Early nutritional programming in sterlet sturgeon (Acipenser ruthenus) with dietary soybean meal: Assessment of growth performance, body composition, and expression of GH, IGF-I, and Ghrelin genes.

This study was performed to assess the impacts of introducing diets containing different levels of soybean meal (SBM) to sterlet sturgeon (Acipenser ruthenus) larvae on growth performance, body composition, and molecular responses in the juvenile stage. The sterlet larvae (57.68 ± 0.66 mg) were weaned onto the formulated diets as follows: a control diet containing 60% fishmeal (FM), and three experimental diets with replacement levels of 15% (SBM15), 30% (SBM30), and 45% (SBM45) of FM with SBM. Then, a total of 260 fish (initial weight: 323.33 ± 11.76 mg) were fed the four different diets for 28 days in triplicates (phase 1, nutritional programming, NP). All treatments were then fed with the FM diet in phase 2 (common phase), and in phase 3 (challenge phase), all experimental groups (6.14 ± 0.08 g) were transitioned to SBM45 for 28 days. At the end of phases 1 and 2, growth performance showed no significant differences among the groups (P > 0.05), while significantly improved in SBM45 than the control at the end of phase 3 (P < 0.05). No significant differences were found among the groups in any phases for whole body composition (P > 0.05). Additionally, the total saturated fatty acids were significantly higher in SBM-based diets than FM at the end of phase 3 (P < 0.05). The mRNA of GH, IGF-I was significantly affected by variation of FM replacement level (P < 0.05). The expression level of Ghrelin was up-regulated in fish fed SBM at the end of phase 3 (P < 0.05). Our findings revealed that NP can positively enhance the adaptation of juvenile sterlet sturgeon to 45% SBM when exposed to the same diets at the larval stage. Further research is being carried out to provide valuable insights into the underlying mechanisms of digestive performance for this species.

Intraperitoneal administration of kisspeptin-10 modulates follicle maturation, gonadal steroids, calcium and metabolites in Sterlet sturgeon, Acipenser ruthenus.

Kisspeptin is a multifunctional neurohormone, primarily involved in the regulation of reproduction. We tested whether peripheral administration of kisspeptin10 (KP-10) via intraperitoneal injection or slow release affects reproductive hormones and metabolites in Sterlet sturgeon (Acipenser ruthenus). Plasma and mucus 17ß-estradiol (E2), and testosterone (T), plasma and follicular vitellogenin (VTG) and calcium (Ca) as well as glucose and lipids were determined. Mature Sterlet sturgeon were grouped into six groups: saline i.p injection (control), human kisspeptin (hKP-10) i.p injection; acipenser kisspeptin (aKP-10) i.p injection; hKP-10 (slow release); aKP-10 (slow-release) and no treatment control. No effect for KP-10 on sturgeon body weight was found after 4 weeks of treatment. Multivariate analysis revealed a significant disparity in plasma E2 levels. It was significantly different between groups (time, P = 0.0022). E2 in epithelia mucosa showed significant difference between and within groups in the acute group (time, P = 0.0252; treatment, P = 0.0423; time × treatment, P = 0.0429). T levels were unaffected by treatments (P > 0.05). The presence of synthetic aKP-10 led to an elevation in oocyte and plasma VTG levels (P < 0.05). Prolonged exposure to this peptide resulted in an increase in plasma calcium levels. Simultaneously, there was an augmentation in the number of mature follicles. Regardless of the duration of exposure, aKP-10 significantly elevated plasma glucose levels in Sterlet (P < 0.0). Additionally, KP-10 led to an increase in plasma lipids and cholesterol in Sterlet. Overall, our data support an involvement for KP-10 in the regulation of gonadal steroid hormones, oocyte maturation and metabolite levels in sturgeon, suggesting a positive role for this peptide in the reproductive physiology of this species.

Ontogeny of the digestive enzyme activity of the pikeperch (Sander lucioperca) under culture condition.

