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BACKGROUNDBlood feeding is a secondary adaptation in hematophagous bugs that ancestrally feed on plants. Many vector proteins are devoted to cope with the host’s defenses and to process the blood meal. In contrast, one can expect that some digestive enzymes devoted to phytophagous diet were lost during or after this peculiar adaptation. And yet, in many strictly hematophagous arthropods, alpha-amylases genes, coding the enzymes that digest starch from plants, are still present and transcribed, including in the blood-sucking bugRhodnius prolixusand its related speciesR. robustus(Hemiptera, Reduviidae, Triatominae). Triatominae bugs are vectors ofTrypanosoma cruzi, the causal agent of Chagas’disease. Besides the parasitic human infection by the vector-borne route via an exposition to infected feces, an oral route is documented by the ingestion of contaminated food or juices made from palm fruit trees.METHODOLOGY/PRINCIPAL FINDINGSWe hypothesized that retaining alpha-amylase could be advantageous if the bugs happen to consume occasionally plant tissues. To this end, we surveyed hundreds of gut DNA extracts from the sylvatic speciesR. robustuscaught on palm trees to detect traces of plant meals. We found plant DNA in over 8 % of theR. robustussamples, mostly the palm treeAttalea speciosa. Moreover, we showed that theR. robustusalpha-amylase retained normal amylolytic activity.CONCLUSIONSPreserving alpha-amylase function could be an important way of optimally harness plant substrates, and plant feeding could be a way for bridging the gap between two blood meals. Our data indicate that plants are a common and yet underestimated food source in the wild for Triatomine.Author SummaryAdaptation to a specific diet is often accompanied by metabolic, behavioral, physiological changes and hence by genetic changes like gene family expansion, gene losses or gains. In blood-sucking insects some adaptive features such as salivary components acting against blood clotting are known. However, it is intriguing that a digestive enzyme, alpha-amylase, which digests starch, is conserved in those animals, because blood does not contain starch nor related glucose polymers. This is the case in the blood-sucking bugs of theRhodniusgenus (Hemiptera, Reduviidae), which are vectors of the Chagas’disease, an important health issue in Latin America. In this study, we evidence for the first time that sylvatic bugsR. robustusalso consume plant tissues in the wild. We detected by PCR performed on DNA from digestive tract that a significant number of wild-caught individuals harbored plant DNA, especially fromAttaleapalm trees, on which they used to nest. We showed that the amylase enzyme is normally active on starch. We suggest plant feeding could be a way for bridging the gap between two blood meals but might not be linked to nutritional distress.

SummaryThe nutritional symbiosis promoted by bacteria is a key determinant for adaptation and evolution of many insect lineages. A complex form of nutritional mutualism that arose in blood-sucking insects critically depends on diverse bacterial symbionts that supplement the diet of their nutrient-poor hosts with B vitamins. For instance, the triatomine bugRhodnius prolixus, one of the main vectors of the Chagas disease in humans, is known to maintain a nutritional symbiosis with the gut symbiontsRhodococcus rhodnii.In this study, we show thatWolbachiasymbionts are also widely distributed in theRhodniusgenus. We have screened a large set ofRhodniusblood-sucking bugs samples belonging to 17 different species and to the three phylogenetic groups,prolixus, pallescensandpictipes. We assembled 13 genomes ofWolbachiainfecting eightRhodniusspecies fromprolixusandpictipesgroups. We demonstrate that theseWolbachiabelong to supergroup F and are closely related toWolbachiainfecting the bedbugCimex lectularius(wCle). Although bedbugs and triatomines are very distantly related hemipteran bugs, the genomes of their respectiveWolbachiawere highly similar, suggesting recent horizontal host switches. We also show thatRhodnius Wolbachiagenomes infecting theprolixusgroup encode intact biotin operon, the hallmark of nutritional symbiosis in bedbugs. This operon is lacking from all the otherWolbachiainfectingR. pictipes. Finally, host genome analyses provide evidence of massiveWolbachia-to-Rhodniusgene transfers in almost samples, providing footprints of past infections that support a widespread and probably ancient symbiotic association betweenWolbachiaand triatomine bugs.Our results suggest that bothWolbachiaandR. rhodniigut symbionts and theirRhodniushost maintain a highly prevalent symbiotic relationship, in which the vertically-inheritedWolbachiahas the metabolic potantial to ensure or complement, the nutritional mutualism provided by the gut symbionts. Specific loss of the biotin operon in some symbiont genomes suggests that the boundaries between obligatory mutualism, facultative mutualism and parasitism inWolbachiaare transient and fluid, supporting a dynamic process of transition and reversion from one state to another.

Endogenous viruses form an important proportion of eukaryote genomes and a source of novel functions. How large DNA viruses integrated into a genome evolve when they confer a benefit to their host, however, remains unknown. Bracoviruses are essential for the parasitism success of parasitoid wasps, into whose genomes they integrated ~103 million years ago. Here we show, from the assembly of a parasitoid wasp genome at a chromosomal scale, that bracovirus genes colonized all ten chromosomes of Cotesia congregata. Most form clusters of genes involved in particle production or parasitism success. Genomic comparison with another wasp, Microplitis demolitor, revealed that these clusters were already established ~53 mya and thus belong to remarkably stable genomic structures, the architectures of which are evolutionary constrained. Transcriptomic analyses highlight temporal synchronization of viral gene expression without resulting in immune gene induction, suggesting that no conflicts remain between ancient symbiotic partners when benefits to them converge.

