Molecular characterization, expression profiling, and functional analysis of prohibitin 1 in red seabream, Pagrus major.

Prohibitin 1 (PHB1) is ubiquitously expressed in multiple compartments within cells and is involved in the cell cycle, cell signaling, apoptosis, transcriptional regulation, and mitochondrial biogenesis at the cellular level and in the inflammation-associated and immunological functions of B and T lymphocytes. PHB1 is an important protein that performs antioxidant regulation and immune functions inside and outside cells but has not been sufficiently studied in teleost fish. Our study aimed to elucidate the functional properties and gain new insights into the biological processes and immune system of red seabream (Pagrus major), a commercially important fish cultured in South Korea and East Asia. PHB1 mRNA was most abundantly expressed in the head kidney of healthy red seabream, and significant changes in its expression were observed after artificial infection with bacteria and viruses. On analysis, reporter gene was also significantly upregulated by polyinosinic-polycytidylic acid, lipopolysaccharides, and hydrogen peroxide. Consequent to the functional characterization of PHB1 in cells via recombinant protein preparation, the activity of leukocytes was enhanced and the reactive oxygen species-induced stress in red blood cells was reduced. The results reveal the functional characteristics of PHB1 and provide new insights into the biological processes and immune system of P. major, with beneficial implications in the study of stress responses.

Risk assessment of wild fish as environmental sources of red sea bream iridovirus (RSIV) outbreaks in aquaculture.

Red sea bream iridovirus (RSIV) causes substantial economic damage to aquaculture. In the present study, RSIV in wild fish near aquaculture installations was surveyed to evaluate the risk of wild fish being an infection source for RSIV outbreaks in cultured fish. In total, 1102 wild fish, consisting of 44 species, were captured from 2 aquaculture areas in western Japan using fishing, gill nets, and fishing baskets between 2019 and 2022. Eleven fish from 7 species were confirmed to harbor the RSIV genome using a probe-based real-time PCR assay. The mean viral load of the RSIV-positive wild fish was 101.1 ± 0.4 copies mg-1 DNA, which was significantly lower than that of seemingly healthy red sea bream Pagrus major in a net pen during an RSIV outbreak (103.3 ± 1.5 copies mg-1 DNA) that occurred in 2021. Sequencing analysis of a partial region of the major capsid protein gene demonstrated that the RSIV genome detected in the wild fish was identical to that of the diseased fish in a fish farm located in the same area in which the wild fish were captured. Based on the diagnostic records of RSIV in the sampled area, the RSIV-infected wild fish appeared during or after the RSIV outbreak in cultured fish, suggesting that RSIV detected in wild fish was derived from the RSIV outbreak in cultured fish. Therefore, wild fish populations near aquaculture installations may not be a significant risk factor for RSIV outbreaks in cultured fish.

Metagenomic profile of caudal fin morphology of farmed red sea bream Pagrus major.

The morphology of farm-reared fish often differs from that of their wild counterparts, impacting their market value. Two caudal fin tip shapes, acutely angled and blunted, are recognized in farmed populations of red sea bream Pagrus major. The angled form is preferred by consumers over the blunt since it resembles that of wild fish. Discovering the cause of the blunted tip is crucial to maximizing the commercial value of farmed red sea bream. We hypothesized that the blunt fin tip is the result of opportunistic bacteria and conducted partial 16S rRNA metagenomic barcoding and generated a clone library of the 16S rRNA gene to compare bacterial communities of the 2 fin forms. Metagenomic barcoding revealed an abundance of 5 bacterial genera, Sulfitobacter, Vibrio, Tenacibaculum, Psychrobacter, and an unknown genus of Rhodobacteraceae, on the caudal fin surface. Sulfitobacter was significantly more common on the angled caudal fin than the blunted. Vibrio is the dominant genus on the blunted caudal fin. The clone library identified these genera to species level, and Sulfitobacter sp., Vibrio harveyi, Tenacibaculum maritimum, and Psychrobacter marincola were frequently observed in blunt caudal fins. Our results suggest that opportunistic pathogenic bacteria such as V. harveyi and T. maritimum are not the primary cause of caudal fin malformation, and multiple factors such as combinations of injury, stress, and pathogenic infection may be involved. The reason for the significantly greater occurrence of Sulfitobacter sp. in the angled caudal fin is unknown, and further investigation is needed.