The pikeperch (Sander lucioperca) is a species with a high potential for aquaculture and a valuable food with high market acceptance. The aim of the study was to evaluate the functional ontogeny of digestive enzyme of pikeperch from hatching to 45 days-post fertilization, 777 degree-day (DPF, dd) under culture condition. The average total length (TL) of larvae measured at hatching was 3.6 ± 0.4 mm (5 DPF; 67 dd) and at the end of experiment (45 DPF, 777 dd) was 27.1 ± 1.1 mm. The survival rate was 80-90% during the experiment period. Inhibition zimography reveals the presence of nine bands with proteolytic activity in the digestive tract of juvenile pikeperch. Zimography results during the ontogeny revealed that in larvae at 8 DPF (108 dd) and 13 DPF (189 dd), three bands were presented. The variations observed in the enzymatic activity reflected a high amount of total protease activity at 10 DPF (133.5 dd). Regarding pepsin, its activity was observed for the first time at 26 DPF (378.9 dd). Lipase activity remained constant from hatching to 26 DPF (378.9 dd). The highest amount of α-amylase activity was detected at 15 DPF (211.5 dd) and 45 DPF (777 dd). The low lipase enzyme activity suggested that live feeds with low lipid were more suitable than diets containing high lipid levels; larvae had also early capability to digest nutrient-dense diet that was high in protein. According to results the pikeperch larvae possess after the exogenous feeding, a functional digestive system with high activities that indicated the gradual development of the digestive system.

Effects of dietary supplementation of multi-strain probiotics on semen quality, seminal plasma compositions, and fertilization ability of rainbow trout (Oncorhynchus mykiss) broodstock spermatozoa.

The present experiment aims to study the effects of dietary multi-strain probiotics on semen quality, seminal plasma compositions, and fertilization ability of male rainbow trout. For this purpose, a total of 48 broodstocks with an average initial weight of 1366.1 ± 33.8 g were divided into 4 groups and 3 replicates. Fish were fed with diets containing 0 (control), 1 × 109 (P1), 2 × 109 (P2), and 4 × 109 (P3) CFU probiotic kg-1 diet for 12 weeks. Results showed that dietary supplementation of probiotics significantly increased plasma testosterone level, motility time of spermatozoa, sperm density, and spermatocrit value in P2 and P3 treatments and Na+ level in P2 treatment compared to the control group (P < 0.05). The activities of aspartate aminotransferase and lactate dehydrogenase had significantly decreased in the P2 treatment compared to the control group (P < 0.05). No considerable variations were observed between control fish and treatment groups (P > 0.05) in semen biochemical parameters, percentage of motile spermatozoa, osmolality, and pH of seminal plasma. Based on the results, the highest fertilization rate (97.2 ± 0.9%) and eyed egg survival (95.7 ± 1.6%) were observed in the P2 treatment, and those values showed remarkable differences with the control group (P < 0.05). The results indicated that multi-strain probiotics have potential efficacy on semen quality and fertilization ability of rainbow trout broodstock spermatozoa.

Dietary supplementation of multi-strain probiotic in male rainbow trout (Oncorhynchus mykiss) broodstock: Effects on feed efficiency, hemato-biochemical parameters, immune response, and semen quality.

The present study aimed to determine the effects of dietary probiotic supplementation on feed efficiency, physiological parameters, and semen quality of male rainbow trout (Oncorhynchus mykiss) broodstock. For this purpose, a total of 48 breeders with an average initial weight of 1366.1 ± 33.8 g were divided into 4 groups and 3 replicates. Fish were fed with diets containing 0 (control), 1 × 109 (P1), 2 × 109 (P2), and 4 × 109 (P3) CFU multi-strain probiotic kg-1 diet for 8 weeks. According to the results, P2 treatment significantly enhanced body weight increase, specific growth rate, and protein efficiency ratio and decreased feed conversion ratio. Moreover, the highest values of red blood cells count, hemoglobin, and hematocrit values were observed in P2 treatment (P < 0.05). The lowest levels of glucose, cholesterol, and triglyceride were found in P1, P2, and P3 treatments, respectively. Also, the highest levels of total protein and albumin were obtained in P2 and P1 treatments (P < 0.05). Based on the results, plasma enzymes contents were significantly decreased in P2 and P3 treatments. In terms of immune parameters, the complement component 3, complement component 4, and immunoglobulin M levels were increased in all probiotic-fed treatments (P < 0.05). For spermatological features, the highest spermatocrit value, sperm concentration, and motility time were observed in the P2 treatment (P < 0.05). Consequently, we conclude that multi-strain probiotics can be used as functional feed additives in male rainbow trout broodstock to enhance semen quality, improve physiological responses, and better feed efficiency.

