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This article presents data on the polymorphism of intermicrosatellite sequences in the sterlet Acipenser ruthenus of the lower reaches of the Irtysh River and the middle reaches of the Ob River. We have assessed the intra- and interpopulation variability and genetic differentiation of A. ruthenus and revealed a high ISSR polymorphism in the species from the central part of the Ob-Irtysh basin. The proportion of polymorphic amplicons is 0.966, genetic diversity is 0.355, and the average number of alleles per locus is 1.97. The highest polymorphism is typical for the sterlet from the Tobol River at the confluence with the Irtysh River. The genetic differentiation between the sterlet groups of the Irtysh and Ob rivers is well pronounced, the interpopulation component accounts for 42% of variability (Gst = 0.42), and the gene flow is limited (Nm = 0.67). The sterlet groups inhabiting the Lower Irtysh from the mouth of the Tobol River to the mouth of the Konda River do not differ genetically and form one population (Gst = 0.08–0.12, Nm = 3.76–5.55). The sterlet from the Irtysh River within the Vagay region is genetically different from the other Irtysh samples (Gst = 0.22, Nm = 1.68) and belongs to a different population group. The differentiation between samples of sterlet from the Ob basin is higher than between samples from the Irtysh basin. Groups of sterlet from the Ob River and the Yuganskaya Ob canal are genetically different (Gst = 0.30, Nm = 1.19) and form various subpopulations. Spawning migrations, as well as confinement to wintering pits, play a decisive role in the formation of the sterlet population structure in the studied part of the distribution area. The sterlet population groups that are identified should be considered separate units of environmental and economic management. [ABSTRACT FROM AUTHOR]

The sterlet (Acipenser ruthenus) is the smallest-bodied endangered species among the six native sturgeon species of the Danube River, and self-sustaining populations still inhabit the Hungarian section of the Danube River and its largest tributary, the Tisza River. Their populations are drastically decreasing; however, they still have natural reproduction in these habitats. For the genetic conservation of the species, an ex situ gene bank is maintained in Hungary. The present study aimed to analyze the genetic resources of a gene bank with a near 40-year history and to compare it with natural populations and farmed stocks. Twelve microsatellites were used for population genetics analyses and individual genotyping of 268 specimens from two natural habitats (Danube and Tisza Rivers) and three captive stocks (a gene bank broodstock and two farms). Microsatellites revealed similar patterns among wild populations and gene bank stocks and did not show genetic differentiation (FST: 0.016–0.017) among them. These results confirmed that the gene bank broodstock properly represents the genetic background of the Danube and Tisza populations and is suitable as a source of breeding materials for the restocking programs. Negative trends were detected in the farmed stocks, reflected in reduced polymorphism at a few loci. The results of the principal component analyses indicate the farm stocks' separation from the wild and gene bank stocks. The present genetic characterization study reveals a valuable captive stock of the endangered sterlet populations and provides unique information about the genetic similarities and differences among farms and wild stocks in Hungary. Our results provide information that contributes to preserving the genetic structure and variability in sterlet populations and supports the management of gene bank broodstock—avoiding inbreeding and preserving the unique genetic background of the Carpathian basin. [ABSTRACT FROM AUTHOR]

Microplastics pervade the hydrosphere and inevitably come into contact with aquatic organisms. The study reports quantitative data on absorption and excretion of polystyrene microspheres 2 and 10 µm in diameter by zooplankton and fish larvae on the example of Artemia salina L. and Acipenser rithenus L. At the initial concentration of 500 µg/L, A. salina accumulated 2 and 10 µm particles in amounts up to 0.103 and 0.151 ng/individual, respectively, at a similar rate. The mass content of large-sized particles in A. salina was significantly higher (p < 0.01) compared to small-sized particles throughout the experiment. Artemia salina and A. rithenus larvae did not accumulate microplastics in the gastrointestinal tract over a period of 96 and 72 h, respectively. Consumption of microplastics by A. ruthenus larvae with A. salina through the food chain was slower and less pronounced in mass than their direct absorption from water. The rates of absorption of 2 and 10 μm particles by fish attained 0.9 and 8.22 ng/individual/h from water, and 0.06 and 0.23 ng/individual/h with food, respectively. In the models of water pollution and food chain transfer, A. ruthenus larvae consumed more 10 µm particles in mass compared to 2 µm particles (p < 0.05) and at a higher rate. For 2 µm particles, the excretion time for 50% of particles from the gastrointestinal tract of fish (T50) was 32–33 h, whereas for 10 µm particles, the excretion of particles consumed with food was slower (T50=45 h) compared to that of particles absorbed directly from water (T50=25 h). The data obtained can be used to simulate transport and circulation of microplastics of different sizes in the environment.

The paper presents the results of the sterlet sturgeon Acipenser ruthenus reintroduction into the Kama Reservoir (Perm Krai, Russia) by sterlet fry from hatcheries into the reservoir since 2001. The effectiveness of hatchery releases was evaluated by monitoring gillnet sampling 2014–2020. The results showed that the species was reported throughout entire Kama Reservoir, which contrasts with 1988–1994 data, when the species was registered only at the upper part of the reservoir near the Kama River mouth. The highest number and biomass values of catch per unit effort (CPUE) of the sterlet were found in submerged river channels – the deepest habitats with flow conditions which are close to the ecological requirements of the species. The distribution of the sterlet within the channel biotopes of the reservoir is defined by reduced variability. The biggest individuals and the widest size range of the sterlet were typical for the upper area of the reservoir and Chusovskoy Bay, which have the greatest flow. The smallest sizes were typical for fish from catches near the dam of the reservoir, which is consistent with the published data on the distribution of sterlet in reservoir conditions. The presented results may indicate the artificial formation of the sterlet stock in the Kama Reservoir maintained by hatchery releases. The revealed distribution of the sterlet in the reservoir determines the direction of further research on natural reproduction and thus formation of an artificially formed population. Also, future studies are required to assess the possibility of hybridization of the sterlet of artificial origin with natural populations of the species, since the low genetic diversity of the sterlet released into the Kama Reservoir which can lead to irreversible loss of genetic individuality of the natural stocks of the species in the catchment of upper course of the Kama River.

The paper presents the results of the sterlet sturgeon Acipenser ruthenus reintroduction into the Kama Reservoir (Perm Krai, Russia) by sterlet fry from hatcheries into the reservoir since 2001. The effectiveness of hatchery releases was evaluated by monitoring gillnet sampling 2014-2020. The results showed that the species was reported throughout entire Kama Reservoir, which contrasts with 1988-1994 data, when the species was registered only at the upper part of the reservoir near the Kama River mouth. The highest number and biomass values of catch per unit effort (CPUE) of the sterlet were found in submerged river channels - the deepest habitats with flow conditions which are close to the ecological requirements of the species. The distribution of the sterlet within the channel biotopes of the reservoir is defined by reduced variability. The biggest individuals and the widest size range of the sterlet were typical for the upper area of the reservoir and Chusovskoy Bay, which have the greatest flow. The smallest sizes were typical for fish from catches near the dam of the reservoir, which is consistent with the published data on the distribution of sterlet in reservoir conditions. The presented results may indicate the artificial formation of the sterlet stock in the Kama Reservoir maintained by hatchery releases. The revealed distribution of the sterlet in the reservoir determines the direction of further research on natural reproduction and thus formation of an artificially formed population. Also, future studies are required to assess the possibility of hybridization of the sterlet of artificial origin with natural populations of the species, since the low genetic diversity of the sterlet released into the Kama Reservoir which can lead to irreversible loss of genetic individuality of the natural stocks of the species in the catchment of upper course of the Kama River. [ABSTRACT FROM AUTHOR]

