Polymorphism in male genitalia of Aedes (Ochlerotatus) scapularis Rondani, 1848.

Morphology of male genitalia of culicids is generally species-specific and often used as a taxonomic marker. However, some characters of the male genitalia vary intraspecifically and are not taxonomically diagnostic. This might be the case of Aedes scapularis, a Neotropical culicid with vector competence for arboviruses and filarial worms. Males of this species may or not present a retrorse process (RP) in the genitalic claspette filaments, which led authors to suspect that this variance might be indicative of population divergence or incipient speciation process. This suspicion has not been investigated hitherto and it is not known if there are variable patterns of RPs. We hypothesized that the presence of the RP varies intraspecifically in Ae. scapularis and then we statistically evaluated the variability of this character in a single population. To this study the genitalia of 73 males of Ae. scapularis were prepared, and their RPs were meristically quantified and categorized according to the phenotypes observed. We noted that the presence or RPs is a polymorphic character because it varied inter and intra-individually. The presence of a single RP on each claspette filament was the predominant pattern (77%), but absent or multiple RPs in each filament were also found either in bilateral symmetry or asymmetry. Thus, we conclude that the presence of RPs owing to its high variability is not indicative of populational divergence or diagnostic of species complex within Ae. scapularis.

Morphometric comparisons of the scanning electron micrographs of the eggs of Anopheles (Nyssorhynchus) darlingi Root(Diptera: Culicidae)

Anopheles darlingi Root is the principal vector of Plasmodium in Brazil, but its biological variability is notwell known. Morphometric analyses of scanning electron microscopy images of the eggs of An. darlingiwere conducted using individuals collected in nine states of Brazil (Acre, Amapá, Espírito Santo, Pará,Paraná, Rio de Janeiro, Rondônia, São Paulo, and Tocantins). Ten attributes of the eggs (seven continuous variables and three discrete variables) were respectively measured or counted and analyzed to determine if populations from different geographical regions or biomes could be distinguished. Univariate analysisshowed that the eggs from Espírito Santo were the narrowest where as representatives from Tocantins populations had the smallest floats. Results of multivariate analyses of continuous variables showed that the first principal component (PC1), mainly represented by all four float attributes, helped to differentiate populations. The second principal component (PC2) comprised roughly the length and width of the egg. PC1 of discrete variables corresponded to the number of ribs on the float where as PC2 was approximately equivalent to the number of discs on the micropyle. Based on those variables (continuous and discrete separately), multivariate discriminant analysis indicated that eggs from individuals collected in Tocantins were distinct from the other populations. Among sampled localities, the one from the state of Tocantins was situated within the Cerrado biome whereas the locality from São Paulo state was at the border of Cerrado, within a transition zone of the Atlantic Forest biome...

A multi-locus approach to barcoding in the Anopheles strodei subgroup (Diptera: Culicidae)

The ability to successfully identify and incriminate pathogen vectors is fundamental to effective pathogen control and management. This task is confounded by the existence of cryptic species complexes.Molecular markers can offer a highly effective means of species identification in such complexes and are routinely employed in the study of medical entomology. Here we evaluate a multi-locus system for the identification of potential malaria vectors in the Anopheles strodei subgroup. Methods: Larvae, pupae and adult mosquitoes (n = 61) from the An. strodei subgroup were collected from 21 localities in nine Brazilian states and sequenced for the COI, ITS2 and white gene. A Bayesian phylogenetic approach was used to describe the relationships in the Strodei Subgroup and the utility of COI and ITS2 barcodes was assessed using the neighbor joining tree and “best close match” approaches...

Immune transcript variations among Aedes aegypti populations with distinct susceptibility to dengue virus serotype 2.

The innate immune response of insects is one of the factors that may dictate their susceptibility to viral infection. Two immune signaling pathways, Toll and JAK-STAT, and the RNA interference (RNAi) pathway are involved in Aedes aegypti responses against dengue virus (DENV), however natural differences in these antiviral defenses among mosquito populations have not been studied. Here, two field Ae. aegypti populations from distinct ecological environments, one from Recife and the other from Petrolina (Brazil), and a laboratory strain were studied for their ability to replicate a primary isolate of dengue virus serotype 2 (DENV-2). Virus infectivity and replication were determined in insect tissues collected after viral exposure through reverse-transcription real time PCR (RT-PCR). The expression of a transcript representing these defense mechanisms (Toll, JAK-STAT and RNAi) in the midgut and fat body was studied with RT-PCR to evaluate variations in innate immune mechanisms possibly employed against DENV. Analyses of infection rates indicated that the field populations were more susceptible to DENV-2 infection than the lab strain. There were distinct expression patterns among mosquito populations, in both control and infected insects. Moreover, lower expression of immune molecules in DENV-2-infected insects compared to controls was observed in the two field populations. These results suggest that natural variations in vector competence against DENV may be partly due to differences in mosquito defense mechanisms, and that the down-regulation of immune transcripts after viral infection depends on the insect strain.

Wing geometry of Anopheles darlingi Root (Diptera: Culicidae) in five major Brazilian ecoregions

We undertook geometric morphometric analysis of wing venation to assess this character’s ability to distinguish Anopheles darlingi Root populations and to test the hypothesis that populations from coastalareas of the Brazilian Atlantic Forest differ from those of the interior Atlantic Forest, Cerrado, and the regions South and North of the Amazon River. Results suggest that populations from the coastal and interior Atlantic Forest are more similar to each other than to any of the other regional populations. Notably,the Cerrado population was more similar to that from north of the Amazon River than to that collected of south of the River, thus showing no correlation with geographical distances. We hypothesize that environmentaland ecological factors may affect wing evolution in An. darlingi. Although it is premature to associate environmental and ecological determinants with wing features and evolution of the species,investigations on this field are promising...