Chinese Sea Bass Research Articles

Characterization of Myxovirus resistance (Mx) gene from Chinese seabass Lateolabrax maculatus: Insights into the evolution and function of Mx genes

Chinese seabass (Lateolabrax maculatus) stands out as one of the most sought-after and economically significant species in aquaculture within China. Diseases of L. maculatus occur frequently due to the degradation of the germplasm, the aggravation of environmental pollution of water, and the reproduction of pathogenic microorganisms, inflicting considerable economic losses on the Chinese seabass industry. The Myxovirus resistance (Mx) gene plays pivotal roles in the antiviral immune response ranging from mammals to fish. However, the function of the Mx gene in L. maculatus is still unknown. Firstly, the origin and evolutionary history of Mx proteins was elucidated in this study. Subsequently, an Mx gene from L. maculatus (designed as LmMxA gene) was identified, and its functions in combating antiviral and antibacterial threats were investigated. Remarkably, our findings suggested that while Mx group genes were present in chordates, DYN group genes were present in everything from single-celled animals to humans. Furthermore, our investigation revealed that the LmMxA mRNA level increased in the kidney, spleen and liver subsequent to Vibrio anguillarum and poly(I:C) challenged. Immunofluorescence analysis indicated that LmMxA is predominantly localization in the nucleus and the cytoplasm. Notably, the expression of MAVS, IFN1 and Mx1 increased when LmMxA was overexpression within the EPC cells. Moreover, through assessment via cytopathic effect (CPE), virus titer, and antibacterial activity, it becomes evident that LmMxA exerts a dual role in bolstering both antiviral and antibacterial immune responses. These compelling findings laid the foundation for further exploring the mechanism of LmMxA in response to innate immunity of L. maculatus.

Monitoring and Risk Assessment of Pesticide Residues in Fishery Products Using GC-MS/MS in South Korea.

The aim of this study was to assess the risk of pesticide contamination in aquaculture and its impact on fishery products. We conducted an assessment of 300 samples collected from nine regions in South Korea, including various types of seafood, such as freshwater fish, marine fish, crustaceans, and shellfish. Pesticide residues in seafood were analyzed using GC-MS/MS after sample preparation using a modified QuEChERS method, revealing the presence of eight pesticides (4,4'-DDE, 4,4'-DDT, boscalid, isoprothiolane, oxadiazon, pendimethalin, thifluzamide, and trifluralin) across seven fish species (carp, far eastern catfish, crucian carp, eel, Chinese muddy loach, mirror carp, and sea bass). Following the grouping of DDE with DDT, a risk assessment of fishery products was conducted. After the estimated daily intake (EDI) of fish was calculated and compared with the acceptable daily intake (ADI), the health risk index (HI, %ADI) of the detected pesticides was evaluated and found to be 1.07% or lower. The results suggest that the consumption of domestically farmed fish products in South Korea poses minimal health risks associated with pesticide residues.

The protective role of condensed tannins on growth inhibition and enterohepatic injury induced by histamine in Chinese seabass (Lateolabrax maculatus)

Histamine has been documented to induce growth inhibition and tissue injury in animals, whereas information regarding the toxicity of histamine and the detoxication of condensed tannins (CT) in Chinese seabass (Lateolabrax maculatus) is rare. In this study, three diets were prepared to contain 0 g/kg of histamine (G1), 0.1 g/kg of histamine (G2), and 0.1 g/kg of histamine plus 1 g/kg of CT (G3). Fish were randomly divided into 12 tanks with 40 fish per tank and 4 tanks per diet. The results showed that the final body weight, weight gain rate, specific growth rate, total antioxidant capacity, and the activities of trypsin, lipase, catalase, superoxide dismutase and lysozyme were lower (P < 0.05) but the serum concentration of aspartate and alanine aminotransferases and glucose were higher (P < 0.05) in G2 than in G1 and G3. These parameters were similar (P > 0.05) between G1 and G3. The FCR was ranked as G2 > G3 > G1 (P < 0.05). Compared with G1 and G3, the deformation and atrophy of the intestinal villus and the vacuolation of hepatocytes were intensified in G2. In conclusion, 0.1 g/kg of histamine inhibited digestion, induced intestinal and liver injury, decreased antioxidant and immune capacity and reduced growth performance of L. maculatus. Supplementation of 1 g/kg of CT in the Lateolabrax maculatus diet alleviated histamine-induced toxicity owing to the protective effect of CT against oxidative damage.