The Caspian Sea has faced many environmental challenges, such as oil pollution. Heat shock proteins (HSPs) play a critical role in stress conditions and physiological changes caused by disease or injury. By evaluating the effects of various HSP inducers (HSPi), including Pro-Tex® (NOP: 800 mM), amygdalin (AMG: 80 mM), and a novel synthetic compound derived from pirano piranazole (SZ: 80 µm) on isolated cells from Sterlet Sturgeon (Acipenser ruthenus) treated with 75% IC50 PAH-benzo[a]pyrene (BaP; B75). This study examines whether there is a correlation between exposure to the BaP pollutant and HSPs in fish. In vitro, after culturing cells from the liver, kidney, and gills, they were treated with HSPi compounds in the presence and absence of BaP. Western blotting was used to assess HSP27, HSP70, and HSP90 expression patterns. A variety of enzyme activities were measured before (without treatment) and after treatment with HSPis and HSPi + B75, including cytochrome P450 (CYP450) activity, specific enzyme activity for acetylcholinesterase (AChE), antioxidant capacity, liver indicator enzymes, cortisol levels, and immunity parameters. When compared to the control group, cells treated with B75 showed the lowest AChE enzyme activity (p < 0.0001). CYP450 activity was highest in group B75, while HSPi caused the opposite effect (p < 0.0001). HSPi + B75 increased HSP levels and antioxidant parameters while decreasing cortisol and liver indicator enzymes (p < 0.0001). HSPi may be a powerful and reliable method for enhancing the resistance of A. ruthenus to BaP stresses before exposure. Treating cells with HSP-inducing compounds, such as NOP, AMG, and SZ, can assist them in managing stress and increase HSP (27, 70, and 90) protein expression. Furthermore, the study findings suggest that HSPis can also mitigate the adverse effects of stress, ultimately increasing cell survival and resistance. [ABSTRACT FROM AUTHOR]

The sterlet (Acipenser ruthenus) is the smallest-bodied endangered species among the six native sturgeon species of the Danube River, and self-sustaining populations still inhabit the Hungarian section of the Danube River and its largest tributary, the Tisza River. Their populations are drastically decreasing; however, they still have natural reproduction in these habitats. For the genetic conservation of the species, an ex situ gene bank is maintained in Hungary. The present study aimed to analyze the genetic resources of a gene bank with a near 40-year history and to compare it with natural populations and farmed stocks. Twelve microsatellites were used for population genetics analyses and individual genotyping of 268 specimens from two natural habitats (Danube and Tisza Rivers) and three captive stocks (a gene bank broodstock and two farms). Microsatellites revealed similar patterns among wild populations and gene bank stocks and did not show genetic differentiation (FST: 0.016–0.017) among them. These results confirmed that the gene bank broodstock properly represents the genetic background of the Danube and Tisza populations and is suitable as a source of breeding materials for the restocking programs. Negative trends were detected in the farmed stocks, reflected in reduced polymorphism at a few loci. The results of the principal component analyses indicate the farm stocks’ separation from the wild and gene bank stocks. The present genetic characterization study reveals a valuable captive stock of the endangered sterlet populations and provides unique information about the genetic similarities and differences among farms and wild stocks in Hungary. Our results provide information that contributes to preserving the genetic structure and variability in sterlet populations and supports the management of gene bank broodstock—avoiding inbreeding and preserving the unique genetic background of the Carpathian basin.

The Acipenser ruthenus (Linnaeus, 1758), albino variety, in the second summer rearing to Brates sturgeons station from Galati was experimented. A number of 513 one year old sterlet were stocked in three Ewos fibreglass tanks, at an individual mean weight of 40 g and total length of 20 cm, in the first day of June 2007. The experiment had extended on 165 days, until half of November. During experimental tries the fishes were monitoring permanently and the essential parameters of technological water (dissolved oxygen, pH and temperature evolution) were checked and recorded. Feeding was achieved with commercial granular food and the conversion coefficient recorded was 1,3. Final body mean weight of sterlet was 130 g/ex. and the average length of 30 cm; the specific growth rate was 0,55g/day., i.e. 90 g/ex, and the survival percent recorded was 89,08 %.

Functional diploid Acipenser ruthenus, functional tetraploid Acipenser gueldenstaedtii and functional hexaploid Acipenser brevirostrum juveniles were sampled monthly for one year, and the white blood cell indicators were determined. The total number of leukocytes (TL) was 40.93 ± 17.24 × 109/l for the diploids, 20.63 ± 11.20 × 109/l for the tetraploids, 14.13 ± 7.72 × 109/l for the hexaploids. The TL decreased with an increasing ploidy level. The highest number of leukocytes was reached during September and October for A. ruthenus and A. brevirostrum, from October to January for A. gueldenstaedtii (a statistically significant finding). The lymphocytes dominated (76.89-80.14%) in the differential counts and were found to be reduced in June and July in each group. Granulocytes were represented by neutrophils and eosinophils. Counting from all the leukocytes, the neutrophils represented 13.0-18.7% and eosinophils represented 5.7-6.1%. Increasing number of nuclear segments in the granulocytes was dependent on the increasing ploidy level. Nuclear segmentation in the lymphocytes was a common finding in higher ploidy level groups. The data suggest a significant effect of ploidy level on the total number of leukocytes and morphological nuclear changes in the granulocytes and lymphocytes. The seasonal variation in the differential leukocyte counts depends on the species and the influence of various external conditions rather than the ploidy level.

The aquaculture of the sturgeons from the Danube River basin is a niche approached by more and more Romanian entrepreneurs. The sterlet (Acipenser ruthenus) is a fresh water sturgeon with some useful characteristics that recommend this species to become a good candidate for intensive aquaculture in RAS. The monitoring of the growth dynamic of the sterlet or any other fish species reared in controlled conditions is very important for the fish farm management, especially for setting and adjustment of the technological parameters that directly influence the growth performances. The aim of this study is to evaluate the correlations and functional dependencies between some morphological traits, like total and standard length, maximum body depth and body weight in sterlet fingerlings reared exclusively into recirculating aquaculture system (RAS). Our results clearly demonstrated that any of the four body measurements (total length, standard length and maximum body depth and body weight) could be monitored in sterlet fingerlings, to accurately assess the growth dynamic, the correlations among these being very high (ranging from 0.982296 to 0.999778). Moreover, the dependencies of these traits are very high. Three of measurements could be calculated based on sterlet body weight with our equations.

