RESUMO
Mosquitoes are medically important insects, and accurate species identification is crucial to understanding vector biology, forming the cornerstone of successful vector control programs. Identification is difficult owing to morphologically similar species. Wing morphometrics can provide a simple, fast, and accurate way to classify species, and using it as a method to differentiate vector species among its cryptic congeners has been underexplored. Using a total of 227 mosquitoes and 20 landmarks per specimen, we demonstrated the utility of wing morphometrics in differentiating species two groups occurring in sympatry - Culex (Culex) vishnui group and Culex (Lophoceraomyia) subgenus, as well as explored population-level variation in the wing shape of Aedes albopictus across habitats. Cytochrome oxidase subunit I (COI) gene region was sequenced to validate the morphological and morphometric identification. Procrustes ANOVA regression and CVA based on wing shape reflected that the wing landmarks across all species differed significantly, and leave-one-out cross validation revealed an overall high accuracy of >97% for the two Culex groups. Wing morphometrics uncovered population-level variation within Aedes albopictus, but cross validation accuracy was low. Overall, we show that wing geomorphometric analysis is able to resolve cryptic Culex species (including vectors) occurring sympatrically, and is a robust tool for identifying mosquitoes reliably.
RESUMO
Aedes albopictus is a successful disease vector due to its ability to survive in a wide range of habitats. Despite its ubiquity and impact on public health, little is known about its differential gene flow capabilities across different city habitats. We obtained a comprehensive dataset of >27,000 genome-wide DNA markers across 105 wild-caught Ae. albopictus individuals from Singapore, a dengue-endemic tropical city with heterogeneous landscapes from densely populated urban areas to forests. Despite Singapore's challenging small-scale heterogeneity, our landscape-genomic approach indicated that dense urban areas are characterized by higher Aedes gene flow rates than managed parks and forests. We documented the incidence of Wolbachia infections of Ae. albopictus involving two strains (wAlbA and wAlbB). Our results dispel the misconception that substantial dispersal of Ae. albopictus is limited to urban greenery, with wide implications for vector management and critical insights into urban planning strategies to combat dengue transmission.
RESUMO
Blood parasites comprise some of the most prevalent pathogens in nature, and their detection and identification are major objectives in varied fields such as ecology and biomedicine. Two approaches were compared, one based on Sanger sequencing and the other next-generation sequencing (NGS) based, in terms of their performance in detecting avian blood parasites across tropical Southeast Asian birds. Across a panel of 528 bird individuals, 43 birds were ascertained to be infected with avian haemosporidians using a polymerase chain reaction-based detection method. Among these samples, NGS-based barcoding confirmed co-infections by multiple blood parasites in all eight cases where Sanger sequencing produced double peaks. Importantly however, the NGS-based method produced another five diagnoses of co-infections (62.5%) in which Sanger-based barcoding remained equivocal. In contrast to Sanger sequencing, the NGS-based method was able to identify co-infecting haemosporidian lineages via their barcodes. The accuracy of avian haemosporidian lineage identification was not compromised by the shorter length of NGS sequences, with ~94% of NGS barcodes producing matches identical to those of the Sanger barcodes. The application of NGS-based barcoding methods promises to enhance parasite identification and reduce erroneous inferences based on artefacts.
RESUMO
BACKGROUND: Wolbachia are intracellular bacterial endosymbionts found in most insect lineages. In mosquitoes, the influence of these endosymbionts on host reproduction and arboviral transmission has spurred numerous studies aimed at using Wolbachia infection as a vector control technique. However, there are several knowledge gaps in the literature and little is known about natural Wolbachia infection across species, their transmission modes, or associations between various Wolbachia lineages and their hosts. This study aims to address these gaps by exploring mosquito-Wolbachia associations and their evolutionary implications. METHODS: We conducted tissue-specific polymerase chain reaction screening for Wolbachia infection in the leg, gut and reproductive tissues of wild mosquitoes from Singapore using the Wolbachia surface protein gene (wsp) molecular marker. Mosquito-Wolbachia associations were explored using three methods-tanglegram, distance-based, and event-based methods-and by inferred instances of vertical transmission and host shifts. RESULTS: Adult mosquitoes (271 specimens) representing 14 genera and 40 species were screened for Wolbachia. Overall, 21 species (51.2%) were found positive for Wolbachia, including five in the genus Aedes and five in the genus Culex. To our knowledge, Wolbachia infections have not been previously reported in seven of these 21 species: Aedes nr. fumidus, Aedes annandalei, Uranotaenia obscura, Uranotaenia trilineata, Verrallina butleri, Verrallina sp. and Zeugnomyia gracilis. Wolbachia were predominantly detected in the reproductive tissues, which is an indication of vertical transmission. However, Wolbachia infection rates varied widely within a mosquito host species. There was no clear signal of cophylogeny between the mosquito hosts and the 12 putative Wolbachia strains observed in this study. Host shift events were also observed. CONCLUSIONS: Our results suggest that the mosquito-Wolbachia relationship is complex and that combinations of transmission modes and multiple evolutionary events likely explain the observed distribution of Wolbachia diversity across mosquito hosts. These findings have implications for a better understanding of the diversity and ecology of Wolbachia and for their utility as biocontrol agents.
Assuntos
Infecções por Anaplasmataceae/microbiologia , Infecções por Anaplasmataceae/transmissão , Culicidae/microbiologia , Interações Hospedeiro-Patógeno/fisiologia , Mosquitos Vetores/microbiologia , Aedes/genética , Aedes/microbiologia , Animais , Evolução Biológica , Culex/genética , Culex/microbiologia , DNA Bacteriano , Feminino , Masculino , Reação em Cadeia da Polimerase , Análise de Sequência , Singapura , Doenças Transmitidas por Vetores , Wolbachia/classificação , Wolbachia/genéticaRESUMO
Accurate identification of mosquitoes is crucial for the management and control of vector species. Although Singapore is a tropical country with high mosquito diversity, there are no identification keys specific to its mosquito fauna. An illustrated identification key to the genera of the adult female mosquitoes of Singapore is presented. Twenty genera are characterized and two genera found in Malaysia, Culiseta and Topomyia, are also included. The key will aid non-taxonomically trained operational officers in adult mosquito identification. The key to the genera provides the first crucial step in the process to species identification.
Assuntos
Culicidae , Animais , Vetores de Doenças , Feminino , Malásia , Mosquitos Vetores , SingapuraRESUMO
Prior to 1965, Singapore was part of the Malaya (now Malaysia) and was usually not mentioned when mosquito records were reported for Malaya. Consequently, many species that occurred in Singapore were not listed in the world mosquito catalog, and the available checklist for Singapore since 1986 is incomplete, with some imprecise species information. In updating this checklist, we examined and verified mosquito specimens collected from Singapore in various depositories, including a thorough review of past taxonomic literature. Here, we report a checklist of 182 mosquito species, 33 new distribution records, and a consolidated status list of vectors for Singapore. As Singapore is a travel hub and hosts one of the busiest container ports in the world, there is a risk of introducing mosquito species and their associated pathogens of human disease to the country. Hence, the distribution records are important to increase our knowledge on mosquito ecology as well as to understand the risk of newly introduced vectors and their associated pathogens.