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 17β-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.

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.

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.

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.

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.

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.

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 SGR_w 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.

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-17β, 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-17β (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.

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.

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.

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, 20β-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.

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.

Effects of nanostructured zeolite and aflatoxin B1 in growth performance, immune parameters and pathological conditions of rainbow trout Oncorhynchus mykiss

The reduction of Aflatoxin B₁ (AF) in juvenile rainbow trout (Oncorhynchus mykiss) diet was analyzed after supplementing Nanostructured Zeolite (NZ) in a 56-day experiment. Two hundred and seventy juveniles with an average weight of 23 ± 3.7 g were placed in 6 different groups of C (control as a basal diet), NZ_0.5 (basal diet + 0.5% NZ), NZ₁ (basal diet + 1% NZ), AF₅ (basal diet + 5 mg AFB₁), AF₅ NZ_0.5 (basal diet + 5 mg AFB₁ + 0.5% NZ), AF₅ NZ₁ (basal diet + 5 mg AFB₁ + 1% NZ) with three replications and were fed four times a day based on their satiation. No significant differences were observed in terms of growth performance among the experimental groups (P > 0.05). However, hepatosomatic index in fish fed by AF₅ NZ_0.5 was reduced compared with NZ_0.5 group (P < 0.05). The carcass moisture content showed a higher amount in treatment AF₅ NZ_0.5 compared to the control group (P < 0.05). There was a decrease in fat content in treatment AF₅ compared to that of the control group (P < 0.05). Serum total protein, albumin and globulin levels in fish fed with aflatoxin were lower than in fish fed the diet without AF for all levels of NZ (P < 0.05); however, the interaction between AF and NZ was not significant (P > 0.05). Concentrations of C₃, C₄ and immunoglobulin M together with serum lysozyme activity showed no significant differences among all treatments (P > 0.05). No considerable histopathological lesions were observed in liver, kidney and spleen for all treatments. Based on the results, NZ showed some effects on physiological functions in juvenile rainbow trout fed by 0.5% dietary NZ which could improve performance in this species.

Effects of dietary green tea (Camellia sinensis L.) supplementation on growth performance, lipid metabolism, and antioxidant status in a sturgeon hybrid of Sterlet (Huso huso ♂ × Acipenser ruthenus ♀) fed oxidized fish oil

Lipid content of diet is very susceptible to oxidation, especially when stored for a long time, so for evaluating protective effects of green tea in fish received oxidized oil, this study was done. Lipid content of diet was replaced by oxidized fish oil (OFO) in 0, 50, and 100%. Green tea extract (GTE) was added to diet in three levels, 0, 5, and 100 mg/kg giving a total of nine experimental diets. Two hundred and seventy sturgeon hybrid of Sterlet (Huso huso ♀ × Acipenser ruthenus ♂) with initial weight of 212.6 ± 0.7 g after 2 weeks adaptation randomly divided in 27 fiberglass tanks with 700 L volume. Fish were fed satiated three times daily. After 6 weeks, biometry was done to evaluate growth performance and blood samples were taken for biochemical analysis. The result showed that feeding with oxidized oil had no effects on growth. However, in fish fed GTE, growth indices improved slightly. Feeding with OFO reduced serum total cholesterol, triacylglycerol, and low-density lipoprotein, while increased high density lipoprotein. Dietary GTE moderated the effects of OFO on lipid metabolism. Feeding with the OFO increased activity of serum superoxide dismutase, catalase, glutathione peroxidase, and malondialdehyde contents. In fish received both OFO and GTE, reduced activity of serum antioxidant enzymes and malondialdehyde content was recorded in compare to fish fed only OFO. According to the result of the present study, it can be argued that feeding of sturgeon hybrid of Sterlet with OFO has negative effects on lipid metabolism and antioxidant status, whereas GTE dosages used in this study have protective effects on fish from the adverse effects of oxidized oil.