The study was conducted within the recirculating aquaculture system for sturgeon rearing in Herneacova village, Timis County, on a population of juvenile sterlet (Acipenser ruthenus) aged between 346-431 days. Specimens were housed in five round tanks (Ø=3 m, V=6 m3, h=100 cm) and fed with commercial extruded pellets (3 mm granulation, 48% CP, and 10% EE). Fish from each tank were individually weighed and measured once every two weeks. Bioproductive indices such body weight gain (BW), specific growth rate (SGR), and feed conversion ratio (FCR) were calculated at the end of an 85 days experimental period. Statistical analysis was performed using the SPPS IBM 22 and Minitab 16 software. Data were reported as Mean±Sx at a significant level of p

Our research was performed on juvenile sterlets (Acipenser ruthenus), aged between 346-431 days, maintained in five round pools (Ø=3 m, V=6 m3, h-100 cm) and fed with a commercial extruded pellet (3 mm granulation, 48% CP, and 10% EE). Body weight and total body length on 30 individuals from each tank were determined every two weeks. Weighing and somatic measurements achieved at the end of experimental period (standard length-l, body weight-G, maximum body high–H, maximum body perimeter (Pmax), head length–lh,, caudal peduncle length-lp) allowed us to calculate the following body indices: profile index, thickness index, Fulton index, Kiselev index, meat index. Statistical analysis was performed by using the SPSS IBM 22 and Minitab 16 software. Data were reported as Mean±Sx at a significant level of p

Sturgeon populations are declining worldwide and are the target of extensive conservation efforts. Addressed in several pieces of legislation, sturgeons have received considerable attention as flagship or umbrella species. Despite the need for a better understanding of the distribution and population status, the use of traditional sampling methods failed in the past, thereby hampering reliable assessments, a prerequisite for conservation. Here, we describe the development and application of an environmental DNA (eDNA) metabarcoding approach for detecting rare sturgeons in large rivers. Exemplarily, we developed a reference database for five native Danube sturgeons (Acipenser stellatus, Acipenser gueldenstaedtii, Acipenser ruthenus, Acipenser nudiventris, and Huso huso) and two non-native species (Acipenser baerii and Acipenser transmontanus), assessed these ex situ, and used eDNA as a detection tool along the entire length of the Danube (Europe, ~ 2850 km) and major tributaries. In ex situ analyses, all assays yielded positive amplifications for the assessed sturgeon species. In the Danube, the presence of A. ruthenus was confirmed at 14 of 29 sites (48.3%), and in 2 of 18 tributary sites (11.1%), providing the first comprehensive large-scale biogeographical snapshot of this species. Relative number of reads assigned to A. ruthenus varied between 0 and 2.5%, with sites registering positive detections being clustered in 3 sections of the Danube. Our findings enabled us to confirm the advantages of eDNA monitoring over traditional sampling methods for comprehensive whole-river snapshot studies of sturgeons conducted on a large geographical scale, and therefore we consider it to be a promising approach for application in conservation measures, fisheries management, scientific studies, and adaptive management plans for sturgeons on a global scale. [ABSTRACT FROM AUTHOR]

Heat shock proteins (HSPs) play a crucial role in antioxidant systems, immune responses, and enzyme activation during stress conditions. Salinity changes can cause stress and energy expenditure in fish, resulting in mortality, especially in fingerlings. The purpose of this study was to examine the relationship between salinity and HSPs in stressed fish by assessing the effects of various HSP inducers (HSPis), including Pro-Tex® (800 mM), amygdalin (80 mM), and a novel synthetic compound derived from pirano piranazole (80 µM), on isolated cells from Sterlet Sturgeon (Acipenser ruthenus) exposed to 13 ‰ salinity (S13). After liver, kidney, and gill cells were cultured, the HSPi compounds were treated in vitro in the presence and absence of salinity. The expression patterns of HSP27, HSP70, and HSP90 were assessed by Western blotting. Biochemical enzymes (aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and lactate dehydrogenase), cortisol levels, and immune parameters (component 3, immunoglobulin M, and lysozyme) were measured before and after treatment with HSPis and HSPi + S13. According to these findings, HSPis positively modulate HSP expression, immune responses, and antioxidant levels. Furthermore, they increased in vitro cell survival by maintaining cortisol levels and biochemical enzyme activities in A. ruthenus under saline conditions (P < 0.0001). In conclusion, HSPis can increase A. ruthenus resistance to salinity stress. However, the results also indicated that these compounds can reverse the adverse effects of salinity. The effectiveness of this approach depends on further research into the effects of these ecological factors on the health status of the species, especially in vivo and in combination with other stresses., Competing Interests: Declarations of interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Sevda Zarei reports financial support was provided by Iran National Science Foundation. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The Siberian sturgeon (Acipenser baerii) is a long-lived and late-maturing fish; its natural populations are considered endangered and listed in the first class of protected animals in Kazakhstan. To date, attempts have been made to increase the number of sturgeons through artificial reproduction in aquaculture and a release of the resultant juveniles into the Ural River, which flows into the Caspian Sea. This species faces an increased risk of Aeromonas infections. Aeromonas hydrophila is the most important sturgeon pathogen in Kazakhstan, but studies on A. hydrophila infection in Kazakhstan are still inconclusive. In the present work, our purpose was to isolate and characterize dominant bacteria in diseased A. baerii. This isolate, tentatively named AB005, was identified as A. hydrophila in an analysis of its morphological, physiological, and biochemical features and 16S ribosomal-RNA and gyrB gene sequences. A pathogenicity test was carried out for the isolate on healthy Oreochromis niloticus and Acipenser ruthenus via intraperitoneal injection along the caudal peduncle of the fish. Half-lethal doses (LD50) of isolate AB005 for O. niloticus and A. ruthenus were determined: 8.37 × 105 and 2.89 × 106 colony-forming units per milliliter, respectively. Virulence gene profiling revealed the presence of seven virulence genes related to pathogenicity (acyltransferase, phospholipase A, serine protease, heat-stable cytotonic enterotoxin, nuclease, and aerolysins A and B) in this A. hydrophila isolate. Drug sensitivity testing showed that the isolate is sensitive to quinolones, aminoglycosides, nitrofurans, amphenicols, and tetracyclines. The present findings will lay the foundation for future research on this pathogen in Siberian-sturgeon aquaculture.

The oocyte is a unique cell, from which develops a complex organism comprising of germ layers, tissues and organs. In some vertebrate species it is known that the asymmetrical localization of biomolecules within the oocyte is what drives the spatial differentiation of the daughter cells required for embryogenesis. This asymmetry is first established to produce an animal-vegetal (A-V) axis which reflects the future specification of the ectoderm, mesoderm, and endoderm layers. Several pathways for localization of vegetal maternal transcripts have already been described using a few animal models. However, there is limited information about transcripts that are localized to the animal pole, even though there is accumulating evidence indicating its active establishment. Here, we performed comparative TOMO-Seq analysis on two holoblastic cleavage models: Xenopus laevis and Acipenser ruthenus oocytes during oogenesis. We found that there were many transcripts that have a temporal preference for the establishment of localization. In both models, we observed vegetal transcript gradients that were established during either the early or late oogenesis stages and transcripts that started their localization during the early stages but became more pronounced during the later stages. We found that some animal gradients were already established during the early stages, however the majority were formed during the later stages of oogenesis. Some of these temporally localized transcripts were conserved between the models, while others were species specific. Additionally, temporal de novo transcription and also degradation of transcripts within the oocyte were observed, pointing to an active remodeling of the maternal RNA pool.

