Sturgeon Aquaculture Research Articles

Effects of Different Cytoprotectants Combination on Sperm Survival, Fertility and Embryo Development in Amur Sturgeon (<i>Acipenser schrenckii</i>)

Development of artificial propagation technology is becoming increasingly important in sturgeon aquaculture whether species recovery efforts or commercial production. The cryopreservation technique of high-quality semen collected during the spawning season could extremely improve reproductive efficiency for year-round availability, especially for off-season use. However, the cryopreservation technique of sperm in Amur sturgeon (Acipenser schrenckii) has not been effectively developed. In the present study, we firstly tested the cryopreservations combination effects of three cryoprotectants, including methanol, dimethyl sulfoxide (DMSO), and propylene glycol (PG) and fresh yolk (Y) addition on sperm motility, fertilization and embryo development in Amur sturgeon. The results indicated that sperm motility was still more than 60% in the MT group but that of the control group was sharply decreased to 4.5% after 72 h of in vitro storage (4°C). The post-thawed sperm motility analysis showed that there was no significant difference between the MT+DMSO group and MT group, but the fertility rate in the MT group was significantly higher with a value of 42.30±2.57(%) than any other experimental groups, including the MT+DMSO group (P<0.05). Meanwhile, we also found that there was no significantly positive effect on post-thawed sperm motility with Y addition. Interestingly, although the results showed that the MT+DMSO group and MT group had similar effects on the post-thawed sperm motility, the MT+DMSO group had higher hatching rate compared to any other tested groups, including the MT group. Meanwhile, we also found that PG as cryoprotectant was unsuitable for sperm cryopreservation of Amur sturgeon. In conclusion, our results provides invaluable basis in further studies for the optimization technology of artificial propagation in Amur sturgeon.

Expression Characterization of Six Genes Possibly Involved in Gonad Development for Stellate Sturgeon Individuals (Acipenser stellatus, Pallas 1771).

Nowadays, in sturgeon's aquaculture, there is a necessity for sex identification at early stages in order to increase the efficiency of this commercial activity. The basis for a correct identification is studying the different factors that influence the gonad development. The research has been directed towards molecular methods that have been employed with various degrees of success in identifying genes with different expression patterns between male and female sturgeons during their development stages. For the purpose of understanding the sexual development of 4-year-old stellate sturgeon (Acipenser stellatus) individuals, we have selected six genes (foxl2, cyp17a1, ar, dmrt1, sox9, and star). We analysed the gene expression of the selected genes for gonads, anal fin, liver, body kidney, and white muscle. The cyp17a1, ar, dmrt1, and sox9 genes have a significant higher expression in male gonads than in female gonads, while the data shows no significant differences in the expression of the investigated genes in the other organs. We investigate these genes to shed light on aquaculture sturgeon sexual development.

Genetic identification of the caviar-producing Amur and Kaluga sturgeons revealed a high level of concealed hybridization

China has recently become the leader country for sturgeon aquaculture and caviar production, deeply changing the traditional geography of this market in few years. As a consequence, some species originating from the Far East Asia increased their economic relevance, joining the ones traditionally harvested for caviar. In this context, the possibility to reliably and promptly identify these species on the market has increasing importance for the enforcement of control actions against illegal trade or commercial frauds. The present study focuses on two commercially relevant species, massively reared in China not only as pure species but also as reciprocal hybrids: the Amur (Acipenser schrenckii) and Kaluga (Huso dauricus) sturgeons. We assess the identification power of two putatively diagnostic markers isolated from two predicted introns of the nuclear coding gene Ribosomal Protein L8. The markers were tested on tissue or caviar of 508 individuals of the two species and 31 hybrids. In order to compare results across loci, most individuals were also checked at two already published microsatellite markers, with a good, even if incomplete, identification efficiency for the two species. No marker showed fixed alternative alleles between Amur and Kaluga sturgeons, confirming the difficulty of distinguishing these two sympatric species in spite of the marked morphological differences and the consequent classification into different genera. So far, the multi-locus panel here used represents the more effective tool for the genetic identification of pure Amur and Kaluga sturgeons and resulted to be fully efficient to validate caviar and tissues obtained from hybrids between the two species.

