Vertical transmission of honey bee viruses in a Belgian queen breeding program

Background: The Member States of European Union are encouraged to improve the general conditions for the production and marketing of apicultural products. In Belgium, programmes on the restocking of honey bee hives have run for many years. Overall, the success ratio of this queen breeding programme has been only around 50%. To tackle this low efficacy, we organized sanitary controls of the breeding queens in 2012 and 2014. Results: We found a high quantity of viruses, with more than 75% of the egg samples being infected with at least one virus. The most abundant viruses were Deformed Wing Virus and Sacbrood Virus (>= 40%), although Lake Sinai Virus and Acute Bee Paralysis Virus were also occasionally detected (between 10-30%). In addition, Aphid Lethal Paralysis Virus strain Brookings, Black Queen Cell Virus, Chronic Bee Paralysis Virus and Varroa destructor Macula-like Virus occurred at very low prevalences (<= 5%). Remarkably, we found Apis mellifera carnica bees to be less infected with Deformed Wing Virus than Buckfast bees ( p < 0.01), and also found them to have a lower average total number of infecting viruses ( p < 0.001). This is a significant finding, given that Deformed Wing Virus has earlier been shown to be a contributory factor to winter mortality and Colony Collapse Disorder. Moreover, negative-strand detection of Sacbrood Virus in eggs was demonstrated for the first time. Conclusions: High pathogen loads were observed in this sanitary control program. We documented for the first time vertical transmission of some viruses, as well as significant differences between two honey bee races in being affected by Deformed Wing Virus. Nevertheless, we could not demonstrate a correlation between the presence of viruses and queen breeding efficacies

The effect of forager loss on honeybee workers temporal polyethism and social network structure

The western honeybee Apis mellifera is perhaps the best-known example of an advanced eusocial species displaying temporal polyethism, a process in which workers perform different tasks in the colony as they age. Previous studies demonstrated that this temporal division of labour is not only regulated by the age of the bees but also by the proportion of workers performing the required tasks in the colony. As we progress through the Anthropocene, the Intergovernmental Panel on Climate Change predicted that a significant increase in both the frequency and intensity of severe weather events can be expected in the coming decades. Here, we performed a controlled interrupted time series experiment with the objective of quantifying the possible effects that these weather events might have in the honeybee colony dynamics. By simulating a significant loss of foragers in the colony, we observed that honeybee workers quickly replaced the missing foragers by accelerating their transition to a subsequent task and, in some cases, completely skipped several of the natural task transitions with respect to their age. In addition, we analysed how the colony social network structure is affected by the sudden loss of foragers. Indeed, our data show that honeybee colonies increased their network cohesion with workers having a higher number of interactions as well as becoming more closely connected to one another soon after the disturbance. Overall, our data shows that even when faced with a substantial perturbation, honeybees can respond swiftly in order to maintain colony homeostasis and likely increase their resilience against future perturbations

Comprehensive bee pathogen screening in Belgium reveals Crithidia mellificae as a new contributory factor to winter mortality

Since the last decade, unusually high honey bee colony losses have been reported mainly in North-America and Europe. Here, we report on a comprehensive bee pathogen screening in Belgium covering 363 bee colonies that were screened for 18 known disease-causing pathogens and correlate their incidence in summer with subsequent winter mortality. Our analyses demonstrate that, in addition to Varroa destructor, the presence of the trypanosomatid parasite Crithidia mellificae and the microsporidian parasite Nosema ceranae in summer are also predictive markers of winter mortality, with a negative synergy being observed between the two in terms of their effects on colony mortality. Furthermore, we document the first occurrence of a parasitizing phorid fly in Europe, identify a new fourth strain of Lake Sinai Virus (LSV), and confirm the presence of other little reported pathogens such as Apicystis bombi, Aphid Lethal Paralysis Virus (ALPV), Spiroplasma apis, Spiroplasma melliferum and Varroa destructor Macula-like Virus (VdMLV). Finally, we provide evidence that ALPV and VdMLV replicate in honey bees and show that viruses of the LSV complex and Black Queen Cell Virus tend to non-randomly co-occur together. We also noticed a significant correlation between the number of pathogen species and colony losses. Overall, our results contribute significantly to our understanding of honey bee diseases and the likely causes of their current decline in Europe

Chemical and behavioural strategies along the spectrum of host specificity in ant-associated silverfish