Molecular genetic characterisation and expression profiling of calpain 3 transcripts in red sea bream (Pagrus major).

Calpains (CAPNs) belong to the papain superfamily of cysteine proteases, and they are calcium-dependent cytoplasmic cysteine proteases that regulate a variety of physiological processes. We obtained the sequence of CAPN3 from an NGS-based analysis of Pagrus major (PmCAPN3) and confirmed the conserved molecular biological properties in the predicted amino acid sequence. The amino acid sequence and predicted domains of CAPN3 were found to be highly conserved in all of the examined species, and one catalytic domain and four calcium binding sites were identified. In healthy P. major, the PmCAPN3 mRNA was most abundantly expressed in the muscle and skin, and ubiquitously expressed in the other tissues used in the experiment. After artificial infections with fish pathogens, significant changes in its expression levels were found in immune-related tissues, most of showed upregulation. In particular, the highest level of expression was found in the liver, a tissue associated with protease activity. Taken together, these results suggest a physiological activity for PmCAPN3 in P. major and reveal functional possibilities that have not yet been reported in the immune system.

Efficacy of mozuku fucoidan in alternative protein-based diet to improve growth, health performance, and stress resistance of juvenile red sea bream, Pagrus major.

We evaluated the efficacy of mozuku fucoidan supplementation to alternative dietary proteins used in fish meal (FM) replacement to enhance growth, immunity, and stress resistance of Pagrus major. Seven isonitrogenous (45% protein) experimental diets were formulated where diet 1 (D1) was FM-based control diet. Diets 2 to 7 were formulated by replacing 25, 50, and 75% of FM protein with soy protein isolate (SPI) protein, and each replacement level was supplemented without or with fucoidan at 0.4% for diet groups D2 (FM25), D3 (FM25Fu), D4 (FM50), D5 (FM50Fu), D6 (FM75), and D7(FM75Fu), respectively. Each diet was randomly allocated to triplicate groups of fish (4.1 g) for 56 days. Significantly higher weight gain and specific growth rate were observed in fish fed FM50Fu diet group, and it was not differed (P > 0.05) with fish fed FM25Fu diet group. FM-based control diet showed intermediate value, and it was not differed (P > 0.05) with or without fucoidan-supplemented ≤ 50% FM replacement groups and FM75Fu diet group. Significantly lower growth performances were observed in FM75 diet group. At each replacement level, fucoidan-supplemented groups showed nonsignificant improvement of feed utilization performances. Fish fed fucoidan-supplemented diets showed best condition of oxidative and freshwater stress resistance. Lysozyme activity, NBT, and peroxidase activity showed higher (P > 0.05) values in fucoidan-supplemented groups compared with the non-supplemented groups. Catalase activity was significantly lower in FM75Fu diet group. Catalase activity is significantly influenced by the interaction effects of fucoidan and FM replacement level. In conclusion, fucoidan supplementation could increase the efficiency of utilizing SPI (≥ 75%) without any adverse effects on red sea bream performance.

Functional analysis and gene expression profiling of extracellular cathepsin Z in red sea bream, Pagrus major.

Cathepsin Z (CTSZ) is a lysosomal cysteine protease that is known to be involved in the maintenance of homeostasis and the biological mechanisms of immune cells. In this study, we have confirmed the tissue specific expression of the cathepsin Z (PmCTSZ) gene in Pagrus major, and confirmed its biological function after producing recombinant protein using Escherichia coli (E. coli). Multiple sequence alignment analysis revealed that the active site of the cysteine proteases and three N-glycosylation sites of the deduced protein sequence were highly conserved among all of the organisms. Phylogenetic analysis revealed that PmCTSZ was included in the clusters of CTSZ and the cysteine proteases of other bony fish and is most closely related to Japanese flounder CTSZ. PmCTSZ was distributed in all of the tissues from healthy red sea bream that were used in the experiment and was most abundantly found in the spleen and gill. Analysis of mRNA expression after bacterial (Edwardsiella piscicida: E. piscicida and Streptococcus iniae: S. iniae) or viral (red seabream iridovirus: RSIV) challenge showed significant gene expression regulation in immune-related tissues, but they maintained relatively normal levels of expression. We produced recombinant PmCTSZ (rPmCTSZ) using an E. coli expression system and confirmed the biological function of extracellular rPmCTSZ in vitro. We found that bacterial proliferation was significantly inhibited by rPmCTSZ, and the leukocytes of red sea bream also induced apoptosis and viability reduction.