Functional diploid Acipenser ruthenus, functional tetraploid Acipenser gueldenstaedtii and functional hexaploid Acipenser brevirostrum juveniles were sampled monthly for one year, and the white blood cell indicators were determined. The total number of leukocytes (TL) was 40.93 ± 17.24 × 109/l for the diploids, 20.63 ± 11.20 × 109/l for the tetraploids, 14.13 ± 7.72 × 109/l for the hexaploids. The TL decreased with an increasing ploidy level. The highest number of leukocytes was reached during September and October for A. ruthenus and A. brevirostrum, from October to January for A. gueldenstaedtii (a statistically significant finding). The lymphocytes dominated (76.89–80.14%) in the differential counts and were found to be reduced in June and July in each group. Granulocytes were represented by neutrophils and eosinophils. Counting from all the leukocytes, the neutrophils represented 13.0–18.7% and eosinophils represented 5.7–6.1%. Increasing number of nuclear segments in the granulocytes was dependent on the increasing ploidy level. Nuclear segmentation in the lymphocytes was a common finding in higher ploidy level groups. The data suggest a significant effect of ploidy level on the total number of leukocytes and morphological nuclear changes in the granulocytes and lymphocytes. The seasonal variation in the differential leukocyte counts depends on the species and the influence of various external conditions rather than the ploidy level. [ABSTRACT FROM AUTHOR]

Fertilization of freshwater fish occurs in the environment which negatively affects a lifespan of gametes mostly due to the osmotic shock; therefore, male gametes should reach the female gamete, as soon as possible. The existence of mechanisms controlling the encounter of gametes would be highly expedient in this case. By analogy with other species for which guidance was demonstrated, it is likely that this control may be performed by ovarian fluid or substances released by eggs. The aim was to study the effect of ovarian fluid and egg-released substances on spermatozoa behavior in sterlet. It was found that the presence of a particular concentration of ovarian fluid (30% solution in water) had an inhibiting effect on spermatozoa motility initiation. Lower concentrations of the ovarian fluid improved the longevity of spermatozoa and did not affect their trajectories. Test of chemotactic response (using a microcapillary injection of fluids into the suspension of motile spermatozoa) showed no effect of ovarian fluid on spermatozoa behavior, while at the same time, the attracting effect of the egg-conditioned medium was evident (i.e., due to some substances released from the eggs during their contact with freshwater). The results of the fertilization test showed that the presence of ovarian fluid prevented the eggs from losing the fertilizing ability due to the contact with water, as well as promoted the spermatozoa to fertilize the eggs during a longer period of time. Thus, the combined physicochemical action of "female factors" affects sterlet gametes during fertilization and may be involved in the guidance and selection mechanisms. [ABSTRACT FROM AUTHOR]

Diazinon (DZN) is an organophosphate pesticide frequently used in agriculture and released into aquatic environments. In this study, sterlet sturgeon cells were exposed to DZN to investigate possible defense mechanisms via HSP induction (HSPi). Liver, kidney, and gill cells of Acipenser ruthenus were isolated and cultured and then treated with HSPi (Pro-Tex®, amygdalin, and a novel pirano-piranazole-based synthesized compound: SZ) in the presence and absence of DZN. MTT assays were used to evaluate the effects of different HSPis and their combinations with DZN. Western blotting analysis was conducted to evaluate HSP27, HSP70, and HSP90 expression patterns in each group. The highest rates of caspase-3 and caspase-8 activities were found in the DZN group, whereas HSPi treatment resulted in the lowest rates. The combination of HSPi+DZN resulted in increased HSP levels and antioxidant parameters but decreased cortisol, immune parameters, and metabolic enzymes. Many of the studied parameters (caspases, acetylcholinesterase, antioxidant, immune, and metabolic parameters) showed significant correlations with HSP expression, indicating that HSPs may be associated with markers of sterlet cell health. The results of this study demonstrate that using HSP inducers may be a powerful and reliable way to increase A. ruthenus resistance prior to exposure to DZN. [Display omitted] • HSPs play a critical role in antioxidant systems and immune responses. • The cells of sterlet sturgeon were treated with HSP inducers in the presence and absence of diazinon. • A significant increase of the HSPs expression was found after HSPi and diazinon exposure. • The studied parameters indicated significant level of correlation with HSP expression. • HSPi can be an important modulator of the acetylcholinesterase activity, immune response, antioxidant, metabolic, and overall vitality in Acipenser ruthenus against diazinon. [ABSTRACT FROM AUTHOR]

The oocyte of Sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baeri) was evaluated after incubation with 17α, 20β‐Dihydroxyprogesterone (DHP) in artificial media. Concentration of testosterone (T), progesterone (P4) and 17‐β estradiol (E2) in blood and their relation to fertilization rate were measured during experimental period. The oocytes at the same developmental stages were incubated in SIS (based on sturgeon blood ionic composition), RM2 (Ringer solution modified for sturgeons) and L‐15 (Leibovitz medium) artificial mediums in the presence of 1 μg/ml of 17α, 20β‐Dihydroxyprogesterone for 12, 18 and 24 hr. The result of this study demonstrated that fertilization rate decreased with the increasing duration of incubation in all mediums. In the Siberian and Sterlet sturgeon, the highest fertilization rate was observed in the oocytes incubated in RM2 (0.81 ± 0.4) and SIS (0.44 ± 0.8) mediums for 12 hr respectively. In the Siberian sturgeon, fertilization rate decreased significantly (p <.05) with incubation time in all three mediums. In Starlet, fertilization rate decreased significantly (p <.05) with time and reached a minimum after 24 hr (0.16 ± 0.1) in L‐15 medium. No significant (p >.05) differences were observed between blood plasma hormones and fertilization rate. The results of this study indicated that 17α, 20β‐Dihydroxyprogesterone is essential for induction of in vitro oocyte maturation in these species. [ABSTRACT FROM AUTHOR]

Thyroid hormones (THs) play important roles in regulating growth, development and physiological functions in vertebrates. To study the role of short‐term effects of thyroxine (T4) on metabolism and growth in female Sterlet sturgeon, thirty fish with a weight of 707.97 ± 37.15 g were divided into six tanks. Fish were injected intraperitoneal with (a) coconut oil alone (control), (b) 1 mg T4 kg per BW in coconut oil (T1) and (c) 10 mg T4 kg per BW in coconut oil (T10). Blood samples were collected at 0, 4, 7, 14, 28 and 60 days for plasma biochemical analysis, and body length and mass were determined at day 60. Based on results, higher growth was indicated in T10 group. The highest T4 levels were observed on day 4 in the T1 and T10 treatments and gradually declined during the trial. Plasma T3 levels were highest on days 4 and 7 in the T1 and T10 groups, respectively. Plasma triglyceride levels were significantly elevated on day 28 in the T1 group and on day 60 in the T10 group. Plasma glucose concentrations were significantly elevated on days 7 and 14 in T10 group. Overall, the present results suggest that a single injection of T4 can improve growth via changes in the metabolic profile of Sterlet sturgeon. [ABSTRACT FROM AUTHOR]

Bromelain is a proteolytic enzyme extracted from Ananas comosus and has great potential to affect several physiological functions. The current study examined the effect of bromelain added to commercial feed at concentrations of 0 g (control), 10 g (B1) and 20 g (B2) per kg diet on growth, feed utilization, intestinal morphology, digestive enzyme and immune response of juvenile Sterlet (Acipenser ruthenus) for 56 days. At the end of this experiment, the highest final body weight was detected in fish fed diet of B2 compared to control. The protein content of whole fish was higher in fish fed diet of B1 and B2, but the content of calcium, iron, copper and zinc was noted lower in fillets of fish fed diet of B1 and B2. Supplementation with bromelain significantly increased the height of mucosal folds, enterocytes and the supranuclear zone of the epithelial cells compared to control diet. The enzymatic activity of lipase and pepsin was significantly (p < 0.05) higher in fish fed diet of B1 and B2. The highest activity of lysozyme, total protein level and total immunoglobulin and the proliferative activity of T and B cells were detected in fish fed diet of B2 compared to control, where no significant (p > 0.05) difference was found in ceruloplasmin, metabolic activity of spleen macrophages and potential killing activity of spleen phagocytes between different treatments. [ABSTRACT FROM AUTHOR]

