Flow cytometry for assessing the efficacy of interspecific gynogenesis induction in sturgeon.

The efficacy of ploidy analysis for separating progeny of Siberian sturgeon Acipenser baerii after induced gynogenesis was demonstrated using sperm of a paternal species differing in ploidy level from the maternal species. Gynogenesis was induced in tetraploid A. baerii with UV-C irradiated sperm from the diploid sterlet Acipenser ruthenus and vice-versa. The success of sperm UV irradiation and diploidy restoration by heat-shock was estimated based on the ploidy level of progeny, confirmed by microsatellite parentage assignment. Hatching rates of interspecific gynogenotes were comparable with rates reported for gynogenesis induction using sperm and eggs of the same species. Juvenile mortality was similar to that observed in the control hybrids. The efficiency and reliability of this method may foster its use for production of gynogenotes in aquaculture, potentially allowing interspecific gynogenesis to replace intraspecific.

Technical note: Production of tetraploid sturgeons.

Studies and practical application of androgenesis and gynogenesis in sturgeon are significantly hindered by strong influence of ploidy restoration treatment on survivability of progeny; therefore, developed method of production of tetraploid broodstock and, consequently, use of their diploid gametes might help to avoid ploidy restoration treatment. In the present study, for the first time was developed a protocol for tetraploidy induction in 2 model sturgeon species, sterlet () and Siberian sturgeon (). A high efficiency of treatment was achieved by optimization of heat shock using a temperature of 37°C for 2 min timed between the end of female pronuclei formation and the beginning of pronuclei migration, that is, 0.8 to 1.0 τ (duration of 1 mitotic cycle during the period of synchronous cleavage division). Fertilized eggs developed in tetraploid larvae, up to 31 (89.6% in control) and 34% (70.9% in control) in sterlet and Siberian sturgeon, respectively. Most of the tetraploid larvae exhibited body malformations; as a result, consequent large scale study revealed high larval mortality, which drastically decreased after 2 mo of age. Consequent comparison of BW, length, and malformation rate and mortality between diploid and tetraploid progeny of sterlet did not reveal significant differences in fitness of diploid and tetraploid juveniles at 9 and 11 mo of age. The present study can be considered the first step towards improving the androgenesis methods of conservation of endangered sturgeons as well as understanding the sturgeon sex determination system through induction of mitotic gynogenesis.

Genetic analysis of four European huchen (Hucho hucho Linnaeus, 1758) broodstocks from Poland, Germany, Slovakia, and Ukraine: implication for conservation.

Four broodstocks of European huchen (Hucho hucho) from: Poland, Germany, Slovakia, and Ukraine were investigated using ten microsatellite DNA loci. Microsatellite DNA analysis was successfully applied for the first time in the Polish broodstock of this fish species. The genetic variation and genetic distance between these broodstocks were evaluated. In addition, we examined the potential effects of a genetic bottleneck on the genetic variation of the broodstocks. The European huchen broodstocks exhibited moderate genetic diversity (PIC = 0.405-0.496 and I = 0.831-1.047) with the exception of German broodstock which presented higher genetic diversity (PIC = 0.590 and I = 1.254). Observed (Ho) and expected (He) heterozygosity across the investigated loci in all broodstocks ranged from 0.434 to 0.686 and from 0.452 to 0.650, respectively. Overall, the studied broodstocks were in Hardy-Weinberg equilibrium (HWE); however, from 8 to 42% of the loci deviated from HWE in each stock. The Garza-Williamson index (M = 0.146-0.279) and values of the heterozygosity excess revealed a reduction of genetic variation in all studied broodstocks because of the founder or bottleneck effect. The analysis of genetic differentiation (Fst) and Nei's genetic distance between pairs of broodstocks revealed that Polish and Ukrainian broodstocks of European huchen were characterized by the closest genetic distance. In contrast, the highest genetic divergence parameters (Fst and Nei's distance) were observed among German, Slovak, and Ukrainian broodstocks.