BACKGROUND: Host range is a fundamental trait to understand the ecological and evolutionary dynamics of symbionts. Increasing host specificity is expected to be accompanied with specialization in different symbiont traits. We tested this specificity-specialization association in a large group of 16 ant-associated silverfish species by linking their level of host specificity to their degree of behavioural integration into the colony and to their accuracy of chemically imitating the host's recognition system, i.e. the cuticular hydrocarbon (CHC) profile. RESULTS: As expected, facultative associates and host generalists (targeting multiple unrelated ants) tend to avoid the host, whereas host-specialists (typically restricted to Messor ants) were bolder, approached the host and allowed inspection. Generalists and host specialists regularly followed a host worker, unlike the other silverfish. Host aggression was extremely high toward non-ant-associated silverfish and modest to low in ant-associated groups. Surprisingly, the degree of chemical deception was not linked to host specificity as most silverfish, including facultative ant associates, imitated the host's CHC profile. Messor specialists retained the same CHC profile as the host after moulting, in contrast to a host generalist, suggesting an active production of the cues (chemical mimicry). Host generalist and facultative associates flexibly copied the highly different CHC profiles of alternative host species, pointing at passive acquisition (chemical camouflage) of the host's odour. CONCLUSIONS: Overall, we found that behaviour that seems to facilitate the integration in the host colony was more pronounced in host specialist silverfish. Chemical deception, however, was employed by all ant-associated species, irrespective of their degree of host specificity.status: publishe

Worker policing in the German wasp Vespula germanica

In some ants, bees, and wasps, workers kill or "police” male eggs laid by other workers in order to maintain the reproductive primacy of the queen. Kin selection theory predicts that multiple mating by the queen is one factor that can selectively favor worker policing. This is because when the queen is mated to multiple males, workers are more closely related to the queen's sons than to the sons of other workers. Earlier work has suggested that reproductive patterns in the German wasp Vespula germanica may contradict this theory, because in some colonies a large fraction of the adult males were inferred to be the workers' sons, despite the effective queen mating frequency being greater than 2 (2.4). In the present study, we reexamine the V. germanica case and show that it does support the theory. First, genetic analysis confirms that the effective queen mating frequency is high, 2.9, resulting in workers being more related to the queen's sons than to other workers' sons. Second, behavioral assays show that worker-laid eggs are effectively killed by other workers, despite worker-laid eggs having the same intrinsic viability as queen-laid ones. Finally, we estimate that approximately 58.4% of the male eggs but only 0.44% of the adult males are worker derived in queenright colonies, consistent with worker reproduction being effectively police

Special Issue on Stingless bees: Integrating basic biology and conservation

It is easy to see why stingless bees (Meliponini) were chosen for this special issue, entitled Stingless bees: Integrating basic biology and conservation. Interest in these bees is increasing each day, with their role as ecosystemservices providers in the pollination of wild and cultivated plants, and their fascinating biology and social behavior. Yet, despite having been kept by the Native Americans for hundreds of years for their honey, they remain much understudied compared to their better known relatives, the bumblebees and honeybees. This is in part due to their massive biodiversity, with known species now numbering over 500 – all with a tropical distribution. The diversity and rich social behavior of the stingless bees has often been compared to the knowledge of the other group of eusocial bees, including the bumblebees (Bombini) and honeybees (Apini). Yet, the development of new scientific techniques and research methods, and progress in deciphering their phylogeny, now allows for an updated interpretation of the evolution, biology and conservation of Meliponini bees

Cuticular hydrocarbons as caste-linked cues in Neotropical swarm-founding wasps

Wasps (Vespidae) are important organisms to understand the evolution of social behaviour. Wasps show different levels of sociality, which includes solitary to highly eusocial organisms. In social insect species, queens and workers differ in physiology and morphology. The Neotropical swarm-founding wasps (Epiponini) show a variety of caste syndromes. In this clade, the caste-flexibility is a unique characteristic, in which workers can become queens and swarm to start a new nest. The investigation of the caste system comparing several Epiponini species show a clear-cut morphological distinction between queens and workers, with a morphological continuum between queens and workers. However, whether cuticular hydrocarbons (CHCs) are used as cues for caste recognition in swarm-founding wasps is still unknown. We studied whether CHCs may display caste-linked differences in eleven species of Epiponini wasps and if CHCs differences would follow morphological patterns. Our results suggest that queens and workers of Epiponini wasps are chemically different from each other at two levels, qualitatively and quantitatively, or merely quantitatively. This variation seems to exist regardless of their morphological traits and may be useful to help us understanding how chemical communication evolved differently in these species

Working-class royalty: bees beat the caste system

The struggle among social classes or castes is well known in humans. Here, we show that caste inequality similarly affects societies of ants, bees and wasps, where castes are morphologically distinct and workers have greatly reduced reproductive potential compared with queens. In social insects, an individual normally has no control over its own fate, whether queen or worker, as this is socially determined during rearing. Here, for the first time, we quantify a strategy for overcoming social control. In the stingless bee Schwarziana quadripunctata, some individuals reared in worker cells avoid a worker fate by developing into fully functional dwarf queens

A high recombination rate in eusocial Hymenoptera: evidence from the common wasp Vespula vulgaris

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