25 research outputs found

    Host Specificity in the Honeybee Parasitic Mite, <i>Varroa spp</i>. in <i>Apis mellifera</i> and <i>Apis cerana</i>

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    <div><p>The ectoparasitic mite <i>Varroa destructor</i> is a major global threat to the Western honeybee <i>Apis mellifera</i>. This mite was originally a parasite of <i>A</i>. <i>cerana</i> in Asia but managed to spill over into colonies of <i>A</i>. <i>mellifera</i> which had been introduced to this continent for honey production. To date, only two almost clonal types of <i>V</i>. <i>destructor</i> from Korea and Japan have been detected in <i>A</i>. <i>mellifera</i> colonies. However, since both <i>A</i>. <i>mellifera</i> and <i>A</i>. <i>cerana</i> colonies are kept in close proximity throughout Asia, not only new spill overs but also spill backs of highly virulent types may be possible, with unpredictable consequences for both honeybee species. We studied the dispersal and hybridisation potential of <i>Varroa</i> from sympatric colonies of the two hosts in Northern Vietnam and the Philippines using mitochondrial and microsatellite DNA markers. We found a very distinct mtDNA haplotype equally invading both <i>A</i>. <i>mellifera</i> and <i>A</i>. <i>cerana</i> in the Philippines. In contrast, we observed a complete reproductive isolation of various Vietnamese <i>Varroa</i> populations in <i>A</i>. <i>mellifera</i> and <i>A</i>. <i>cerana</i> colonies even if kept in the same apiaries. In light of this variance in host specificity, the adaptation of the mite to its hosts seems to have generated much more genetic diversity than previously recognised and the <i>Varroa</i> species complex may include substantial cryptic speciation.</p></div

    Parasites and Pathogens of the Honeybee (<i>Apis mellifera</i>) and Their Influence on Inter-Colonial Transmission

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    <div><p>Pathogens and parasites may facilitate their transmission by manipulating host behavior. Honeybee pathogens and pests need to be transferred from one colony to another if they are to maintain themselves in a host population. Inter-colony transmission occurs typically through honeybee workers not returning to their home colony but entering a foreign colony (“drifting”). Pathogens might enhance drifting to enhance transmission to new colonies. We here report on the effects infection by ten honeybee viruses and <i>Nosema</i> spp., and <i>Varroa</i> mite infestation on honeybee drifting. Genotyping of workers collected from colonies allowed us to identify genuine drifted workers as well as source colonies sending out drifters in addition to sink colonies accepting them. We then used network analysis to determine patterns of drifting. Distance between colonies in the apiary was the major factor explaining 79% of drifting. None of the tested viruses or <i>Nosema</i> spp. were associated with the frequency of drifting. Only colony infestation with <i>Varroa</i> was associated with significantly enhanced drifting. More specifically, colonies with high <i>Varroa</i> infestation had a significantly enhanced acceptance of drifters, although they did not send out more drifting workers. Since <i>Varroa-</i>infested colonies show an enhanced attraction of drifting workers, and not only those infected with <i>Varroa</i> and its associated pathogens, infestation by <i>Varroa</i> may also facilitate the uptake of other pests and parasites.</p></div

    RESTseq – Efficient Benchtop Population Genomics with RESTriction Fragment SEQuencing

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    <div><p>We present RESTseq, an improved approach for a cost efficient, highly flexible and repeatable enrichment of DNA fragments from digested genomic DNA using Next Generation Sequencing platforms including small scale Personal Genome sequencers. Easy adjustments make it suitable for a wide range of studies requiring SNP detection or SNP genotyping from fine-scale linkage mapping to population genomics and population genetics also in non-model organisms. We demonstrate the validity of our approach by comparing two honeybee and several stingless bee samples.</p></div

    Frequency of control and neonicotinoid honeybee (<i>Apis mellifera</i>) queens mated by Drones Source Colony.

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    <p>Singletons that mated with different types of queen (i.e. control or neonicotinoid) were paired. Frequency of queens that mated with drones from each Drone Source Colony is represented in light grey and dark grey for the control and neonicotinoid queens, respectively.</p

    Information on the genotyped individuals.

