Induced chromosomal aberrations and linkage group-chromosome correlation in Anopheles stephensi

Pattern of mitochondrial DNA variation between and within Anopheles stephensi (Diptera: Culicidae) biological forms suggests extensive gene flow

Anopheles stephensi Liston is the most prevalent anopheline species and plays an important role in malaria transmission in Indian subcontinent and Middle East including southern parts of Iran. It exists as three biological forms; "type", "intermediate", and variety mysorensis. The type form is reported to be an efficient vector of urban malaria, whereas mysorensis and intermediate are considered to be rural species and poor vectors. Moreover, differences in cuticular hydrocarbon and chromosomal characters have been described between urban and rural forms. However, the genetic structure of the biological forms remains unclear. This study was conducted to determine the genetic structure of the An. stephensi biological forms in south of Iran where all three forms are present. Live specimens were collected from the field and transferred to insectaries, reared, and identified based on egg morphological characters. Genetic structure of the biological forms was studied using PCR-RFLP of 1512 bp of mitochondrial DNA (mtDNA) cytochrome oxidase subunit I and II (COI-COII) and sequence of about 712 bp of COI and 562 bp of COII genes. Sequence analysis showed that except for a few substitutions in COII, all three forms and populations were nearly identical. The high homology of COI and COII sequence of An. stephensi forms indicates extensive gene flow between populations and forms in the region. This data will serve as first report on the sequence of mDNA COI-COII of biological forms of An. stephensi, which could be used as a diagnostic tool to identify vector/non-vector, gene flow, and geographical exchanges.

Cytological, linkage and insecticide studies on a genetic sexing line in Anopheles stephensi Liston

T(Y-D1)35 is a genetic sexing line in Anopheles stephensi (2n = 6; XX female, XY male) based on the translocation of the dieldrin resistance gene to the male determining chromosome. A cytological analysis demonstrated the presence of a 3 chromosome multiple translocation in which part of the Y chromosome formed the differential segment. An analysis of egg karyotypes enabled the segregation behaviour of the complex to be determined and only alternate and adjacent I segregations could be demonstrated. The breakpoint of the translocation in chromosome 3 was located using polytene salivary gland preparations. Linkage studies using chromosome three markers revealed contrasting effects of the translocation on recombination in this chromosome. An insecticide treatment method, based on the exposure of newly emerged adults, was developed enabling large numbers of individuals to be treated for the production of only males.