The genome size of five Rhodnius species (R. milesi, R. nasutus, R. neivai, R. prolixus, and R. robustus) and two Psammolestes species (P. coroedes and P. tertius) were estimated using flow cytometry and/or k-mer distributions in genome sequences. Phylogenetic generalized linear mixed models highlighted significant genome size variations among species and between sexes, with R. prolixus showing the largest genome. In this study we provide the first data on female genome size in Triatominae. For five species, female genome size did not differ from males, except for R. robustus, where females had smaller genomes. Genome size estimations based on the k-mer distribution method were less than those estimated from flow cytometry, but both methods exhibited the same pattern of sexual differences. Further genomic studies are needed to infer whether genome size variation could be an adaptive trait in Rhodnius.

Endogenous viruses form an important proportion of eukaryote genomes and a source of novel functions. How large DNA viruses integrated into a genome evolve when they confer a benefit to their host, however, remains unknown. Bracoviruses are essential for the parasitism success of parasitoid wasps, into whose genomes they integrated ~103 million years ago. Here we show, from the assembly of a parasitoid wasp genome at a chromosomal scale, that bracovirus genes colonized all ten chromosomes of Cotesia congregata. Most form clusters of genes involved in particle production or parasitism success. Genomic comparison with another wasp, Microplitis demolitor, revealed that these clusters were already established ~53 mya and thus belong to remarkably stable genomic structures, the architectures of which are evolutionary constrained. Transcriptomic analyses highlight temporal synchronization of viral gene expression without resulting in immune gene induction, suggesting that no conflicts remain between ancient symbiotic partners when benefits to them converge., Jeremy Gauthier et al. present the chromosome scale assembly of the genome of the parasitic wasp C. congregata and show that bracovirus genes have colonized all ten chromosomes. Comparison with genome scaffolds of another wasp reveals a striking stability of these regions over ~53 million years, suggesting strong evolutionary constraints.

With frequent host shifts involving the colonization of new hosts across large geographical ranges, crop pests are good models for examining the mechanisms of rapid colonization. The microbial partners of pest insects may also be involved in or affected by colonization processes, which has been little studied so far. We investigated the demographic history of the rosy apple aphid, Dysaphis plantaginea, a major pest of the cultivated apple (Malus domestica) in Europe, North Africa and North America, as well as the diversity of its microbiota. We genotyped a comprehensive sample of 714 colonies from Europe, Morocco and the US using mitochondrial (CytB and CO1), bacterial (16s rRNA and TrnpB), and 30 microsatellite markers. We detected five populations spread across the US, Morocco, Western and Eastern Europe and Spain. Populations showed weak genetic differentiation and high genetic diversity, except the ones from Morocco and North America that are likely the result of recent colonization events. Coalescent-based inferences revealed high levels of gene flow among populations during the colonization but did not allow determining the sequence of colonization of Europe, North America and Morroco by D. plantaginea, likely because of the weak genetic differentiation and the occurrence of gene flow among populations. We found that D. plantaginea rarely hosts other endosymbiotic bacteria than its obligate nutritional symbiont Buchnera aphidicola. This suggests that secondary endosymbionts did not play an important role in the rapid spread of the rosy apple aphid. These findings have fundamental importance for understanding pest colonization processes and implications for sustainable pest control programs.

Innovative approaches used to combat Chagas disease transmission tend to combine a set of comprehensive efforts to understand the ecology of local vectors. In this work we identified molecularly the blood meal of 181 Triatoma brasiliensis, distributed in 18 populations (8 sylvatic and 10 peridomestic), which were collected across a range of 240 km (East-West) and 95 km (North-South) in the semi-arid region of northeastern, Brazil. We used the vertebrate mitochondrial gene (cytochrome B) sequencing applied to DNA isolated from bug midgut to identify the insect blood meal sources via the BLAST procedure. The peridomestic populations were classified according to two main hypotheses of site-occupancy for T. brasiliensis: the first says that the infestation is mainly driven by structures that resemble its natural habitat (stony-like ecotopes) and the second assumes that it is associated with key-hosts (rodents and goats). Rodents of the Caviidae family (Galea spixii and Kerodon rupestris) were identified as the key-host of T. brasiliensis, but also the potential Trypanosoma cruzi reservoir–able to connect the sylvatic and domestic T. cruzi cycle. Cats also deserve to be studied better, as potential T. cruzi reservoirs. By modeling the food sources + site-occupancy + T. cruzi natural infection, we identified man-made ecotopes suitable for forming dense triatomine infestations with high rates of T. cruzi natural infection, which may be taken into account for vector control measures., Author summary Blood-sucking bugs are vectors of the parasite Trypanosoma cruzi, which causes the Chagas disease. Triatoma brasiliensis is the main Chagas disease vector in the Caatinga eco-region of northeastern Brazil. Previous studies have already indicated that this species is associated with rodents of the Caviidae family–mainly in the sylvatic environment. In this study, we showed that these rodents are the main food sources of T. brasiliensis also in peridomestic environments. This association is frequently followed by numerous populations of T. cruzi infected insects in man-made ecotopes to store materials of mineral and wood origin. We suggest that the key-host that drives these infestations are mainly Galea spixii, followed by Kerodon rupestris (both Rodentia: Caviidae), which seem to be in synanthropic processes because they were found as frequent blood meals for T. brasiliensis in the sylvatic and domestic environments. Other mammals–mainly cats–may play an important role in Chagas disease eco-epidemiology for also being an important source of food for triatomines in the sylvatic and peridomestic environments. We conclude that educational programs to avoid Chagas disease transmission should include advising local people to avoid storing wood and tiles/bricks in the peridomestic environment–shelters for key-host rodents. Besides, they must be aware that these cavies may be infected by T. cruzi; and cautions are needed if they are to be used as a source of protein by hunting.

