Exposure to pesticides during development negatively affects honey bee (Apis mellifera) drone sperm viability

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.

Initial Exposure of Wax Foundation to Agrochemicals Causes Negligible Effects on the Growth and Winter Survival of Incipient Honey Bee (Apis mellifera) Colonies

“…Furthermore, the presence of amitraz, tau -fluvalinate, and coumaphos in the brood-rearing wax environment has been shown to cause lower spermatozoa viability in queen spermathecae, lower queen reproductive potential, higher supersedure rates, and lower egg-laying rates [16,17,33,34,35,36,37]. These miticides also affect drone development, as they can reduce drone production [38] and survival [39], as well as spermatozoa production and viability [40,41,42,43].…”

“…Although not much is known about the effects of chlorpyrifos on honey bees, it can cause substantial synergistic effects when combined with other pesticides, leading to high larval mortality [45]. Moreover, a recent study in which wax was contaminated with field-relevant concentrations of chlorpyrifos in combination with chlorothalonil showed decreased spermatozoa viability in sexually mature drones [43]. The most recent data published has estimated that, conservatively, the U.S. used over 5 million pounds of products with chlorpyrifos as the active ingredient from 2000–2010.…”

Honey Bee Queens and Virus Infections

“…The queen is a critical member of the honey bee colony, and her primary roles are prolific egg production and the release of pheromones that maintain social cohesion [8][9][10]. In addition to the queen's genetic make-up, queen quality-including health status and reproductive vigor-is a consequence of the nurse bees' care during development of the queen larva, the health and fertility of the~15 drones with which she mates, and the care she receives from worker bees in her colony after mating [11][12][13][14][15][16][17][18][19]. Simultaneously, queen health and reproductive capacity have direct impacts on the health, well-being, and vigor of the colony she is heading [8,20,21].…”

Lethal and Sublethal Effects of Pyriproxyfen on Apis and Non-Apis Bees

“…However, this does not exclude that the molecule could have adverse effects on the reproductive males and females. Indeed, there is increasing evidence that pesticides can negatively impact reproduction of Apis and non- Apis bees including egg laying, sperm viability and production [ 47 , 71 , 163 , 164 , 165 , 166 ]. Interestingly, Thompson et al [ 163 ] showed that the number of queens of A. mellifera that successfully mated and laid eggs was affected by fenoxycarb.…”