The effectiveness of Ovaprim, Ovopel, and their combinations in artificial reproduction of common rudd Scardinius erythrophthalmus under controlled conditions.

In this study, a practical protocol for artificial reproduction was developed for the rudd, Scardinius erythrophthalmus, to help to produce this fish for aquaculture industries and also for restocking programs. For this purpose, the efficiency of different hormonal agents and their combinations for spawning induction of female breeders of rudd was evaluated. Ovulations were stimulated using different treatments as: two injections of Ovaprim (Ova), two injections of Ovopel (Ovo), a priming dose of Ovopel with a resolving dose of Ovaprim (Comb1), a priming dose of Ovaprim with a resolving dose of Ovopel (Comb2), and two injections of sterile 0.9% NaCl solution as a control group. During the study, ovulation success, egg developmental competence as well as the performance of the freshly hatched larvae were recorded. There was no ovulation in females from the control group. In hormone-treated groups, 84-100% of fish ovulated, but no differences were observed in ovulation success (P > 0.05). The shortest latency period in treated fish was recorded in the Ovo group (431.6 degree-hour, P < 0.05). The best results in terms of working fecundity (number of obtained eggs per fish), relative fecundity, fertilization success, hatching rate, and embryo survival up to the eyed stage were achieved in the Ova and Comb1 groups (P < 0.05). Moreover, better survival rates up to the absorbing yolk sac stage and the lowest abnormality of larvae were observed in Ova and Comb1 groups (P < 0.05). There was no significant difference in the incubation time among different groups (P > 0.05). The obtained results indicate that two injections of Ovaprim and/or a priming dose of Ovopel with a resolving dose of Ovaprim are suitable for the artificial reproduction of rudd female breeders. Due to the proper effects and ease of use, two injections of Ovaprim could be recommended for the production of this species for restocking or aquaculture programs.

Sex and reproductive development impact skin mucosal epithelium immunity, antimicrobial capacity, and up-regulation of immune-related gene of goldfish (Carassius auratus).

This study evaluated the epidermis mucosal capacity of goldfish (Carassius auratus) during different stages of reproductive development in both females and males. In this regard, the activity of mucolytic immune enzymes, i.e., lysozyme, complement and peroxidase, as well as the activity of alkaline phosphatase (ALP) were evaluated. There were five stages for females i.e., immature (f1), cortical alveoli (f2), early and late-vitellogenesis (vtg) (f3 and f4) and ripe (f5); as well as two stages for males spermatogenesis (m1) and spermiation (m2). Some stages were also examined for the mucosal antimicrobial activity against specific pathogens. The results showed that the mucosal lysozyme activity increased significantly during vitellogenesis (P < 0.05), but no lysozyme activity was detected in plasma. On the contrary, the complement activity was only observed in female plasma, and it was significantly higher at f3 compared to the other developmental stages. Both the plasma and mucosal ALP and peroxidase activities showed a significant increase by female reproductive development with the highest amounts at f4. Contrary to the female, no significant changes were observed in plasma and mucosal immune agents and biochemistry of the male. The f5-staged goldfish showed the highest antimicrobial activities against Gram-positive bacteria, i.e., Streptococcus faecium, Staphylococcus aureus and Micrococcus luteus (P < 0.05). Our results also represented the up-regulation of lysozyme (c-lys) gene expression by effects of female maturational development in ovary, liver and skin, while male goldfish showed no significant changes in c-lys expression. Moreover, there were positive correlations between c-lys expression, mucosal lysozyme activity and calcium levels in females (P < 0.01). Overall, our findings revealed that vtg process improves mucosal innate immunity that leads to activate antimicrobial components at spawning season.

The effectiveness of human chorionic gonadotropin in stimulation of second spermiation in pikeperch Sander lucioperca during the spawning season.

