ИСТИНА

The clonal inheritance of natural clonal vertebrate species, which are represented only by females, is based on two mechanisms: 1) premeiotic endoreduplication of chromosomes resulting in the production of unreduced eggs, genetically identical to mothers, and 2) blocking of spermatozoa that only stimulate egg development. Besides, artificial interspecific hybrids which are capable to produce unreduced eggs are known in different fish taxa, but were not still found among hybrid sturgeons. These facts stimulated our attempts to obtain clonal progenies in hybrid sturgeons. For experimental crosses we used hybrids between kaluga Acipenser dauricus (2n~260) (K) and sterlet A. ruthenus (2n=120) (S) produced earlier; only a few of these hybrid females were fertile. We conducted two types of back-crosses (KxS x K and KxS x S), and two crosses performed by using UV-inactivated sperm from Amur sturgeon, A. schrenckii or sterlet. To study genomes of parental specimens and their progenies karyological and microsatellite analyses were used. All the progenies from back-crosses were triploids: in crosses (KxS)xK they had ~320 chromosomes, in (KxS)xS ~250 chromosomes. These numbers prove the production of unreduced eggs by KxS females. That is why the insemination of these eggs by UV-inactivated sperm resulted in a few normal progenies without any signs of haploid syndrome. Fourteen of them are successfully growing till now and they reached 253-420 mm TL in May. The analysis of five microsatellite loci demonstrated them to be genetically identical to their mothers, that is clonal inheritance is observed. Conclusions. 1. Clonal progeny was firstly obtained in sturgeons. 2. The developed cloning technology is also a technology for obtaining all-female progenies, since clones from females should be all-female. 3. Artificial production of clonal lines from hybrid vertebrates can be considered as experimental reproduction of the first stages of reticular speciation in nature.