The atypical chemokine receptor 4 in red sea bream (Pagrus major): Molecular characterization and gene expression analysis.

Atypical chemokine receptor 4 (ACKR4) is regulated by cytokines, binds chemokines and regulates the chemokine gradient. We verified the cDNA sequence by confirming ACKR4 from red sea bream (PmACKR4) by next generation sequencing (NGS) and analysed the molecular characteristics and gene expression profile. In the analysis using the predicted amino acid sequence of PmACKR4, a highly conserved G protein-coupled receptor 1 region and two cysteine residues were identified and included in the ACKR4 teleost cluster in the phylogenetic analysis. In healthy red sea bream, PmACKR4 mRNA was expressed at the highest levels in head kidney and was upregulated in all immune -related tissues used in the experiment after challenges with Streptococcus iniae (S. iniae) and red sea bream iridovirus (RSIV). These results suggest that ACKR4 is highly conserved in red sea bream and may play an important role in the immune system as previously reported. It is thought that ACKR4 acts as a regulator of immune -related cells via immune reactions after pathogenic infection.

The effect of dietary fucoidan on growth, immune functions, blood characteristics and oxidative stress resistance of juvenile red sea bream, Pagrus major.

We determined the supplementation effects of dietary fucoidan on growth, immune responses, blood characteristics, and oxidative stress resistance of juvenile red sea bream. A fishmeal (FM)-based basal diet supplemented with 0% (D1, control), 0.05% (D2), 0.1% (D3), 0.2% (D4), 0.4% (D5), and 0.8% (D6) mozuku fucoidan to formulate six experimental diets. Each diet was randomly allocated to triplicate groups of fish (3.8 g) for 60 days. Results showed that fish-fed diet D5 showed significantly higher (P < 0.05) growth performance compared to the control (D1). Diet groups D2 to D4 also showed intermediate values compared to D1. Feed conversion efficiency and protein efficiency ratio were significantly higher in diet group D5, which was not significantly different with D3. Fucoidan supplementation increased whole-body lipid, which was significantly higher in the D5 group. Condition factor (CF) was significantly higher in fish fed ≥ 0.2% fucoidan-supplemented diet groups. Diet group D5 and D4 showed significantly lower blood urea nitrogen (BUN) and aspartate aminotransferase (AST) level, respectively. Dietary fucoidan reduced the oxidative stress of fish. Among the measured nonspecific immune parameters, only peroxidase activity (PA) and total serum protein (TSP) were significantly influenced by dietary supplementation and it was higher in D4 group. Fucoidan supplementation reduces thiobarbituric acid reactive substance (TBARS) values numerically and it was lowest in fish-fed diet group D5. Under the present experimental condition, finally, we concluded that 0.3-0.4% dietary fucoidan supplementation enhanced the growth and health performance of red sea bream by increasing growth, immune response, blood characteristics, and oxidative stress resistance.

Dietary supplementation of selenium nanoparticles modulated systemic and mucosal immune status and stress resistance of red sea bream (Pagrus major).

Dietary supplementation of selenium nanoparticles (Se-NPs) at different levels (0, 0.5, 1, and 2 mg kg-1 diet) was evaluated to find out the effects on serum and skin immune responses as well as stress resistance in the red sea bream (Pagrus major). After 45 days of experimental trial, serum and mucosal immune responses were significantly high in fish fed 1 mg Se-NPs kg-1 diet (P < 0.05). In this group, alternative complement pathway, total serum protein, antioxidant activity of catalase enzyme, serum bactericidal activity, serum lysozyme activity, and amounts of skin mucus secretions as well as stress resistance against low salinity stress increased significantly, when compared to fish fed Se-NP-free diet (P < 0.05). Furthermore, fish fed Se-NPs at 2 mg kg-1 diet exhibited higher alternative complement pathway, total serum protein, mucus lysozyme activity, serum and mucus peroxidases, amount of mucus secreted, and tolerance against low salinity stress than the fish fed Se-NP-free diet (P < 0.05). Interestingly, the nitro blue tetrazolium activity in all groups fed with diets supplemented with Se-NPs are significantly higher than Se-NP-free diet (P < 0.05). The present results demonstrate that the dietary supplementation with Se-NPs (mainly from 1 to 2 mg kg-1 level) could be useful for maintaining the overall health status of red sea bream.