A Typology for Investigating the Effects of Sturgeon Aquaculture on Conservation Goals

AbstractThis essay will explore the impact of sturgeon aquaculture on conservation efforts by presenting a typology of sturgeon aquaculture positions aimed at sturgeon preservation. The paper will also connect the primary types of sturgeon aquaculture to related research topics, ranging from global commodity chains to changing protein production systems.

Finishing diet, genetics, and other culture conditions affect ovarian adiposity and caviar yield in cultured white sturgeon (Acipenser transmontanus)

The on-going and precipitous decline in sturgeon abundance and increased demand for caviar have promoted the development of sustainable sturgeon aquaculture. One common problem that confounds caviar farming efficiency is highly variable roe yield associated with the proliferation of ovarian fat: sturgeon females with fatty ovaries tend to produce a smaller yield of inferior quality roe compared to those with lean ovaries. Here, we evaluated the effects of finishing diet, farm origin, age at maturity, tank, and genotype on ovarian adiposity and caviar yield in cultured white sturgeon (Acipenser transmontanus). We conducted a feeding trial in which fish aged 5+years at two different commercial farms were either maintained on a high fat production diet or received a low fat finishing diet for 19 and 33months before caviar harvest; at this time fish were aged 7 or 8years, respectively. Measurements of ovarian fattiness, caviar yield, and morphology were collected at the time of harvest. Microsatellite genotyping was performed to estimate relatedness among experimental fish and subsequent heritability of these traits. Mean caviar yield normalized by body weight increased from 7.6–8.6% to 8.0–9.2% and mean caviar yield scaled by ovary weight increased from 55.5–59.8% to 61.3–64.6% in white sturgeon fed the high and low fat diets, respectively. All females were classified post hoc according to degree of ovarian fattiness: low, medium, or high. Regardless of diet, farm, or age, females in the high ovarian adiposity group had larger body size, higher condition factor, but lower caviar yields than those in the low fattiness group because of the presence of large ovarian fat lobes and adipocytes surrounding individual oocytes. Furthermore, only 11.8–17.2% of female white sturgeon given the low fat finishing diet displayed a high degree of ovarian fattiness compared to 18.0–33.2% of those on the high fat diet. Robust negative correlations were found between measurements of ovarian adiposity and caviar yield further illustrating this inverse relationship observed by caviar farmers. The fixed effects of diet, farm, age, and tank all significantly influenced ovarian adiposity and caviar yield except farm origin did not significantly impact ovarian fat lobe weight. Heritability values for measurements of ovarian adiposity and caviar yield were moderate and ranged from 0.20–0.39, however heritability of ovarian tissue weight was slightly lower (h2=0.11). Our study demonstrates that finishing diet, farm origin, age at maturity, tank and genotype significantly affect and may be manipulated to increase caviar yield in cultured white sturgeon. Statement of relevanceStudy findings will increase sturgeon aquaculture profits.

Peritoneal bacterial infection repressed the expression of IL17D in Siberia sturgeon a chondrostean fish in the early immune response

IL17s are pro-inflammatory cytokines that play important roles in host fighting against extracellular bacteria and auto-immune and allergic diseases. IL17D is believed to be the most ancient IL17 member and its functions are far from clarity. Although it has been found in invertebrates, jawless fish, teleosts, and tetrapods, it has not been described in chondrostean fish. Moreover, there are discrepancies concerning its expression pattern in these animals. In this study, we cloned and characterized the cDNA of il17d in Siberia sturgeon (Acipenser baerii), a chondrostean fish and commercially important species in aquaculture. The sturgeon il17d cDNA encodes a deduced protein of 210aa. The classical characteristics of IL17, such as IL17 domain, cysteine and serine residues importantly for cystine-knot formation, and signal peptide, were observed in sturgeon IL17D. Phylogenetic analysis and multiple alignment suggest it is a counterpart of mammalian IL17D. However, in vivo studies demonstrated that the expression pattern of sturgeon il17d mRNA is different from that of other teleosts and jawless fish, and in most cases its expression was down-regulated at the early time points and gradually increasing at late time points when sturgeon were challenged with bacteria (Aernomas hydrophila or Staphylococcus aureus). The In vitro study by using primary spleen cells stimulated with polyI:C revealed a similar expression pattern to that in vivo studies, while the stimulation with β-glucan or LPS, which normally induced expression of il17d mRNA in target cells in vitro in other animals, did not show apparent changes in the expression of il17d mRNA. The results of present study indicated sturgeon IL17D may possess some different characteristics from its counterparts of other fish and invertebrates in the immune response, and may contribute to the understanding of IL17D functions in evolution as well as the potential use in sturgeon aquaculture.

