Mosquitoes in the Culex (Culex) pipiens complex of species, known as vectors of periodic filariasis and deadly encephalitides, have recently emerged as important vectors of West Nile virus in the United States. Highly conserved morphology but marked differences in potential vectorial capacity require the development of polymerase chain reaction (PCR)-based tests that unambiguously distinguish among the different species. We introduce and describe a series of PCR-based assays that use polymorphisms in the second intron of the acetylcholinesterase-2 (ace-2) locus for the identification of members of the Cx. pipiens complex (Cx. pipiens, Cx. quinquefasciatus, Cx. p. pallens, Cx. australicus), two other species that are commonly mislabeled as Cx. pipiens (Cx. torrentium and Cx. pervigilans), as well as hybrids between Cx. pipiens and Cx. quinquefasciatus.

Rapid assays for identification of members of the culex (culex) pipiens complex, their hybrids, and other sibling species (diptera: culicidae)

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Biochemical genetics and genomics of insect esterases

Biochemical Genetics and Genomics of Insect Esterases

The host-feeding patterns of mosquitoes (n = 247) collected in the Borough of Queens in New York City in July and August 2000 were investigated using an indirect ELISA and a polymerase chain reaction (PCR)-heteroduplex assay. Culex pipiens L. and Cx. restuans Theobald fed primarily on birds, and their feeding habits support their implication as enzootic vectors of West Nile virus. Culex salinarius Coquillett and Coquillettidia perturbans (Walker) fed mainly on mammals, with fewer blood meals taken from birds, and these two species are potential bridge vectors of West Nile virus. Culex mosquitoes took blood meals (n = 54) from 11 different avian species. Only the northern cardinal (Cardinalis cardinalis), American robin (Turdus migratorius), and Brown-headed cow bird (MolIothrus ater) were fed upon by all three Culex species. Multiple blood feedings on avian hosts were detected in Cx. pipiens and Cx. restuans. Species identifications of Culex mosquitoes made using morphological characteristics were confirmed with a PCR assay that employed species-specific primers. All Cx. pipiens (n = 20) and Cx. salinarius (n = 10) specimens were correctly identified, but three (20%) of 15 Cx. restuans were misidentified as Cx. pipiens.

https://bioone.org/journals/journal-of-medical-entomology/volume-39/issue-5/0022-2585-39.5.777/Host-Feeding-Habits-of-Culex-and-Other-Mosquitoes-Diptera/10.1603/0022-2585-39.5.777.pdf

Host-feeding habits of Culex and other mosquitoes (Diptera: Culicidae) in the Borough of Queens in New York City, with characters and techniques for identification of Culex mosquitoes.

Gene duplication is thought to be the main potential source of material for the evolution of new gene functions. Several models have been proposed for the evolution of new functions through duplication, most based on ancient events (Myr). We provide molecular evidence for the occurrence of several (at least 3) independent duplications of the ace-1 locus in the mosquito Culex pipiens, selected in response to insecticide pressure that probably occurred very recently (<40 years ago). This locus encodes the main target of several insecticides, the acetylcholinesterase. The duplications described consist of 2 alleles of ace-1, 1 susceptible and 1 resistant to insecticide, located on the same chromosome. These events were detected in different parts of the world and probably resulted from distinct mechanisms. We propose that duplications were selected because they reduce the fitness cost associated with the resistant ace-1 allele through the generation of persistent, advantageous heterozygosis. The rate of duplication of ace-1 in C. pipiens is probably underestimated, but seems to be rather high.

/pdf/independent-duplications-of-the-acetylcholinesterase-gene-wqlcjfhih0.pdf

Independent Duplications of the Acetylcholinesterase Gene Conferring Insecticide Resistance in the Mosquito Culex pipiens

The taxonomy of the Culex pipiens complex remains a controversial issue in mosquito systematics. Based on morphologic characters, 2 allopatric taxa are recognized, namely Cx. pipiens (including the form "molestus") in temperate areas and Cx. quinquefasciatus in tropical areas. Here we report on variability at the nucleotide level of an acetylcholinesterase gene in several strains and natural populations of this species complex. Few polymorphisms were found in coding regions within a subspecies but many polymorphisms were observed between subspecies in noncoding regions. We describe a method based on a restriction enzyme polymorphism in polymerase chain reaction-amplified DNA, in which the presence or absence of one restriction site discriminates Cx. pipiens, Cx. quinquefasciatus, and their hybrids. This technique reliably discriminates mosquitoes from more than 30 worldwide strains or populations. Polymerase chain reaction amplification of specific alleles may also be a useful tool for characterizing specific alleles of each sibling taxon.

G Vourch

Papers

The acetylcholinesterase gene Ace: a diagnostic marker for the Pipiens and Quinquefasciatus forms of the Culex pipiens complex.