The aim of the present study was to evaluate the effectiveness of human chorionic gonadotropin (hCG) in stimulation of second spermiation in already reproduced pikeperch males during the same spawning season. Fish (mean weight 919.9 ±â€¯236.9 g) were divided into the control saline-injected group, and two groups injected with 200 and 400 IU hCG/kg body weight. Forty-eight hours following injection (at a temperature of 16.7 °C) the percentage of fish producing useable amounts of semen increased from 30% in the control group up to 80% in the treated fish and the highest volume of semen was recorded in fish treated with 400 IU/kg BW hCG. Spermatocrit (50.7 ±â€¯9.1%) and sperm concentration (17.5 ±â€¯5.0 × 109 spermatozoa/mL) were significantly higher in control fish than those recorded in hCG-treated fish (24.8 ±â€¯7.7% and 8.1 ±â€¯2.4 × 109 spermatozoa/mL in 200 IU/kg; 32.3 ±â€¯17.6% and 10.9 ±â€¯7.5 × 109 spermatozoa/mL in 400 IU/kg). No significant differences were observed between the groups with respect to sperm motility (as a spermatozoa activity time and percentage); however, a change in plasma alkaline phosphatase activity was found in the group injected with 400 IU/kg of hCG. The lack of significant differences in plasma metabolites and cortisol between control and hCG-treated fish indicated that the hCG had no effect on the stress response. Testosterone levels were significantly increased in the hCG-treated fish, whereas no significant differences in 17ß-estradiol were recorded. No differences between the groups in plasma levels of thyroid hormones suggested lack of hCG-induced effect on hypothalamus-pituitary-thyroid axis. The results of this study demonstrated that the spermiation of already reproduced pikeperch males could be induced by hCG during the same spawning season. Based on the results on semen volume and concentration, injection with hCG could improve the efficiency of pikeperch reproduction to reduce the number of brooders and costs of juvenile pikeperch production.

Repeated intraperitoneal injection of ovine growth hormone accelerates growth in sub-yearling Siberian sturgeon Acipenser baerii.

The role of growth hormone (GH) in chondrosteans is poorly understood, particularly with regard to its effects on growth. In this study, we examined the influence of exogenous GH on growth performance and body composition in juvenile Siberian sturgeon (Acipenser baerii). Fish with initial weight of 80.2 ± 0.1 g (mean ± S.E) were injected once every 10 days with either purified ovine GH (oGH) at 1, 2, 4, and 8 µg oGH/g body weight (BW) or with saline over a 50-day period. Treatment with the highest dose of oGH significantly enhanced growth performance (final body weight and length, body weight increase and specific growth rate, SGR). Notably, 8 µg oGH/g BW increased body weight by 33% and SGRw by 141% compared to control fish. GH-stimulated (8 µg oGH/g BW) growth was accompanied by increased crude protein content; however, oGH treatment did not affect levels of total protein, total lipid, cholesterol, triglyceride, or glucose in plasma. oGH decreased plasma levels of thyroxine (at 4 µg oGH/g BW), but had no significant effect on plasma levels of triiodothyronine or cortisol compared to controls. These findings indicate that 8 µg oGH/g BW enhances somatic growth and synthesis of body protein in juvenile Siberian sturgeon and demonstrate the feasibility of exogenous oGH treatment in conservation and aquaculture programs for this ancient species.

Effect of water temperature and food availability on growth performance, sex ratio and gonadal development in juvenile convict cichlid (Amatitlanianigrofasciata).