It is largely accepted that larval experience influence host-plant preference of larvae. In general, larval experience with a host plant induces both an odour and feeding preference for that plant. In a previous study, exposure of three noctuid stem borer species, i.e. Sesamia nonagrioides, Busseola fusca and B. nairobica, to a vanillin-enriched medium induced an olfactory preference for the odours of this medium in the larvae of these species. Here, we checked if the exposure to a vanillin-enriched medium also induced a feeding preference for this diet. Different life stages (i.e. neonate larvae to adults) of the three species were conditioned to an artificial diet enriched with vanillin over two generations. Thereafter, two-choice tests on third-generation larvae were done using a Y-tube olfactometer for odour preferences and diet choice experiments. Larvae of all three-species conditioned to the vanillin diet oriented significantly towards the odour of this diet, whereas the non-conditioned larvae did not. Still, apart for B. fusca, the conditioned larvae did not exhibit a feeding preference for this diet, thus odour preference did not match the feeding choice of the conditioned larvae. The implication of this result on insect's adaptability to a new host plant in a changing environment is discussed.

Background Mosquitoes belonging to the Anopheles gambiae complex are the main vectors of malaria in sub-Saharan Africa. Among these, An. gambiae, Anopheles coluzzii and Anopheles arabiensis are the most efficient vectors and are largely distributed in sympatric locations. However, these species present ecological and behavioural differences that impact their vectorial capacity and complicate vector-control efforts, mainly based on long-lasting insecticidal bed nets (LLINs) and indoor residual spraying (IRS). In this study, the genetic structure of these three species in a Senegalese village (Dielmo) was investigated using microsatellite data in samples collected in 2006 before implementation of LLINs, in 2008, when they were introduced, and in 2010, 2 years after the use of LLINs. Results In this study 611 individuals were included, namely 136 An. coluzzii, 101 An. gambiae, 6 An. coluzzii/An. gambiae hybrids and 368 An. arabiensis. According to the species, the effect of the implementation of LLINs in Dielmo is differentiated. Populations of the sister species An. coluzzii and An. gambiae regularly experienced bottleneck events, but without significant inbreeding. The Fst values suggested in 2006 a breakdown of assortative mating resulting in hybrids, but the introduction of LLINs was followed by a decrease in the number of hybrids. This suggests a decrease in mating success of hybrids, ecological maladaptation, or a lesser probability of mating between species due to a decrease in An. coluzzii population size. By contrast, the introduction of LLINs has favoured the sibling species An. arabiensis. In this study, some spatial and temporal structuration between An. arabiensis populations were detected, especially in 2008, and the higher genetic diversity observed could result from a diversifying selection. Conclusions This work demonstrates the complexity of the malaria context and shows the need to study the genetic structure of Anopheles populations to evaluate the effectiveness of vector-control tools and successful management of malaria vector control. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-1992-8) contains supplementary material, which is available to authorized users.

International audience; Triatoma petrocchiae is the newly member of the Triatoma brasiliensis species complex. This species overlaps with T. brasiliensis in geographic and ecotypic occupation in the sylvatic habitat because both inhabit rocky outcrops in the semi-arid portion of Brazilian northeast. In this region T. brasiliensis is the most important Chagas disease vector because it constantly colonizes domiciles. In contrast, T. petrocchiae is rarely found in peri or intradomiciliary habitats-reason why little is known about this species. Therefore, Here, we present information for the first time on. the T. petrocchiae ecotopes, genetic diversity, Trypanosoma cruzi prevalence/genotyping in comparison to T. brasiliensis. We found T. brasilensis (N = 223) and T. petrocchiae (N = 69) in co-habitation in rocky outcrops in three Districts of Paraíba and Rio Grande do Norte states. Forty-tree T. petrocchiae insects of eleven sampling spots (composing three geographic populations) were genotyped for the mitochondrial Cyt B gene and little geographic structure was observed. Tajima's D test suggested that species is evolving toward a mutation-drift equilibrium in our collection range. Sylvatic T. petrocchiae had 4% (3/68) of infected insects by T. cruzi, whereas T. brasiliensis had 26% (59/223). Fluorescent Fragment Length Barcoding demonstrated that all three T. petrocchiae harbored TcI whereas T. brasiliensis had TcI, but also TcIII, TcII/TcVI and T. rangeli genotype A, sometimes under mixed infections. None of infected T. petrocchiae were carrying mixed infections. However, this result should be confirmed using a larger pool of infected bugs. We here presented the first documentation of T. rangeli infecting T. brasiliensis. The finding of infected T. petrocchiae calls for constant vector monitoring because the epidemiologic scenario is dynamic and sylvatic vectors are progressively found in adaptation to anthropic environments.