Telomere-to-telomere gapless genome assembly of the Chinese sea bass (Lateolabrax maculatus)

Chinese sea bass (Lateolabrax maculatus) is a highly sought-after commercial seafood species in Asian regions due to its excellent nutritional value. With the rapid advancement of bioinformatics, higher standards for genome analysis compared to previously published reference genomes are now necessary. This study presents a gapless assembly of the Chinese sea bass genome, which has a length of 632.75 Mb. The sequences were assembled onto 24 chromosomes with a coverage of over 99% (626.61 Mb), and telomeres were detected on 34 chromosome ends. Analysis using Merqury indicated a high level of accuracy, with an average consensus quality value of 54.25. The ONT ultralong and PacBio HiFi data were aligned with the assembly using minimap2, resulting in a mapping rate of 99.9%. The study also identified repeating elements in 20.90% (132.25 Mb) of the genome and inferred 22,014 protein-coding genes. These results establish meaningful groundwork for exploring the evolution of the Chinese sea bass genome and advancing molecular breeding techniques.

Dietary condensed tannin exhibits stronger growth-inhibiting effect on Chinese sea bass than hydrolysable tannin

A 56-d feeding trial was carried out to assess the effects of dietary hydrolysable tannin (HT) and condensed tannin (CT) on growth performance, whole body composition, digestive enzyme activities, serum metabolites, antioxidant and immune response, and intestinal and liver histomorphology of Chinese sea bass (Lateolabrax maculatus). Four diets were formulated to contain 0 (T1), 2 g/kg of CT (T2), 2 g/kg of HT (T3), and 1 g/kg of CT plus 1 g/kg of HT (T4). A total of 640 fish were randomly divided into 16 tanks with 4 tanks per diet. Results showed that the final body weight, weight gain rate and specific growth rate were ranked as T1 > T2 > T4 > T3 (P < 0.05). Feed conversion ratio was ranked as T1 < T4 < T2 < T3 (P < 0.05). Compared to T2, feed intake was higher (P < 0.05) in T1 but lower (P < 0.05) in T3 and T4, intestinal trypsin, lipase and amylase activities were higher (P < 0.05) in T1 but lower (P < 0.05) in T3, the total cholesterol and triacylglycerol were higher (P < 0.05) in T1 but lower (P < 0.05) in T3, the aspartate aminotransferase was lower (P < 0.05) in T1 but higher (P < 0.05) in T3, the serum total antioxidant capacity, superoxide dismutase and lysozyme were lower (P < 0.05) in T1 but higher (P < 0.05) in T3. Intestinal villus and hepatocyte in T2, T3, and T4 had different degrees of injury. The villus length was higher (P < 0.05) but the villus width was lower (P < 0.05) in T1 than those in other groups. In summary, dietary 2 g/kg of CT and HT inhibited digestion, induced intestinal and liver injury and reduced growth of L. maculatus. Compared to HT, CT had stronger growth-inhibiting effect and damage on fish, suggesting CT should be chosen carefully as dietary supplement in L. maculatus.

Dietary hydrolyzable tannins reduce growth performance and induce histological damage of Chinese seabass (Lateolabrax maculatus)

Chinese seabass (Lateolabrax maculatus) is a popular carnivorous fish with delicious taste. Although the feed value of condensed tannins has been well documented for L. maculatus, information about the effects of hydrolyzable tannins (HTs) on the growth and health of L. maculatus is limited. This study was conducted to assess the effects of dietary HTs on growth performance, body composition, intestinal digestive enzyme activities, serum metabolites, antioxidant and immune response, and intestine and liver morphology of L. maculatus. A total of 640 fish were randomly divided into four groups with four replicates per group and 40 fish per replicate. Four diets were prepared to contain 0 (G0), 1 (G1), 2 (G2), and 4 (G4) g/kg of HTs. Fish were fed to apparent satiation twice a day during the 56-day feeding trial. Results showed that the final body weight, weight gain rate, specific growth rate, and feed intake were linearly decreased (p&amp;lt; 0.001) as dietary HTs increased. All fish had similar (p &amp;gt; 0.05) whole body compositions. Fish fed G2 and G4 had lower (p&amp;lt; 0.05) intestinal trypsin and lipase activities than those fed G0 and G1, whereas G4 had higher (p&amp;lt; 0.05) aspartate aminotransferase and alanine aminotransferase activities than G0. Serum total antioxidant capacity and lysozyme were linearly decreased (p&amp;lt; 0.01), but the malondialdehyde concentration was linearly increased (p&amp;lt; 0.01) as dietary HTs increased. Intestinal villi in G2 and G4 showed increased deformation, and the vacuolation of liver cells began to appear in G1 and was aggravated as dietary HTs increased. This study showed that HTs should be used with caution due to their growth-inhibiting effect, and the dietary HT level for L. maculatus is recommended to be less than 1 g/kg.