The aim of the present study was to develop an in vitro system for functional investigation of ovarian follicular cells in Sterlet, Acipenser ruthenus. Oocytes for the primary culture were obtained from the ovaries of a 6 years old Sterlet 729 g in weight and 47 cm in total length. The oocytes were in advanced vitellogenesis stage (PI >10). A part of the ovary (containing about 300 follicles) was removed, ovarian follicles isolated by manually removing those from the interstitial tissue and washed with sterile phosphate buffered saline (PBS) containing antibiotics and Amphotericin B. Follicular cells were separated by treating oocytes with 0.25% trypsin-EDTA in Ca2+ and Mg^2+ free PBS and cultured in medium L-15 supplemented with 20% FBS, streptomycin sulphate (Gibco, 100 g.ml-1), penicillin G potassium (Gibco, 100 IU.ml^-1) and Amphotericin B (Gibco, 2.5 g.ml^-1) at 22 °C. The concentrations of Testosterone (T), Estradiol-17β (E2), Progesterone (P4) and 17α-hydroxyprogestron (17αOHP) in the medium were measured at days 3, 5 & 7 by the Enzyme-Linked Immunosorbent Assay. According to the results, the ovarian follicular cells of Sterlet proliferated in L-15 medium were steroidogenically active as expressed by the secretion of T, E2, P4 & 17αOHP. Testosterone was the dominant hormone secreted by cultivated follicular cells, which was correlated closely with the end of vitellogenesis in the isolated oocytes. Decrease in production of these hormones was greater at days 3 & 4 in comparison with those at days 5 & 6. By successfully culturing ovarian follicular cells of Sterlet in L-15 culture medium, an in vitro system was developed which enables functional studies to be carried out similar to the in vivo situation in the ovarian follicles.

Sturgeons are valued as specialty black caviar, which is very expensive. Only females are used in the technology of caviar aquaculture. Universal method of sex determination has not yet been developed. Most of known methods are not sufficiently accurate, or used at a relatively late age, or difficult to use. Perfect early determination of sex is considered to be impossible. Because of the dark colour of most sturgeons and important morphological differences, which fish of almost all ages have, were overlooked. We first found that the scute structure of sterlet sturgeon depends on the sex. The found dependencies with the help of machine learning algorithms open a possibility for creation of sex determination equipment using the artificial intelligence. Our results open a perspective for creation of sex determination methods for other 23 sturgeon species, which can increase the efficiency of caviar aquaculture and restoration of sturgeons in natural waters. [ABSTRACT FROM AUTHOR]

A novel gene encoding the mitochondrial manganese superoxide dismutase from sterlet Acipenser ruthenus (Ar-MnSOD) was cloned. The full-length cDNA of MnSOD was of 1040 bp with a 672 bp open reading frame encoding 224 amino acids and the deduced amino acid sequence was located in mitochondria. Sequence comparison analysis showed that Ar-MnSOD was highly similar to MnSODs of invertebrates and vertebrates, especially those of freshwater Cyprinidae fishes and mammals. Phylogenetic analysis revealed that Ar-MnSOD was distant from MnSODs of other fishes and belonged to the family of mitochondrial MnSODs (mMnSOD). Consistently, Ar-MnSOD was located in mitochondria. The 3D structure of Ar-MnSOD was predicted and the overall structure was similar to that of MnSODs of humans and the bay scallop Argopecten irradians. In addition, mRNA of Ar-MnSOD was detected to extensively express in all tissues, with the highest level in brain and liver. Spleen and head kidney inoculation of Aeromonas hydrophila led to a significant up-regulation of Ar-MnSOD transcript levels. Also, hypoxia induced a transient increase in transcription of Ar-MnSOD in the gills, but not in the heart and brain, suggesting metabolic depression in these vital organs. The results also implied the anti-hypoxia properties of Ar-MnSOD in the related tissues and proved that Ar-MnSOD was involved in the stress response and (anti) oxidative processes triggered by hypoxia. The results indicated that Ar-MnSOD is induced upon A. hydrophila infection and hypoxia, consistent with its role in host immune and stress-induced anti-oxidative responses. • Mitochondrial manganese superoxide dismutase from Acipenser ruthenus, a primitive fish species, was cloned and identified • The responses of ArMnSOD to Aeromonas. hydrophila challenge in head kidney and spleen of sterlet were analyzed • The responses of ArMnSOD to hypoxic stress in gills, heart and brain of sterlet were analyzed. [ABSTRACT FROM AUTHOR]

This study investigates the basis of the stimulatory effects of thyroxine (T4) on the growth and physiological changes in Sterlet sturgeon broodstock and their larval offspring. Groups of fish received four injections of 0, 1 or 10 mg kg BW−1 of T4 over a 170-day period. At the end of trial, blood was taken and plasma biochemical parameters, sex steroid and thyroid hormone (THs) levels were measured. Broodstock were induced to ovulate by the injection of LHRHa2 and ovarian fluid (OF) and eggs were obtained through a minimally invasive surgical technique. The eggs were fertilized and resulting larvae were assessed after 14 days of grow out. Weight gain, protein and lipid efficiency and food efficiency of broodstock in T 10 were higher than the other treatments (P < 0.05). The cholesterol, triglyceride, total protein, albumin and glucose levels in OF were higher in the T 10 group than the other groups (P < 0.05). Similarly, calcium, magnesium and phosphorus concentrations in the OF of the T 10 group were higher than the other treatments. Furthermore, plasma cholesterol, triglyceride, HDL, VLDL and calcium levels were significantly enhanced in the T 10 group compared to the other groups, while, plasma phosphorus and magnesium were not significantly affected. Additionally, the T 10 group displayed lowest LDL plasma levels (P < 0.05). The highest and lowest concentrations of testosterone and 17β-estradiol were recorded in T 10 group. Moreover, the highest levels of TH were found in T 10 , while, control group had the lowest TH concentrations. The offspring from the T 10 treatment had the lowest mortality rate at 3 dph. This study highlights that 10 mg T4 kg BW−1 promoted biochemical and metabolic changes in the adult Sterlet broodstock that were associated with enhanced egg fertility and larval survivability. • Knowledge of the effects of Thyroxine (T4) on physiological performance of sturgeon species is scared. • T4 enhanced Sterlet sturgeon growth performance. • High doses of T4 led to the increase in plasma concentrations of thyroid hormones. • T4 administration had great impacts on blood plasma biochemistry. • Fish in the high doses of T4 had significantly greater levels of ovarian fluid Ca2+, P and Mg2+ than the other experimental groups. • The findings could assist to improve the fertilization and survival rate of Sterlet sturgeon. [ABSTRACT FROM AUTHOR]

In this study, a cell line, designated as Acipenser ruthenus testis (ART), was successfully established from testis tissues of the sterlet Acipenser ruthenus and characterized by studying and comparing the expression of specific genes between the cell line and the parent gonad tissues. The results suggested that the developed ART cell line was composed of a mixture of germ cells and somatic cells. Ploidy analysis indicated that the cell line exhibited a high degree of genetic stability and that the cells remained in a good proliferating state after being subcultured to passage 80. [ABSTRACT FROM AUTHOR]

