Odd ploidy levels in sturgeons suggest a backcross of interspecific hexaploid sturgeon hybrids to evolutionarily tetraploid and/or octaploid parental species

Flajshans M. Vajcova V.

Three presumably purebred aquaculture stocks of sturgeons (Acipenser ruthenus, A. gueldenstaedtii and A. baerii) were investigated. Analyses of DNA contents by flow cytometry and of erythrocyte nuclear dimensions by microscope-coupled, computer-assisted image analysis revealed that only an A. ruthenus stock was purebred tetraploid in 93.33%; whereas both A. gueldenstaedtii and A. baerii stocks under study consisted of hexaploids, yet unknown penta- or heptaploid specimens and purebred octaploids. We hypothesized that the hexaploid specimens were F-1 interspecific hybrids of tetra- and octaploid sturgeon species, whereas pentaploid specimens may have originated from an intentional or accidental backcross of the F-1 hybrid to tetraploid parental species in aquaculture, and the heptaploid specimens may have originated from similar backcross of the F-1 hybrid to octaploid parent.