Abstract
Honey bee (Apis mellifera) colonies invest a substantial amount of colony resources in the production of drones during the reproductive season to enable mating with virgin queens from nearby colonies. Recent studies have shown significant differences in the production of sperm cells that are viable (i.e., sperm viability) and can fertilize an ovule among sexually mature drones that are exposed to different environmental conditions during development or as adults. In particular, sperm viability may be negatively affected during drone development from exposure to pesticides in contaminated beeswax. To assess whether sperm viability is negatively affected during drone development from exposure to beeswax contaminated with in-hive pesticides, we compared the viability of sperm collected from drones reared in pesticide-free beeswax with that of drones reared in beeswax contaminated with field-relevant concentrations of the pesticides most commonly found in wax from commercial beekeeping operations in the United States. These pesticides include the miticides fluvalinate, coumaphos and amitraz, and the agro-chemicals chlorothalonil and chlorpyrifos. Sperm from drones collected at 10 and 18 days post emergence were classified as viable or non-viable to calculate sperm viability. For all pesticide treatment groups, drones that were reared in pesticide-laden beeswax had lower sperm viability compared to those reared in pesticide-free beeswax. This difference was especially pronounced among drones reared in miticide-laden wax. Our results reinforce the notion that pesticide contamination of beeswax negatively affects the reproductive quality of drones, which can affect the queens they mate with, ultimately compromising colony health.
Highlights
Among species of eusocial Hymenoptera, males live sheltered lives inside their hives, where they are raised by sister workers until they are ready to mate [1]
Given that we found no significant difference in sperm viability between drones collected at 10 days and 18 days post emergence in either the pesticide-free control group (t = 0.06, P = 0.48), or the amitraz-treated group (t = 0.23, P = 0.83), we pooled the data from both age cohorts and performed an overall comparison between treatment groups using all the drones reared in each treatment group
Likewise in 2017, we found that drones reared in frames coated with wax exposed to miticides or agro-chemicals had lower sperm viability than those reared in pesticide-free frames (F = 22.5, P
Summary
Among species of eusocial Hymenoptera (ants, wasps, and bees), males live sheltered lives inside their hives, where they are raised by sister workers until they are ready to mate [1]. A substantial amount of colony resources is invested in the care and nurturing of males, despite the fact that they provide no contributions to colony maintenance apart from reproduction [2]. Male rearing by workers appears regularly among eusocial insects [3], especially in swarmfounding species such as honey bees in the genus Apis, which exhibit an extreme male-biased. Pesticides affect drone sperm viability collection and analysis, decision to publish, or preparation of the manuscript
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