ИСТИНА

The problem of functional diploidization of genomes in polyploid vertebrates is of great interest foremost in connection with the rate of general, chromosomal, and molecular evolution. Of particular interest are sturgeons, which have undergone several acts of polyploidization, and generally demonstrate extremely slow evolution. To evaluate this problem we conducted series of experimental crosses by using normal or inactivated sperm; to study genomes of parental specimens and their progenies karyological and microsatellite analyses were performed. Fertile hybrid female was obtained from sturgeons with different ploidy: female of sterlet Acipenser ruthenus (2n=120) (S) x male of kaluga A. dauricus (2n~260) (K). Microsatellite and cytometric analyses revealed that the genome of this SxK female originated from the fertilization of the spontaneously diploidized egg from sterlet by haploid sperm from kaluga. Thus, its genome does not contain the sum of haploid sets from sterlet and kaluga (190 chromosomes), as might be expected, but includes a diploid genome of sterlet and a haploid (evolutionary diploid) set of kaluga. Back-cross hybrids (SxK)xS had ~185 chromosomes, that is, hybrid female produced eggs with ~125 chromosomes. In this regard, it can be assumed that in meiosis 120 chromosomes from sterlet grouped in 60 bivalents, and 130 chromosomes from kaluga - 65 bivalents. This pattern of meiosis is confirmed by the microsatellite analysis. The offspring of SxK female obtained after insemination of its eggs by inactivated sperm was viable and had ~ 125 chromosomes. Therefore, we put an experiment to test the possibility of obtaining offspring from unfertilized eggs of kaluga. As a result, a small number of viable larvae were obtained. Thus, a haploid, but evolutionary diploid set of chromosomes of kaluga can exhibit the properties of a normal diploid set. This is additional evidence that cytogenetic and molecular evolution of sturgeon is a very slow process.