Cytogenetic studies in model groups of insects (Odonata and Heteroptera) and arachnids (Dysderoidea and Buthidae) with holokinetic chromosomes allowed us to identify differences in autosomes and sex chromosomes meiotic behaviour (pre-or post-reductional meiosis, chiasmatic or achiasmatic meiosis, telokinetic or holokinetic activity). Also, we detected differences in the frequency and distribution of chromosomal mutations (fusions, fragmentations and translocations both in homozygosity or heterozygosity) in the karyotype evolution mechanisms.

Los estudios citogenéticos en grupos modelo de insectos (Odonata y Heteroptera) y arácnidos (Dysderoidea y Buthidae) con cromosomas holocinéticos nos han permitido determinar diferencias en el comportamiento meiótico de autosomas y cromosomas sexuales (meiosis pre- o post-reduccional, quiasmática o aquiasmática, actividad telocinética u holocinética) y en la frecuencia y distribución de las mutaciones cromosómicas (fusiones, fragmentaciones y translocaciones en homocigosis o heterocigosis) en la evolución del cariotipo.

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.