Triatoma sordida and T. guasayana are competent Trypanosoma
cruzi vectors, with overlapping distribution areas in Argentina. Both
species are morphologically similar, and their immature stages are hard to
discriminate. Cytogenetic studies in the genus Triatoma reveal
scarce karyotypic variations, being 2n= 20 + XY the most frequent diploid
number in males.
In the present work the meiotic behaviour of different Argentinian
populations of T. sordida and T. guasayana has been analyzed;
the meiotic karyotype of both species has also been compared. The species
differ in total chromosome area and in the relative area of the sex
chromosomes. These meiotic karyotypic differences constitute an additional
tool for the taxonomic characterization of T. sordida and T.
guasayana. The analysis of an interpopulation hybrid of T.
sordida (Brazil x Argentina) reveals a regular meiotic behaviour,
despite the presence of heteromorphic bivalents. Our observations support
the hypothesis that karyotype variations through the gain or loss of
heterochromatin can not be considered as a primary mechanism of
reproductive isolation in Triatoma.