Transcriptomic Modulation Reveals the Specific Cellular Response in Chinese Sea Bass (Lateolabrax maculatus) Gills under Salinity Change and Alkalinity Stress.

Salinity and alkalinity are among the important factors affecting the distribution, survival, growth and physiology of aquatic animals. Chinese sea bass (Lateolabrax maculatus) is an important aquaculture fish species in China that can widely adapt to diverse salinities from freshwater (FW) to seawater (SW) but moderately adapt to highly alkaline water (AW). In this study, juvenile L. maculatus were exposed to salinity change (SW to FW) and alkalinity stress (FW to AW). Coordinated transcriptomic responses in L. maculatus gills were investigated and based on the weighted gene co-expression network analysis (WGCNA), 8 and 11 stress-responsive modules (SRMs) were identified for salinity change and alkalinity stress, respectively, which revealed a cascade of cellular responses to oxidative and osmotic stress in L. maculatus gills. Specifically, four upregulated SRMs were enriched with induced differentially expressed genes (DEGs) for alkalinity stress, mainly corresponding to the functions of "extracellular matrix" and "anatomical structure", indicating a strong cellular response to alkaline water. Both "antioxidative activity" and "immune response" functions were enriched in the downregulated alkaline SRMs, which comprised inhibited alkaline specific DEGs, revealing the severely disrupted immune and antioxidative functions under alkalinity stress. These alkaline-specific responses were not revealed in the salinity change groups with only moderately inhibited osmoregulation and induced antioxidative response in L. maculatus gills. Therefore, the results revealed the diverse and correlated regulation of the cellular process and stress response in saline-alkaline water, which may have arisen through the functional divergence and adaptive recruitment of the co-expression genes and will provide vital insights for the development of L. maculatus cultivation in alkaline water.

Transcriptome, intestinal microbiome and histomorphology profiling of differences in the response of Chinese sea bass (Lateolabrax maculatus) to Aeromonas hydrophila infection.

The Chinese sea bass (Lateolabrax maculatus) is an important aquaculture fish, but diseases caused by Aeromonas hydrophila have led to severe economic losses to the aquaculture industry in recent years. To date, only a few studies have focused on the relationship between the intestinal immune response and changes in intestinal microbes by A. hydrophila infection. Here, we report the transcriptome and intestinal changes in infected sea bass. Histopathological results showed that severe steatosis and vacuolation occurred in the liver and that the intestinal villi and mesentery were seriously affected after infection. By extracting total RNA from intestinal tissue and studying the transcriptome profile, 1,678 genes (1,013 upregulated and 665 downregulated) were identified as significantly differentially expressed genes (DEGs). These genes are involved in many immune-related signalling pathways, such as the NOD-like receptor, C-type lectin receptor, and Toll-like receptor signalling pathways. Moreover, the intestinal microbes of sea bass changed significantly after infection. Interestingly, at the genus level, there was an increase in Serratia, Candida arthromitus and Faecalibacterium as well as a decrease in Akkermansia and Parabacteroides after infection. The results also indicated that some of the DEGs involved in the immune response were related to the genus level of intestinal microbiota. Finally, there was a relationship between gene expression patterns and the bacterial structure in the host intestine. Our study provides a reference for the study of the immune response and particular functions of intestinal microbes of sea bass after pathogen infection.