A total of 2,431 Triatoma brasiliensis were collected from 39 populations of Paraíba (PB) and Rio Grande do Norte (RN) states, Brazil. In PB, Trypanosoma cruzi infection was not detected in either peridomestic or domestic vector populations. In contrast, in RN, T. brasiliensis was detected with high parasite prevalence in these ecotopes (30.7-40.0%). Moreover, peridomicile insect population densities were more than double the average densities of all other settings evaluated (19.17 versus < 8.94 triatomine/man-hour). Genotyped parasites evidenced a mix of T. cruzi lineages circulating in both peridomestic and sylvatic populations. Although vector control efforts have dramatically decreased Chagas disease transmission to humans, recent outbreaks have been detected in four municipalities of RN state. Our results clearly evidence a worrisome proximity between infected vectors and humans in RN. Indeed, finding of infected T. brasiliensis inside homes is routinely recorded by local vector control surveillance staff around the outbreak area, challenging the current and conventional view that vector transmissions are controlled in northeastern Brazil. This scenario calls for strengthening vector control surveillance and interventions to prevent further Chagas transmission, especially in RN State., Universidade Federal da Paraíba, Centro de Estudios Parasitológicos y de Vectores, Universite Paris Saclay, Centers for Disease Control and Prevention, Consejo Nacional de Investigaciones Científicas y Técnicas, Fundación Oswaldo Cruz, Universidade Estadual de Campinas

In Lepidoptera, larval dietary experience of volatile cues can induce adult preference for these cues. However, such induction may require several generations, depending in part on the degree of specialization of the insects. In a previous study, using species of noctuid stem borers with different diet breadths, namely the polyphagous Sesamia nonagrioides, the oligophagous Busseola fusca and monophagous Busseola nairobica, it was shown that in S. nonagrioides, one generation was enough to induce a preference for vanillin in the resulting gravid females, whereas even two generations failed to induce a response in adults of Busseola spp. In this study, we checked whether a higher number of generations of exposure to a vanillin-enriched medium could induce a significant olfactory preference for this medium in the species B. fusca and B. nairobica, which have narrower host-plant utilization ranges than S. nonagrioides. Larvae were reared to the adult stage on an artificial diet enriched with vanillin for periods of from 2 to 7 or 8 generations, followed by two-choice tests on gravid females using a Y-tube olfactometer. The results showed different responses according to the species: for the oligophagous B. fusca, there was no significant effect of the conditioning, while a significant preference for the odours emitted by this new vanillin-enriched diet was recorded for the polyphagous S. nonagrioides and monophagous B. nairobica, but after different numbers of generations. In conclusion, different diet breadths seem to be associated with different levels of plasticity in the odour preference of adults. The implication of this result for insects' adaptability in a changing landscape is discussed.

International audience; The implementation of long-lasting insecticidal-treated bed nets (LLINs) has contributed to halving the mortality rate due to malaria since 2000 in sub-Saharan Africa. These tools are highly effective against indoor-feeding malaria vectors. Thus, to achieve the World Health Assembly's new target to reduce the burden of malaria over the next 15 years by 90%, it is necessary to understand how the spatiotemporal dynamics of malaria vectors and human exposure to bites is modified in the context of scaling up global efforts to control malaria transmission. This study was conducted in Dielmo, a Senegalese village, after the introduction of LLINs and two rounds of LLINs renewals. Data analysis showed that implementation of LLINscorrelatedwith a significant decrease in the biting densities of themainmalaria vectors, Anopheles gambiae s. l. and Anopheles funestus, reducing malaria transmission. Other environment factors likely contributed to the decrease in An. funestus, but this trend was enhanced with the introduction of LLINs. The bulk of bites occurred during sleeping hours, but the residual vector populations of An. gambiae s. l. and An. funestus had an increased propensity to bite outdoors, so a risk of infectious bites remained for LLINs users. These results highlight the need to increase the level and correct use of LLINs and to combine this intervention with complementary control measures against residual exposure, such as spatial repellents and larval source management, to achieve the goal of eliminating malaria transmission.

We used the gut contents of triatomines collected from rural areas of Ceará State, northeastern Brazil, to identify their putative hosts via vertebrate cytb gene sequencing. Successful direct sequencing was obtained for 48% of insects, comprising 50 Triatoma brasiliensis, 7 Triatoma pseudomaculata, and 1 Rhodnius nasutus. Basic local alignment search tool (BLAST) procedure revealed that domestic animals, such as chickens (Gallus gallus) and goats (Capra hircus), are the main food source, including in sylvatic environment. Native hosts were also detected in peridomestic environment such as reptiles (Tropidurus sp. and Iguana iguana) and the Galea spixii (Rodentia: Caviidae). The role of goats and Galea spixii in Chagas disease epidemiology calls for further studies, because these mammals likely link the sylvatic and domestic Trypanosoma cruzi cycles.

A total of 2,431 Triatoma brasiliensis were collected from 39 populations of Paraíba (PB) and Rio Grande do Norte (RN) states, Brazil. In PB, Trypanosoma cruzi infection was not detected in either peridomestic or domestic vector populations. In contrast, in RN, T. brasiliensis was detected with high parasite prevalence in these ecotopes (30.7–40.0%). Moreover, peridomicile insect population densities were more than double the average densities of all other settings evaluated (19.17 versus < 8.94 triatomine/man-hour). Genotyped parasites evidenced a mix of T. cruzi lineages circulating in both peridomestic and sylvatic populations. Although vector control efforts have dramatically decreased Chagas disease transmission to humans, recent outbreaks have been detected in four municipalities of RN state. Our results clearly evidence a worrisome proximity between infected vectors and humans in RN. Indeed, finding of infected T. brasiliensis inside homes is routinely recorded by local vector control surveillance staff around the outbreak area, challenging the current and conventional view that vector transmissions are controlled in northeastern Brazil. This scenario calls for strengthening vector control surveillance and interventions to prevent further Chagas transmission, especially in RN State.