Status of scientific knowledge, recovery progress, and future research directions for the Gulf Sturgeon,Acipenser oxyrinchus desotoiVladykov, 1955

Summary The Gulf Sturgeon, Acipenser oxyrinchus desotoi, is an anadromous species of Acipenseridae and native to North America. It currently inhabits and spawns in the upper reaches of seven natal rivers along the northern coast of the Gulf of Mexico from the Suwannee River, Florida, to the Pearl River, Louisiana, during spring to autumn. Next to the Alligator Gar (Atractosteus spatula), the Gulf Sturgeon is currently the largest fish species occurring in U.S. Gulf Coast rivers, attaining a length of 2.35 m and weights exceeding 135 kg, but historically attained a substantially larger size. Historically, the spawning populations existed in additional rivers from which the species has been wholly or nearly extirpated, such as the Mobile and Ochlockonee rivers, and possibly the Rio Grande River. Most Gulf Sturgeon populations were decimated by unrestricted commercial fishing between 1895–1910. Subsequently most populations remained unrecovered or extirpated due to continued harvest until the 1970s–1980s, and the construction of dams blocking access to ancestral upriver spawning grounds. Late 20th Century harvest bans and net bans enacted by the several Gulf Coast states have stabilized several populations and enabled the Suwannee River population to rebound substantially and naturally. Hatchery supplementation has not been necessary in this regard to date. Sturgeon are resilient and adaptable fishes with a geological history of 150 million years. Research undertaken since the 1970s has addressed many aspects of Gulf Sturgeon life history, reproduction, migration, population biology, habitat requirements, and other aspects of species biology. However, many knowledge gaps remain, prominently including the life history of early developmental stages in the first year of life. Natural population recovery is evident for the Suwannee River population, but seems promising as well for at least four other populations. The Pascagoula and Pearl River populations face a challenging future due a combination of natural and anthropogenic factors. These two populations, and perhaps the Escambia River population, are particularly vulnerable to periodic mass mortality due to major stochastic events including hurricanes, flooding, hypoxia, and toxic spills. The present manuscript provides a comprehensive synthesis of knowledge regarding the Gulf Sturgeon at the organismal and population levels, identifying knowledge gaps as priorities for future research. Topics not treated in the present synthesis include morphology, internal biology, physiology, and endocrinology. Topics only briefly treated include parasites and diseases, contaminants, and sturgeon aquaculture.

Determination of cortisol in lake sturgeon (Acipenser fulvescens) eggs by liquid chromatography tandem mass spectrometry.

Quantifying cortisol concentrations in fish eggs is important to understand the effects of environmental conditions on maternal physiological condition and on egg provisioning and quality. Data are particularly relevant to studies of the ecology of threatened species such as lake sturgeon (Aciperser fulvescens) as well as assessments of larval physical and behavioral phenotypes, fish health and caviar quality in sturgeon aquaculture. This study focuses on development of bioanalytical methods for high sensitivity and robust determination of cortisol in sturgeon eggs. Sample preparation was optimized after investigating protein precipitation and liquid-liquid extraction techniques. Ethyl acetate was found to be the most efficient solvent (recovery parameter) and also provided the best sample clean up (matrix effect parameter). The method was determined to be linear for cortisol concentrations between 0.025 and 100ng/mL. The limits of detection and quantification were 0.025 and 0.1ng/mL respectively. Intra- and inter-day performances of the method were validated at three concentrations (0.25; 10 and 100ng/mL). The method was applied to field-collected samples for the determination of endogenous cortisol in lake sturgeon eggs. Cortisol was detected in all egg samples and statistical analysis showed significant differences between fertilized and non-fertilized eggs.

