G-banding patterns were obtained for chromosomes of A. scabripinnis paranae after trypsin treatment and BamHI treatment (Figures 1b-c, 2b-c). The cleavage with the RE HinfI also resulted in a longitudinal differentiation pattern on the chromosomes which differed from normal G-band-

The absence of longitudinal bands in fish chromosomes has been associated with technical problems in chromosome preparations or the absence of a structural compartmentalization in the fish genome. In the present study, a R-banding pattern was obtained using a replication banding technique by in vivo treatment with 5-bromodeoxyuridine (5-BrdU). G-banding patterns were obtained after trypsin treatment and also after chromosome cleavage by in situ treatment with the restriction endonuclease BamHI. A similar G-banding pattern was also obtained after cleavage with the endonuclease HinfI. Presence of a resolute Rand G-banding patterns shows that Astyanax scabripinnis paranae chromosomes could present an isochore-like structure similar to that found in other vertebrates. Instituto de Farmácia e Nutrição, Universidade de Alfenas, 37130-000 Alfenas, MG, Brasil. Departamento de Morfologia, Instituto de Biociências, UNESP, 18618000 Botucatu, SP, Brasil and CAUNESP, Jaboticabal, SP, Brasil. Send correspondence to E.L.M.