Transmission rate variation among three B chromosome variants in the fish Prochilodus lineatus (Characiformes, Prochilodontidae).

Cytogenetic studies were developed in Prochilodus lineatus (Valenciennes 1836), describing an interesting system of small supernumerary chromosomes. The purpose of this work is to study the frequency and morphology of B chromosomes in individuals from the parental line and the inheritance patterns of these elements in individuals obtained from controlled crosses in the species P. lineatus. The transmission rate of B chromosomes revealed a k(B)=0.388 for the acrocentric type, a kB=0.507 for the metacentric type and a k(B)=0.526 for the submetacentric type. The obtained results raise hypothesis that B-acrocentric chromosomes are involved in an extinction process in this species, while the metacentric and submetacentric supernumerary elements comprises a neutral mechanism and follows a Mendelian transmission rate.