Short-term effects of 17β-estradiol on physiological responses in stellate sturgeon Acipenser stellatus

There is no evidence of the effect of 17β-estradiol (E2) administration on stress response and related metabolites after a short-period in chondrostean. In this study, we examined whether E2 is capable of inducing the hypothalamus-pituitary-interrenal axis activity. To accomplish this, sexually immature Acipenser stellatus were injected intraperitoneally with saline or E2 (5mg/kg body mass) and sampled 0, 1, 3, 6, 12, 24, 48, and 72h later. Plasma E2, cortisol, glucose, lactate, hematocrit (Hct), total protein (TP), cholesterol, triglyceride, alkaline phosphatase activity (ALP), calcium (Ca), and phosphorus concentrations were examined. Plasma levels of E2 significantly increased after 1h in E2-injected fish and remained high after 12h. E2 injection enhanced plasma TP and Ca concentrations, but had no effect on other parameters. Injection of either saline or E2 enhanced plasma glucose, lactate, TP, and Ca concentrations, but had no effect on Hct, cholesterol, triglyceride, and ALP. The results demonstrated that acutely elevated level of E2 did not lead to intense changes of stress metabolites and altered biochemical changes compared to the fish in control or saline treatment groups. Therefore, we found no exhibition of E2 on the rate of cortisol synthesis or stress indicators in this species, while E2 could modulate some other related metabolites on vitellogenesis pathway.

Physiological changes and reproductive performance of Sterlet sturgeon Acipenser ruthenus injected with thiamine

To evaluate the effects of thiamine on physiological changes and spawning performance of Sterlet sturgeon Acipenser ruthenus, 45 farmed female fish (698.6±8.9g) were randomly distributed in 9 tanks (1000L) and fed a diet with 1g/kg of an anti-thiamine drug. This was provided for 5 months prior to spawning. Thiamine hydrochloride was intraperitoneally injected to fish at three different doses: 0 (T₀, as control), 5 (T₅) and 50 (T₅₀) mg/kg body weight at days 30, 90 and 150 after the experiment started. After five months, the results showed no significant differences in weight gain and hemoglobin level, but hematocrit significantly increased in T₅ group. There was no significant difference in glucose-6-phosphate dehydrogenase and estradiol-17β, but testosterone was significantly increased in the T₅₀ group. Total thiamine concentration in the eggs was significantly higher in T₅₀ than that detected in the control group. Fecundity and larval mortality at 6day post hatch (dph) showed no significant differences among treatments, while the number of eggs per gram was significantly lower in T₀ than that observed in T₅₀. Larval weights at 1 (11.6mg) and 6 (23.1mg) dph and larval lengths at 6 (15.6mm) dph were significantly affected by the treatment with the highest level of thiamine injection (T₅₀). Diseases symptoms such as yolk sac deformation, erratic pattern of swimming, and loss of equilibrium were observed at 4 dph in T₀ and T₅ groups. The overall results revealed that thiamine injection has positive effects on reproductive performance in the sturgeon and the negative impacts of anti-thiamine in the offspring can be reduced by the injection of this vitamin to the broodstock.

Changes of vitellogenin and Lipase in captive Sterlet sturgeon Acipenser ruthenus females during previtellogenesis to early atresia

Plasma chemistry, lipid metabolism and vitellogenin gene expression of captive Sterlet sturgeon Acipenser ruthenus were studied in different maturity stages. A total of 32 fish were sampled, and maturity stages were identified on the basis of histological criteria and direct observation. Females were classified to four groups: previtellogenic, vitellogenic, post-vitellogenic, and atresia. Blood, gonad and liver tissue samples were taken through non-lethal biopsy. Our results showed that plasma levels of glucose, cholesterol, triacylglycerol, high-density lipoprotein, low-density lipoprotein, very low-density lipoprotein, calcium, phosphorus, alkaline phosphatase activity, albumin and total protein increased during ovarian development and were highest at post-vitellogenic stage. The lowest amounts in atresia stage demonstrate that lipid and energy imbalance was related to reabsorption and digestion of the yolk. These results suggested that the VLDL was the main plasma lipoprotein component of Sterlet. We determined that lipoprotein lipase and hepatic lipase activity increased during vitellogenesis process which suggested the role of lipase enzymes in regulating blood lipid metabolism. RT-PCR analysis indicates that Vitellogenin (VTG) mRNA could be detected both in livers and ovaries of female Sterlet. Throughout the study, the expression level of VTG gene showed an increase both in ovaries and in livers reaching its peak at late vitellogenesis stage. This strongly indicated a relation between VTG mRNA and ovarian development.

