Main purpose of this work is the identification of females of artificial sturgeon hybrids capable to produce unreduced oocytes. The importance of this task is due to the ability to receive clonal all‐female lines. Experiments were performed on the previously obtained reciprocal hybrids of sterlet, Acipenser ruthenus (S) with ~120 chromosomes and kaluga, Acipenser dauricus (K) with ~260 chromosomes. Karyotypes of backcross hybrids of (S × K) female (obtained by crossing sterlet female with kaluga male) and sterlet male included 180 – 190 chromosomes. This means that (S × K) female produced eggs with ~125 chromosomes and its karyotype consisted of ~250 chromosomes. This number was confirmed by a comparative analysis of erythrocyte size in this female and species with different ploidy. Karyotype with ~250 chromosomes can occur in (S x K) female only as a result of fertilization of a diploid sterlet egg (120 chromosomes) with kaluga haploid sperm (~130 chromosomes). Eggs of hybrid fertile (S × K) female, inseminated with inactivated sperm of Amur sturgeon and sterlet, developed into viable gynogenetic offspring, confirmed by the analysis of five microsatellite loci in this progeny, (S x K) female, and males used for UV‐inactivated sperm. These data allow us to propose a method for obtaining fertile females of sturgeon hybrids from species with different ploidy. For this, experimentally obtained diploidized eggs from diploid 120‐chromosome species must be fertilized by 250–270‐chromosome male. Karyotypes of backcross hybrids of (K × S) female (obtained by crossing kaluga female with sterlet male) and sterlet male included ~250 chromosomes and hybrids of this female with kaluga male had ~320 chromosomes. These results proved an ability of hybrid (K × S) female to produce unreduced eggs, resulting in triploid backcrosses. The absence of reduction during egg development is well known in clonal forms (species) of vertebrates, which are of hybrid origin, and in artificially created fish hybrids. However, this has not been reported previously for sturgeons. Insemination of eggs of (K × S) female with UV‐inactivated sperm of sterlet and Amur sturgeon led to offspring generation for which the genetic identity to their mother was proved using microsatellite analysis. That is, clonal inheritance was observed. These results suggest the possibility of developing a technology to produce all‐female offspring. Artificial production of clonal lines in hybrid vertebrates can be also considered as experimental reproduction of the first stages of reticular speciation in nature.
Biological and production indices are presented for spawning females of triple hybrid between russian sturgeon, siberian sturgeon and amur sturgeon (RS × SS) × AS and other commercial forms of sturgeon grown in cages of the warm-water fish farm in Luchegorsk, Far East of Russia. In conditions of warm-water pools, survival rate of the triple hybrid larvae and juveniles was higher than that of amur sturgeon and russian-siberian hybrid sturgeon. Weight of the triple hybrid specimens at the age of 3 and 4 years was 1.58 kg and 2.36 kg, respectively, that was higher than that of the russian-siberian hybrid sturgeon and close to the values for amur sturgeon. Fish harvest reached 94 kg/m2 of cage, or 134 kg/m2 of cage in sum with the realized fish. Up to 93 % of females matured after using of hormonal stimulation. The first female of the triple hybrid sturgeon matured at the age of 9 years, with its body weight of 13.1 kg. Other females became matured in different age, up to 16 years, but ¾ of them were matured at the age of 10–12 years. The maximum registered weight of the triple hybrid female was 29 kg (age 14 years). Inter-spawning intervals for 97 % of females were 1–2 years. Average annual yield of hard roe obtained from one female at the age of 9–16 years was 2.28 kg, average weight of one egg was 17.6 mg, average fecundity was 132 . 103 eggs/female or 7.4 . 103 eggs/kg, average oosomatic index was 12.8 %. These values of production indices for the triple hybrid females are mainly intermediate between the indices of initial species. In 3–4 spawning seasons, the yield of 5.25 kg of hard roe, on average, was harvested from one female of the triple hybrid, or 30 % of its body weight. The yield from the most productive females was 10.8–11.0 kg of roe, or 55–73 % of their body weight. These values are lower than the yeild from amur sturgeon but similar to the yield value for russian-siberian hybrid sturgeon. Caviar manufactured from the roe of triple hybrid sturgeon is distinguished by high quality. Its females are technologically advanced for the eggs harvesting and have a good survival, about 98 % during long-term exploitation. So, the triple hybrid of russian, siberian and amur sturgeon can be recommended for commercial cultivation in warm-water sturgeon farms with intensive harvesting.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.