Abstract
The anomaly that Anopheles culicifacies (Diptera: Culicidae) species B is a major vector of malaria in Sri Lanka, but a non-vector in India, has been noted for several years. In 1999, a Y chromosome dimorphism associated with Plasmodium vivax infectivity within the Indian A. culicifacies species B suggested that this was itself a complex of two sibling species, B and E. A recent cytogenetic analysis shows the sympatric presence of these sibling species in Sri Lanka, a situation similar to that reported from nearby Rameshwaram Island, India. Species E, with a submetacentric Y chromosome, is a more effective vector of P. vivax than species B with an acrocentric Y chromosome. Larval karyotyping, however, is time-consuming and labour-intensive. Recently, the development of a PCR-RFLP assay distinguishing species B and E of A. culicifacies from India, based on differences in one region of the cytochrome oxidase subunit II (COII) gene, was reported. Here we show that whilst this diagnostic approach reveals polymorphism in Sri Lankan A. culicifacies, this variation is not correlated with Y chromosome karyotype. Hence this assay will not be useful for distinguishing species B and E in Sri Lanka. Further, we found no difference between the sequences of Sri Lankan specimens in any of three other regions (ITS2, D3 region of 28S rDNA, and guanylate cyclase intron) often used for species dis- crimination.
Highlights
Anopheles culicifacies Giles sensu lato (Diptera: Culicidae) is the main vector of malaria in Sri Lanka (Ramasamy et al, 1994; AHB, 2001)
The digestion pattern and sequence of these 6 samples match that shown by Indian species E, in that study the band sizes observed did not match those predicted from the sequence
There is polymorphism within this region of cytochrome oxidase subunit II (COII) in A. culicifacies from Sri Lanka, but it does not correlate with Y karyotype
Summary
Anopheles culicifacies Giles sensu lato (Diptera: Culicidae) is the main vector of malaria in Sri Lanka (Ramasamy et al, 1994; AHB, 2001). Only sibling species B was reported from Sri Lanka (Abhayawardana et al, 1996a), but in India species B is a poor vector of malaria (Subbarao et al, 1992). Recent studies of A. culicifacies from Rameshwaram Island in India, which is in close proximity to Sri Lanka, found evidence for assortative mating correlated with cytogenetic variation. No malaria infections were found in mothers of acrocentric Y males; these were designated species B and the submetacentric Y-chromosome vectors were designated species E (Kar et al, 1999). Goswami et al (2005) reported a PCR-RFLP assay distinguishing species B and E of A. culicifacies from India, based on differences in one region of the cytochrome oxidase subunit II (COII) gene. The aim of this work was to investigate the variability in this and other loci in A. culicifacies specimens from Sri Lanka
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