The onset of stress response in rainbow trout Oncorhynchus mykiss embryos subjected to density and handling

The present study made an attempt to measure the cortisol content, as an indicator of stress response, in rainbow trout embryos which were exposed to different densities and handling stress (air exposure) during incubation. The three densities of experimental embryos at early development stages were considered as 2.55 embryos/cm(2) (low density), 5.10 embryos/cm(2) (normal density) and 7.65 embryos/cm(2) (high density). The cortisol content of eggs (5.09 ± 0.12 ng/g) decreased to 3.68 ± 0.14 ng/g in newly fertilized eggs. Resting level of cortisol dropped at three densities by day 18 of post fertilization. Then, cortisol increased at hatching stage to 1.16 ± 0.11, 1.20 ± 0.12 and 1.21 ± 0.14 ng/g at low, normal and high densities, respectively. There were no statistically significant differences between cortisol concentrations in three densities. The acute handling stress test (5-min out-of-water), conducted on embryos (48 h post fertilization, organogenesis and eyed stage) in three densities, revealed no differences in whole-body cortisol levels between stressed and unstressed experimental groups. At hatching stage in low-density group, level of cortisol increased but the difference with the pre-stress levels was not statistically significant. Furthermore, significant differences in cortisol levels of stressed and unstressed embryos were detected on hatching in normal and high density groups [1.20 ± 0.12 at time 0-1.49 ± 0.11 ng/g at 1 hps (hours post stress) and from 1.21 ± 0.14 at time 0 to 1.53 ± 0.10 ng/g at 3 hps, respectively]. The results showed no difference in profile of cortisol in different densities, but acute stress conducted on embryos, incubated in different densities, revealed differences in cortisol stress response at hatching between normal and high density, which lead to cortisol increase at hatching time. It indicates that the lag time in the cortisol response to stressors immediately after hatching does not occur when the siblings were stressed during the embryo stage. Results, finally, indicated that hypothalamus-pituitary-interrenal axis was active and responded to an acute stressor under normal and high density, but it is unresponsive to a stressor around hatching under low density.

Variations of some physiological and immunological parameters in Siberian sturgeon (Acipenser baerii, Brandt, 1869) subjected to an acute stressor

This study was carried out to investigate the effect of an acute stressor on the variation of some physiological and immunological parameters of Siberian sturgeon (Acipenser baerii) juveniles. Fish, reared in 3 tanks for 10 weeks, were used for this study. The acute stress of fish consisted of 2 min of air exposure stress. Plasma levels of cortisol, glucose, and lactate as well as lysozyme activity in plasma were measured before stress and 1 hr, 3 hr, 6 hr, 9 hr, 12 hr, and 24 hr after stress. The plasma cortisol significantly increased in the highest level 1 hr after stress, yet it gradually declined after 3 hr. The glucose significantly increased only 1 hr after stress. There was no significant difference between plasma lactate prestress and poststress. Moreover, lysozyme activity was enhanced by stress, thus reaching the highest level 9 hr after stress. The results of this study indicate that Siberian sturgeon not only have a rapid response to acute stress, but also a great capacity for recovery from stress, thus returning physiological parameters to prestress levels after 6 hr.

