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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]

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]

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 article describes the results of hydrochemical analysis of the water of breeding pond No. 1A of PrJSC “Vilshanka” in the spring-autumn period of 2023 for the cultivation of carp (Cyprinus carpio) and sterlet (Acipenser ruthenus) in polyculture. The results of the study of the hydrogen index (pH) of water during the entire period of research showed that it was in the range of 7.6 to 8.4 and did not exceed the norms. The concentration of ammonium nitrogen in water due to anthropogenic load increased in all experiment periods; however, the studied indicator, which ranged from 0.39 ± 0.03 to 0.68 ± 0.05 mg N/dm³, did not exceed the standard's requirements. The results of studies of nitrite nitrogen content in water ranged from 0.05 ± 0.002 to 0.12 ± 0.009 mg N/dm³ . Still, it, like the content of ammonium nitrogen, did not exceed the standard's requirements, indicating the absence of nitrification processes of ammonium nitrogen in the water. The analysis of the results of research on the concentration of nitrate nitrogen in water was within 1.37 ± 0.07 – 1.75 ± 0.11 mg N/dm³ of fluctuations in the content of nitrogen compounds in water, which is associated with anthropogenic load, which includes getting into water runoff from the fields, as well as biological decomposition of organic substances that enter the water at different times of the year. The content of phosphates ranged from 0.41 to 0.53 mg/dm³ and did not exceed the standard's requirements. Dichromate oxidizability ranged from 14.4 to 28.3 O2/dm³, but, if compared with average values, it was 1.17 times higher in spring, 1.89 times higher in summer, and 1.89 times higher in autumn 1.83 times, indicating possible emissions of chemical compounds into water, such as heavy metals and other toxic substances, which will lead to disruption of natural ecosystems. Analyzing the data of BSK5, which ranged from 4 to 6.9 mg/dm³ in the water of growth pond No. 1A, was similar to changes to dichromate oxidation and changed depending on the season. [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.

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 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 %.

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

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]

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.)

Aim. The aim of the research is to study the influence of various environmental factors (abiotic and biotic) on some fish-biological indicators in the cultivation of sturgeons with the use of a recirculating aquaculture system (RAS). Methods. A complete biological analysis was carried out according to the generally accepted ichthyological methods. Monitoring of the hydrochemical regime in the RAS was carried out throughout the study period. The temperature and pH of water were measured daily and the concentration of oxygen in the basins was measured three times a day. Results. Taking into account that the fish specimens studied did not show any pathology and also taking into consideration their genetic homogeneity and absolutely identical conditions in the RAS, the findings obtained can be explained by the different degree of oxygen supply under artificial growth conditions. The results of the biochemical analysis show that the blood of fish grown in the RAS with an elevated oxygen content (experimental group) by the end of the experiment (4 weeks) contains an increased amount of malondialdehyde (MDA) which could lead to the observed difference in the dynamics of growth parameters of the young of the year. Conclusions. When the oxygen content of the water is below 70% the growth rate slows down, as food consumption is almost halved, while the saturation of O2 by 40% is considered critical. When sterlet is grown to produce a high mass, it is necessary to set the temperature of the water in the pools in the interval of 21-220°C in the ultrasonic complexes. For industrial cultivation of sterlet, we recommend using a planting density of 60 kg/m3.

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.

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.

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]

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.

The sub-lethal effects of water-born Cadmium (Cd) on histopathological changes of gill tissues were investigated on Sterlet, Acipenser ruthenus. In this research, 60 fish (41.69 ± 0.95 g and 23.98 ± 0.14 cm) were randomly distributed in 4 experimental groups, each with 3 replicates. The fish were exposed to different concentrations of Cd for 21 days under semistatic experimental condition as: 0, 16, 32 and 64 μg/L Cd. At the end of the experiment, the gill tissues were fixed in Bouin's solution for histopathological studies. Qualitative and quantitative changes of the gill tissues were analyzed. Several qualitative changes including hyperplasia, hypertrophy of epithelial cells and epithelial edema as well as necrosis, rings and fusion of gill filaments and secondary lamellae were observed in all treated fish including control group. Quantitative analysis based on organ index (Iorg) showed significant increase in histopathological changes in the gill tissues coincided by elevation of Cd concentration in the water. However, there was no significant differences in the organ index between control and 16Cd group.The results of this study demonstrate severe histopathological changes in the gill tissues after exposing to sub-lethal concentration of water-born Cd under experimental condition. The results of this study might be used as a guildline for evaluation of histopahological changes being induced by heavy metals in natural or cultivated environment for sturgeon fish.

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]