Analysis of the Ecosystem Characteristics and Ecological Carrying Capacity of the Main Commercial Fish in the Artificial Reef Ecosystem in Laizhou Bay Using the Ecopath Model

In this study, we constructed an Ecopath model of the artificial reef ecosystem in Laizhou Bay, with special emphasis on the stock enhancement opportunities. Laizhou Bay is the largest semi-enclosed bay in the Bohai Sea, China, where multiple factors, especially overfishing, have led to the decline of many commercial marine fish stocks. Artificial oyster reefs were developed in 2011 in this region, providing shelter, feeding, and breeding sites for marine organisms. Additionally, stock enhancement by release can be used to replenish fishery species resources. Ad hoc stock enhancement, however, can fail to bring economic benefits and may impact ecosystem stability. Therefore, we estimated the ecological carrying capacity of the three main economic fish species in Laizhou Bay, including black rockfish (Sebastes schlegelii), fat greening (Hexagrammos otakii), and Chinese seabass (Lateolabrax maculatus) before release to ensure the sustainable use of fishery resources. The Ecopath model in Laizhou Bay was divided into 17 functional groups based on commercial relevance, dietary similarity, and habitat needs of the species present in the area. The ecological parameters, such as the ratio of total primary productivity to total respiration (1.205), connectance index (0.207), and system omnivory index (0.090) indicated that the artificial reef ecosystem in Laizhou Bay has a relatively simple food web structure. The ecological carrying capacities of S. schlegelii, H. otakii, and L. maculatus were assessed at 0.4676 t/km2, 0.5472 t/km2, and 0.3275 t/km2, respectively. This study provides a reference for the formulation of fishery strategies to maintain ecosystem stability and biodiversity and to maximize fishery returns and sustainability in Laizhou Bay.

Steroidogenic Effects of Salinity Change on the Hypothalamus-Pituitary-Gonad (HPG) Axis of Male Chinese Sea Bass (Lateolabrax maculatus).

As lower vertebrates, teleost species could be affected by dynamic aquatic environments and may respond to environmental changes through the hypothalamus–pituitary–gonad (HPG) axis to ensure their normal growth and sexual development. Chinese sea bass (Lateolabrax maculatus), euryhaline marine teleosts, have an extraordinary ability to deal with a wide range of salinity changes, whereas the salinity decrease during their sex-maturation season may interfere with the HPG axis and affect their steroid hormone metabolism, resulting in abnormal reproductive functioning. To this end, in this study, 40 HPG axis genes in the L. maculatus genome were systematically characterized and their copy numbers, phylogenies, gene structures, and expression patterns were investigated, revealing the conservation of the HPG axis among teleost lineages. In addition, freshwater acclimation was carried out with maturing male L. maculatus, and their serum cortisol and 11-ketotestosterone (11-KT) levels were both increased significantly after the salinity change, while their testes were found to be partially degraded. After salinity reduction, the expression of genes involved in cortisol and 11-KT synthesis (cyp17a, hsd3b1, cyp21a, cyp11c, hsd11b2, and hsd17b3) showed generally upregulated expression in the head kidneys and testes, respectively. Moreover, cyp11c and hsd11b2 were involved in the synthesis and metabolism of both cortisol and 11-KT, and after salinity change their putative interaction may contribute to steroid hormone homeostasis. Our results proved the effects of salinity change on the HPG axis and steroidogenic pathway in L. maculatus and revealed the gene interactions involved in the regulation of steroid hormone levels. The coordinated interaction of steroidogenic genes provides comprehensive insights into steroidogenic pathway regulation, as well as sexual development, in teleost species.

The Landscape of Liver Chromatin Accessibility and Conserved Non-coding Elements in Larimichthys crocea, Nibea albiflora, and Lateolabrax maculatus.

Large yellow croaker (Larimichthys crocea), yellow drum (Nibea albiflora), and Chinese seabass (Lateolabrax maculatus) are important economic marine fishes in China. The conserved non-coding elements (CNEs) in the liver tissues of the three kinds of fish are directly or indirectly involved in the regulation of gene expression and affect liver functions. However, the fishes' CNEs and even chromatin accessibility landscape have not been effectively investigated. Hence, this study established the landscapes of the fishes' genome-wide chromatin accessibility and CNEs by detecting regions of the open chromatin in their livers using an assay for transposase-accessible chromatin by high-throughput sequencing (ATAC-seq) and comparative genomics approach. The results showed that Smad1, Sp1, and Foxl1 transcription factor binding motifs were considerably enrichedin thechromatin accessibility landscape in theliver of the three species, and the three transcription factors (TFs) had a wide range of common targets. The hypothetical gene set was targeted by one, two, or all three TFs, which was much higher than would be expected for an accidental outcome. The gene sets near the CNEs were mainly enriched through processes such as a macromolecule metabolic process and ribonucleoprotein complex biogenesis. The active CNEs were found in the promoter regions of genes such as ap1g1, hax1, and ndufs2. And 5 CNEs were predicted to be highly conserved active enhancers. These results demonstrated that Smad1, Sp1, and Foxl1 might be related to the liver function in the three fishes. In addition, we found a series of ATAC-seq-labeled CNEs located in the gene promoter regions, and highly conserved H3k27ac + -labeled CNEs located in the liver function genes. The highly conserved nature of these regulatory elements suggests that they play important roles in the liver in fish. This study minedthelandscape of chromatin accessibility and CNEs of three important economic fishes to fill the knowledge gaps in this field. Moreover, the work provides useful data for the industrial application and theoretical research of these three fish species.