Rule of accumulation of enrofloxacin in Acipenser baerii and drug-induced damage to the tissues.

Enrofloxacin (ENX) has been widely used in the prevention and control of bacterial diseases in sturgeon aquaculture due to its characteristics of wide antibacterial spectrum, strong antibacterial activity, less toxicity and fewer side effects, rapid action, extensive invivo distribution, and little cross-resistance with other antibiotics. However, the spinal abnormality was found in Acipenser baerii soon after ENX administration, which resulted an "S"-shaped curvature of the spine and retarded fish growth. It was still not clear whether ENX could cause spinal abnormality in sturgeons by now. The aim of this work was to determine the accumulation rule and toxicity of ENX to A. baerii when used at a high dose and/or unusually long durations. Here, ENX was orally given to A. baerii for 3-5 d continuously at the dosage of 0, 20, 40, and 80 mg/kg once daily, respectively. The accumulation of ENX in blood, liver, kidney, and cartilage was detected after withdrawal, and the tissues were made into sections for morphological examination. The results showed that the levels of ENX increased in the four tissues with the increase of dose and duration, and the ENX level in serum was far lower than that in other tissues. At 240 h, ENX levels in the four tissues decreased significantly. The histology indicated that the liver, kidney, and cartilage began to show structural damages at 5 d after withdrawal of 40 mg/kg ENX. The damage was aggravated at 3-5 d after withdrawal of 80 mg/kg ENX. At 240 h, the damaged tissues showed signs of recovery. These results suggested that ENX should be no more than 40 mg/kg and that exposure time should not be greater than 5 d to prevent liver, kidney, and cartilage damage. More attention should be paid to the impact of ENX on the occurrence and development of chondrocytes in juvenile A. baerii and the potential damage to the cartilage.

Anesthetic Efficacy of Clove Oil, Propofol, 2‐Phenoxyethanol, and Ketamine Hydrochloride on Persian Sturgeon, Acipenser persicus, Juveniles

AbstractAnesthetics are commonly used in the aquaculture industry to reduce stress and prevent mortality of fish during transportation, handling, and surgical procedures. This study assessed the efficacy of four anesthetic agents (clove oil, propofol, 2‐phenoxyethanol [2‐PE], and ketamine hydrochloride) on Persian sturgeon, Acipenser persicus, juveniles. In addition, results of the first experiment were used to evaluate sedation concentrations suitable for transportation of Persian sturgeon. The concentrations of anesthetics or sedatives evaluated in the first experiment were: 25, 50, 75, and 100 mg/L for clove oil; 1, 1.25, 2.5, and 5 mg/L for propofol; 110, 330, 550, and 770 mg/L for 2‐PE; and 1250, 2500, 3750, and 5000 mg/L for ketamine hydrochloride. Results show significant reduction in time to anesthesia and significant increase in recovery time with increase in concentration of all anesthetics. The most clinically useful concentrations of anesthetics tested were between 25 and 50 mg/L for clove oil, less than 1 mg/L for propofol, 330 mg/L for 2‐PE, and none of the tested concentrations for ketamine hydrochloride. In the second experiment, juveniles were placed in low concentrations of anesthetic solutions for 24 h and survival assessed. The four anesthetics tested are suitable for light sedation during transportation of A. persicus juveniles. Results are helpful to scientists working with Persian sturgeon aquaculture and restocking programs.