Fishmeal replacement by soya protein concentrate with inosine monophosphate supplementation influences growth, digestibility, immunity, blood health, and stress resistance of red sea bream, Pagrus major.

We assessed the effects of fishmeal (FM) replacement by soy protein concentrate (SPC) with inosine monophosphate (IMP) supplementation on growth, digestibility, immunity, blood health, and stress resistance of red sea bream, Pagrus major. FM protein of a FM-based control diet (FM100) was replaced with 25 (FM75), 50 (FM50), 75 (FM25), and 100% (FM0) by SPC protein, and each replacement group was supplemented with 0.4% IMP to formulate five experimental diets. Each diet was randomly allocated to triplicate groups of fish (4.8 g) for 56 days. Results demonstrated that fish fed diet groups FM50 and FM75 had significantly the highest final weight, weight gain, specific growth rate, and feed intake. Meanwhile, in comparison to the control, growth performance and feed utilization did not significantly differ with the 75% FM-replaced diet group by SPC with IMP supplementation. Apparent digestibility coefficient of dry matter, protein, and lipid also followed a similar trend. All growth, feed utilization, and digestibility parameters were significantly lower in the FM0 diet group. Triglyceride level was increased (P < 0.05) with the increasing replacement level and it was significantly highest in the FM0 diet group. The fish fed diet groups FM100 and FM50 showed the best condition of oxidative and freshwater stress resistance, respectively. Meanwhile, the groups with up to 75% FM-replaced diet also showed acceptable stress resistance status. Overall, enhanced innate immune responses were observed in the entire FM replaced with IMP-supplemented diet groups in comparison to the control. Considering SGR as a model, the regression analysis determined that 71.7% FM protein could be replaced by SPC protein with IMP supplementation in diets for the growth of red sea bream.

Influence of dietary inosine and vitamin C supplementation on growth, blood chemistry, oxidative stress, innate and adaptive immune responses of red sea bream, Pagrus major juvenile.

Both inosine (INO) and vitamin C (l-ascorbic acid, AsA) play important roles in growth performance, feed utilization and health status of fish. Therefore, a 56 days feeding trial was conducted to determine the interactive effects of dietary INO and AsA on growth performance, oxidative status, innate and adaptive immune responses of red sea bream. Fish growth performance and fed utilization parameters were significantly affected by dietary INO supplementation but not by AsA. Fish fed diets with INO at 4 g kg-1 diet in combination of high and low levels of AsA (3.1 g kg-1 and 9.3 g kg-1) produced the highest growth and feed utilization performances. In terms of growth and feed utilization performances no significant interaction effects were observed between INO and AsA. Dietary INO significantly influenced hematocrit, glucose and glutamyl oxaloacetic transaminase (GOT) content of red sea bream meanwhile AsA also significantly influenced hematocrit, glucose, total cholesterol, blood urea nitrogen (BUN) and glutamic-pyruvate transaminase (GPT) content of the test fish. No significant interaction effects was also observed between INO and AsA on measured hematological parameters. Reactive oxygen metabolites (d-ROMs) significantly influenced by both INO and AsA. Fish fed diet groups D1, D4 and D6 showed best oxidative stress resistance. Only INO was a significant factor on nitro-blue-tetrazolium activity (NBT) and bactericidal activity (BA). Neither INO nor AsA was a significant factor on serum catalase activity (CAT), total serum protein (TSP), peroxidase activity (PA) and lysozyme activity (LA). No significant interaction effects was observed between INO and AsA on measured innate immune parameters. Agglutination antibody titer was significantly influenced by dietary supplementation, after 15 days of vaccination but not in 21 days. In the day 15th fish and diet group D3 and D5 showed significantly higher values compared to diet groups control and D1. INO was the only significant factor of increasing agglutination antibody titer in 15 t h day. While AsA was not a significant factor on agglutination antibody titer values in day 15 t h, there was an interaction between dietary INO and AsA levels. Finally under the experimental conditions, fish fed high INO and low AsA levels (4 g kg-1 and 0.31 g kg-1 diet, respectively) showed best growth and feed utilization performance. Simultaneously, low level of INO and high level of AsA (2 g kg-1 and 0.93 g kg-1 diet, respectively) improved blood chemistry and immunological parameters. Furthermore, combined use of INO and AsA is possible to improve hemato-immunological responses of red sea bream.

