Table S1. A list of the species per country found in this study. References to previous research of Culicoides fauna in the same countries are made, as well as remarks on the distribution of the species as described in the IIKC. (XLSX 14 kb)
Abstract Dosage compensation has evolved in concert with Y-chromosome degeneration in many taxa that exhibit heterogametic sex chromosomes. Dosage compensation overcomes the biological challenge of a "half dose" of X chromosome gene transcripts in the heterogametic sex. The need to equalize gene expression of a hemizygous X with that of autosomes arises from the fact that the X chromosomes retain hundreds of functional genes that are actively transcribed in both sexes and interact with genes expressed on the autosomes. Sex determination and heterogametic sex chromosomes have evolved multiple times in Diptera, and in each case the genetic control of dosage compensation is tightly linked to sex determination. In the Anopheles gambiae species complex (Culicidae), maleness is conferred by the Y-chromosome gene Yob , which despite its conserved role between species is polymorphic in its copy number between them. Previous work demonstrated that male An. gambiae s.s. males exhibit complete dosage compensation in pupal and adult stages. In the present study we have extended this analysis to three sister species in the An. gambiae complex: An. coluzzii , An. arabiensis , and An. quadriannulatus . In addition, we analyzed dosage compensation in bi-directional F1 hybrids between these species to determine if hybridization results in the mis-regulation and disruption of dosage compensation. Our results confirm that dosage compensation operates in the An. gambiae species complex through the hyper-transcription of the male X chromosome. Additionally, dosage compensation in hybrid males does not differ from parental males, indicating that hybridization does not result in the mis-regulation of dosage compensation.
Additional file 1: Table S1. Metadata for all of the locations including their full names and coordinates as well as information on vegetation and tick density. Table S2. Number of samples collected from different tick life stages at different locations. Table S3. Location and tick life stage per sample.
West Nile virus (WNV) is a highly pathogenic flavivirus transmitted by Culex spp. mosquitoes. In North America (NA), lineage 1 WNV caused the largest outbreak of neuroinvasive disease to date, while a novel pathogenic lineage 2 strain circulates in southern Europe. To estimate WNV lineage 2 epidemic potential it is paramount to know if mosquitoes from currently WNV-free areas can support further spread of this epidemic.We assessed WNV vector competence of Culex pipiens mosquitoes originating from north-western Europe (NWE) in direct comparison with those from NA. We exposed mosquitoes to infectious blood meals of lineage 1 or 2 WNV and determined the infection and transmission rates. We explored reasons for vector competence differences by comparing intrathoracic injection versus blood meal infection, and we investigated the influence of temperature. We found that NWE mosquitoes are highly competent for both WNV lineages, with transmission rates up to 25%. Compared to NA mosquitoes, transmission rates for lineage 2 WNV were significantly elevated in NWE mosquitoes due to better virus dissemination from the midgut and a shorter extrinsic incubation time. WNV infection rates further increased with temperature increase.Our study provides experimental evidence to indicate markedly different risk levels between both continents for lineage 2 WNV transmission and suggests a degree of genotype-genotype specificity in the interaction between virus and vector. Our experiments with varying temperatures explain the current localized WNV activity in southern Europe, yet imply further epidemic spread throughout NWE during periods with favourable climatic conditions. This emphasizes the need for intensified surveillance of virus activity in current WNV disease-free regions and warrants increased awareness in clinics throughout Europe.
Metarhizium anisopliae is being considered as a biocontrol agent against the adult stage of the malaria mosquito Anopheles gambiae. In the current study we investigated behavioral effects of female An. gambiae in the presence of the fungus. In three different bioassays we tested whether the behaviour of female An. gambiae s.s. mosquitoes was affected by conidia of the entomopathogenic fungus M. anisopliae. From two bioassays where mosquitoes (1) were allowed to escape from a cylinder containing dry conidia, and (2) could choose between two cages (one containing dry conidia, the other not) to feed from a glucose-solution, it became clear that dry conidia have a significant repelling effect (p<0.05). When conidia were applied in a suspension of 8% adjuvant vegetable-oil formulation and impregnated on paper, it appeared that these oil-treated conidia had no repelling effect (p=0.205). In addition to the already known positive effects of suspending conidia in oil (preventing conidia from becoming airborne and protection from drying out), we here show another positive effect, namely absence of repellency, suggesting that in field applications the conidia should be oil-formulated.
The force of vector-borne disease transmission is greatly affected by interactive processes between parasites and their arthropod hosts. In recent years significant advances in knowledge about the mechanisms of these interactions have been made, notably concerning the impact of arthropod immune responses on parasite establishment and propagation in the arthropod host, genetic and phenotypic variation affecting these interactions, the impact of these interactions on parasite and arthropod fitness, and how environmental factors affect parasite transmission. The current volume of the Ecology and Control of Vector-Borne Diseases highlights significant and novel aspects of parasite-vector interactions and contributes to a better understanding of vector-borne disease transmission. Better insight in these interactive processes will be useful for studies on the epidemiology and control of vector-borne diseases and is expected to contribute to the development of novel intervention strategies.
The Anopheles gambiae complex is comprised of eight morphologically indistinguishable species and has emerged as a model system for the study of speciation genetics due to the rapid radiation of its member species over the past two million years. Male hybrids between most An. gambiae complex species pairs are sterile, and some genotype combinations in hybrid males cause inviability. We investigated the genetic basis of hybrid male inviability and sterility between An. coluzzii and An. quadriannulatus by measuring segregation distortion and performing a QTL analysis of sterility in a backcross population. Hybrid males were inviable if they inherited the An. coluzzii X chromosome and were homozygous at one or more loci in 18.9 Mb region of chromosome 3. The An. coluzzii X chromosome has a disproportionately large effect on hybrid sterility when introgressed into an An. quadriannulatus genetic background. Additionally, an epistatic interaction between the An. coluzzii X and a 1.12 Mb, pericentric region of the An. quadriannulatus 3L chromosome arm has a statistically significant contribution to the hybrid sterility phenotype. This same epistatic interaction occurs when the An. coluzzii X is introgressed into the genetic background of An. arabiensis, the sister species of An. quadriannulatus, suggesting that this may represent one of the first Dobzhansky–Muller incompatibilities to evolve early in the radiation of the Anopheles gambiae species complex. We describe the additive effects of each sterility QTL, epistatic interactions between them, and genes within QTL with protein functions related to mating behavior, reproduction, spermatogenesis, and microtubule morphogenesis, whose divergence may contribute to post-zygotic reproductive isolation between An. coluzzii and An. quadriannulatus.
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