Induction of Spermiation in Sterlet Acipenser ruthenus by PLGA Microparticle Delivery with Sustained Alarelin Release

Carp pituitary treatment versus poly (lactiac-co-glycolic acid) microparticles with slow release of Alarelin at 35 µg kg−1 or 200 µg kg−1 body weight to induce spermiation was compared in sterlet Acipenser ruthenus. All hormone treatments initially increased testosterone and 11-ketotestosterone, with a subsequent decline in testosterone but consistent high levels of 11-ketotestosterone at 48 and 72 h post-treatment. Spermiation did not differ between hormone-treated groups, and was not detected in controls receiving saline solution. Administration of the carp pituitary led to maximum sperm production 24 h post-treatment, followed by a decrease at 48 h post-treatment, with no sperm obtained at 72 h. The effect of Alarelin at 35 µg kg−1 bw and carp pituitary did not differ at 24 and 48 h post-treatment, whereas 200 µg kg−1 bw Alarelin was associated with significantly lower spermatozoon concentration 24 h post-treatment compared to carp pituitary, with no difference in milt volume. Higher relative sperm production was observed 48 h after injection of Alarelin at 200 µg kg−1 bw compared to carp pituitary. Spermatozoon motility was significantly higher in fish receiving Alarelin at 35 µg kg−1 bw than 200 µg kg−1 bw. The treatment with optimal effect on inducing spermiation was poly (lactic-co-glycolic acid) microparticles with slow release of Alarelin at 35 µg kg−1 bw.

Comparison of Metabolic Rates of Young of the Year Beluga (Huso huso), Sterlet (Acipenser ruthenus) and Bester Hybrid Reared in a Recirculating Aquaculture System

In the present study, oxygen consumption of two sturgeon species, beluga (Huso huso), sterlet (Acipenser ruthenus), and their hybrid reared in a recirculating aquaculture system were compared over body intervals from 54–107 g to determine the interspecific variation of metabolic rate. Metabolic rates were measured using the intermittent-flow respirometry technique. Standard oxygen consumption rates (SMR, mg O2 h−1) of sterlet were 30% higher compared with beluga and 22% higher compared with bester hybrid. The routine metabolic rate (RMR, mg O2 h−1) averaged 1.58 ± 0.13 times the SMR for A. ruthenus, 1.59 ± 0.3 for H. huso, and 1.42 ± 0.15 for the hybrid bester. However, the study revealed no significant differences (p > 0.05) between mean values of SMR and RMR for beluga and bester hybrid. The scaling coefficient reflected a closed isometry for the hybrid (b = 0.97), while for the purebred species the coefficient of 0.8 suggests a reduction in oxygen consumption with increasing body mass. These findings may contribute to understanding the differences in growth performances and oxygen requirements of the studied species reared in intensive aquaculture system.

Influence of Environmental Temperature and Hormonal Stimulation on the In Vitro Sperm Maturation in Sterlet Acipenser ruthenus in Advance of the Spawning Season

Sturgeon sperm maturation occurs outside the testes during the transit of testicular spermatozoa (TS) through the kidneys and the Wolffian ducts. A method of in vitro TS maturation in sterlet Acipenser ruthenus was used to investigate the effects of temperature and hormonal stimulation of spermiation on the ability of TS to complete this process. Spermatozoa motility parameters after in vitro maturation of testicular sperm, concentrations of sex steroid hormones and testis morphology were studied in three groups of sterlet: (1) after overwintering in ponds (OW), (2) adapted to spawning temperature (ST), and (3) adapted to spawning temperature with hormonal induction of spermiation (ST-HI). Blood plasma concentrations of testosterone, 11-ketotestosterone and 17,20β-dihydroxy-pregnenolone increased significantly after hormonal induction of spermiation (group ST-HI). In all groups, TS were not motile. After in vitro sperm maturation, motility was up to 60% only in group ST-HI. The data suggest that the ability of TS to be matured in vitro was not related to the environmental temperature, while hormonal stimulation of spermiation during the spawning season was an absolute requirement for optimal in vitro maturation.

