Origin of B chromosomes in (Characiformes, Crenuchidae) and its relationship with supernumerary chromosomes in other species.

B chromosomes are apparently dispensable components found in the genomes of many species that are mainly composed of repetitive DNA sequences. Among the numerous questions concerning B chromosomes, the origin of these elements has been widely studied. To date, supernumerary chromosomes have been identified in approximately 60 species of fish, including species of the genus Reinhardt, 1867 in which these elements appear to have independently originated.