ИСТИНА

The elucidation of genetic mechanisms of sex determination in sturgeons which passed through several stages of polyploidization in their evolution is of great evolution interest since the way of sex determination may significantly affect the mechanisms of polyploidization. A new data on the mechanisms of sex determination in different sturgeon species were obtained by induced meiotic gynogenesis and dispermic androgenesis. Males and females were observed in meiotic gynogenetic progenies of Acipenser baerii and A. transmontanus, thus female heterogametic sex determination system should be concluded for both of them. On contrary, the gynogenetic A. stellatus progeny was all-males. Three hypotheses should be presented to explain this result: 1) A. stellatus is characterized by female heterogamety, but WW homozygotes are lethal and ZW heterozygotes (females) do not appear through the absence of sex chromosome crossing-over; 2) the stellate sturgeon is characterized by ZO female heterogametic sex determination system; 3) the sex determination system of stellate sturgeon is more complicated and connected with the balance of sex chromosomes and autosomes. However, the presence of female in dispermic androgenetic progeny of A. baerii presumes male heterogamety in this fish. Thus it is possible to believe both female and male heterogamety for this species. The interpretation of the data on sex ratio in meiotic gynogenetic A. transmontanus presented by Van Eenennaam et al. (2002) looks unconvincing. And it should be stressed that the analysis of sex ratio in gynogenetic progenies of sturgeons with tetraploid origin must significantly differ from the analysis of species with diploid origin because the analysis of tetraploid species should take into consideration the tetrasomic state of sex determination loci. Aforementioned tetrasomy and an opportunity of both female and male heterogamety significantly complicate the analysis of genetic principles of sex determination in sturgeons.