Condensed tannins increased intestinal permeability of Chinese seabass (Lateolabrax maculatus) based on microbiome-metabolomics analysis

Condensed tannins (CT) have been reported to induce intestinal injury of fish, whereas the injury mechanism is unclear. This study evaluated the effects of dietary grape seed CT on growth, intestinal permeability, tight junction structure, intestinal digestive and brush border enzyme activity, bacterial community and intestinal metabolites of Chinese seabass (Lateolabrax maculatus). A total of 640 fish were randomly distributed into 16 tanks with 4 tanks per group and 40 fish per tank. Four diets were formulated to contain 0 (CT0), 1 (CT1), 2 (CT2), and 2 g/kg of CT plus 4 g/kg of polyethylene glycol (PEG) (CT2 + PEG). PEG specifically binds with CT to neutralize CT activity. The experiment was arranged as complete randomized design. Fish were hand-fed to apparent satiation twice daily and the feeding trial lasted for 63 days. Fish fed CT2 had lower (P < 0.05) final body weight, weight gain rate, specific growth rate and feed intake, but higher (P < 0.05) serum diamine oxidase activity and endotoxin level than other diets. Tight junction structures in CT1 and CT2 showed varying degrees of ambiguity and damage. The trypsin activity ranked as CT0 > CT1 > CT2 (P < 0.05). Fish fed CT2 had lower (P < 0.05) activities of lipase, amylase and creatine kinase than other diets. Na+, K+-ATPase activity was lower (P < 0.05) in CT1 and CT2 than in CT0. All parameters were similar (P > 0.05) between CT0 and CT2 + PEG. Intestinal microbiota analysis showed that the abundances of Bacillus, Acinetobacter and Pseudomonas were decreased (P < 0.05) but Clostridium was increased (P < 0.05) as dietary CT increasing. Fish fed CT2 + PEG had higher (P < 0.05) abundances of Bacillus, Acinetobacter and Pseudomonas but lower (P < 0.05) Clostridium than those of fish fed CT2. Bacterial diversity measurements were not affected (P > 0.05) by dietary treatments. Metabolomics analysis indicated that CT altered the intestinal metabolomics profile of L. maculatus. The valeric acid was decreased (P < 0.05), but phenylacetic acid was increased (P < 0.05) as dietary CT increasing. Compared to CT0, CT2 had lower (P < 0.05) isobutyric acid but higher (P < 0.05) butyric acid and isovaleric acid. In conclusion, this study suggests association between reduced growth and increased intestinal permeability and varying intestinal bacterial microbiota and metabolites of L. maculatus. This study warns that dietary CT at 2 g/kg could induce intestinal injury, microecological imbalance and metabolic disorder of fish, and the resulting adverse effects may neutralize by applying polyethylene glycol in fish diets.

Reevaluation of dietary condensed tannins on growth, antioxidant and immune response and muscle quality of Chinese seabass (Lateolabrax maculatus)

