Selection of VSH-derived “Pol-line” honey bees and evaluation of their Varroa-resistance characteristics

International audienceAbstractHoney bees with Varroa sensitive hygiene (VSH) have good resistance to Varroa destructor. We bred “Pol-line” bees by outcrossing VSH queens to US commercial stocks from 2008 to 2014 and then selecting colonies with low mite infestations. Beginning in 2011, field performance of colonies with outcrossed Pol-line queens was compared to colonies with outcrossed VSH queens. Mite infestations after one season were comparable in colonies of the two bee types. Queens from the most functional colonies of both bee types were added to the Pol-line breeding population each year. Mite resistance was investigated further by exposing mite-infested brood to colonies for 1 week in lab tests. The two bee types did not differ in the percentage of infested brood they removed or in the percentage of non-reproduction among remaining mites. Introgressing the VSH trait into commercial honey bee stock shows promise in creating bees that have useful mite resistance and desirable beekeeping characteristics

Reconstruction of Family-Level Phylogenetic Relationships within Demospongiae (Porifera) Using Nuclear Encoded Housekeeping Genes

Background: Demosponges are challenging for phylogenetic systematics because of their plastic and relatively simple morphologies and many deep divergences between major clades. To improve understanding of the phylogenetic relationships within Demospongiae, we sequenced and analyzed seven nuclear housekeeping genes involved in a variety of cellular functions from a diverse group of sponges. Methodology/Principal Findings: We generated data from each of the four sponge classes (i.e., Calcarea, Demospongiae, Hexactinellida, and Homoscleromorpha), but focused on family-level relationships within demosponges. With data for 21 newly sampled families, our Maximum Likelihood and Bayesian-based approaches recovered previously phylogenetically defined taxa: Keratosap, Myxospongiaep, Spongillidap, Haploscleromorphap (the marine haplosclerids) and Democlaviap. We found conflicting results concerning the relationships of Keratosap and Myxospongiaep to the remaining demosponges, but our results strongly supported a clade of Haploscleromorphap+Spongillidap+Democlaviap. In contrast to hypotheses based on mitochondrial genome and ribosomal data, nuclear housekeeping gene data suggested that freshwater sponges (Spongillidap) are sister to Haploscleromorphap rather than part of Democlaviap. Within Keratosap, we found equivocal results as to the monophyly of Dictyoceratida. Within Myxospongiaep, Chondrosida and Verongida were monophyletic. A well supported clade within Democlaviap, Tetractinellidap, composed of all sampled members of Astrophorina and Spirophorina (including the only lithistid in our analysis), was consistently revealed as the sister group to all other members of Democlaviap. Within Tetractinellidap, we did not recover monophyletic Astrophorina or Spirophorina. Our results also reaffirmed the monophyly of order Poecilosclerida (excluding Desmacellidae and Raspailiidae), and polyphyly of Hadromerida and Halichondrida. Conclusions/Significance: These results, using an independent nuclear gene set, confirmed many hypotheses based on ribosomal and/or mitochondrial genes, and they also identified clades with low statistical support or clades that conflicted with traditional morphological classification. Our results will serve as a basis for future exploration of these outstanding questions using more taxon- and gene-rich datasets

An association in honey bees between autogrooming and the presence of migrating tracheal mites

We evaluated the difference in tracheal mite infestation between nestmate honey bees that were actively autogrooming and those that were not. Bees seen to be actively grooming themselves in an observation hive were immediately removed through a door, narcotized and searched for mites. Nearby bees that were not grooming also were taken and examined. A strong association was found between the act of autogrooming and the presence of tracheal mites, with mites found at a 4-fold greater frequency on the thoraxes of grooming bees (36/50 with mites) than on non-grooming bees. Mites were found most commonly on the metatergum and the propodeum, and near the wing bases

Autogrooming by resistant honey bees challenged with individual tracheal mites

Autogrooming responses of resistant and susceptible strains of honey bees were measured when bees were challenged by placing adult female tracheal mites on their thoraces. Marked, young adult workers of the two strains of bees were added to colonies in observation hives. We transferred a single, live, adult, female mite onto the mesoscutum of a marked bee, monitored the bee for seven minutes and then removed it and searched for the mite. Greater proportions of resistant bees autogroomed, and resistant bees made more grooming attempts. Bees of both strains had equal apparent grooming effectiveness; grooming bees lost approx. 75% of mites. Control-group bees (those only stroked with the brush used to transfer mites) of the two bee strains did not differ in any response parameter. Resistant bees may have a lower threshold for responding by autogrooming when stimulated by mites on their body