Abstract Sturgeons (Acipenseriformes) are ancient and endangered but valuable commercial aquaculture species. Due to an increasing interest in sturgeon aquaculture and breeding, especially for the production of caviar, a precise sex molecular marker is desired for the early sex identification of sturgeon. Because of the smallest size as well as the shortest sexual maturation period, the sterlet (Acipenser ruthenus) is considered to be an excellent model for studying of gonad differentiation in sturgeons. The present work investigated temporal expression of 13 genes, encoding regulatory factors, steroid receptors and transcription factors, during sex differentiation in sterlet from 6 months post-fertilization (mpf) to 15 mpf. Meanwhile, histological observation and determination of steroids levels of 11-ketotestosterone (11-KT) and 17β-estradiol (E2) in serum were performed to aid in sex identification. The gonad development of sterlet showed obvious asynchrony. Sex differentiation was first observed at 6 mpf, while some fish even retained undifferentiated gonads at 15 mpf. Expression of 13 genes revealed that only foxl2 and cyp19a1 maintained significant sexual dimorphic expression and had higher expression in female from the sex differentiation stage of 6 mpf. The male related genes amh and dmrt1 showed sexual dimorphic expression since spermatogonial proliferation stage, while hsd11b2 and gsdf had significantly higher expression in mid-spermatogenesis stage. The expression of dax1 and dkk1 showed a different pattern in sterlets in comparison to different mammals and other teleost: they increased with ovarian development and showed significantly difference since ovary perinucleolus stage, but maintained low expression at all stages of testes. The other five genes (sf-1 , rspo , ar , era and erb) showed no sexual dimorphic expression pattern during sex differentiation. Serum 11-KT and E2 levels remained were low in all individuals with no sexual dimorphic expression pattern during sex differentiation. Taken together, our results suggest that mRNA levels of foxl2 and cyp19a1 could be used as molecular markers for sterlet sexing as early as the beginning of sex differentiation. Highlights • Sex differentiation was first histologically observed at 6 mpf and gonadal development existed obvious asynchrony in artificial breeding sterlet in Beijing. • Ovary development related genes foxl2 and cyp19a1 kept the obvious sexually dimorphic expression with higher expression in female since the sex differentiation stage. • Male related genes amh and dmrt1 presented sexual dimorphism since spermatogonial proliferation stage, and hsd11b2 and gsdf had significantly higher expression in mid-spermatogenesis stage. • Gene expression pattern of dax1 and dkk1 , different from mammals and other teleost, increased with the development of ovary and showed significantly difference since ovary perinucleolus stage, but maintained low expression in all stages of testes. [ABSTRACT FROM AUTHOR]

This study set out to examine the effects of thyroxine (T4) on reproductive success of female Sterlet sturgeon broodstock and subsequent growth and development of the larval offspring. Fish received four intraperitoneal injections of coconut oil (controls), 1 mg T4/kg body weight (BW) in coconut oil (T 1 ) or 10 mg T4/kg BW in coconut oil (T 10 ) over a 170-day treatment period. Ovulation was induced by intramuscular injection of luteinizing hormone-releasing hormone (LHRHa2). Fish in the control group ovulated quicker and had higher fecundity than the fish in experimental groups. Oocyte diameter was highest in the T 10 group. Hatching rate in the control group was lowest among the groups. Larval survival at 3 days post hatch in T 10 group was 92.2% and was highest among the treatments. Larval survival and the specific growth rate were greater in T 10 than in the other treated groups. The T4 concentrations in unfertilized eggs, pre-larvae and post-larvae were higher in the T 10 group than the others. These results showed the maternal injection of T4 has stimulatory effects on larval hatching rates, survival, and growth which make it a valuable treatment in sturgeon aquaculture. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the effects of temperature on the production performance values, as well as on sex differentiation and gonad development, of juvenile sterlet were investigated. For this purpose, fry were reared in the recirculating aquaculture system at three different temperatures (15, 20, and 25°C) in four replicate groups each for 140 days (10–150 dph). Fish were fed mainly with commercial diet. The growth rate in this period was significantly affected by temperature. The best performance values in terms of daily growth rate, thermal growth coefficient, and yield were registered at 20°C, indicating that this value to be near, or close to, the optimal for juvenile sterlet. Gonad samples were taken for histological analysis which revealed that the increased temperature did not cause significant differences in the sex ratio between treatments, but at 25°C resulted in significant deviation from the theoretically expected 1:1 gender ratio to favouring males. We have also found that increased temperature at 25°C accelerated germ cell development. These results indicate that rearing of sterlet juveniles at about 20°C temperature could be considered optimal both from aquaculture, as well as from species conservation viewpoints. [ABSTRACT FROM AUTHOR]

We report the first case of Acipenser iridovirus European (AcIV-E) infection in starry sturgeon (Acipenser stellatus) and in sterlet (A. ruthenus) reared in Northern Italy. During 2018, mortality began in A. stellatus and A. ruthenus specimens reared in co-habitation with Russian sturgeon positive for AcIV-E. Molecular analyses were done on the gills to amplify a fragment of the major capsid protein (MCP) gene using real-time PCR against AcIV-E. DNA of the positive samples was further sequenced and phylogenetic analyses were performed. The MCP gene sequences were highly similar to a virus previously identified in Italy (nucleotide identities between 99.38% and 99.69%). Phylogenetic analysis confirmed our hypothesis of passage of the virus from the infected Russian sturgeon. The detection of AcIV-E in new species of the Acipenseridae family may impact on sturgeon production, with relevant economic losses.

The aim of this study was to fill important gaps in the evolutionary history of immunoglobulins by examining the structure and diversity of IgL genes in non-teleost ray-finned fish. First, based on the bioinformatic analysis of recent transcriptomic and genomic resources, we experimentally characterized the IgL genes in the chondrostean fish, Acipenser ruthenus (sterlet). We show that this species has three loci encoding IgL kappa-like chains with a translocon-type gene organization and a single VJC cluster, encoding homogeneous lambda-like light chain. In addition, sterlet possesses sigma-like VL and J-CL genes, which are transcribed separately and both encode protein products with cleavable leader peptides. The Acipenseriformes IgL dataset was extended by the sequences mined in the databases of species belonging to other non-teleost lineages of ray-finned fish: Holostei and Polypteriformes. Inclusion of these new data into phylogenetic analysis showed a clear subdivision of IgL chains into five groups. The isotype described previously as the teleostean IgL lambda turned out to be a kappa and lambda chain paralog that emerged before the radiation of ray-finned fish. We designate this isotype as lambda-2. The phylogeny also showed that sigma-2 IgL chains initially regarded as specific for cartilaginous fish are present in holosteans, polypterids, and even in turtles. We conclude that there were five ancient IgL isotypes, which evolved differentially in various lineages of jawed vertebrates.

