Biological aspects of Amazonian fishes. IX. Cytogenetic studies in two species of the genus <i>Semaprochilodus</i> (Pisces, Prochilodontidae)

Abstract

The karyotype of Semaprochilodus insignis and Semaprochilodus taeniurus were analyzed through the conventional Giemsa staining, C-banding, and the nucleolar organizer regions. The diploid number is the same (2n = 54) in both species, but S. taeniurus shows a chromosomic system of the ZZ/ZW type. This and some other differences between the two karyotypes will be useful in further studies on the possible hybrid origin of the "jaraqui açú," a low frequency form that is observed together with S. insignis and S. taeniurus. Key words: fish, ZZ/ZW system, constitutive heterochromatin, nucleolar organizing regions.