Intraspecific polymorphism of sex chromosome heterochromatin in two species of the Anopheles gambiae complex.

The Hoechst 33258 banding pattern of the mitotic chromosomes of several laboratory and natural populations of the sibling species A. gambiae and A. arabiensis has been analyzed. A clear intraspecific polymorphism of sex chromosome heterochromatin has been observed. Nevertheless in each species heterochromatic variations fall within a characteristic species-specific pattern. Moreover, while laboratory polulations tend to be monomorphic for a given heterchromatic variant, natural populations exhibit a high degree of intrapopulation polymorphism. The possible role of sex chromosome heterochromatin in controlling fertility and mating behaviour of Anopheles mosquitoes is discussed.