Sex-Specific Differences in Pathogen Susceptibility in Honey Bees (Apis mellifera)

Abstract

Sex-related differences in susceptibility to pathogens are a common phenomenon in animals. In the eusocial Hymenoptera the two female castes, workers and queens, are diploid and males are haploid. The haploid susceptibility hypothesis predicts that haploid males are more susceptible to pathogen infections compared to females. Here we test this hypothesis using adult male (drone) and female (worker) honey bees (Apis mellifera), inoculated with the gut endoparasite Nosema ceranae and/or black queen cell virus (BQCV). These pathogens were chosen due to previously reported synergistic interactions between Nosema apis and BQCV. Our data do not support synergistic interactions between N. ceranae and BQCV and also suggest that BQCV has limited effect on both drone and worker health, regardless of the infection level. However, the data clearly show that, despite lower levels of N. ceranae spores in drones than in workers, Nosema-infected drones had both a higher mortality and a lower body mass than non-infected drones, across all treatment groups, while the mortality and body mass of worker bees were largely unaffected by N. ceranae infection, suggesting that drones are more susceptible to this pathogen than workers. In conclusion, the data reveal considerable sex-specific differences in pathogen susceptibility in honey bees and highlight the importance of ultimate measures for determining susceptibility, such as mortality and body quality, rather than mere infection levels.

On the Front Line: Quantitative Virus Dynamics in Honeybee (Apis mellifera L.) Colonies along a New Expansion Front of the Parasite Varroa destructor

“…Such multiple infections create opportunities for interactions between viruses and other honeybee pathogens, which are likely to have cumulative (additive) and possibly also synergistic (interactive) effects on honeybee health at both individual and colony level [55]. Such synergistic interactions have been reported between the fungal pathogen Nosema and CBPV with respect to virus replication [56] and between Nosema and BQCV with respect to virus infectivity [57] although more recent research suggests that the effect of Nosema and BQCV on longevity are additive rather than synergistic, with Nosema by far the more damaging partner [58], and with drones much more susceptible to these pathogens than worker bees. Interactions of this kind are known to create unpredictable epidemiological effects in plants and other animal models [59], [60].…”

Improving the future of honey bee breeding programs by employing recent scientific advances

“…Viruses, such as chronic bee paralysis virus, can also directly affect queens by increasing their mortality [53]. Another study showed that while black queen cell virus had a limited effect, drones infected with a microsporidian N. ceranae exhibited higher mortality and lower body weight [54] suggesting a possible effect on semen quality and/or mating success, but these parameters were not quantified. Nosema infection can also alter mandibular gland pheromone production which could be associated with higher queen replacement rates [55].…”

The Ability of Honey Bee Drones to Ejaculate

“…The difficulty in the eversion of the endophallus and ejaculation of semen are usually explained by the drones being too immature to copulate (Mindt, 1962;Tozetto, 1997;Rhodes et al, 2011). The problems with ejaculating semen may also be caused by anatomical abnormalities or physiological disorders, which often stem from poor rearing conditions or from the existence of diseases, including the presence of Varroa destructor (De Jong, 1997;Duay et al, 2002;Retschnig et al, 2014), and viral diseases (Fievet et al, 2006;Cruz-Landim et al, 2012). The objective of this study was to compare the effectiveness of two methods of collecting semen from drones, and to analyse the causes of the problems associated with the eversion of the endophallus and the ejaculation of semen.…”