Meiotic studies in Dysdercus Guerin Meneville 1831 (Heteroptera : Pyrrhocoridae). I. Neo-XY in Dysdercus albofasciatus Berg 1878, a new sex chromosome determining system in Heteroptera

The genus Dysdercus Guerin Meneville 1831 represents the only taxon within the family Pyrrhocoridae in the New World. Based on morphological features, it has been suggested that American species derived from immigrants from t he Old World, most probably from the Ethiopian Region. So far, 10 species f rom Dysdercus, including six species from the Old World and four species fr om the Neotropical Region have been cytogenetically analyzed. As is charact eristic of Heteroptera, they possess holokinetic chromosomes and a prereduc tional type of meiosis. While the X(1)X(2)0 sex chromosome system has been reported in all cytologically analyzed species of Dysdercus from the Old Wo rld, the system X0 has been found in all but one species from the New World , regardless of the number of autosomes in the complement. In the present s tudy the male meiosis of D. albofasciatus Berg 1878 was studied in specimen s from four different populations from Argentina. The diploid chromosome nu mber was found to be 2n = 10 + neo-XY. The neo-X shows at each subterminal region a positively heteropycnotic and DAPI-bright segment which correspond s to the ancestral X-chromosome. The origin of this neo-XY system involved, most probably, a subterminal insertion of the ancestral X chromosome in an autosome, followed by a large inversion, which included part of the origin al X chromosome.