Chinese seabass (Lateolabtax maculatus) is a popular carnivorous fish that is widely cultured in China in recent years. Previous studies suggested that low dose of CT enhanced antioxidant and immune response, but high dose of CT inhibited growth and induced tissue damage of fish. Meanwhile, information regarding effects of CT on muscle quality of L. maculatus is limited. A 63-day feeding trial was performed to assess the effects of dietary CT on growth, antioxidant and immune response and muscle quality of L. maculatus. Four diets were formulated to contain 0 g/kg of CT (G1), 1 g/kg of CT (G2), 2 g/kg of CT (G3), and 2 g/kg of CT plus 4 g/kg of polyethylene glycol (PEG) (G4, as positive control). PEG specifically binds with CT to neutralize CT activity. Fish were randomly distributed into 16 tanks with 4 tanks per diet and 40 fish per tank, and were fed to apparent satiation twice daily during the feeding trial. Results indicated that dietary CT at the concentration of 1 g/kg did not alter (P > 0.05) growth and feed utilization of L. maculatus. Fish fed G3 had lower (P < 0.05) final body weight, weight gain rate, thermal growth coefficient and feed intake than those of fish fed G1, G2 and G4. Fish fed G3 had lower (P < 0.05) total feed intake than those fed other diets in the 1, 2, 3, 4 and 5 week of the feeding trial. As compared with G1, serum catalase and superoxide dismutase activities were higher (P < 0.05) in G2, lower (P < 0.05) in G3, and similar (P > 0.05) in G4. Serum lysozyme activity and immune globulin M concentration were higher (P < 0.05) in G2 and G3 than those in G1 and G4. Muscle fiber density was increased (P < 0.05) as dietary CT increasing from 0 to 2 g/kg, but was similar (P > 0.05) between G1 and G4. Muscle water loss rate of post thawing was higher (P < 0.05) in G2 and G3 than that in G1 and G4, but was similar (P > 0.05) between G1 and G4 as well as G2 and G3. All fish had similar (P > 0.05) muscle amino acid compositions. Fish fed G3 had lower (P < 0.05) mRNA relative expressions of GH, IGF-1, Myf5, MyoD and Pax7 than those of fish fed other diets. The mRNA relative expressions of GH, IGF-1, Myf5, MyoD and Pax7 were similar (P > 0.05) among G1, G2 and G4. All fish had similar (P > 0.05) RNA relative expressions of IGF-2, MyoG and Mstn2 among groups. In summary, inclusion of 1 g/kg CT in L. maculatus diets did not alter growth but enhanced serum antioxidant and immune response, whereas 2 g/kg of CT declined feed intake and growth, decreased antioxidant enzyme activities but enhanced immune response of fish. Supplementation of CT increased muscle fiber density, decreased muscle water holding capacity but did not affect muscle amino acid compositions of L. maculatus. Dietary CT at the concentration of 2 g/kg down-regulated the majority of muscle growth-related genes expression, which may account for the decreased growth performance of L. maculatus.

Condensed Tannins Improve Glycolipid Metabolism but Induce Liver Injury of Chinese Seabass (Lateolabrax maculatus)

A 63-day feeding trial with 640 juvenile L. maculatus was conducted to assess the effects of dietary CT on serum metabolites, antioxidant and immune response, liver histomorphology and glycometabolism enzyme activities of fish. Four diets were formulated to contain 0 (T1), 1 (T2), 2 (T3), and 2 g/kg of CT plus 4 g/kg of polyethylene glycol (PEG) (T4). PEG specifically binds with CT to neutralize CT activity. Fish were randomly distributed into 16 tanks (4 tanks per group and 40 fish per tank) and were fed to apparent satiation twice daily. Results indicated that fish fed T2 and T3 had lower (P&amp;lt;0.05) concentrations of serum albumin, total cholesterol and triacylglycerol, but higher (P&amp;lt;0.05) alanine aminotransferase activity than T1 and T4. T3 had lower (P&amp;lt;0.05) serum glucose but higher (P&amp;lt;0.05) insulin concentrations than other groups. Fish fed T2 and T3 had higher (P&amp;lt;0.05) liver superoxide dismutase, catalase, lysozyme and immune globulin M than T1 and T4. Compared with T1 and T4, hepatocytes in T2 and T3 were shown to have obvious vacuolar degeneration along with different degree of inflammatory cell infiltration. Fish fed T2 and T3 had higher (P&amp;lt;0.05) values of eosinophilic infiltrate and necrosis and greater (P&amp;lt;0.05) pyruvate kinase, but lower (P&amp;lt;0.05) glucokinase activities than those of fish fed T1 and T4. All parameters were similar (P&amp;gt;0.05) between T1 and T4. In summary, dietary CT up to 2 g/kg reduced serum lipid and glucose concentrations, enhanced liver antioxidant and immune response, improved glucose utilization but of L. maculatus. CT induced liver injury of L. maculatus which provided a caution for its application in aquaculture.