Larval Pollen Stress Increases Adult Susceptibility to Clothianidin in Honey Bees

Neonicotinoid insecticides have come under scrutiny for their potential role in honey bee declines. Additionally, reduced access to forage in agricultural areas creates the potential for risk interactions with these pesticides in regions critical for honey production. In this study, we sought to determine whether sufficient access to pollen during larval development could mitigate stress associated with oral clothianidin exposure in honey bee adults. An apiary was established where pollen traps deprived half of the colonies of pollen, which was then supplemented to the others. Adults were fed 0, 10, 40, 200, or 400 µg/L clothianidin in the laboratory, and larval and adult lipids and superoxide dismutase (SOD) activities were compared between feeding treatments. Survival at sublethal concentrations of clothianidin was significantly reduced for adult bees reared in pollen deprived colonies. Adult SOD activity was affected by clothianidin dose but not larval feeding treatment, though within the pollen-deprived cohort, SOD was greater in controls than those fed clothianidin. Larval SOD differed between field replicates, with supplemented colonies having slightly higher activity levels during a period of pollen dearth, indicating that supplementation during these periods is particularly important for mitigating oxidative stress within the hive. Larval lipids were significantly higher in supplemented colonies during a substantial pollen flow, though adult lipids were unaffected by feeding treatment. These results suggest that during periods of pollen dearth, oxidative stress and adult worker longevity will be improved by supplementing colonies with locally collected pollen

Selecting honeybees for worker brood that reduces the reproduction of Varroa destructor

International audienceAbstractWe investigated an effect of Apis mellifera worker brood on the reproduction of Varroa destructor as a resistance trait by conducting seven generations of bidirectional selection. Initial tests showed twofold differences in mite fecundity (progeny per foundress mites) between colonies of different origins. In the first two generations of selection, low and high lines differed significantly in mite fecundity (2.6 vs. 2.9 and 2.3 vs. 2.8), but in five subsequent generations the average values of the low fecundity lines (ranges of 2.7 to 3.3) became indistinguishable from high lines (2.9 to 3.1). Similarly, the relationship between mite fecundity in 117 offspring colonies and in their 26 queen and 22 drone parent colonies was partly significant in the first three generations but not in subsequent generations. These findings suggest that adaptation of mites to host cues, loss of resistance alleles in a small breeding population, or environmental effects present challenges to breeding for this trait

Influence of Varroa Mite (Varroa destructor) Management Practices on Insecticide Sensitivity in the Honey Bee (Apis mellifera)

Since Varroa mites may cause devastating losses of honey bees through direct feeding, transmitting diseases, and increasing pathogen susceptibility, chemical and mechanical practices commonly are used to reduce mite infestation. While miticide applications are typically the most consistent and efficacious Varroa mite management method, miticide-induced insecticide synergism in honey bees, and the evolution of resistance in Varroa mites are reasonable concerns. We treated colonies with the miticide amitraz (Apivar®), used IPM practices, or left some colonies untreated, and then measured the effect of different levels of mite infestations on the sensitivity of bees to phenothrin, amitraz, and clothianidin. Sensitivity to all insecticides varied throughout the year among and within treatment groups. Clothianidin sensitivity decreased with increasing mite levels, but no such correlation was seen with phenothrin or amitraz. These results show that insecticide sensitivity is dynamic throughout the 5 months test. In-hive amitraz treatment according to the labeled use did not synergize sensitivity to the pesticides tested and this should alleviate concern over potential synergistic effects. Since IPM practices were largely ineffective at reducing Varroa mite infestation, reliance on chemical methods of Varroa mite management is likely to continue. However, miticides must be used judiciously so the long term effectiveness of these compounds can be maximized. These data demonstrate the complex and dynamic variables that contribute to honey bee colony health. The results underscore the importance of controlling for as many of these variables as possible in order to accurately determine the effects of each of these factors as they act alone or in concert with others

DIFFERENTIAL DRONE PRODUCTION BY AFRICANIZED AND EUROPEAN HONEY BEE COLONIES

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