Long-term effects of intraperitoneal injection of estradiol-17β on the growth and physiology of juvenile stellate sturgeon Acipenser stellatus

Juvenile stellate sturgeon Acipenser stellatus were intraperitoneally injected with estradiol-17β (E2; 0 and 5 mg/kg fish) to investigate the possibility of sex reversal and also determine the changes in biochemical parameters. Five-month-old fish (40.9 ± 1.1 g) were injected every 3-week interval during a 190-day trial. At the termination of the experiment, final weight and other growth parameters including weight gain and specific growth rate, hepatosomatic and viscerosomatic indices were not affected by repetitive injection of E2. Hematological features of E2-treated fish showed significant reductions in number of red blood cells, hemoglobin concentration, hematocrit value and mean corpuscular hemoglobin (P < 0.05), but no significant changes were observed in number of white blood cells, mean corpuscular volume and mean corpuscular hemoglobin concentration (P > 0.05). Calcium, phosphorus, glucose, triacylglycerol, cholesterol, total protein and estradiol concentrations were significantly increased in fish injected with E2 (P < 0.001). Plasma progesterone and testosterone levels were noticeably lower in fish injected with 5 mg/kg E2 rather than the control fish (P < 0.001). Histological observations of gonads showed that all fish injected with 5 mg/kg E2 apparently feminized, while 66.6 % of the control group was female. These results revealed that the injection of E2 is an effective method for feminization of stellate sturgeon without having significant inhibitory effects on growth and survival.

Physiological changes in male and female pikeperch Sander lucioperca (Linnaeus, 1758) subjected to different photoperiods and handling stress during the reproductive season

Pikeperch broodstocks were exposed to different photoperiods: constant light (24L:0D), constant darkness (0L:24D), and 12 h light, 12 h darkness (12L:12D), for 40 days. Half of the broodstocks of each photoperiod were exposed to handling stress at a specific time of the day. Results showed that cortisol and lactate did not reveal any significant difference. However, glucose levels in females increased in the stress-free darkness period in comparison with stressful darkness photoperiods (0L:24D-s). Red blood cells in males and white blood cells in females showed a significant difference under different photoperiod regimes. Both sexes showed no significant difference in the differential count of leukocytes under different photoperiods and handling stress. Constant photoperiods and handling stress affected the hematological parameters, particularly, the number of lymphocytes and neutrophils in females. Our findings revealed that due to a long-term exposure to stressors, pikeperch brooders become adapted to stressful conditions.

Physiological responses in wild broodstocks of the Caspian Kutum (Rutilus frisii kutum) subjected to transportation stress

Caspian Kutum (Rutilus frisii kutum) broodstocks in the wild were subjected to 2 different densities (100 and 300 kg m(-3)) for 2 hr of transport, and their physiological responses were examined. Fifteen fish were placed into the plastic container for each replicate and blood was taken at 0, 10, 30, 60, and 120 min after transportation in different densities. Mean levels of cortisol and glucose as primary and secondary responses to the stress were significantly different between densities. Significant differences in both densities were observed in cortisol for all times and glucose levels at 30 and 120 min after transportation, and the highest values were found in both densities at 120 min. Testosterone concentrations declined considerably in the first 10 min, and then they showed a gradual decrease with a significant difference between 2 densities at 10 and 30 min after transportation. Serum estradiol reached the lowest level at 120 min after transportation, and differences were significant between the 2 densities after 30 min. Based on the results, it was concluded that Kutum broodstocks are sensitive to transport, especially at high density. Therefore, welfare during transport should be considered.