In holometabolous phytophagous insects, adult females and larvae determine host plant selection through oviposition and feeding preferences. Pre-imaginal and/or imaginal experiences with plant chemical cues can modulate these preferences. Various studies found evidence, or not, of host preference modulation through previous experience but they appear to contradict each other. Most probably, modulation of host preference depends on the degree of specialization of the insects. Our literature analysis revealed that the positive influence of experience in the modulation of host plant preference occurred equally in polyphagous, oligophagous and monophagous species, but was significantly more influenced by the phylogeny of the insect and the developmental stage involved in plant cue experience. Identification of phylogenic and developmental stage factors of “host learning” abilities appeared to be key information for predicting the response of species to habitat modifications rather than the insect’s degree of host plant specialization. The signification of this output on the fact that some insect species or populations shifted from the wild to cultivated habitats to become important pests is discussed.

Species delimitation and identification can be arduous for taxa whose morphologic characters are easily confused, which can hamper global biodiversity assessments and pest species management. Exploratory methods of species delimitation that use DNA sequence as their primary information source to establish group membership and estimate putative species boundaries are useful approaches, complementary to traditional taxonomy. Termites of the genus Nasutitermes make interesting models for the application of such methods. They are dominant in Neotropical primary forests but also represent major agricultural and structural pests. Despite the prevalence, pivotal ecological role and economical impact of this group, the taxonomy of Nasutitermes species mainly depends on unreliable characters of soldier external morphology. Here, we generated robust species hypotheses for 79 Nasutitermes colonies sampled throughout French Guiana without any a priori knowledge of species affiliation. Sequence analysis of the mitochondrial cytochrome oxidase II gene was coupled with exploratory species-delimitation tools, using the automatic barcode gap discovery method (ABGD) and a generalized mixed Yule-coalescent model (GMYC) to propose primary species hypotheses (PSHs). PSHs were revaluated using phylogenetic analyses of two more loci (mitochondrial 16S rDNA and nuclear internal transcribed spacer 2) leading to 16 retained secondary species hypotheses (RSSH). Seven RSSHs, represented by 44/79 of the sampled colonies, were morphologically affiliated to species recognized as pests in the Neotropics, where they represent a real invasive pest potential in the context of growing ecosystem anthropization. Multigenic phylogenies based on combined alignments (1426-1784 bp) were also reconstructed to identify ancestral ecological niches and major-pest lineages, revealing that Guyanese pest species do not form monophyletic groups.

Summary 1. Simulation models are essential tools in landscape genetics to study how genetic processes are affected by landscape heterogeneity. However, there is still a need to develop different simulation approaches in landscape genetics, so that users may dispose of additional programs to explore further the impact of land-use and land-cover changes on population genetics. 2. We developed a spatially explicit, individual-based, forward-time, landscape-genetic simulation model combined with a landscape cellular automaton to represent evolutionary processes of adaptation and population dynamics in changing landscapes, using the NetLogo environment. 3. This simulation model represents a unique tool for scientists and scholars looking for a practical and pedagogical framework to explore both empirical and theoretical situations.

International audience; Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the cornerstones of malaria vector control. However, the effectiveness of these control tools depends on vector ecology and behaviour, which also largely determine the efficacy of certain Anopheles mosquitoes (Diptera: Culicidae) as vectors. Malaria vectors in sub-Saharan Africa are primarily species of the Anopheles gambiae complex, which present intraspecific differences in behaviour that affect how they respond to vector control tools. The focus of this study is the change in species composition in the An. gambiae complex after the implementation of LLINs in Dielmo, Senegal. The main findings referred to dramatic decreases in the proportions of Anopheles coluzzii and An. gambiae after the introduction of LLINs, and an increase in the proportion of Anopheles arabiensis. Two years after LLINs were first introduced, An. arabiensis remained the most prevalent species and An. gambiae had begun to rebound. This indicated a need to develop additional vector control tools that can target the full range of malaria vectors.

International audience; High Throughput Sequencing capabilities have made the process of assembling a transcriptome easier, whether or not there is a reference genome. But the quality of a transcriptome assembly must be good enough to capture the most comprehensive catalog of transcripts and their variations, and to carry out further experiments on transcriptomics. There is currently no consensus on which of the many sequencing technologies and assembly tools are the most effective. Many non-model organisms lack a reference genome to guide the transcriptome assembly. One question, therefore, is whether or not a reference-based genome assembly gives better results than de novo assembly. The blood-sucking insect Rhodnius prolixus-a vector for Chagas disease-has a reference genome. It is therefore a good model on which to compare reference-based and de novo transcriptome assemblies. In this study, we compared de novo and reference-based genome assembly strategies using three datasets (454, Illumina, 454 combined with Illumina) and various assembly software. We developed criteria to compare the resulting assemblies: the size distribution and number of transcripts, the proportion of potentially chimeric transcripts, how complete the assembly was (completeness evaluated both through CEGMA software and R. prolixus proteome fraction retrieved). Moreover, we looked for the presence of two chemosensory gene families (Odorant-Binding Proteins and Chemosensory Proteins) to validate the assembly quality. The reference-based assemblies after genome annotation were clearly better than those generated using de novo strategies alone. Reference-based strategies revealed new transcripts, including new isoforms unpredicted by automatic genome annotation. However, a combination of both de novo and reference-based strategies gave the best result, and allowed us to assemble fragmented transcripts.

