Polytene chromosome study on Anopheles gambiae in Benin and Togo, West Africa
1995
Akogbeto, M. (Centre de Recherches Entomologiques OCCGE, Cotonou (Benin)) | Deco, M.A. di
The geographical distribution of the members of the Anopheles gambiae complex and their chromosomal variability due to paracentric inversions were investigated in Benin and Togo. Anopheles were collected in 37 localities chosen along a transect crossing the three main vegetation zones. More than 3700 half-gravid females of A. gambiae sensu lato were studied. Based on examination of polytene chromosome preparations obtained from the ovarian nurse cells, species and karyotypes were scoted following the nomenclature by Coluzzi. Polytene chromosome observations were carried out on 3755 specimens of A. gambiae s. l. of wich 1302 (36.7 percent) Anopheles melas, 2382 (63.43 percent) A. gambiae sensu stricto and 71 (1.9 percent) Anopheles arabiensis. A. gambiae s.s. is the most wide-spread species. The distribution is similar to that shown in West Africa. Concerning the inversion polymorphism three chromosomal forms are found in A. gambiae s.s.: a forest form in the south part of the two contries, a savanna form in the center and the North part and a Mopti chromosomal form in the inundation and rice cultivation zones of Sadori and Kantindi. Based on chromosomic forms described by Coluzzi, these chromosomic variations may be interpreted as a continual intergradation between the predominant Forest form to the South and the Savannah form to the North. These forms are in Hardy-Weinberg balance.
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