Assessment of the accuracy of physiological blood indicators for the evaluation of stress, health status and welfare in Siberian sturgeon (Acipenser baerii) subject to chronic heat stress and dietary supplementation

There is growing interest in the evaluation of stress, health and welfare of farm-raised fish. However, there is no scientific consensus about the methodology that is used to assess them. Sturgeon aquaculture is a recent industry with increasing interest in the production of caviar, which is characterized by high turnover and costs. To improve aquaculture efficiency, this study was conducted on routine blood samples, taken from Siberian sturgeon (Acipenser baerii), to test the robustness of using only physiological indicators to assess heat stress, health, and welfare. Sampling was performed after 1 month of prebiotic dietary supplementation followed by 4 weeks of sublethal heat stress. Data interpretation was achieved with a multivariate statistical tool. The expression of heat shock proteins (HSP) was assessed for the first time in sturgeon erythrocytes. Hsp70 and hsp90 expression was triggered by both stress and dietary supplementation. Indicators of non-specific immunity were modified mainly by stress. Complement activity increases with stress while lysozyme activity decreases, but to a lesser extent in supplemented fish. The antioxidant capacity increases with stress while oxidant metabolites decrease and overall oxidative stress was lower for fish that received dietary supplementation. The positive impact of dietary supplementation on health status was observable after a stress challenge. A principal component analysis was used to combine all the measured parameters and to observe patterns in physiological fish status. The four experimental groups of fish were clearly discriminated with this statistical tool. Physiological indicators from blood samples may enable heat stress, health, and welfare to be assessed in Siberian sturgeon.

Exterior Features of Siberian Sturgeon Underyearlings when Applying Bs 225 Microbiological Preparation

BS 225 impact on the exterior features of the Acipenseridae has been studied. BS 225 is a microbiological preparation containing Bacilus Siamensisas as a basis. The efficiency of its application in sturgeon aquaculture is demonstrated by a scientific and commercial experiment. Each test group of sturgeon underyearlings had its own feeding schedule at a definite dosage. It was proved experimentally that the dosage determines exterior features and essential biological parameters, such as Fulton’s condition factor, fineness ratio, scale factor, thickness ratio and mass buildup. The obtained data confirm that microbiological preparation initiates sturgeon growth, is beneficial for fish exterior features and improves winter resistance, environmental resistance and survivability of fish.

STATUS AND PROSPECTS OF BREEDING STURGEON AT JST "SHIROKOLSKI FISH FARM"

Aim. Tthe article presents the results of breeding broodstock of sturgeon in the Shirokolski fish farm. The volume of commodity output reached 50 tonnes of sturgeon, and two tones black caviar. After drilling termal well volume growth may reach 100 t, obtaining food caviar 5 t. Location. Russian Federation, Dagestan Republic. Methods. We used the standard ichthyological research methodology. Results. At the present time the plant formed one of the largest sturgeon broodstock total biomass of more than 50 t, which include clean lines: Beluga, Russian and Siberian sturgeon, sterlet, paddlefish, and hybrid forms. The plant research for the early detection of sex by ultrasound scan. The main role of bester, which is used to obtain the food caviar. The biomass of the herd is about 30 tonnes per year is about 10 tons of breeders. Mature females Bester in our conditions in 7-8 years. Sterlet is used as producers for the purpose of reproduction and food caviar. Maintenance of broodstock is 6000 fishes and approximately 2000 breeders of medium weight from 1.5 to 6.0 kg. Mature female starlet at age 4- 5 years. Main conclusions. The results convince us that the development of sturgeon aquaculture is one of the feasible ways not only to increase employment and reduce social poaching, but also stabilizing the feedstock, substantial improvements in the efficiency of hatcheries and processors.