Background The Triatomine bug Rhodnius prolixus is a vector of Trypanosoma cruzi, which causes the Chagas disease in Latin America. R. prolixus can also transfer transposable elements horizontally across a wide range of species. We have taken advantage of the availability of the 700 Mbp complete genome sequence of R. prolixus to study the dynamics of invasion and persistence of transposable elements in this species. Results Using both library-based and de novo methods of transposon detection, we found less than 6 % of transposable elements in the R. prolixus genome, a relatively low percentage compared to other insect genomes with a similar genome size. DNA transposons are surprisingly abundant and elements belonging to the mariner family are by far the most preponderant components of the mobile part of this genome with 11,015 mariner transposons that could be clustered in 89 groups (75 % of the mobilome). Our analysis allowed the detection of a new mariner clade in the R. prolixus genome, that we called nosferatis. We demonstrated that a large diversity of mariner elements invaded the genome and expanded successfully over time via three main processes. (i) several families experienced recent and massive expansion, for example an explosive burst of a single mariner family led to the generation of more than 8000 copies. These recent expansion events explain the unusual prevalence of mariner transposons in the R. prolixus genome. Other families expanded via older bursts of transposition demonstrating the long lasting permissibility of mariner transposons in the R. prolixus genome. (ii) Many non-autonomous families generated by internal deletions were also identified. Interestingly, two non autonomous families were generated by atypical recombinations (5' part replacement with 3' part). (iii) at least 10 cases of horizontal transfers were found, supporting the idea that host/vector relationships played a pivotal role in the transmission and subsequent persistence of transposable elements in this genome. Conclusion These data provide a new insight into the evolution of transposons in the genomes of hematophagous insects and bring additional evidences that lateral exchanges of mobile genetics elements occur frequently in the R. prolixus genome. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-2060-9) contains supplementary material, which is available to authorized users.

This work evaluated the occurrence and genetic structure of Rhodnius nasutus sampled in two sites using morphometry and microsatellites. These sites, presented distinct abiotic features and palm trees: (i) nine Attalea speciosa palm trees, so called babacu, were sampled from the Meruoca Mountain Ridge, a sloping region of reminiscent forest in the state of Ceara, Brazil, and (ii) 17 Copernicia prunifera palm trees, so called carnauba, were sampled in the scrub savanna region (Sobral district) that surrounds the mountain ridge. Of the twenty-six palm trees dissected, 70.6% of carnauba and 88.9% of babacu were infested by R. nasutus. The micro-climatic data where R. nasutus were sheltered demonstrated that the babacu and carnauba palm trees presented significant differences (p < 0.05) in relation to the external environment, except for temperature and relative humidity regulation, suggesting that the architecture of the babacu crown keeps a more stable micro-environment. The morphometric studies of the F1 generation demonstrated that insects from the babacu (A. speciosa) were significantly larger (p = 0.000) than those collected in carnauba (C. prunifera) palm trees. Also, microsatellite analysis demonstrated a high genetic differentiation between the two groups of R. nasutus (Rst = −0.77). Our results suggest that the difference in size between the populations is probably related to an incipient process of genetic drift in populations associated to each palm tree, probably also driven by the different climatic features observed in these micro-environments.

A sylvatic infection focus of Trypanosoma rangeli, whose cycle involves the anteater Tamandua tetradactyla and triatomine insect Rhodnius robustus was observed in a pasture-dominated landscape of the rural riparian community of São Tomé located along the Tapajós river in the municipal district of Aveiro (State of Pará, Brazil), the Brazilian Amazon region. During a field work campaign with the objective of Chagas disease diagnosis in the Tapajós region, an anteater and 31 triatomines were found inhabiting in the same Attalea phalerata palm tree crown. Collected triatomines were identified as R. robustus with morphological and molecular procedures. The analysis of infection by T. rangeli using the repetitive ARN nucleolar Cl1 (sno-RNA-Cl1) gene showed that 25 triatomines of all stages were infected by T. rangeli (total infection rate of 80.6%). Infection by Trypanosoma cruzi using mini-exon markers was not identified. Examination of the digestive content of the triatomines demonstrated that the only feeding source found was the anteater. These results demonstrate that T. tetradactyla can be an important reservoir for T. rangeli and a good vehicle of the parasite within the Brazilian Amazon region.

Six polymorphic microsatellite loci were isolated and characterized using a microsatellite-enriched genomic library from the Chagas' disease vector Triatoma pseudomaculata. This species is found in Brasil in Caatinga areas and predominantly in peridomestic habitats. All the microsatellites tested on a population of T. pseudomaculata sampled in the Bahia State, Brazil, were polymorphic (2-15 alleles). Markers amplification was also tested on six Triatoma species and some loci successfully amplified in the most phylogenetically related species, in particular Triatoma brasiliensis.

Ten microsatellites were isolated and characterized from a partial genomic library of Rhodnius prolixus, the principal Chagas disease vector in Venezuela, Colombia and Central America. These polymorphic molecular markers could be particularly useful in Chagas disease control initiatives. A wider applicability of the primer-pairs isolated was shown, from 6 to 10 loci being amplifiable in five out of the ten Rhodnius species tested, namely R. domesticus, R. nasutus, R. neglectus, R. neivai and R. robustus. Interestingly, all the loci were amplified in the latter. These markers may be of interest to trace the colonization of human dwellings from triatomine sylvatic populations in order to better define epidemiological risk patterns.

