A standard cytogenetic map forAnopheles sundaicus(Diptera: Culicidae) and evidence for chromosomal differentiation in populations from Thailand and Indonesia

Abstract

A standard photographic map of polytene chromosomes of Anopheles sundaicus was constructed from ovarian nurse cells and is described herein. Polytene chromosomes of wild specimens collected from 9 different geographical areas in Thailand and Indonesia have been analyzed. Specimens from these populations appear to share banding patterns with standard gene arrangements, except for some specimens from Purworejo, in Central Java, and South Tapanuli and Asahan, both of North Sumatra, which exhibited distinct banding patterns at the tip of chromosome X (Xb) compared with the standard sequence (Xa). Moreover, some specimens collected from Asahan, North Sumatra, consistently showed distinct loosely diffuse bands in zone 19 of chromosome arm 2R (2Rb) compared with the standard banding patterns (2Ra). The existence of the 2Rb pattern correlates perfectly with the presence of an extra block of centromeric heterochromatin in autosome 2 as revealed by mitotic karyotype analysis (2n = 6). These cytological differences have led to the recognition of 3 distinct forms, viz., A, B, and C, within the taxon An. sundaicus. In addition, forms A and C show a normal size for chromosome Y, (Y1), while form B has a relatively larger type of chromosome Y, (Y2). Form A is widely distributed in Thailand and Indonesia, while form B has been found in North Sumatra and Central Java. Form C, however, has been found only in Asahan, North Sumatra. Key words : Anopheles sundaicus, polytene chromosome map, mitotic karyotype, chromosomal differentiation.