The metabolic effects of feeding and fasting in beluga Huso huso

A six week-study was conducted to determine the effect of starvation and feeding on growth, hematology and biochemical variables in sub-yearling beluga. Fish were placed on six feeding strategies: i) starved condition for 6 weeks, ii) a 2-week starvation, 2-week feeding and 2-week starvation, iii) a 2-week feeding, 2-week starvation and 2-week feeding, iv) a 3-week starvation followed by a 3-week feeding, v) a 3-week feeding with following 3-week starvation, and vi) fed throughout the 6 weeks. After 6 weeks, hematology, triacylglycerol, cholesterol, total protein, HSI, VSI, crude fat in muscle, final weight, feed conversion, specific growth rate, and condition factor were significantly affected by feeding strategies. The results suggested that most of the growth and physiological variables responded to a short period of starvation or re-feeding. These findings indicated that beluga could partially recover in weight and some physiological indices from periods of starvation when provided subsequently ad libitum feeding.

Effects of dietary bovine lactoferrin on growth, physiological performance, iron metabolism and non-specific immune responses of Siberian sturgeon Acipenser baeri

The present experiment was carried out to investigate the effects of different levels of dietary lactoferrin (LF) on growth performance, physiological status, iron absorption and innate immune response of juvenile Siberian sturgeon Acipenser baeri. Fish were fed with six different rations including 0, 100, 200, 400, 800 and 1600 mg LF kg(-1) diet for 8 weeks. At the end of the experiment, samples were collected for estimating the physiological and immunological parameters. Dietary LF did not change the fish growth performance, hematological parameters, serum proteins or hepatic enzymes. Moreover, stress indicators (plasma cortisol, glucose and lactate) were not affected by dietary LF. The iron absorption of fish was considerably affected by LF; thus, plasma iron in LF-treatments greatly declined and the total iron binding capacity (TIBC) significantly increased in fish fed with 800 mg LF kg(-1). In addition, the liver iron content markedly increased in some LF-treatments, but the variation of muscle iron concentration in treatments was insignificant. The amount of mucus secretion and serum bactericidal activity rose in fish fed on dietary LF, although other non-specific immune responses such as mucus bactericidal activity, serum and mucus lysozyme activity, serum peroxidase, serum natural hemolytic complement activity and serum IgM were not influenced by LF. This study revealed the ability of dietary LF to sequester iron, which is an essential nutrient required for the growth of bacteria. LF was also shown to improve some physiological and immunological parameters of Siberian sturgeon, to some extent.

Effect of dietary vitamin E on cortisol and glucose responses to handling stress in juvenile beluga Huso huso

An 8-week feeding experiment was conducted to investigate the effect of dietary vitamin E on the physiological response to handling stress in juvenile beluga Huso huso. Fish were fed six experimental diets supplemented with 0, 25, 50,100, 200, or 400 mg Dl-all-rac-alpha-tocopherol acetate/kg diet. At the end of the experiment, the fish in each tank were subjected to acute handling and air exposure stress. Cortisol and glucose were measured as the primary hormonal and secondary metabolic responses to the stressors, both before and 3 h after application of the stressors. The growth parameters and feed utilization rates were significantly lower in fish fed the diet not supplemented with vitamin E than in fish fed diets supplemented with vitamin E. Cortisol concentration was not affected by dietary treatment but glucose concentration was. Fish fed vitamin E at 0, 25, 100, and 400 mg/kg diet had higher concentrations of glucose than those fed vitamin E at 50 and 200 mg/kg. However, fish fed diets with 50 and 200 mg/kg exhibited higher growth rates. These results indicate that dietary vitamin E has some effect on plasma glucose but no effect on plasma cortisol. In general, when the stressors were applied to belugas, the glucose and cortisol responses were relatively low. This may be due to higher resistance and lower physiological responses to these types of stressors by this species or by chondrosteans in general.