Abstract: We evaluated the growth and survival rate of sterlet (Acipenser ruthenus) larvae fed Artemia nauplii enriched with Olioω3 or Red Pepper commercial emulsions (BernAqua NV, Belgium). Sterlet larvae, 0.022 ± 0.002 g body weight, were randomly assigned to one of three feeding regimes with two different feeding durations. After administering live feed for 7 or 14 days, larvae were weaned onto commercial food and reared to 36 days posthatching (28 days of feeding). There were no significant differences in body weight among groups at the end of the trial. A significantly higher survival rate (p < 0.05) was observed in larvae fed Artemia enriched with Red Pepper for 14 days compared to other feeding regimes. Based on the analysis of growth parameters, we can conclude that 7 days of live feeding to be sufficient for efficient rearing of sterlet larvae. And longer duration of live feeding with use of special enrichment can be recommended for a higher survival rate. [ABSTRACT FROM AUTHOR]

One of the challenges of sturgeon aquaculture is that sturgeon takes an extended amount of time to reach sexual maturity. The pattern of the protein expression in relation to the late maturity of sturgeon can help to better understand changes in sexual maturity. 17β-estradiol (E2), testosterone (T) and vitellogenin (Vtg) levels were examined at all stages of sexual maturation in Sterlet sturgeon ( Acipenser ruthenus ). Two-dimensional gel electrophoresis and mass spectrometry analysis were used to show the pattern of the ovarian proteins. The T levels increased from the previtellogenic to the postvitellogenic stages ( P  < 0.05) and Vtg showed a decremental pattern in pre- and postvitellogenic, and atresia (not significantly). The analysis showed 900 protein spots, 19 of which were successfully identified and had significant differences between the previtellogenic and the vitellogenic groups ( P  < 0.05). Among the identified proteins, 40% involved in cell defense (heat shock protein, Glutathione peroxidase, natural killer enhancing factor, peroxiredoxin-2), 30% in transcription and translation (constitutive photomorphogenesis 9 and Ybx2), 20% in metabolism and energy production (triose-phosphate isomerase (TPI)) and 10% in transport (glycolipid transfer protein). In the vitellogenic stage, the proteins were related to metabolism and energy production (TPI, ES1, creatin kinase, enolase, nucleoside diphosphate kinase, 50%), cell defense (thioredoxin and dislophid isomerase, 20%) and transport (fatty acid binding protein, 10%). Our findings show changes in protein expression pattern from cell defense to metabolism during egg development. [ABSTRACT FROM AUTHOR]

The aquaculture of the sturgeons from the Danube River basin is a niche approached by more and more Romanian entrepreneurs. The sterlet (Acipenser ruthenus) is a fresh water sturgeon with some useful characteristics that recommend this species to become a good candidate for intensive aquaculture in RAS. The monitoring of the growth dynamic of the sterlet or any other fish species reared in controlled conditions is very important for the fish farm management, especially for setting and adjustment of the technological parameters that directly influence the growth performances. The aim of this study is to evaluate the correlations and functional dependencies between some morphological traits, like total and standard length, maximum body depth and body weight in sterlet fingerlings reared exclusively into recirculating aquaculture system (RAS). Our results clearly demonstrated that any of the four body measurements (total length, standard length and maximum body depth and body weight) could be monitored in sterlet fingerlings, to accurately assess the growth dynamic, the correlations among these being very high (ranging from 0.982296 to 0.999778). Moreover, the dependencies of these traits are very high. Three of measurements could be calculated based on sterlet body weight with our equations. [ABSTRACT FROM AUTHOR]

The aim of this study was to fill important gaps in the evolutionary history of immunoglobulins by examining the structure and diversity of IgL genes in non-teleost ray-finned fish. First, based on the bioinformatic analysis of recent transcriptomic and genomic resources, we experimentally characterized the IgL genes in the chondrostean fish, Acipenser ruthenus (sterlet). We show that this species has three loci encoding IgL kappa-like chains with a translocon-type gene organization and a single VJC cluster, encoding homogeneous lambda-like light chain. In addition, sterlet possesses sigma-like VL and J-CL genes, which are transcribed separately and both encode protein products with cleavable leader peptides. The Acipenseriformes IgL dataset was extended by the sequences mined in the databases of species belonging to other non-teleost lineages of ray-finned fish: Holostei and Polypteriformes. Inclusion of these new data into phylogenetic analysis showed a clear subdivision of IgL chains into five groups. The isotype described previously as the teleostean IgL lambda turned out to be a kappa and lambda chain paralog that emerged before the radiation of ray-finned fish. We designate this isotype as lambda-2. The phylogeny also showed that sigma-2 IgL chains initially regarded as specific for cartilaginous fish are present in holosteans, polypterids, and even in turtles. We conclude that there were five ancient IgL isotypes, which evolved differentially in various lineages of jawed vertebrates. [ABSTRACT FROM AUTHOR]

Abstract: In oocytes, RNA localization has critical implications, as assembly of proteins in particular subcellular domains is crucial to embryo development. The distribution of mRNA molecules can identify and characterize localized transcripts. The goal of this study was to clarify the origin of primordial germ cells in the oocyte body plan and to reveal the generation of cell lineages by localized RNAs. The distribution of 12 selected mRNAs in sterlet Acipenser ruthenus oocytes was investigated by qPCR tomography and compared with known patterns of mRNA localization in Xenopus laevis. We investigated the distribution of two gene clusters in the ooplasm along the animal–vegetal axis of the sturgeon oocyte, both of which showed clearly defined intracellular gradient pattern remarkably similar to their distribution in the frog oocyte. We elucidated the localization of sturgeon egg germplasm markers belonging to the vegetal group of mRNAs. The mRNAs coding otx1, wnt11, and veg1 found to be localized in the sturgeon animal hemisphere are, in contrast, distributed in the vegetal hemisphere in amphibian. Actinopterygii and Sarcopterygii, two major lineages of osteichthyan vertebrates, split about 476 Ma (Blair & Hedges, ), albeit basal lineages share conserved biological features. Acipenseriformes is one the most basal living lineages of Actinopterygii, having evolved about 200 Ma (Bemis, Birstein, & Waldman, ), contemporaneous with modern amphibians (Roelants et al., ). [ABSTRACT FROM AUTHOR]

The Danube sturgeons are fishes with high economic value, and their intensive aquaculture shown a wide interest from the Romanian investors. The sterlet (Acipenser ruthenus) is the smallest sturgeon which could be found in the Danube basin, being a fresh water species with many useful characteristics which recommend it as a very good candidate for intensive aquaculture, in recirculating aquaculture systems (RAS). This species can be found at this time in many Romanian farms, which are rearing sturgeons in RAS. The aim of this study is to emphasize the growth dynamic of the main morphological traits and the body indices in a population of sterlet fingerlings, during 4 months, between 2 to 6-month-old, reared into a RAS. The juveniles of sterlet (Acipenser ruthenus) used in this study were obtained using artificial reproduction of the broodfish reared exclusively in RAS in the spring of the year 2016. The juveniles were reared in RAS until the age of 2 months, when the biometrical study started. The RAS used for trials had 3 tanks, with one cubic meter of water each, and the water exchange rate was about once per hour. One hundred and fifty sterlet, 2 months old, were introduced into the 3 tanks of the RAS, 50 fish per tank, in triplication. The main body traits were measured twice per month, from the age of 60 days to the end of 6th month of fish life. The following measurements were carried out: total length (TL), standard length (SL), head length (HL), head width (HW), snout length (SnL), maximum body depth (MBD), mouth width (MW) and body weight (BW). During the experimental period, the fish were fed with sturgeon feed produced by Coppens International (Nederland), with different sizes, from 1.2-1.5 mm to 3 mm according to fish sizes. The amount of feed per day was calculated as a percent of the total fish biomass established at each measurement made at every two weeks. The growth dynamic of the sterlet in the 4 months of study was very fast, with significant differences (p ≥ 0.05) between measurements at every 2 weeks, in almost all cases. The TL of the fish increased from 134.37±11.92 mm to 359.53±22.04 mm and the BW greatly increased, from 10.2±2.27 g to 180.53±45.28 g. The other traits registered also good dynamics with certain patens emphasized in the paper. All of these allowed the drafting of growth curves for different traits, very useful for sturgeon farmers but not only. [ABSTRACT FROM AUTHOR]

