Metaphase karyotypes of Anopheles of Thailand and Southeast Asia: I. The Hyrcanus Group.

Metaphase karyotypes of 6 species of the Hyrcanus Species Group of the subgenus Anopheles show constitutive heterochromatin variation in X and Y chromosomes. Anopheles peditaeniatus exhibits the most extensive variation in the size and shape of heterochromatic sex chromosomes, with 3 types of X and 5 types of Y chromosomes. Anopheles nitidus shows the least variation, with only 2 types of X chromosomes. Anopheles sinensis and An. crawfordi each have 2 forms of metaphase karyotype in the heterochromatin of the Y chromosome. It is not known whether the 2 forms of metaphase karyotype in these 2 species represent inter- or intraspecific differences. The 2 forms of heterochromatic sex chromosomes observed in An. argyropus and An. nigerrimus may suggest the existence of sibling species complexes within each of these species.