Growth performance, blood health, antioxidant status and immune response in red sea bream (Pagrus major) fed Aspergillus oryzae fermented rapeseed meal (RM-Koji).

This study evaluated the effects of dietary substitution of fishmeal by graded levels of a blend composed of Aspergillus oryzae fermented rapeseed meal [0% (RM0), 25% (RM25), 50% (RM50), 75% (RM75) and 100% (RM100)] on growth performance, haemato-immunological responses and antioxidative status of Pagrus major (average weight 5.5 ±â€¯0.02 g). After 56 days, growth performances were significantly improved in fish fed RM25 diet compared to control (P < 0.05). Meanwhile, up to 50% replacement of fishmeal did not affect growth performance, feed conversion efficiency, protein efficiency ratio, protein apparent digestibility, protease activity, fish somatic indices and survival compared to control. While blood hematocrit and plasma protein were significantly enhanced in groups fed RM0 and RM25 diets, most of the hematological parameters did not change through the trial except glutamic pyruvate transaminase which was significantly increased in RM75 and RM100 groups and blood cholesterol which was gradually decreased with the increasing level of the blend. Interestingly, feeding fish with RM25 and RM50 diets significantly showed enhanced lysozyme, bactericidal and peroxidase activities and fish fed the same diets showed high resistance against oxidative stress (biological antioxidant potential and reactive oxygen metabolites). Additionally, catalase activity and tolerance against low salinity seawater were higher in fish fed RM25 diet. These findings suggested that, at a moderate level (25% and 50%), substitution of fishmeal by the fermented rapeseed meal promoted growth, nutrient utilization, and exerted immune responses and anti-oxidative effects in red sea bream.

Dietary substitution of fishmeal by alternative protein with guanosine monophosphate supplementation influences growth, digestibility, blood chemistry profile, immunity, and stress resistance of red sea bream, Pagrus major.

We determined the effects of complete fishmeal (FM) replacement by alternative protein (soy protein concentrate, SPC) with guanosine monophosphate (GMP) supplementation on growth, digestibility, immunity, blood chemistry profile, and stress resistance of juvenile red sea bream, Pagrus major. FM protein of a FM-based control diet (FM0) was replaced with 33.3 (FM33.3), 66.6 (FM66.7), and 100% (FM100) by SPC protein, and each replacement group was supplemented with 0.4% GMP to formulate four experimental diets. Each diet was randomly allocated to triplicate groups of fish (4.8 g) for 56 days. Results demonstrated that fish fed diet group FM33.3 had the significantly highest final weight, weight gain-specific growth rate, and feed intake. Meanwhile, in comparison to control, growth performance and feed utilization did not significantly differ with 66.7% FM replacement by SPC with GMP supplementation. Apparent digestibility coefficient of protein and lipid also followed a similar trend. All growth, feed utilization, and digestibility parameters were significantly lower in FM100 diet group. Blood urea nitrogen (BUN) and triglycerides (TG) increased (P < 0.05) with increasing FM replacement level by SPC. Interestingly, total cholesterol level reduces with the increasing level of FM replacement by SPC with GMP supplementation. Fish fed FM0 diet group showed the best condition of both oxidative and freshwater stress resistance. Meanwhile, FM33.3 and FM66.7 diet groups showed acceptable conditions. Innate immune responses enhanced with the increasing FM replacement level by SPC with GMP supplementation. In conclusion, FM could be replaced ≤66.7% by SPC with GMP supplementation in diets for red sea bream without any adverse effects on fish performances.

Dietary effects of adenosine monophosphate to enhance growth, digestibility, innate immune responses and stress resistance of juvenile red sea bream, Pagrus major.