Pseudomonas alcaligenes infection and mortality in cultured Chinese sturgeon, Acipenser sinensis

Abstract Chinese sturgeon (Acipenser sinensis) is a rare and endangered species, and also an important resource for the sturgeon aquaculture industry in China. Recently, a fatal bacterial disease occurred in farmed Chinese sturgeon. The clinical signs of the diseased fish were systemic blood loss and anemia. The gills were very pale with swollen and hemorrhagic gill filaments. Discrete blood spots were apparent in the oral cavity. Small petechial hemorrhages were present in pale livers and the digestive tract. Hemorrhages were also present in the kidney and gonad. The spleen was red and swollen. Additionally, a small amount of clear ascites fluid was present in the body cavity. A bacterial pathogen was isolated from the internal organs of diseased fish and subsequently identified as Pseudomonas alcaligenes by morphology, biochemical testing and phylogenetic analysis of the 16S rDNA. Experimental infection in healthy hybrid sturgeon confirmed the pathogenicity of the bacterial isolate. The results of this study represent the first isolation and identification of Pseudomonas alcaligenes in cultured Chinese sturgeon in China and provide a foundation for the diagnosis, prevention and treatment of this new disease. Statement of relevance The authors declare that there is no conflict of interests regarding the publication of this paper.

Development of aquaculture on Сhirkeyskoe reservoir in the republic of Daghestan

In the article is given the description of Chirkeyskoe reservoir located in the republic of Dagestan. Are shown the prospects for development and the results of researchers on the organization of market salmon and sturgeon aquaculture. The unique experience of the use of the not specialized concrete ponds for the cultivation of trout and hybrids of sturgeon with the year-round feeding is presented.

Sturgeon Aquaculture in China: status, challenge and proposals based on nation-wide surveys of 2010-2012

At the end of 2012 and beginning of 2013, the authors conducted a nationwide survey of sturgeon aquaculture in China from 2010 to 2012. The survey results, combined with previous data, show that the dominant cultured species are Acipenser baerii, Huso dauricus♀ × A. schrenckii♂, A. baerii♀ × A. schrenckii♂, A. schrenckii, and A. gueldenstaedtii, accounting for 90% of the total production. Sturgeon farms have grown to include almost all provinces except Xizang, and are grouped principally in Shandong, Hubei, Sichuan and Chongqing, Beijing. The main culture systems are cage culture, and cement pond culture with running water. Sturgeon production rose from 34800 tonnes (t) in 2010 to 44500 t in 2012. The commercial sturgeon price dropped from 45 yuan per kg (5.5€/7.3$) in 2010 to 25 yuan per kg (3€/4$) in 2012. Nine caviar-processing enterprises qualified for or were striving to process caviar, for a total production of 56.6 t caviar in 2012, of which 90% was exported. Major problems were also identified during the survey, including: disorderly hybridization and germplasm degradation; a stagnant domestic consumption demand; dramatic price fluctuations in different regions and at different times. Specialized sturgeon cooperatives had obtained government support to a certain extent, but did not use this to their advantage because of a lack of policy guidance and technical support. The processing of sturgeon products developed slowly. In view of the existing problems, certain proposals are discussed: publication of propagation standards, culture and processing to define the parental source of the commercial sturgeon and their by-products; promulgate sturgeon consumption to expand market demand; establish a ‘Sturgeon Industry Association’ to constrain bad competition and cultivate good competitive mechanisms; build a protective pricing system to secure effectively the interests of some of the weaker farms; and conduct professional technical training courses on culture improvement and deep processing technology.

Use of sex steroid profiles and hematological indices to identify perinucleolus and migratory gonadal stages of captive Siberian sturgeon Acipenser baerii (Brandt, 1869) females

This study describes the sex steroid profiles and hematological indices of 5-year-old reared female Siberian sturgeon, Acipenser baerii, at perinucleolus and migratory stages to ascertain whether they are influenced by the maturity stage. Fish of 2923 g mean weight and 89 cm mean length were reared in rectangular concrete tanks (25 × 3 × 0.6 m, mean water temperature 16.2 ± 2.2°C, fed a diet with 38.2% crude protein and 7% crude fat in 10 kg m−2). Blood samples were taken for serum steroid levels, including 17-β estradiol (E2), testosterone (T), 17α-hydroxy progesterone (P) and hematological indices (packed cell volume, hemoglobin, red blood cells, white blood cells, mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration as well as leukocyte differential counts). Hematological indices and the leukocyte differential count showed no significant differences among fish at the perinucleolus and migratory stages. The results indicated significant differences in E2 levels among fish at the perinucleolus and migratory stage, but the T and P levels showed no significant differences between stages. This study indicates that serum sex steroid measurements and histological observations can segregate females effectively at the perinucleolus and migratory stages; however, the hematological parameters did not discriminate females at these stages. Such observations provide basic information to achieve a method to determine with high accuracy the stage of sexual maturity, for better sturgeon aquaculture management.