Temperature and food availability are key drivers of growth and reproductive development in fishes, but information on how they interact is poorly understood. This study investigates the effects of water temperature and food availability on growth, sex ratio and gonadal development of the convict cichlid (Amatitlania nigrofasciata) which is an ornamental fish that may be a useful lab model. For this experiment, 180 juvenile convict cichlid (0.3 ± 0.02 g) were held at three different temperatures (26, 29 and 32 °C as T1, T2 and T3) and fed to satiation (S) or a restricted diet (R: half satiation) during a 56-day experimental period. Specific growth rate was significantly higher in T2S treatment than the other groups. The highest and lowest mean oocyte sizes were recorded in T1S and T3R groups, respectively. The sex ratio of fish held at 29 °C was male biased (female, 21.0%; male, 78.9%), but this was not seen at 26 °C (female, 47.6%; male, 52.4%) or 32 °C (female, 57.1%; male, 42.9%). In T1S and T1R treatments, oocytes developed more than the other treatments and in T2S group testicular development was more advanced than other groups. These results demonstrate the complex interplay of temperature and food availability on growth and reproductive development in the convict cichlid. Appropriate food availability significantly improves growth and reproductive processes, while restricted feeding decreases growth, survival rate and reproductive performance.

Artificial reproduction of Caspian roach, Rutilus caspicus following stimulating ovulation with Ovaprim, Ovopel, and their combinations under controlled conditions.

The aim of this study was to evaluate the efficiency of different hormonal agents and their combinations for spawning induction of females Caspian roach, Rutilus caspicus. Five groups of fish were injected intraperitoneally as follows: two injections of Ovaprim (T1), two injections of Ovopel (T2), a priming dose of Ovopel with a resolving dose of Ovaprim (T3), a priming dose of Ovaprim with a resolving dose of Ovopel (T4), and two injections of sterile 0.9% NaCl solution as a control group. The results showed that no fish ovulated in the control group. In hormone-treated groups, no differences were observed in ovulation success (P > 0.05). The shortest latency time and highest working and relative fecundities were observed in fish stimulated with two injections of Ovaprim (T1 group). The mean values of fertilization success in treated fish were in the range of 87.9-93.1% and the highest values were observed in T3 and T1 groups (P < 0.05). The best results in terms of ovulation index (92.1%), hatching rate (93.7%), and survival up to the eyed egg stage (89.4%) were achieved after administering two injections of Ovaprim (T1 group). There were no significant differences in the incubation time and embryos survival rates up to absorbing the yolk sac among different groups (P > 0.05). Overall, the best results of controlled reproduction of Caspian roach were obtained after using two injections of Ovaprim. Consequently, the Ovaprim is more suitable for restocking and aquaculture purposes of endangered populations of Caspian roach.

A potential role of nettle (Urtica dioica) extract on growth, biochemical changes and reproductive performance of convict cichlid (Amatitlania nigrofasciata).

This study was carried out to investigate the effects of methanolic extract of nettle (Urtica dioica) on growth, reproduction, biochemical and immunological parameters of female convict cichlid (Amatitlania nigrofasciata). For this purpose, 54 fish were distributed in 3 treatments included: without supplementation (control), 0.1 g (NE0.1), and 0.5 g (NE0.5) nettle extract per kilogram feed over 56 days. The highest final weight (4.2 ± 0.1 g), weight gain (2.8 ± 0.1 g), and specific growth rate (2.0 ± 0.0% day-1) were recorded in NE0.1 group. Higher and lower feed conversion ratio were obtained in control and NE0.1 treatments, respectively. Hepatosomatic and viscerosomatic indices in NE0.1 treatment were significantly lower compared with control treatment. Fish fed NE0.1 showed significantly lower glucose (55.2 ± 6.5 mg g-1), cholesterol (28.4 ± 3.3 mg g-1), and triglyceride (211.5 ± 39.0 mg g-1) levels. Total protein (36.3 ± 3.4 mg g-1) and albumin (2.7 ± 0.1 mg g-1) showed a marked increase in NE0.1 treatment. Same trend was observed in C3, C4, and IgM concentrations. NE0.1 showed the highest number of eggs per female (183.7 ± 10.2), hatching rate (97 ± 0.7%), and larval survival rate at 3 days post hatch (86.3 ± 0.6%) compared with the other treatments. These findings indicated that 0.1 g methanolic extract of nettle kg feed-1 could enhance growth, improve metabolic, and immune function of convict cichlid. Moreover, this study confirmed that appropriate dose of nettle can positively promote reproductive performance which makes it as a valuable and cost-effective herb in aquaculture industry.

