-Mosquito cytogenetic studies have revealed that the majority of disease vector species exist as cryptic species complexes. In relevance to this, the present results include the sequence analysis of r-DNA internal transcribed spacer 2 (ITS2) of two populations of Anopheles subpictus Grassi collected from Chandigarh (Pop.A) and Hoshiarpur, Punjab, India (Pop.B). These sequences were compared with fi ve other populations C, D, E, F and G worked out earlier. ITS2 sequence in Pop. A was 681 bp compared to 491 bp in Pop. B. All the sequences were G:C rich. In populations A-E, which form the Indian component of An. subpictus, the ts/tv frequencies ranged from 0.25 to 0.77. Populations F and G, which represent the Srilankan fauna, were much higher at 0.83 to 0.90 in inland and coastal populations respectively. The SRF revealed various common interspersed repeats in the form of dimers, trimers, tetramers, pentamers and polymers. The TG repeat motif, which was repeated 50 to 60 times, was common in Indian and Srilankan populations of An. subpictus. Further, there were as many as seven different types of polymers/repeats in populations A-E of Indian region but none was shared by F and G of Srilanka. Phylogeny analysis of ITS2 sequence had well supported India and Srilanka clades in accordance with their allopatric status.

Objectives:In this study we have evaluated the mutagenicity of organophosphate pesticides acephate, chlorpyrifos, and profenofos using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay with the mosquito Culex quinquefasciatus taken as an experimental model.Materials and Methods:Second instar larvae were treated with LC20 of each pesticide for 24 h and mutations induced in the sequence of mitochondrial COII gene (690bp) were studied from restriction patterns generated with AluI, PacI, and PsiI restriction endonucleases.Results:Variations in the number and size of digested fragments were recorded from treated individuals compared with controls showing that the restriction enzymes created a cut at different locations. In addition, sequences of COII gene from control and treated individuals were also used to confirm the RFLP patterns. From the sequence alignment data, it was found that mutations caused the destruction and generation of restriction sites in the gene sequence of treated individuals.Conclusion:This study indicates that all the three pesticides had potential to induce mutations in the normal sequence of COII gene and also advocates the use of PCR-RFLP assay as an efficient, rapid, and sensitive technique to detect mutagenicity of pesticides.

SummaryThe extensive use of chemical pesticides has greatly increased the mutational load on the genome of living organisms. The problems of genetic toxicology have generated more concern than any other problem because the residual inclusion of pesticides in the environment leads to a number of direct and indirect effects on the genetic material. Induced chromosomal mutations provide a reliable index of the mutagenic potential of a chemical or a physical agent. Experience has shown that the mutagenic effect of the semilethal doses of chemicals induce a of variety of structural changes in the polytene chromosomes out of which ectopic pairings are the most frequent types of aberrations. As a consequence of these points of genetic interest, the present paper deals with the incidence of ectopic pairing of the intercalary heterochromatic bands in the polytene chromosomes of those larvae of Anopheles subpictus, which were treated with LC 20 of 4 organophosphate pesticides viz. chlorpyrifos, monocrotophos, acephate and dimethoate. When compared with the data of nontreated controls the treated larvae had an elevated incidence of intercalary heterchromatic linkages in the X-chromosome and the right and left arms of autosomes 2 and 3 (2R, 2L, 3R, 3L). The results are discussed in relevance to the fact that ectopic associations are established between those heterochromatic bands which are homologous in their chemical and genetic properties. These properties are attributed to the presence of identical A : T rich nucleotide sequences resulting from gene duplications which are induced by the cellular environments altered by the pesticides.

The present article deals with the polymerase chain reaction (PCR)-based genotoxicity evaluation of neonicotinoid pesticides, imidacloprid and thiamethoxam, by using the genome of a mosquito Anopheles stephensi taken as an experimental model. After treatment of the second instar larvae with LC20 of the pesticides for 24 h, the induced nucleotide sequence variations in the internal transcribed spacer 2 (ITS2) of freshly hatched unfed control and treated individuals was studied from the sequence alignment data and the mutations in the form of insertion, deletion and substitution of bases were recorded. Measurable differences, indicative of the genetic damage due to imidacloprid and thiamethoxam were observed when ITS2 sequences of control and treated individuals were compared. It was found that imidacloprid-treated individual had 8 deletions, 29 insertions, 18 transitions and 33 transversions, whereas thiamethoxam-treated individual had 10 deletions, 8 insertions, 47 transitions and 68 transversions.

Abstract:The present paper deals with the genotoxicity evaluation of profenofos by applying dominant lethal test (DLT) on Culex quinquefasciatus taken as an experimental model. For this, the males hatched from the larvae treated with LC 20 of pesticide were crossmated with normal females and the results were based on the number of hatched and unhatched eggs laid by these females. Mean percentage frequency of unhatched eggs was as low as 3.97 in the normal stocks as compared to treated stocks in which the frequency of unhatched eggs had increased to 9.50. The statistical analysis of the data from treated groups gave values of 9.50±1.35 as against 3.97± 0.38 in the control groups. Profenofos induced significant (p<0.05) dominant lethality.