Assessment of the correlation between wing size and body weight in captive Culex quinquefasciatus.

INTRODUCTION: Mass production of mosquitoes under laboratory conditions allows implementing methods to control vector mosquitoes. Colony development depends on mosquito size and weight. Body size can be estimated from its correlation with wing size, whereas weight is more difficult to determine. Our goal was to test whether wing size can predict the weight. METHODS: We compared dry weight and wing centroid size of Culex quinquefasciatus reared at different temperatures and four diets. RESULTS: Weight and wing size were strongly correlated. The diets did not influence wing size. CONCLUSIONS: Wing centroid size is a good predictor of Cx. quinquefasciatus body weight.

Morphological and molecular characterization of the ecological, biological and behavioural variants of the JE vector Culex tritaeniorhynchus: an assessment of its taxonomic status.

BACKGROUND & OBJECTIVES: Culex tritaeniorhynchus (Diptera: Culicidae), an important vector of Japanese encephalitis belongs to the Culex vishnui subgroup which includes two other vector species namely, Cx. Vishnui and Cx. pseudovishnui. Many varieties and types of Cx. tritaeniorhynchus have been reported, besides populations that exhibit behavioural and biological differences. This study was undertaken to find out whether Cx. tritaeniorhynchus populations exhibiting behavioural and biological variations, and those from different geographical areas, are comprised of more than one taxon or belong to a single taxon. METHODS: Morphological characterization was done by examining 153 morphological and morphometric characters in the larval (75), pupal (60) and adult stages (18) of five geographical populations of Cx. tritaeniorhynchus. Molecular characterization was done by PCR amplification of mitochondrial cytochrome c oxidase (COI) gene sequences (DNA barcodes) and another hypervariable genetic marker, the ribosomal DNA (16S). One-way ANOVA, principal component analysis (PCA) and discriminant factor analysis (DFA) were done for statistical analyses using the statistical package SPSS IBM version 19.0. RESULTS: Morphological characterization showed that no intraspecific differentiation can be made among the five geographical populations of Cx. tritaeniorhynchus. Molecular characterization done by DNA barcoding also showed that the COI sequences of all the five populations of Cx. tritaeniorhynchus grouped into a single taxonomic clade plus the genetic differentiation among these was non-significant and the overall gene flow among the populations was very high. Analysis of the ribosomal DNA also confirmed that the Cx. tritaeniorhynchus populations belonged to a single taxon. INTERPRETATION & CONCLUSION: Culex tritaeniorhynchus is a taxon that does not involve cryptic species.

A critical assessment of available molecular identification tools for determining the status of Culex pipiens s.l. in the United Kingdom.

Until the relatively recent application of molecular identification tools, identification of Culex pipiens f. pipiens and Cx. pipiens f. molestus relied on expressed ecological characteristics, including autogeny, host preference and stenogamy. Herein we test two DNA assays, one based on the microsatellite locus CQ11 and the other on species-diagnostic nucleotide bases in the mtDNA cytochrome oxidase I, on 322 wild-caught Cx. pipiens s.l. collected in above ground habitats from 6 counties across southern England and Wales. Of the 322 Culex pipiens s.l. screened using the CQ11 assay, 205 were identified as Cx. pipiens f. pipiens, 95 as Cx. pipiens f. molestus and 22 were determined as hybrids. Neither above ground Cx. pipiens f. molestus, nor hybrids have previously been reported in UK. However, comparison of COI barcodes (658bp) from 30 individuals from the above defined grouping indicated that inadvertent inclusion of specimens of Cx. torrentium resulted in the expected product sizes purportedly diagnostic for Cx. pipiens f. molestus, Cx. pipiens f. pipiens and hybrids in the CQ11 assay. COI sequences showed Cx. torrentium was misidentified as Cx. pipiens s.l. in more than 50% of cases and that all above ground Cx. pipiens s.l. collected in this study were in fact Cx. pipiens f. pipiens. Thus in regions of the Palearctic where Cx. torrentium and Cx. pipiens s.l. are sympatric, we showed that the CQ11 assay produces misleading results and should not be used.