Assessment of the toxic effect of pesticides on honey bee drone fertility using laboratory and semifield approaches: A case study of fipronil

Abstract

Concern about the reproductive toxicity of plant protection products in honey bee reproducers is increasing. Because the reproductive capacity of honey bees is not currently considered during the risk assessment procedure performed during plant protection product registration, it is important to provide methods to assess such potential impairments. To achieve this aim, we used 2 different approaches that involved semifield and laboratory conditions to study the impact of fipronil on drone fertility. For each approach, the drones were reared for 20 d, from emergence to sexual maturity, and exposed to fipronil via a contaminated sugar solution. In both groups, the effects of fipronil were determined by studying life traits and fertility indicators. The results showed that the survival and maturity rates of the drones were better under laboratory conditions than under semifield conditions. Moreover, the drones reared under laboratory conditions produced more seminal fluid. Although these differences could be explained by environmental factors that may vary under semifield conditions, it was found that regardless of the approach used, fipronil did not affect survival rates, maturity rates, or semen volumes, whereas it did affect fertility by inducing a decrease in spermatozoa quantity that was associated with an increase in spermatozoa mortality. These results confirm that fipronil affects drone fertility and support the relevance of each approach for assessing the potential reproductive toxicity of plant protection products in honey bees.

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 2: impacts on organisms and ecosystems

“…Drones that were raised in semi-field and laboratory conditions and exposed to fipronil through feeding showed a decrease in quantity of spermatozoa and increased mortality of spermatozoa (Kairo et al 2017). This confirmed earlier research by the same authors had shown that queens inseminated with sperm of fipronil exposed drones had less and less viable spermatozoa stored in their spermatheca (Kairo et al 2016).…”

Factors affecting the reproductive health of honey bee (Apis mellifera) drones—a review

“…Furthermore, queens inseminated with semen collected from fipronil-exposed drones contained sperm with significantly lower viability in their spermathecae compared to those inseminated with drones that were fed the insecticide-free syrup. Similar results were obtained for drones reared in laboratory conditions following exposure to fipronil in the sugar syrup, which experienced significantly lower sperm viability and concentration (Kairo et al 2017a). Interestingly, the same research group found that fipronil interacts with the microsporidian parasite Nosema ceranae and their interaction causes lower drone sperm viability and antioxidant activity compared to untreated drones (Kairo et al 2017b).…”

“…In conclusion, the few studies that have explored the effects of exposure to commonly used systemic insecticides in the food have consistently shown significant negative effects to drone reproductive quality by causing lower sperm viability in laboratory, semifield, and field conditions (Straub et al 2016;Kairo et al 2016Kairo et al , 2017a. Furthermore, the insecticide fipronil seems to synergize with, and exacerbate the severity of, infection with N. ceranae .…”

Assessment of ecological risks of agrochemicals requires a new framework.

“…This is the case of the lady beetle Hippodamia variegata exposed to sublethal concentrations of thiamethoxam [80]. Neonicotinoids can also negatively affect honeybee drone sperm quality [81,82] while fipronil affects drone fertility by inducing a decrease in spermatozoa quantity that is associated with an increase in spermatozoa mortality [83], so these insecticides may ultimately lead to colony failure [84].…”