Etude chromosomique d'Anopheles gambiae et Anopheles arabiensis à Ouagadougou (Burkina Faso) et dans quelques villages voisins.

Abstract. Adult females of Anopheles gambiae sJ. wete collected by pyrethrum spray catch in Ouagadougou (purkina Faso, formetly Upper Volta) and in four-nèighbouring -viliages. The collections have been carried out mostly during the 1984 rainy season. Monthly collectionJin some sampling sites allowed a ,preliminary longitudinal study. By analysis of nurse cell polytene chromosomes in adult females, An. gambiae s.str. and An. arabiensis were identified in the itudv area. Both species showed polymorphisms for various paracentric inversions. In all samples oÎ An. arabiensis.the frequencies of the alternative karyotypes were in Hardy-I7einberg -equilibrium,. suggesting panmictic conditions. Conversely, An. gambiae s.su. showed a -different situation, since most of its samples had strong defiçiency of certain expected heterokaryotypes. Ihis same phenomenon was already observed in Mali, leading to the silitting of. gambiae'sitr. into different chromosomal forms, partially or totally reproductively isolated from each other. Each chromosomal form is characterized by different ôhromosomal pôlymorphisms. Two of these forms, Mopti and Savanna, were detected in the study area. Moirti ôhromosomal form is apparently,âssociated with the presence of permanent waiers (i.e. thé < banages > north of the t_own), while Savanna,,is usu-ally found _in situations where breeding places are mainly dependent from rain (e.g. in villages far from <<b arrages) > or at the town's cênter).