Our study explored the dietary effects of adenosine monophosphate (AMP) to enhance growth, digestibility, innate immune responses and stress resistance of juvenile red sea bream. A semi-purified basal diet supplemented with 0% (Control), 0.1% (AMP-0.1), 0.2% (AMP-0.2), 0.4% (AMP-0.4) and 0.8% (AMP-0.8) purified AMP to formulate five experimental diets. Each diet was randomly allocated to triplicate groups of fish (mean initial weight 3.4 g) for 56 days. The results indicated that dietary AMP supplements tended to improve growth performances. One of the best ones was found in diet group AMP-0.2, followed by diet groups AMP-0.1, AMP-0.4 and AMP-0.8. The Apparent digestibility coefficients (dry matter, protein and lipid) also improved by AMP supplementation and the significantly highest dry matter digestibility was observed in diet group AMP-0.2. Fish fed diet groups AMP-0.2 and AMP-0.4 had significantly higher peroxidase and bactericidal activities than fish fed the control diet. Nitro-blue-tetrazolium (NBT) activity was found to be significantly (P < 0.05) greater in fish fed diet groups AMP-0.4 and AMP-0.8. Total serum protein, lysozyme activity and agglutination antibody titer were also increased (P > 0.05) by dietary supplementation. In contrast, catalase activity decreased with AMP supplementation. Moreover, the fish fed AMP supplemented diets had better improvement (P < 0.05) in body lipid contents, condition factor, hematocrit content and glutamyl oxaloacetic transaminase (GOT) level than the control group. Supplementation also improved both freshwater and oxidative stress resistances. Interestingly, the fish fed diet groups AMP-0.2 and AMP-0.4 showed the least oxidative stress condition. Finally it is concluded that, dietary AMP supplementation enhanced the growth, digestibility, immune response and stress resistance of red sea bream. The regression analysis revealed that a dietary AMP supplementation between 0.2 and 0.4% supported weight gain and lysozyme activity as a marker of immune functions for red sea bream, which is also inline with the most of the growth and health performance parameters of fish under present experimental conditions.

Effects of dietary administration of guanosine monophosphate on the growth, digestibility, innate immune responses and stress resistance of juvenile red sea bream, Pagrus major.

The present study explored the dietary administration effects of guanosine monophosphate (GMP) on growth, digestibility, innate immune responses and stress resistance of juvenile red sea bream, Pagrus major. A semi-purified basal diet supplemented with 0% (Control), 0.1% (GMP-0.1), 0.2% (GMP-0.2), 0.4% (GMP-0.4) and 0.8% (GMP-0.8) purified GMP to formulate five experimental diets. Each diet was randomly allocated to triplicate groups of fish (mean initial weight 3.4 g) for 56 days. The obtained results clearly indicated that, growth performance of red sea bream enhanced by dietary GMP supplementation compared to control and significantly higher final weight was found in fish fed diet group GMP-0.4. Specific growth rate (SGR) and percent weight gain (%WG) also significantly higher in diet group GMP-0.4 in compared to control and it was not differed (P > 0.05) with diet group GMP-0.8. Feed intake significantly increased with the supplementation of GMP. Feed conversion efficiency (FCE) and protein efficiency ratio (PER) also improved (P < 0.05) when fish fed the diets containing GMP and diet group GMP-0.4 showed the significantly higher value in compared to control. The Apparent digestibility coefficients (dry matter, protein and lipid) also improved by GMP supplementation and the significantly higher protein digestibility was observed in fish fed diet groups GMP-0.2, GMP-0.4 and GMP-0.8. Among the measured non specific immune parameters peroxidase activity (PA), respiratory burst activity (NBT), Bactericidal activity (BA) were significantly affected by dietary supplementation and highest value obtained in diet group GMP-0.4. Total serum protein, lysozyme activity (LA), and agglutination antibody titer also increased (P > 0.05) by GMP supplementation. In contrast, catalase activity decreased with GMP supplementation. In terms of oxidative stress GMP-0.2 showed best condition with low oxidative stress and high antioxidant level. Moreover, the fish fed GMP supplemented diets had better improvement (P < 0.05) in body protein contents, hepatosomatic index, hematocrit content and glutamyl oxaloacetic transaminase (GOT) and glutamic-pyruvate transaminase (GPT) level than the control group. Supplementation also improved (P < 0.05) freshwater stress resistances. Quadratic regression analysis of WG and LA revealed that, the optimal levels of dietary GMP were 0.45 and 0.48%, respectively, for juvenile red sea bream, which is also in line with the most of the growth performance and health parameters of the fish.

