to queen exposure to pesticides19C22 and biological agents, such as the ectodermic parasite Varroa destructor, the microsporidium Nosema ceranae, or viruses18,23,24 . A shortage of available healthy drones (i.e., male honey bees) with high-quality semen may also cause queens to become poorly mated, thus diminishing queen quality18,25,26 . Although queens have been studied more often than drones, few reports have characterized the impacts of environmental stressors on drone survival and fertility. These studies are mainly focused on the effects of parasites and veterinary treatments26C28 . However, no studies have established a direct relationship between insecticides, drone fertility, and the final impact on the queen. Thus, we assessed whether reduced queen quality could also be the result of disrupted drone fertility induced by sublethal exposures to insecticides. Our attention was focused on Fipronil, a pesticide widely used for its systemic properties29 in numerous varieties of agricultural and veterinary applications. Because Fipronil diffuses into plant tissues, it contaminates nectar and pollen, which are food sources for the honey bee29 . In addition, honey bees in hives could be exposed to Fipronil when it is used to control the small hive beetle Aethina tumida30 . This neurotoxic phenylpyrazole insecticide is known to induce lethal and sublethal effects at the cellular31,32 , behavioral33C36 and colonial level36 in honey bees as well as in non-target invertebrates37 . Interestingly, Fipronil also alters the reproductive functions of some terrestrial and aquatic vertebrates and invertebrates38C42 . To study the impact on fertility, drones, which depend on workers for their food supply, were chronically exposed throughout their sexual maturation to a contaminated food source gathered by foragers. This food was a syrup solution contaminated with Fipronil at 0.1?μ?g.L?1 (0.087?μ?g.kg?1 ;

density, d?=??1.1488), which is an environmen- tally relevant concentration29 . The impacts of this exposure on foraging activity and drone life cycle traits and sperm quality were monitored. The impacts on queen fertility were also investigated by analyzing the spermathe- cal content of queens instrumentally inseminated with sperm from exposed or unexposed drones. The results are discussed in terms of potential impacts on queen performance at the colony level. Results and Discussion Fipronil affects male fertility.? The apparent effects of sublethal exposure to Fipronil were investigated under semi-field conditions (Fig.?1A). No significant effects were observed on the foraging behavior of workers (Fig.?1B,C) or on drone survival (Table?1). These results are not surprising because behavioral effects of Fipronil are observed in worker bees only at concentrations ≥?1?μ?g.kg?1?33,34,36 . However, no information about the effects of Fipronil on drones was available. In this context, drones were exposed to Fipronil via food brought back to the hive by foragers during the period from emergence to drone sexual maturity. However, drones directly consum- ing the syrup with Fipronil at 0.1?μ? g/L upon the return of foragers cannot be excluded. In addition, drones could also have consumed contaminated food stored in the hive with concentrations of Fipronil different from that of the syrup. During hive storage and while the honey matures, Fipronil could be concentrated, partly transferred to bees or metabolized by bees or by enzymes excreted in honey43 , and metabolites could appear. Thus, drone exposure is not directly controlled during this period. Hence, to assess the Fipronil exposure, the concentra- tion of Fipronil and its metabolites in honey stored in hives after