Molecular mechanism of sex determination and differentiation of sturgeon, a primitive fish species, is extraordinarily important due to the valuable caviar; however, it is still poorly known. The present work aimed to identify the major genes involved in regulating gonadal development of sterlet, a small species of sturgeon, from 13 candidate genes which have been shown to relate to gonadal differentiation and development in other teleost fish. The sex and gonadal development of sterlets were determined by histological observation and levels of sex steroids testosterone (T), 11-ketotestosterone (11-KT), and 17β-estradiol (E2) in serum. Sexually dimorphic gene expressions were investigated. The results revealed that gonadal development were asynchronous in 2-year-old male and female sterlets with the testes in early or mid-spermatogenesis and the ovaries in chromatin nucleolus stage or perinucleolus stage, respectively. The levels of T and E2 were not significantly different between sexes or different gonadal development stages while 11-KT had the higher level in mid-spermatogenesis testis stage. In all the investigated gonadal development stages, gene dmrt1 and hsd11b2 were expressed higher in male whereas foxl2 and cyp19a1 were expressed higher in female. Thus, these genes provided the promising markers for sex identification of sterlet. It was unexpected that dkk1 and dax1 had significantly higher expression in ovarian perinucleolus stage than in ovarian chromatin nucleolus stage and in the testis, suggesting that these two genes had more correlation with ovarian development than with the testis, contrary to the previous reports in other vertebrates. Testicular development-related genes ( gsdf and amh) and estrogen receptor genes ( era and erb) differentially expressed at different testis or ovary development stages, but their expressions were not absolutely significantly different in male and female, depending on the gonadal development stage. Expression of androgen receptor gene ar or rspo, which was supposed to be related to ovarian development, presented no difference between gonadal development stages investigated in this study whenever in male or female. [ABSTRACT FROM AUTHOR]

Histological examination of thymi from juvenile Acipenser ruthenus and Acipenser brevirostrum after haematoxylin and eosin staining revealed the presence of Hassall's corpuscles, in a scattered distribution within the thymic medulla in two of seven, and one of nine examined specimens, respectively. Morphologically, the Hassall's corpuscles were of the juvenile and premature type and no degenerative changes were seen.

Artificial mitotic gynogenesis, a chromosome set manipulation, is applied to provide the homozygous progeny with only maternal inheritance. Here, gynogenetic development was induced in the sterlet Acipenser ruthenus L. (Acipenseridae) by activation of the eggs originating from albino females with the UV-irradiated spermatozoa from wild-coloured males, followed by the heat shock applied to suppress the first mitotic division in the haploid zygotes. All experimentally obtained gynogenetic offspring possessed recessive albino coloration. Moreover, the genetic verification, based on three microsatellite DNA markers, confirmed the only maternal inheritance in the albino progeny. Cytogenetic screening enabled identification of the aneuploids, haploids, diploids, triploids, tetraploids and mosaic individuals among the gynogenetic larvae that hatched from the eggs subjected to the heat shock. Furthermore, 40% of the larvae from the haploid variants of the research that were not exposed to the temperature shock showed the diploid chromosome number. A variation of the ploidy level observed in the gynogenetic sterlets may be the consequence of the spontaneous polyploidisation that occurred in the haploid zygotes. Moreover, observation during embryogenesis showed varied stages of eggs development and the asynchronous cell cleavages that may have resulted in the chromosomal disturbances observed in the gynogenetic sterlets here. [ABSTRACT FROM AUTHOR]

Contents The aim of this study was to assess monthly testicular development in the cultured breeding stock of sterlet, Acipenser ruthenus, using histological and serum sex steroid changes. Testicular development in the adult male was examined monthly and showed four distinct phases including resting, pre-spawning, spawning and post-spawning. Also, seasonal changes of the testes were described according to its variations in gonadosomatic index (GSI) during different phases of testicular development. Using histology, we identified continuous spermatogenesis and asynchronous gonad development pattern in the testes of male sterlet, which shows that regulation of annual gonadal cycle is influenced by season. Results also showed variation in the GSI value and number of spermatogenic cells according to each season during annual cycle of gonad, as the highest value of GSI was recorded during spawning phase (spring; March-May). Hormonal profiles of 11-ketotestosterone (11-KT) showed peak, which indicated a seasonal pattern of gonadal development. The 11-KT concentration increased considerably during the spermatogenesis (pre-spawning phase) and remained quite high throughout the pre-spermiation period. In the final phase of testicular development (spawning phase), the 11-KT markedly dropped. This study undertook an examination of complete reproductive development in cultured sterlet sturgeon to provide a valuable guide for the future sterlet studies, and allows comparison of reproductive development between sturgeon species. [ABSTRACT FROM AUTHOR]

Sturgeons had played an important role in the history of Hungarian fisheries, but due to over-fishing, followed by extensive river regulations and deterioration of habitats, there has been a considerable decrease in populations which are now on the verge of extinction. Sterlet (Acipenser ruthenus) is only a common species caught for commercial and recreational purposes. The main factors of sterlet population dynamics were evaluated according to the new international efforts for sturgeon con¬servation. A moderate correlation was confirmed between the annual sterlet catches and the fluctuation of the hydrological regime of the Danube. Assessment of restocking activity and population recruitment demonstrated low efficiency of remedial measures for the Danubian sterlet.

Helminths of sterlet (Acipenser ruthenus L.) from the Danube River were studied as a part of ichthyoparasitological research in Serbia. The fish were collected during the period of 2002 - 2003 along the Danube's course through the Belgrade region. A total of 517 specimens of sterlet of different ages (0+ to 1+) were examined. Helminths were found in 342 or 66.15% of the collected specimens. The examined fish yielded a total of 13 helminth species: four species of Trematoda, one species of Cestoda, four species of Nematoda, and four species of Acanthocephala.

The study was conducted within the recirculating aquaculture system for sturgeon rearing in Herneacova village, Timis County, on a population of juvenile sterlet (Acipenser ruthenus) aged between 346-431 days. Specimens were housed in five round tanks (Ø=3 m, V=6 m3, h=100 cm) and fed with commercial extruded pellets (3 mm granulation, 48% CP, and 10% EE). Fish from each tank were individually weighed and measured once every two weeks. Bioproductive indices such body weight gain (BW), specific growth rate (SGR), and feed conversion ratio (FCR) were calculated at the end of an 85 days experimental period. Statistical analysis was performed using the SPPS IBM 22 and Minitab 16 software. Data were reported as Mean±Sx at a significant level of p<0.05. Testing differences between means was realized by ANOVA completed with post-hoc Tukey test. The results obtained indicate that the growth performance of juvenile Acipenser ruthenus seems to be similar and even better than that of other sturgeons species reared in recirculating aquaculture system. [ABSTRACT FROM AUTHOR]