Karyotypes of Danubian lineage brown trout and their hybrids

Cytogenetic analysis of brown trout, Salmo trutta, have been described for different populations and morphs; however, cytogenetic analysis of interspecific brown trout hybrids is unknown. Cultured kidney cells from four brown trout subspecies (Salmo trutta abanticus, S.t. caspius, S.t. fario and S.t. labrax) and their reciprocal hybrids were karyotyped using conventional staining, C-banding and Ag-NOR staining techniques. Chromosome number (2N) and chromosome arm number (NF) ranged from 76 to 80 and 98 to 102, respectively. Silver staining revealed the presence of NOR sites on the short arm of the submetacentric chromosome. The size and number of NOR sites showed uniformity. The presence of heterochromatin on different chromosome arms was confirmed by C-banding. The presence and position of constitutive heterochromatin showed variability among individuals. Chromosome structures of purebred brown trout subspecies belonging to the Danubian linage and their hybrids were similar, and no distinctive characteristics were observed in any of the species. The results of this study are applicable to the development of improved conservation and management strategies for brown trout.