Comparative study on accuracy of mucosal estradiol-17ß, testosterone and 11-ketotestosterone, for maturity, and cutaneous vitellogenin gene expression in goldfish (Carassius auratus).

Providing a non-invasive procedure to track fish maturity remains a priority in broodstocks' management. In the present study, the main goal was to assess reproduction status by measuring sex steroids and vitellogenin (VTG) in the skin mucosa, as a non-invasive method. For this purpose, the present study compared the levels of estradiol-17ß (E2 ), testosterone (T), 11-ketotestosterone (11-KT), VTG and calcium (Ca) in skin mucosa and blood plasma of goldfish (Carassius auratus). Skin mucosal and blood samples were collected, as well as gonad tissues, from goldfish, as a seasonal spawner. Histological analysis confirmed the gender and maturity status from females' ovaries (as primary-growth, cortical-alveoli, initial and late-vitellogenesis) and males' testes (as spermatogenesis and spermiation). Furthermore, vitellogenin (vtg) expression was observed in skin, liver and gonads. The results indicate that mucosal E2 concentrations were significantly higher during initial and late vitellogenesis than the other stages. Mucosal 11-KT concentrations significantly increased at spermiation (P < 0.05). E2 /T and 11-KT/E2 ratios significantly increased at early vitellogenesis and spermatogenesis, respectively (P < 0.05). Females' mucosal VTG levels were significantly fluctuated according to the maturity stage. Ca showed a similar trend, but Ca was more accurate for sex identification than the VTG. Although mucus showed high levels of VTG, ovarian vtg expression was strongest while liver and skin had the similar results. These results show that measuring the mucosal androgens could be considered as an accurate, non-invasive method to monitor fish maturity.

Changes in lipid biology during ovarian development in farmed beluga sturgeon, Huso huso L.

The present study was conducted to understand key biochemical, physiological, and molecular changes associated with ovarian growth and with lipid transfer and/or accumulation into the ovary during oogenesis in captive beluga sturgeon. Plasma levels of triacylglycerides, cholesterol, phospholipid, and sex steroid hormones were determined and all were found to increase notably throughout development from the perinucleolar to the tertiary yolk stage. Using fast protein liquid chromatography, we recognized three major lipoprotein peaks in chromatograms from all samples. These peaks were characterized as containing very low-density lipoprotein (Vldl), low-density lipoprotein/high-density lipoprotein (Ldl/Hdl), and plasma proteins. While Ldl/Hdl represented the most abundant lipoprotein fraction, the relative abundance of different lipoprotein classes did not change with the stage of oogenesis. Eluted lipoproteins were separated using sodium dodecyl-sulfate polyacrylamide gel electrophoresis and sequenced. The peptide sequence spectra for 66-kDa, 205-kDa, 29-kDa, and 70-kDa bands matched with albumin, vitellogenin (Vtg) AB2b, immunoglobulin light-chain precursor, and immunoglobulin heavy-chain, respectively. The large amount of albumin in the plasma protein peak and the confined presence of Vtg AB2b to within Ldl/Hdl reinforce the lipoprotein classification. Lastly, transcript levels of genes encoding ovarian lipoprotein lipase (lpl), apolipoprotein E (apoe), very low-density lipoprotein receptors (vldlr), and low-density lipoprotein receptor-related protein 8-like (lrp8) were estimated using quantitative RT-PCR. The high mRNA levels of lpl, apoe, and lipoprotein receptors vldlr and lrp8 in previtellogenic females suggest that sturgeon oocytes need to be prepared to accept and traffic Vtg and lipids internally, before the start of vitellogenesis.

Stimulatory effects of short-term calcitonin administration on plasma calcium, magnesium, phosphate, and glucose in juvenile Siberian sturgeon Acipenser baerii.