Immune responses and stress resistance in red sea bream, Pagrus major, after oral administration of heat-killed Lactobacillus plantarum and vitamin C.

The present study evaluated the interactive benefits of dietary administration of heat-killed Lactobacillus plantarum (LP) and vitamin C (VC) on the growth, oxidative status and immune response of red sea bream (Pagrus major). A diet without LP and VC supplements was employed as a control diet. Four other test diets with 0 or 1 g LP kg(-1) combined with 0.5 or 1 g VC kg(-1) (2 × 2 factorial design) were fed to red sea bream (2 ± 0.01 g) for 56 days. A significant interaction was found between LP and VC on final body weight (FNW), weight gain (WG), hematocrit (HCT), serum bactericidal (BA) and lysozyme (LZY) activities, mucus LZY and peroxidase (PA) activities, nitro blue tetrazolium (NBT), catalase, mucus secretion and tolerance against low salinity stress test (LT50) (P < 0.05). In addition, FNW, WG, specific growth rate, feed and protein efficiency ratio, serum (BA, LZY, PA and NBT), mucus (LZY and PA), superoxide dismutase, malondialdehyde and mucus secretion were significantly affected by either LP or VC (P < 0.05). Furthermore, only LP was a significant factor on survival, plasma total cholesterol, mucus BA and alternative complement pathway (P < 0.05). However, VC supplementation affected on HCT and LT50. Interestingly, fish fed with both LP at 1 g kg(-1) diet with VC at 0.5 or 1 g kg(-1) diet showed higher growth, humoral and mucosal immune responses, anti-oxidative status, mucus secretion and LT50 as well as decreased plasma, triglyceride and total cholesterol levels than the fish fed control diet (P < 0.05). These results demonstrated that dietary LP and VC had a significant interaction for red sea bream with the capability of improving growth performance and enhancing stress resistance by immunomodulation.

The selenium accumulation and its effect on growth, and haematological parameters in red sea bream, Pagrus major, exposed to waterborne selenium.

Juvenile Pagrus major (mean length 15.8±1.6cm, and mean weight 90.4±4.7g) were exposed for 4 weeks with waterborne selenium concentration (0, 50, 100, 200, and 400µg/L). The profile of Se accumulation among tissue in P. major is dependent on the exposure periods and Se concentration. After 4 weeks, the highest accumulation of Se was observed in the kidney, and the order of Se accumulation in tissues was kidney≈liver>spleen>intestine>gill>muscle. Se decreased the growth rate, and there was an inverse proportion between growth and Se concentration. The major hematological findings were significant decrease in the RBC count, Ht value, and Hb concentration exposed to ≥100µg/L Se concentrations. Se exposure (≥100µg/L) led to significant increase in the glucose, GOT, and GPT levels, whereas the levels of calcium, magnesium, cholesterol, and total protein did not increase. The results suggest that waterborne Se exposure can induce significant Se accumulation in tissues, inhibition of growth, and hematological alterations.

Benzo[a]pyrene modulation of acute immunologic responses in Red Sea bream pretreated with lipopolysaccharide.

The effects of polycyclic aromatic hydrocarbons (PAHs) have been reported to modulate the immune response in aquatic animals, but the collected information of their effects on fish immunity is so far ambiguous. This study demonstrated that Benzo[a]pyrene (BaP) exposure altered the expression pattern of an antimicrobial peptide hepcidin (PM-hepc) gene and the activities of some immune-associated parameters in the lipopolysaccharide (LPS)-challenged red sea bream (Pagrus major). It was observed that LPS could increase respiratory burst, lysozyme and antibacterial activity in P. major. However when the P. major was exposed to different concentrations of BaP (1, 4, or 8 µg L(-1) ) for 14 days and then challenged with LPS there was no significant change in the lysozyme and antibacterial activity. It was further observed that LPS could induce the PM-hepc mRNA expression at 3, 6, and 12-h post-LPS challenge. However, when P. major was exposed first to BaP for 14 days and then challenged with LPS, the expression of PM-hepc mRNA was delayed in the liver until 24 h and not significantly induced until 48 and 96 h. The mRNA expression pattern was completely different from that only with LPS challenge, showing that BaP exposure changed the PM-hepc mRNA expression pattern of fish with LPS challenge. This study demonstrated that BaP exposure can weaken or inhibit the induction of lysozyme and antibacterial activity in the LPS-challenged P. major; conversely BaP exposure could enhance the mRNA expression of PM-hepc gene, indicating that the effect of BaP has different modulatory mechanism on hepcidin genes and immune-associated parameters.

