Electrophoretic and DNA identification of Anopheles bwambae and A-gambiae (Diptera: Culicidae) in western Uganda

Collections of mosquitoes of the Anopheles gambiae Giles complex were made from the geothermal springs and surrounding area in the Semliki Valley, Bwamba County, Uganda, which is the only known locality of A. bwambae White. Specimens were analysed in one of three ways: rDNA-PCR for unequivocal species identification, allozyme electrophoresis to determine superoxide dismutase (Sod) and octanol dehydrogenase (Odh) genotypes, or both methods. Ribosomal DNA PCR identification revealed the presence of A. bwambae and A. gambiae. Allozyme electrophoresis of 181 individuals showed that A. bwambae possessed the Sod(105) and Sod(100) alleles and was not monomorphic for Sod(105) as reported previously. In adults reared from collections made in the vicinity of the geothermal springs, the frequency of Sod(105) was found to be 0.614. Anopheles gambiae was fixed for Sod(100) The majority of individuals homozygous for the Sod(100) allele could be identified to species using Odh. Odh(95) was found to be common in A. bwambae (frequency = 0.988) while A. gambiae appeared to be fixed for Odh(100). Since Odh(100) occurred at a frequency of 1.2% in A. bwambae (concomitant with Sod genotypes of 105/105, 100/105 or 100/100), individuals homozygous for Sod(100) and Odh(100) could be either species. Among 25 A. bwambae specimens homozygous for Sod(100), one (4%) was also homozygous for Odh(100). At present, this subset of the A. bwambae population can only be correctly identified to species using rDNA-PCR analysis.