Calcitonin (CT) has a potential function in calcium (Ca) regulation, but there are conflicting observations in fishes. Because of the lack of calcified endoskeleton, sturgeons have low Ca circulating compared with teleost fish and the function of CT on Ca in sturgeon is very less understood. The purpose of this study was to investigate the impact of injection of salmon CT on plasma Ca, magnesium (Mg), phosphate (PHO), and glucose levels of juvenile Siberian sturgeon Acipenser baerii. Sixteen-month-old fish (429.6 ± 12.1 g) were intraperitoneally injected with a single dose of CT (5 µg kg-1 BW) and saline solution as a control group. Thereafter, blood sampling was performed at 0, 1, 2, 4, 6, 12, 24, and 48 h after injection. CT produced marked increases in all variables measured. The highest levels of Ca (6.77 ± 0.53 mg dL-1), Mg (9.79 ± 0.16 mg dL-1) and PHO (1.74 ± 0.05 mg dL-1) were recorded at 2 h after CT injection and showed significant difference compared with control treatment (Ca 4.75 ± 0.12 mg dL-1; Mg 5.47 ± 0.16 mg dL-1 and PHO 1.23 ± 0.06 mg dL-1). It also likely produced hyperglycemia. However, the differences with the controls were not statistically significant, possibly due to interference with the hyperglycemia induced by the stress of injection. Our results showed that the injection of 5 µg kg-1 BW CT to Siberian sturgeon has an incremental effect on plasma Ca, Mg, and PHO. The increase in plasma Ca level indicated that CT has a potent hypercalcemic effect in sturgeon under laboratory condition, in contrast to the hypocalcemic effects reported for teleosts.

The effects of 11-ketotestosterone implants on transcript levels of gonadotropin receptors, and foxl2 and dmrt1 genes in the Previtellogenic ovary of cultured beluga (Huso huso).

The in vivo effect of 11-ketotestosterone (11KT) on transcript levels of the gonadotropin receptors (fshr and lhr) and sex differentiation-related genes (dmrt1 and foxl2) was examined in the ovaries of immature female beluga. For this purpose, six fish were treated with implants containing 2.5 mg 11KT and a placebo group of six females of the same age and gametogenic stage were given a blank implant. The implants were intraperitoneally inserted into 4-year-old females at the previtellogenic stage (mean body weight 5580 ± 165 g) and maintained under culture conditions for 8 weeks. Ovary samples for gene expression analysis of lhr, fshr, dmrt1 and foxl2 were collected by biopsy at 3 and 8 weeks post implantation. Diameters of oocytes increased in response to 11KT treatment, both at 3 and at 8 weeks post implantation, but no obvious changes were evident in cytology. Three weeks of 11KT treatment did not affect target gene expression, but a tendency for a time-dependent decrease of lhr and dmrt1 mRNA levels was observed in both treatment and placebo groups. By 8 weeks of treatment, however, 11KT implants provoked the upregulation of fshr and foxl2 transcript levels. Furthermore, lhr and dmrt1 transcript abundances recovered by 8 weeks of exposure in both blank- and 11KT-implanted beluga. These results suggest that 11KT, either directly or indirectly, may affect gametogenesis and regulate some key components of the reproductive axis in female beluga.

Design, production and purification of a novel recombinant gonadotropin-releasing hormone associated peptide as a spawning inducing agent for fish.

GnRH is a neuropeptide known to regulate reproduction in vertebrates. The purpose of this study was to design and produce recombinant gonadotropin-releasing hormone associated peptide (rGnRH/GAP) as an alternative of the previous GnRHs and native extracted hormone from tissue, to induce final maturation in fish. Decapeptide as well as GAP area sequences were compared between GnRH1, GnRH2, and mGnRH from Acipenser sp and Huso huso, respectively. Considering the conserved amino acids and the replacement of un-stable amino acids with those that were more stable against proteolytic digestion as well as had a longer half-life, the sequence was designed. The sequences of decapeptide and GAP region were synthesized and then cloned on pET28a expression vector and transformed into expression host Escherichia coli BL21(DE3). The supernatant of cultured recombinant bacteria was used for purification using TALON Metal affinity resin. The purity of the GnRH/GAP was confirmed by single 8 kDa band on SDS-PAGE and Western blot. Bioinformatics studies were performed for evaluation of homology between GnRH protein sequences and prediction of 3D protein structure using Swiss Model. The result showed that the structure prediction of the recombinant GnRH decapeptide was relatively similar to decapeptide of GnRH2 from Beluga (Huso huso). The GAP structure was similar to GAP1 of Nile tilapia (Oreochromis niloticus) and sturgeon and GnRH2 of Chinese sturgeon (Acipenser sinensis). The mass analysis showed that the sequence was exactly the same as designated sequence. Biology activity of rGnRH/GAP was tested in mature goldfish (Carassius auratus) and results showed that rGnRH/GAP had a positive effect in final maturation. Indeed 17α, 20ß-dihydroxy-4-pregnen-3-one (DHP) was increased 17 h and 24 h after injection with rGnRH/GAP and spawning stemmed from that injection. These novel findings introduce the potential of utilizing rGnRH/GAP in aquaculture.