Condensed tannins protect against aflatoxin B1-induced toxicity in Lateolabrax maculatus by restoring intestinal integrity and regulating bacterial microbiota

Condensed tannins (CT) have been shown to enhance the exogenous stress resistance of fish, whereas the protective effects of CT against damage induced by dietary aflatoxin B1 (AFB1) on the growth and health of fish have not been evaluated. A 56-day feeding trial was carried out to assess the effects of CT on alleviating dietary AFB1-induced damages in growth, antioxidant and immune response, intestinal integrity and bacterial microbiota of the Chinese sea bass (Lateolabrax maculatus). Three diets were formulated to contain 0 mg/kg of AFB1 and 0 g/kg of CT (G1), 1 mg/kg of AFB1 and 0 g/kg of CT (G2), and 1 mg/kg of AFB1 and 1 g/kg of CT (G3), respectively. Each diet was randomly assigned to three tanks with 40 fish in each tank. Fish were fed to apparent satiation twice daily. Results indicated that fish fed G2 had lower (P < 0.05) final body weight, weight gain rate, specific growth rate, feed intake, viscerosomatic index, total antioxidant capacity, superoxide dismutase, catalase, alkaline phosphatase and lysozyme, but higher (P < 0.05) malondialdehyde, diamine oxidase and lipopolysaccharide compared to those of fish fed G1 and G3. Fish fed G3 had higher (P < 0.05) villus length and intestinal tight junction protein gene expression (ZO-1, Claudin-3 and Occludin), but lower (P < 0.05) villus width than G2. Fish had similar growth performance, serum parameters and intestinal morphology between G1 and G3. In the top 10 dominant genera of intestinal microbiota, the relative abundance of Pseudomonas was higher in G2 but lower in G3 than in G1 (P < 0.05). Compared with G1, G2 and G3 had higher relative abundances of Aeromonas and Klebsiella, but lower relative abundance of Plesiomonas (P < 0.05). Dietary treatments did not alter the alpha and beta diversity of bacterial communities. In conclusion, dietary inclusion of 1 mg/kg of AFB1 reduced feed intake and decreased growth of L. maculatus. AFB1 reduced serum antioxidant capacity and immunity, increased intestinal permeability, induced intestinal damage and altered bacterial microbiota of fish. Supplementation of 1 g/kg of grape seed CT effectively protected against AFB1 toxicity by alleviating the negative impacts of dietary AFB1 exerted on fish. This study provides a rational for the application of CT in aquaculture to prevent fish from AFB1-induced damage.

Condensed tannins alleviate aflatoxin B1-induced injury in Chinese sea bass (Lateolabrax maculatus)

A 56-day feeding trial was conducted to evaluate the protective mechanism of condensed tannins (CT) on the dietary aflatoxin B1 (AFB1)-induced changes in body compositions, intestinal digestive enzyme activities, antioxidant and immune parameters, liver histomorphology, and the AFB1 residue contents in the liver and muscle of Chinese sea bass (Lateolabrax maculatus) (initial body weight 2.9 ± 0.1 g). Three diets were formulated to contain 0 mg/kg of AFB1 and 0 g/kg of CT (T1), 1.0 mg/kg of AFB1 and 0 g/kg of CT (T2), and 1.0 mg/kg of AFB1 and 1.0 g/kg of CT (T3), respectively. Each diet was randomly assigned to three tanks with 40 fish per tank. Fish were fed to apparent satiation twice daily. Results indicated that the survival rate, whole body compositions of dry matter, crude protein and crude lipid contents, and intestinal digestive enzyme activities of amylase, lipase and trypsin were not significantly different among diets (P > 0.05). Fish fed T2 had lower (P < 0.05) albumin, high density lipoprotein cholesterol, superoxide dismutase, catalase and glutathione peroxidase, but higher (P < 0.05) triacylglycerol, aspartate aminotransferase, malondialdehyde, alkline phosphatase, lysozyme and immunoglobulin M than those of fish fed T1 and T3. As compared with T1, hepatocytes in T2 and T3 had obvious and slight vacuolar degeneration, some white spots of necrosis and inflammatory cell infiltration, respectively. T2 had higher (P < 0.05) AFB1 residue contents in the liver and muscle than T1, and the AFB1 residue contents in liver and muscle were not significantly different (P > 0.05) between T1 and T3. In conclusion, inclusion of 1.0 mg/kg AFB1 in L. maculatus diet induced liver injury and lipid dysmetabolism, caused imbalance of liver antioxidant and immune system, and increased AFB1 residue contents in liver and muscle of fish. Supplementation of 1.0 g/kg CT protected against AFB1-induced injury and reduced AFB1 residue contents in L. maculatus.

