V. P. Sharma

EGG-FLOAT RIDGE NUMBER IN ANOPHELES STEPHENSI: ECOLOGICAL VARIATION AND GENETIC ANALYSIS

Abstract. Eight Indian laboratory stocks of Anopheles stephensi Liston could be grouped into three categories with, respectively, 14–22, 12–17 and 9–15 ridges on the egg‐floats. The mode number of ridges among the eggs laid by individual females in these stocks was 16–19,13‐16 and 10–14, respectively. The category with the highest egg‐float ridge number corresponded with the type‐form and the lowest with var. mysorensis Sweet and Rao; the new egg‐float category with ridge number modes of thirteen to sixteen was designated as ‘intermediate’. All three forms, i.e. type‐form, intermediate and mysorensis were observed in semi‐urban areas while only intermediate and mysorensis were seen in rural areas. Breeding experiments indicated no post‐copulatory barriers between the populations. Likelihood analysis of the results of crosses and back crosses indicated that variation in ridge number is controlled by more than one genetic factor. The stocks with different ridge numbers are best considered as ‘ecological variants’.

Lactate dehydrogenase allozyme differentiation of species in the Anopheles culicifacies complex

Abstract Genetically controlled enzyme variation exists within and between four sibling species of the Anopheles culicifacies complex of malaria vectors in India. A study on electrophoretic variation of nine enzymes in An.culicifacies sibling species revealed that the lactate dehydrogenase (Ldh) locus has Fast (F) and Slow (S) allozymes distinguishing species A+D from species B+C with a probability of c. 95%.

Responses of Anopheles culicifacies sibling species A and B to DDT and HCH in India: implications in malaria control

ABSTRACT. Differential responses of Anopheles culicifacies Giles sibling species A and B to DDT were evident from higher survival rate of species B in laboratory bioassays and greater proportions of species B in DDT‐sprayed villages of northern India, compared with those under HCH pressure. Both species A and B have become almost completely resistant to HCH in this area due to regular house‐spraying with HCH for about the last 10 years. Because species A predominates in northern India, where it has been incriminated as an important vector of malaria, and species A is more susceptible than species B to DDT, it is suggested that DDT would control malaria transmission more effectively than HCH in this situation. Monitoring of insecticide resistance in species A is therefore recommended as the basis for future choice of insecticides to be used by the National Malaria Eradication Programme.

Genetics of isocitrate dehydrogenase inAnopheles stephensi

The polymorphic biochemical markers are useful in the genetic characterization of species, differentiation of members of species complex, construction of linkage maps, and population genetics. The genetics and linkages of different morphological mutants and biochemical markers have been reported in Anopheles stephensi, an important vector of malaria in the Indian subcontinent (Narang and Seawright, 1982; Subbarao and Sharma, 1984; Parvez et al., 1985). A survey of laboratory colonies of A. stephensi has uncovered the presence of two zones of isocitrate dehydrogenase (IDH) enzyme activity. We report here the mode of inheritance and linkage analysis of one zone of the IDH (EC 1.1.1.42) enzyme.

Genetics of three esterase loci in Anopheles stephensi liston

A survey of laboratory strains of Anopheles stephensi for nonspecific esterases by polyacrylamide gel electrophoresis revealed 10 zones of esterase activity. In 3 of the 10 zones, three electromorphs were observed. Genetic analysis revealed that these three zones are controlled by three loci, viz., Est-3, Est-4, and Est-5, and that the electromorphs are codominant alleles at each locus. The three esterase loci were found linked to each other and to an autosomal marker colorless-eye. The esterase loci have tentatively been placed in linkage group II. The probable gene sequence on chromosome 2 is either c-Est-3-Est-4-Est-5 or c-Est-4-Est-3-Est-5.

Assignment of 6-phosphogluconate dehydrogenase and malate dehydrogenase to chromosome 3 of Anopheles stephensi

Genetics and linkage analysis of 6-phosphogluconate dehydrogenase (6-PGD) and malate dehydrogenase (MDH) have been investigated inAnopheles stephensi. Both these markers were found to be autosomal and linked and have been assigned to linkage group III. Two mutant markers,Black larva (Bl) andgolden-yellow larva (gy), were used to establish the map distances, and the current sequence of loci on chromosome 3 is as follows:Bl (3.75)-gy (14.53)-Mdh-2 (49.83)-6-pgd.

Inheritance and linkage of aspartate aminotransferase inAnopheles stephensi

Anopheles stephensi is a primary vector of urban malaria on the Indian subcontinent. Biochemical markers are very useful in genetic characterization and have been used in chromosome mapping and linkage analysis inAn. stephensi (Parvez et al., 1985; van Driel et al., 1987; Adak et aI., 1984, 1990, 1991, 1992, 1993). This Note reports the mode of inheritance of aspartate aminotransferase (AAT; EC 2.6.1.1) and its linkage analysis with an autosoreal recessive chromosome morphological mutant, golden-yellow larva (Adak et al., 1990).