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    <p>Sample size and population genetic estimators for each sampling location (P for Philippines and V for Vietnam, followed by the closest city to the sampled apiaries) and host species (<i>A</i>.<i>c</i>: <i>A</i>. <i>cerana</i>, <i>A</i>.<i>m</i>: <i>A</i>. <i>mellifera</i>) on which the mites were collected, together with the clusters provided by the Principal Component Analysis. Number of apiaries <i>(</i><b><i>N</i></b><sub><b><i>A</i></b></sub>); Number of colonies (<b><i>N</i></b><sub><b><i>C</i></b></sub>); Number of individual mites (<b><i>N</i></b><sub><b><i>I</i></b></sub>); Mean number (± se) of alleles over the six microsatellite markers (<b>N</b><sub><b>al</b></sub>); allelic richness ± se; mean observed heterozygosity ± se (<b>H</b><sub><b>O</b></sub>).</p><p>Information on the genotyped individuals.</p

    Functional analysis of honey bee genes affected <i>N. ceranae</i> parasitism.

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    <p>The lists of genes regulated by <i>N. ceranae</i> parasitism were analyzed for statistical enrichment of associated Gene Ontology (GO) and InterPro (IPR) terms (<i>p</i><0.005), relative to the representation of these terms for all expressed genes.</p

    Network map of colonies from Simonswald on accepting drifters according to their <i>indegree centrality</i>.

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    <p>Here we represent the observed <i>indegree centrality</i> based on the actual number of drifters. Each square represents a colony (“+”high <i>Varroa</i>; “-” low <i>Varroa</i>) whilst the number refers to the colony position at the apiary, with +1 and -1 being the two central hives and +7 and -7 those at the two ends of the row. The arrows represent the flow of drifters and their width is proportional to the number of drifters (from 1 to 4) going from one colony to another. Only Simonswald network is represented since more drifters were found in this site than in Kenzingen, which illustrates better our results.</p

    Number of bees drifting from neighbouring colonies (N = 47).

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    <p>The distance of “one” means that the bees came from the neighbouring colony, “two” from the colony next to the neighbouring colony and so on. The equation for the relationship is: y = a + b/x where a = 0.716 and b = 13.96.</p

    Activity of antioxidant enzymes in the midguts of bees challenged by <i>N. ceranae</i>.

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    <p>Differences in enzymatic activity of A) superoxide dismutase (SOD), B) glutathione reductase (GR), C) glutathione peroxydase (GP) and D) glutathione-S-transferase (GST) were estimated by a Mann-Whitney U test. Means±SE are shown for 4 pools of 3 midguts per replicate (<i>n</i> = 3 replicates, 36 bees total/treatment). * and ** denote significant differences at <i>p</i><0.05 and <i>p</i><0.01, respectively.</p

    Relative expression (mean ± s.e.) of candidate genes important for apoptosis in <i>Nosema</i> infected honeybees.

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    <p><i>Nosema</i> sensitive (SN, solid circles) and tolerant (TN, solid squares) honeybees infected with 10<sup>5</sup><i>N</i>. <i>ceranae</i> spores, and their controls uninfected (SC, open circles and TC, open squares), were sampled at 1 day (green) and 6 days (blue) after inoculation. The genes JNK/<i>bsk</i> (Jun N–terminal kinase/ <i>basket</i>), <i>p53</i> (<i>tumor protein p53-like</i>), <i>iap–2</i> (<i>inhibitor of apoptosis protein 2;</i> predicted homologous gene to <i>Diap–1</i> in <i>D</i>. <i>melanogaster</i>), <i>casp–2</i> (<i>caspase–2–like; homologous gene to Dcp–1</i>), <i>casp–10</i> (<i>caspase–10–like; homologous gene to Dredd</i>) were predicted from <i>Drosophila melanogaster</i>. Sample sizes are ranging between six and ten pools of three individual honeybee midguts (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0140174#pone.0140174.s003" target="_blank">S3 Table</a>). Significance between treatment groups ***, <i>P</i> < 0.001.</p
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