B-chromosomes and their incidence on the meiotic division in two species belonging to the Leptysminae subfamily (Orthoptera: Acrididae)

Abstract

Here we present a study on B-chromosomes in two species of the Leptysminae subfamily: Cornops frenatum cannae Roberts and Carbonell and Stenopola bohlsii Giglio Tos, collected in Monteros, Tucumán. Accessory elements such as B chromosomes, also called supernumerary chromosomes, may be present in the eucaryotic genome (animals – plants). The presence of this type of chromosomes is frequent in orthopterans. Conventional cytogenetic techniques were used in order to describe the karyotype and male meiosis of C. frenatum cannae and S. bohlsii . The cytogenetic analysis revealed a karyological formula of 2n=23 ( Ÿ ). When analyzing the cells during the meiotic division, some intrafollicular differences related to B chromosome number appeared, such as lagging chromosomes, anomalies during chromosome segregation and the presence of abnormal spermatids. Observation of these results allowed us to evaluate the incidence of accesory chromosomes in cell division. There is evidence that these extra genetic elements are involved in cytologic as well as in physiological disorders that determine endophenotypic rather than exophenotypic changes. It is worth noting that this paper represents the first cytogenetic contribution for these species, and also that Cornops frenatum cannae is endem- ic in the province of Tucumán.