International audience; Aquatic and semi-aquatic bugs (Heteroptera) represent a remarkable diversity and a resurging interest has been given to documenting at the species level these insects inhabiting Cameroon in Central Africa due to their potential implication in the transmission of the bacterium Mycobacterium ulcerans, the causal agent of Buruli ulcer, an emerging human disease. A survey was carried out over two years in Cameroon. Morphological analyses were done in two steps. A first step consisted in separating the specimens based on broadly shared characters into morphotypes. The specimens were then separated into two independent batches containing each the same representation of each morphotype. One batch (309 specimens) was used by taxonomy experts on aquatic bugs for species level identification and/or to reconcile nymph with their corresponding adult species. The second batch (188 specimens) was used to define species based on the COI DNA sequences (standard sequence used for "DNA barcoding") and using the Automatic Barcode Gap Discovery (ABGD) method. The first morphological analysis step separated the specimens into 63 different morphotypes (49 adults and 14 nymphs), which were then found to belong to 54 morphological species in the infra-orders Gerromorpha and Nepomorpha based on the species-level morphological identification, and 41-45 putative molecular species according to the gap value retained in the ABGD. Integrating morphology and "DNA barcoding" reconciled all the specimens into 62 aquatic bug species in Cameroon. Generally, we obtained a good congruence between species a priori identified based on morphology from adult morphotypes and molecular putative species. Moreover, molecular identification has allowed the association of 86% of nymphs with adults. This work illustrates the importance of integrative taxonomy.

International audience; Among the proposed mechanisms of local adaptation to different ecological environments, transcriptional changes may play an important role. In this study, we investigated whether such variability occurred within the chemosensory organs of a herbivorous insect, for which chemosensation guides most of its host preferences. A European and an African population of the noctuid Sesamia nonagrioides that display significant differences in their ecological preferences were collected on Zea mays and Typha domingensis, respectively. RNAseq were used between the two populations for digital expression profiling of chemosensory organs from larval antennae and palps. Preliminary data on adult female antennae and ovipositors were also collected. We found 6,550 differentially expressed transcripts in larval antennae and palps. Gene ontology enrichment analyses suggested that transcriptional activity was overrepresented in the French population and that virus and defense activities were overrepresented in the Kenyan population. In addition, we found differential expression of a variety of cytochrome P450s, which may be linked to the different host-plant diets. Looking at olfactory genes, we observed differential expression of numerous candidate odorant-binding proteins, chemosensory proteins, and one olfactory receptor, suggesting that differences in olfactory sensitivity participate in insect adaptation.

International audience; In Lepidoptera, host plant selection is first conditioned by oviposition site preference of adult females followed by feeding site preference of larvae. Dietary experience to plant volatile cues can induce larval and adult host plant preference. We investigated how the parent's and self-experience induce host preference in adult females and larvae of three lepidopteran stem borer species with different host plant ranges, namely the polyphagous Sesamia nonagrioides, the oligophagous Busseola fusca and the monophagous Busseola nairobica, and whether this induction can be linked to a neurophysiological phenotypic plasticity. The three species were conditioned to artificial diet enriched with vanillin from the neonate larvae to the adult stage during two generations. Thereafter, two-choice tests on both larvae and adults using a Y-tube olfactometer and electrophysiological (electroantennography [EAG] recordings) experiments on adults were carried out. In the polyphagous species, the induction of preference for a new olfactory cue (vanillin) by females and 3rd instar larvae was determined by parents' and self-experiences, without any modification of the sensitivity of the females antennae. No preference induction was found in the oligophagous and monophagous species. Our results suggest that lepidopteran stem borers may acquire preferences for new olfactory cues from the larval to the adult stage as described by Hopkins' host selection principle (HHSP), neo-Hopkins' principle, and the concept of 'chemical legacy.'

Rhodnius prolixus not only has served as a model organism for the study of insect physiology, but also is a major vector of Chagas disease, an illness that affects approximately seven million people worldwide. We sequenced the genome of R. prolixus, generated assembled sequences covering 95% of the genome (∼702 Mb), including 15,456 putative protein-coding genes, and completed comprehensive genomic analyses of this obligate blood-feeding insect. Although immunedeficiency (IMD)-mediated immune responses were observed, R. prolixus putatively lacks key components of the IMD pathway, suggesting a reorganization of the canonical immune signaling network. Although both Toll and IMD effectors controlled intestinal microbiota, neither affected Trypanosoma cruzi, the causal agent of Chagas disease, implying the existence of evasion or tolerance mechanisms. R. prolixus has experienced an extensive loss of selenoprotein genes, with its repertoire reduced to only two proteins, one of which is a selenocysteine-based glutathione peroxidase, the first found in insects. The genome contained actively transcribed, horizontally transferred genes from Wolbachia sp., which showed evidence of codon use evolution toward the insect use pattern. Comparative protein analyses revealed many lineage-specific expansions and putative gene absences in R. prolixus, including tandem expansions of genes related to chemoreception, feeding, and digestion that possibly contributed to the evolution of a blood-feeding lifestyle. The genome assembly and these associated analyses provide critical information on the physiology and evolution of this important vector species and should be instrumental for the development of innovative disease control methods., La lista completa de autores que integran el documento puede consultarse en el archivo, Este documento tiene una corrección (ver documento relacionado)., Centro Regional de Estudios Genómicos, Instituto de Investigaciones Bioquímicas de La Plata

Little is known about the relationship between soil biological function and the physical and chemical characteristics of soil-feeding termite nests in the Lope tropical rainforest (Gabon). We compared nine soil-feeding termite nests of Cubitermes of different ages (fresh to mature to old) and six surrounding soils that originated from three forests differing with respect to age and vegetative cover according to 14 physical and chemical variables and acid (pH 4) and alkaline (pH 9) phosphatase activities. Physical and chemical variables of the studied samples were influenced by the three factors tested: (1) forest age, (2) termite activity (nest versus soil), (3) termite nest age. Soils from the gallery forest were strongly discriminated from all the other soils studied notably due to their high organic matter contents. All mature nests showed significant increases in K, P, clay and fine silt, pH, and cationic exchange capacity compared to soils. Some nests also had increased amounts of organic matter and larger water retention capacities. Moreover, we observed that with age the termite nests possessed decreased values of these variables from fresh to mature to old. Likewise, phosphatase activities also differed according to the three factors tested. Due to its high organic matter contents, the highest phosphatase activities were noted in the gallery forest. Within each forest, phosphatase activities decreased in mature nests compared to soils and tended to be higher in fresh nests compared to mature nests. These differences might be due to an inhibition by high inorganic P contents, as mature nests were enriched in this element and to the quality of organic matter as nests are built with termite faeces. Termite activity has an important role in influencing physical and chemical variables and phosphatase activities.