Probiotic, prebiotic and synbiotic supplements in sturgeon aquaculture: a review

AbstractThis study addressed the issue of the dietary supplements; probiotic, prebiotic and synbiotics considered as functional food ingredients in sturgeon aquaculture. Developments of this strategy have been suggested and practiced as an alternative to antibiotic administration in aquaculture. Sturgeons are commercially valuable species due to their meet and roe, which is made into caviar. Aquaculture of sturgeons up to marketable size has increased during the last decade while disquieting decreases have been noticed of the natural populations. In line with the expand evaluations of microbial dietary supplements and prebiotics in finfish and shellfish aquaculture, the scientific community has also increased their interest in approaches to these issues in sturgeon aquaculture. The present review summarizes and discusses the results on intestinal microbiota of sturgeon species and the effects of probiotic, prebiotic or synbiotic administration on growth performance, gut physiology, intestinal microbiota, immune response and health. Furthermore, this study tries to cover the gaps of existing knowledge and suggest issues that merits further investigations.

Identification of genes involved in gonadal sex differentiation and the dimorphic expression pattern in undifferentiated gonads of Russian sturgeonAcipenser gueldenstaedtiiBrandt &amp; Ratzeburg, 1833

Summary The establishment of a sexing technique at an early developmental stage is an important issue in sturgeon aquaculture, yet the mechanism of sex differentiation in sturgeons remains poorly understood. This study aimed to identify genes involved in gonadal sex differentiation and to investigate sexually dimorphic gene expression in undifferentiated gonads. RNA-seq analyses using next-generation sequencers were carried out on undifferentiated gonads of five 9-month-old juvenile Russian sturgeon Acipenser gueldenstaedtii. A total of 45 686 832 (8498 Mb) and 79 743 269 (7887 Mb) quality-controlled reads were obtained using Ion PGM and HiSeq 2000 sequencers, respectively, and were assembled into 338 648 contigs (N50: 532 b). tBLASTx analyses identified 26 transcripts potentially involved in gonadal differentiation. Read-mapping analyses were performed to obtain relative transcript levels (RPKM values). Multivariate analyses of the RPKM values of five transcripts (gsdf, dmrt1a, dmrt1b, foxl2 and cyp19a1a) showed that the five individuals could be separated into two distinct groups. One group, comprising two individuals, had increased levels of foxl2, hsd17b1 and cyp19a1a, suggesting differentiation into females. Alternatively, levels of gsdf were higher in the other three individuals, suggesting differentiation into males. We describe the levels of 26 transcripts potentially involved in gonadal differentiation in undifferentiated sturgeon gonads and suggest that levels of gsdf, foxl2, hsd17b1 and cyp19a1a are appropriate sexing markers for sturgeon at an early developmental stage.

Ontogeny of the immune system in Acipenserid juveniles

Sturgeon aquaculture has increased considerably worldwide but little is known about their immunological development and competence in early life stages. Culture of larvae is one of the most critical stages in intensive sturgeon farming, often associated with high mortality rates. The objective of this study was to characterize the developmental morphology (light and transmission electron microscopy, LM and TEM) of the meningeal myeloid tissue, spleen and thymus in Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus) from hatching until 5months old (2895°C·day(dd)). The spleen was first visible on 541dd larvae LM sections and the other two immune organs in 768dd samples (approximately 400 and 600dd after onset of feeding). Generally, younger fish had significantly higher percentages of undifferentiated cells (meningeal myeloid tissue and spleen) and effective adaptive immune competence would not be expected in these fish on the onset of feeding, but further functional immune assessment is needed.