Rice Distillers Dried Grain Is a Promising Ingredient as a Partial Replacement of Plant Origin Sources in the Diet for Juvenile Red Seabream (Pagrus major).

This study was designed to test the effects of dietary distillers dried grain (DDG) level on the growth performance, feed utilization, body composition and antioxidant activity of juvenile red seabream (Pagrus major). Six isonitrogenous and isocaloric diets were formulated to contain 0%, 5%, 10%, 15%, 20%, and 25% DDG from rice (designated as DDG0, DDG5, DDG10, DDG15, DDG20, and DDG25), respectively. Juvenile red seabream averaging 10.1±0.05 g were randomly distributed into 400-L tanks in a flow through systems. Three replicate groups of fish were fed one of the experimental diets to visual satiation two times a day for 10 weeks. Survival, weight gain, feed efficiency, protein efficiency ratio and hepatosomatic index of fish were not affected by dietary DDG levels (p>0.05). Proximate and amino acid composition of whole body in juvenile red seabream were not affected by dietary DDG levels (p>0.05). Plasma content of total protein, glucose, cholesterol, glutamic-pyruvic transaminase, phospholipid and triglyceride were not affected by dietary DDG levels (p>0.05). 1, 1-Diphenyl-2-picryl-hydrazyl radical and alkyl radical scavenging activities in plasma and liver of fish were not affected by dietary DDG levels (p>0.05). The results of this experiment suggest that DDG has the potential to replace plant origin ingredients such as wheat flour and corn gluten meal and could be used up to 25% in diet without incurring negative effects on the growth performance of juvenile red seabream.

Expression Patterns of TGF-ß1, TßR-I, TßR-II, and Smad2 Reveal Insights into Heterosis for Growth of Hybrid Offspring between Acanthopagrus schlegelii and Pagrus major.

TGF-ß1/Smads is a classic signaling pathway, which plays important roles in the development process of organisms. Black porgy Acanthopagrus schlegelii and red porgy Pagrus major are valuable economic fishes, and their hybrid offspring show excellent heterosis traits. Yet the molecular regulation mechanism of the heterosis traits is less clear. Here, we explored the TGF-ß1/Smads pathway's molecular genetic information for heterosis in A. schlegelii ♂ × P. major ♀ (AP) and A. schlegelii ♀ × P. major ♂ (PA) in terms of growth and development. The mRNA expression levels of TGF-ß1, TßR-I, TßR-II, and Smad2 genes in different developmental stages of A. schlegelii were detected. Furthermore, the expression levels of TGF-ß1, TßR-I, TßR-II, and Smad2 genes in different tissues of adult (mRNA level) and larva (mRNA and protein level) of A. schlegelii, P. major, and their hybrids were determined by both real-time quantitative PCR and Western blot techniques. The results indicated the ubiquitous expression of these genes in all developmental stages of A. schlegelii and in all tested tissues of A. schlegelii, P. major, and its hybrids. Among them, the mRNA of TGF-ß1, TßR-I, and TßR-II genes is highly expressed in the liver, gill, kidney, and muscle of black porgy, red porgy, and their hybrid offspring. There are significant changes in gene and protein expression levels in hybrid offspring, which indirectly reflect hybrid advantage. In addition, there was no correlation between protein and mRNA expression levels of Smad2 protein. The results provide novel data for the differential expression of growth and development genes between the reciprocal hybridization generation of black porgy and red porgy and its parents, which is conducive to further explaining the molecular regulation mechanism of heterosis in the growth and development of hybrid porgy.