Summary Molecular microbial ecology has revealed remarkable biodiversity ‐ prokaryotic and eukaryotic ‐ in numerous soil environments. However, no cultureindependent surveys of the termitosphere exists, although termites dominate tropical rainforests. Here, we focused on soil feeders, building nests with their soil-born faeces, enriched with clay‐organic complexes, thus contributing to the improvement of soil fertility. In order to assess the fungal community composition of these termitaries compared with soils not foraged by termites, samples of the two types were collected in the Lope rainforest, Gabon, and processed for generation of fungal internal transcribed spacer (ITS) clone libraries. Although primers were universal, most of the recovered sequences represented Ascomycete that were previously uncharacterized and the proportions of which reached 72.5% in soils and 80% in termitaries. Their affiliation with identified fungi was analysed in performing a phylogenetic tree based on 5.8S rDNA. Furthermore, the ascomycete communities of soil-feeding termitaries and soils shared only 6.3% of sequences. This discrepancy of composition between soil and nest may result from the building behaviour of termites, as the organic matter in the nest is chemically modified, and some vacant ecological microniches are available for more specialized fungi.

Background Understanding the mechanisms that influence the population dynamics and spatial genetic structure of the vectors of pathogens infecting humans is a central issue in tropical epidemiology. In view of the rapid changes in the features of landscape pathogen vectors live in, this issue requires new methods that consider both natural and human systems and their interactions. In this context, individual-based model (IBM) simulations represent powerful yet poorly developed approaches to explore the response of pathogen vectors in heterogeneous social-ecological systems, especially when field experiments cannot be performed. Methodology/Principal Findings We first present guidelines for the use of a spatially explicit IBM, to simulate population genetics of pathogen vectors in changing landscapes. We then applied our model with Triatoma brasiliensis, originally restricted to sylvatic habitats and now found in peridomestic and domestic habitats, posing as the most important Trypanosoma cruzi vector in Northeastern Brazil. We focused on the effects of vector migration rate, maximum dispersal distance and attraction by domestic habitat on T. brasiliensis population dynamics and spatial genetic structure. Optimized for T. brasiliensis using field data pairwise fixation index (FST) from microsatellite loci, our simulations confirmed the importance of these three variables to understand vector genetic structure at the landscape level. We then ran prospective scenarios accounting for land-use change (deforestation and urbanization), which revealed that human-induced land-use change favored higher genetic diversity among sampling points. Conclusions/Significance Our work shows that mechanistic models may be useful tools to link observed patterns with processes involved in the population genetics of tropical pathogen vectors in heterogeneous social-ecological landscapes. Our hope is that our study may provide a testable and applicable modeling framework to a broad community of epidemiologists for formulating scenarios of landscape change consequences on vector dynamics, with potential implications for their surveillance and control., Author Summary Worldwide, humans are modifying landscapes at an unprecedented rate. These modifications have an influence on the ecology of pathogen vectors, yet this issue has received relatively little input from modeling research. The current study presents guidelines for the use of a modeling framework for the representation of the dynamics and spatial genetic structure of pathogen vectors. It allows considering spatiotemporal landscape modifications explicitly, to represent human-altered modifications and consequences. We applied this modeling framework to Triatoma brasiliensis, vector of the pathogen Trypanosoma cruzi responsible for the Chagas disease, in the semi-arid Northeastern Brazil. Using field data of pairwise fixation index (FST) from microsatellite loci, we found that migration rate, maximum dispersal distance and attraction by domestic habitat were all key parameters to understand vector spatial genetic structure at the landscape level. At the interface across disciplines, this study provides to the community of epidemiologists a testable and applicable framework to foresee landscape modification consequences on vector dynamics and genetic structure, with potential implications for their surveillance and control.

International audience; Pheromone-binding proteins (PBPs) are thought to contribute to the specificity of the pheromone detection system through an initial selective binding with pheromone molecules. Here, we report different expression levels of PBP transcripts in the antennae of two populations of the stemborer Sesamia nonagrioides (Lepidoptera: Noctuidae), one collected in Europe and one in sub-Saharan Africa. The three PBP transcripts previously identified in this species were found to be expressed in both male and female antennae. Whereas PBP3 did not show any differential expression, PBP1 and PBP2 appeared to be expressed differently according to the population origin and sex. Simultaneously, we measured and compared the ratio of the three components of the S. nonagrioides pheromone blend (Z11-16:Ac; Z11-16:OH; Z11-16:Ald) in females of the two populations. The ratio of Z11-16:OH and Z11-16:Ald varied significantly according to the population origin of this species. Cluster analyses revealed similar differentiation patterns between PBP1 and PBP2 expression levels and the ratios of Z11-16:OH and Z11-16:Ald. Different female sexual signals may thus correspond to different male reception systems, which are adjusted by the PBP expression levels, thereby ensuring optimal communication within populations.