CHROMOSOMAL LOCATION OF NORS AND C-BANDS IN F1 HYBRIDS OF BIGHEAD CARP AND SILVER CARP REARED IN BRAZIL

The bighead carp (Aristichrhys nobilis) and the silver carp (Hypophtha lmichthys molitrix) were introduced into Brazil in 1979 from China for the aquaculture programs conducted by the Centro de Pesquisas e Trein amento em Aquicultura (CEPTA), Pirassununga, SP. Hybrids between bighe ad carp females and silver carp males were obtained in 1989. Reported here are the cytogenetic analysis of parental lines and hybrids, inclu ding Ag-stained NORs and C-banding patterns. The two species and hybri ds have 2n=48 chromosomes, consisting of 12 pairs of meta-submetacentr ics and 12 pairs of subtelocentrics. The Ag-NOR pattern, which consist ed of four pairs of nucleolus organizers in both species and the conve ntional Giemsa staining of chromosomes were ineffective for the cytoge netic characterization of the hybrids and of the two parental species. C-bands, in contrast, were effective markers in the characterization of the karyotypes of the two species and of their hybrids because of t he presence of distinct heterochromatin blocks in one chromosome pair of A. nobilis. This chromosome marker was useful in the identification of the parental haploid sets in the hybrids.