Effect of dietary vitamin E on growth, muscle composition, hematological and immunological parameters of sub-yearling beluga Huso huso L

This study was designed to determine the effect of dietary vitamin E on growth, some hematological and immunological parameters and muscle proximate analysis of beluga Huso huso. Experimental fish were fed practical diets supplemented with 0, 25, 50, 100, 200 and 400 mg Dl-all-rac-α-tocopherol acetate kg diet(-1) for 8 weeks. 360 fish (mean initial weight 49.7 ± 0.1 g) were distributed into eighteen 785 L circular concrete tanks and each diet was fed to triplicate groups of fish. At the end of experiment (8 weeks), growth parameters such as final weight (FW), weight gain (WG), total length (TL), feed conversion ratio (FCR), specific growth rate (SGR), protein efficiency ratio (PER), condition factor (CF), hepatosomatic index (HSI), muscle composition, and some physiological indicators, including hematological and immunological parameters, such as hematocrit (Hct), total leukocyte count (WBC), lymphocyte, neutrophil, eosinophil and monocyte, cortisol, glucose, erythrocyte fragility, lysozyme and complement activity were determined. FW, WG, SGR, PER and CF in fish fed unsupplemented vitamin E were significantly lower than those fish fed the other five diets. However FW and PER in fish fed control diet had not significant differences with fish fed at 400 mg kg(-1). FCR were significantly higher in fish fed control diet than other groups. TL and survival rate had no significant differences among fish groups. HSI in fish fed 0 and 25 mg vitamin E kg diet(-1) were significantly lower than the other treatments. Muscle composition analysis showed no significant differences among the treatments. Erythrocyte fragility, Hct, WBC, lymphocyte, neutrophil, eosinophil and monocyte, lysozyme and complement activities were not significant. Also cortisol and glucose concentrations had not significant differences between treatments. Results indicated that vitamin E had no significantly effect on muscle proximate analysis, hematological and immunological parameters of sub-yearling beluga but has a direct effect on growth performance of beluga sturgeon and this vitamin is an essential nutrient required for normal growth in this species.

Responses to handling and confinement stressors in juvenile great sturgeon Huso huso

The effects of acute stressors on physiological responses of juvenile great sturgeon or beluga Huso huso L. were investigated in two experiments. In the first experiment, fish were handled by placing them in containers at either low density (LD, one fish l(-1)) or high density (HD, four fish l(-1)) for 60 s. Concentrations of plasma cortisol, glucose and lactate were determined from blood collected at 0, 1, 3, 6 and 12 h after application of the stressor. Plasma cortisol concentrations increased after the disturbance in H. huso from both handling treatments, but changes were not significant. Plasma glucose rose significantly by 22.9 and 31.6% in LD and HD handling treatments, respectively, after 3 h. Significant increases in plasma lactate occurred within 1 h in both treatment groups, but that of the HD group was much higher. In the second experiment, fish were held at two different densities, LD (2 kg m(-2) tank bottom surface area) and HD (7 kg m(-2)), for 8 weeks and then subjected to an aerial emersion handling stressor in a net for 60 s; blood samples were taken before handling (resting, 0 h) and at 1, 3, 6 and 9 h after handling. Plasma cortisol increased significantly in fish from the HD treatment from 8.8 +/- 0.3 to 19.2 +/- 2.4 ng ml(-1) (mean +/-s.e.) by 1 h after stress, but post-handling changes in the LD group were not significant. Significant increases in both plasma glucose and lactate were observed by 1 h in both treatment groups, with peak levels of plasma glucose evident at 3 h [69.4 +/- 2.9 and 60.9 +/- 1.7 mg dl(-1) (mean +/-s.e.) in LD and HD groups, respectively]. Plasma glucose levels were significantly higher in the LD group than in the HD group at 3 and 6 h. Post-handling haemoglobin content increased by 1 h and white blood cell numbers were reduced by 3 and 6 h in the HD treatment group compared with resting values, but changes in these blood features in the LD group were not significant. Acute handling did not affect haematocrit in either treatment. The results suggest that H. huso is relatively resistant to handling and confinement, and could tolerate normal hatchery practices associated with aquaculture. Because changes in cortisol concentrations were relatively low compared with those in most teleosts, glucose and lactate concentrations may be more useful as stress indicators in juvenile H. huso. This study also demonstrated that prior exposure to a chronic stressor, specifically high stocking density, could alter the physiological response to subsequent acute handling in H. huso.