11-Ketotestosterone induces oocyte growth, but does not affect oocyte cytology in pre-vitellogenic captive beluga, Huso huso L.

An effect of 11-ketotestosterone (11-KT) on growth of previtellogenic (PV) ovaries of eel, salmon and Atlantic cod has been demonstrated. The purpose of this study was to investigate the effects of 11-KT treatment (in vivo) on ovarian growth, on hormonal and biochemical changes in blood, and on ovarian mRNA levels of lipidation-related genes in captive beluga with PV oocytes. In addition, the potential involvement of lipoprotein lipase (Lpl), an important enzyme for extracellular hydrolysis of lipoprotein-associated lipids, was evaluated. Twelve beluga (4-year olds) were treated with an intraperitoneal slow-release implant of either 11-KT (2.5 mg) or a compressed matrix (control). Ovarian biopsy was done to obtain pre- (day 0: T0) and post-treatment (day 21: T21) data on histology and target gene expression. Three weeks of exposure resulted in an increase in serum 11-KT levels from 2.2 ng/mL to 83 ng/mL but did not yield significant changes in serum levels of triacylglycerides and cholesterol. Furthermore, 11-KT implantation increased oocyte diameters from 259 µm (T0) to 309 µm by T21. Regardless of the increase in oocyte size, ovaries remained in the PV stage, mostly as late perinucleolar oocytes. Meanwhile, at the molecular level, the expression of lipidation-related transcripts [lpl, apolipoprotein E (apoe), very low density lipoprotein receptors (vldlr), low-density lipoprotein receptor-related protein 8-like (lrp8)] was significantly up-regulated after three weeks. Immunostaining for Lpl by Western blotting indicated three immunoreactive bands (70, 58 and 37 kDa) in ovarian homogenates from beluga, but signal intensity was not affected by treatment. Altogether, the administration of 11-KT increased 11-KT serum levels, oocyte size, and the expression of genes associated with lipid uptake. However, this treatment did not advance ovarian development beyond the PV stage.

Growth performance and plasma metabolites in juvenile Siberian sturgeon Acipenser baerii (Brandt, 1869) subjected to various feeding strategies at different sizes.

The effect of various feeding strategies was evaluated on growth performance and biochemical parameters in two sizes of Siberian sturgeon (465.75 ± 11.18 and 250.40 ± 12 g) during 45 days. Fish were distributed into six experimental treatments including large fish with satiation feeding (LA), small fish with satiation feeding (SA), large fish with 50% satiation feeding (LR), small fish with 50% satiation feeding (SR), large starved fish (LS), and small starved fish (SS). Differences in final weight between LA and LR treatments were not noticeable, whereas SA and SR treatments showed significant differences. Growth parameters were more affected in small fish. In condition factor and weight gain in starved treatments, a considerable reduction occurred by interaction between feeding strategies and fish size, so the lowest values were obtained in SS treatment. Glucose levels significantly decreased in small fish during the starvation. Interaction between feeding strategy and fish size indicated the highest and lowest albumin level in SA and SS treatment, respectively. Cholesterol, triglyceride, total protein, and globulin showed no significant differences. It can be deduced that small fish are more sensitive to starvation than the large fish. Since glucose and albumin showed significant decrease in starved small fish, these parameters can help to monitor nutritional status and feeding practices. It was indicated that in both sizes of Siberian sturgeon, feeding 50% satiation reduced the food cost without negative impact on physiological condition, and it can be considered as an appropriate strategy to face unfavorable circumstances.