Monitoring of the main parameters of pond water in order to obtain safe products for joint cultivation of sturgeon and carp fish

The article presents the results of studying the hydrochemical regimes of carp ponds in polyculture and for the introduction of sterlet (Acipenser ruthenus) into polyculture. The highest pH values were in pond 2, and in the second half of June and the first half of July exceeded the upper limit of normal (norm 6.5–8.5) by 0.3 and 0.5, respectively. In July, the upper limit of the norm was exceeded in the water of pond 1, by 0.1 and 0.2, respectively. From August, the pH of water increased in both ponds until October and in pond 2 the active reaction of water was higher, compared to pond 1, 5.08.2020, by 18.3 %, 20.08.2020 by 12.3 %, 5.09.2020, by 3.8 %, 20.09.20 and 5.10.20, respectively by 2.5 and 2.4 %. Higher in pond 2, compared with pond 1, was the permanganate oxidation of water in all studied periods, but the largest difference was 5.07.2020 and amounted to 6.9 mg O/l. In the second half of July, permanganate oxidation of water was the lowest, but was at the upper limit of normal, then in August increased sharply and was highest in October – 26.3 mg O/l in the pond 1 and 26.5 mg O/l in the pond 2. Dichromatic oxidation of water of the studied ponds was during the experiment in pond 2 slightly higher than normal and ranged from 50.5 (5.06.2020) to 57.9 (5.07.2020) mg O/l and only 20.07.2020 it was the lowest and was 34.2 mg O/l. In pond 1, the dichromate oxidation of water at the beginning of the experiment was 52 mg O/l, gradually decreased and 20.06.2020, was 46 mg O/l, in July, the chemical oxygen demand (COD) increased sharply to 63.6 and also decreased sharply up to 40.5 mg O/l. From 05.08.2020, COD rose by 27.8 % above normal, remained at approximately the same level during September and decreased to 62 mg O/l in early October. The content of free ammonia in the water during the whole period of fish farming exceeded the norm from 2.6 to 5 times, and the highest, except for 20.06.2020, it was in pond 2. The highest difference in ammonia content in the water of the studied ponds was 5.07.2020 and 5.10.2020, and was, respectively, 0.1 and 0.08 mg N/l. The content of ammonium nitrogen and mineral phosphorus in the water of the studied ponds exceeded the norm, and the nitrogen content of nitrates and nitrites was within the norm. In pond water, the concentration of Ca2+, Mg2+, Na+, CO32-, HCO3-, SO42-, Cl-did not exceed the norm. was 5.07.2020, and was 1.20 mg/dm³, which is higher than the norm by 20 %. The total hardness and mineralization of water in the studied ponds did not exceed the norm.

Formation of broodstocks and commercial productive stocks of sterlet (Acipenser ruthenus Linnaeus, 1758), beluga (Huso huso Linnaeus, 1758) and bester (Huso huso × Acipenser ruthenus) in Azerbaijan

The results of formation of broodstocks and commercial productive stocks of sterlet (Acipenser ruthenus Linnaeus, 1758), beluga (Huso huso Linnaeus, 1758) and bester (Huso huso × Acipenser ruthenus) on the Samukh commercial farm in Republic of Azerbaijan are presented. In 2019, for the first time in the history of fishbreeding in Azerbaijan, a progeny was received from grown “from eggs” sterlet females at age of 4 years at the Samukh fish farm using RAS. The mature eggs were stripped using minimally invasive microsurgery method by S.B. Podushka. After the egg collection sterlet females were transferred into holding basins for rehabilitation, further growing and second maturation. The total number of sterlet larvae from domestic broodstock exceeded 100 thousand. An ovulated beluga eggs were received from grown in aquaculture females at the age of 15 in December 2020. In result of fertilization of beluga eggs by sterlet sperm, hybrid (♀ Huso huso × ♂ Acipenser ruthenus) progeny was obtained and successfully grown on the farm. In future the domestic bester broodstock would be formed. The received data demonstrated that functional development of fingerlings and juveniles of sterlet “from eggs” sterlet farm took place without noticeable deviations from physiological normal physiological indices. The number of red blood cells per unit volume of blood increased in ontogenesis. On the contrary the number of white blood cells had seasonal variability and did not directly depend on the age of young sterlet.

Estimation the influence of vitamin-mineral complex on reproductive characteristics of sterlet (Acipenser ruthenus L.)

The article provides data on the use of a complex preparation, which includes sodium selenite and tocopherol (vitamin E) in the form of injections for sterlet breeders (Acipenser ruthenus Linnaeus, 1758). Obtained data confirm the ability of E-selenium to regulate metabolic processes towards the formation of reproductive tissue by optimizing them. Positive dynamics is manifested during the gametogenesis, in particular, the number of individuals with reproductive cells at the IV stage of maturity is increased.