Characterization of 14 polymorphic microsatellite loci for the facultatively eusocial sweat bee Halictus rubicundus (Hymenoptera, Halictidae) and their variability in related species

Sweat bees display considerable variation in social organization and a few species, such as Halictus rubicundus, are even facultatively eusocial. Fourteen polymorphic, unlinked microsatellite loci were isolated from H. rubicundus and characterized in 45 females. The number of alleles per locus ranged from two to 18 (mean 10.1), observed heterozygosity ranged from 0.24 to 0.98 (mean 0.71) and expected heterozygosity ranged from 0.24 to 0.98 (mean 0.70). Six or more loci cross-amplified in four other sweat bees. These loci will be useful for the study of social evolution and population genetic structure in H. rubicundus and many other sweat bees.

Deformed wing virus and drone mating flights in the honey bee (Apis mellifera): implications for sexual transmission of a major honey bee virus

Deformed wing virus (DWV) represents an ideal model to study the interaction between mode of transmission and virulence in honey bees since it exhibits both horizontal and vertical transmissions. However, it is not yet clear if venereal-vertical transmission represents a regular mode of transmission for this virus in natural honey bee populations. Here, we provide clear evidence for the occurrence of high DWV titres in the endophallus of sexually mature drones collected from drone congregation areas (DCAs). Furthermore, the endophallus DWV titres of drones collected at their maternal hives were no different from drones collected at nearby DCAs, suggesting that high-titre DWV infection of the endophallus does not hinder the ability of drones to reach the mating area. The results are discussed within the context of the dispersal of DWV between colonies and the definition of DWV virulence with respect to the transmission route and the types of tissues infected.

Body size differs in workers produced across time and is associated with variation in the quantity and composition of larval food in Nannotrigona perilampoides (Hymenoptera, Meliponini)

Although variation in body size has been recently reported in stingless bees (Meliponini), empirical evidence evaluating possible factors related to such variation is lacking, and thus it is not clear if it may have an adaptive significance. We evaluated if variation in the body size and weight of workers of stingless bees fluctuates across a seasonal pattern and if this could be related to characteristics of the food consumed during the larval stage. The weight of larval provisions, their protein, and sugar content were evaluated in four colonies of Nannotrigona perilampoides every 2 months across 1 year. Worker-destined larvae from the same combs were allowed to develop and were sampled as callow workers to determine their weight and size using morphometric data. The weight and size of workers were highly correlated and varied across the seasons in established colonies, suggesting that size variation cycles across the year in stingless bees. An increase in the protein content and, to a lesser degree, the quantity of larval food were positively linked to variation in body weight and size; food with richer protein content resulted in larger and heavier workers. This study provides the first evidence of an effect of the quantity and composition of larval food on the size of workers in stingless bees. Although body weight and size of workers differed across seasons, they were not readily noticeable as changes seem to occur as a continuum across the year. Since size polymorphism was of a larger magnitude across time but not within age cohorts and as it was highly determined by food resources, it may not be an adaptive feature in stingless bees. However, more studies are needed to determine the role of the cyclical change in worker body size on colony performance and thus its adaptive significance in stingless bees.

Honey bee (Apis mellifera) venom induces AIM2 inflammasome activation in human keratinocytes

Following allergen exposure, cytokines and other pro-inflammatory signals play an important role in the immunological cascade leading to allergic sensitization. Inflammasomes sense exogenous and endogenous danger signals and trigger IL-1β and IL-18 activation which in turn shape Th2 responses. Honey bee venom (BV) allergies are very common; however, the local inflammatory cascade leading to the initiation of allergic sensitization is poorly understood. In this study, the local inflammatory cascades in skin after exposure to BV were investigated.