Toxic Effects of Aflatoxin B1 in Chinese Sea Bass (Lateolabrax maculatus).

This study was performed to assess the effects of dietary aflatoxin B1 (AFB1) on the growth, antioxidant and immune response, digestive enzyme activities, and intestinal morphology of Lateolabrax maculatus during a 56-day feeding trial. Four diets were formulated including 0, 0.1, 0.5, and 1.0 mg/kg of AFB1. Each diet was randomly assigned to 3 fish tanks with 40 fish per tank. Results indicated that the fish’s final body weight, weight gain rate, specific growth rate, feed intake, condition factor, viscerosomatic index, hepatosomatic index, and intestinesomatic index decreased (p < 0.01) as dietary AFB1 increased. AFB1 levels in diets increased (p < 0.05) serum total antioxidant capacity (TAOC), superoxide (SOD), catalase, malondialdehyde (MDA), alkaline phosphatase (AKP), and lysozyme (LZM), and increased (p < 0.05) the TAOC, SOD, MDA, AKP, LZM, and immunoglobulin M in the livers of the fish. Dietary AFB1 decreased (p < 0.05) intestinal trypsin activity and induced intestinal injury. In summary, dietary AFB1 up to 1.0 mg/kg was toxic to L. maculatus as judged by reduced growth, enhanced antioxidant and immune response, decreased intestinal trypsin activity, and impaired intestinal morphology.

Effects of acute low salinity stress on the liver structure, physiology and biochemistry of juvenile Chinese sea bass (Lateolabrax maculatus)

In order to explore the effects of acute low salinity stress on the liver structure, physiology and biochemistry of the larvae of Lateolabrax maculatus, the experiment was carried out to transfer the juveniles direct from salinity 30‰ (control group) to salinity 20‰, 10‰, and 0‰, respectively. Changes in liver microstructure and related physiological and biochemical indexes at different time points were observed. The results showed that no fish died during the whole experiment and all of them returned to normal behavior within 15 minutes. The liver cells of juvenile Chinese sea bass showed pathological changes such as swelling, vacuolation and nuclear pyknosis after low salinity stress, and the lower the salinity, the earlier the abnormal phenomenon appeared. The total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) of liver showed a rapid increase and then decrease; The level of malondialdehyde (MDA) returned to normal after high fluctuations. The activity of lysozyme (LZM) in experimental groups were higher than that in control group between 12h and 48h, while there was not significantly different before 6h in each group (P&gt;0.05), all of them returned to normal in 96 h. The activity of alkaline phosphatase (ALP) and acid phosphatase (ACP) increased firstly and then decreased during the time of stress, and there was no significant difference between each group at the same time point (P&gt;0.05). The comprehensive analysis showed that the juvenile Chinese sea bass had strong osmotic pressure regulation ability, and the acute low salinity stress had little effect on the liver structure and physiological and biochemical indexes.

An Active Gelatin Coating Containing Eugenol and Vacuum Delays the Decay of Chinese Seabass (Lateolabrax maculatus) Fillets during Cold Storage: A Microbiome Perspective

The purpose of this study was to evaluate the effect of an active gelatin coating containing eugenol and vacuum on the microbial diversity of Chinese seabass (Lateolabrax maculatus) during cold (−0.9 °C) storage. The bacterial sequences in Chinese seabass were observed using a high-throughput sequencing technique targeting the V3–V4 region of the 16S Ribosomal DNA (rDNA) on 0, 12th, and 24th day, which showed a more comprehensive estimate of the microbial diversity in seabass samples compared with microbial enumeration. The results revealed that the species diversity of fresh seabass was rich, mainly including Carnobacterium, Glutamicibacter, and Pseudomonas, with abundance ratios of 0.286, 0.160, and 0.130, respectively. Pseudomonas and Shewanella were the primary contaminants in the spoiled control samples, where the abundance ratios increased from 0.220 and 0.174 on the 12th day to 0.802 and 0.163 on the 24th day, respectively. Vacuum treatment could inhibit the growth of Pseudomonas and Shewanella such that when stored on the 12th day, Brochothrix became the superior genus. However, Pseudomonas and Shewanella dominated the storage until the 24th day, where their abundance ratios were 0.343 and 0.279, respectively. The inhibition of Pseudomonas and Carnobacterium was gradually enhanced with increasing concentrations of eugenol. Furthermore, an active gelatin coating containing eugenol and vacuum treatment was more effective at inhibiting the increase of the total volatile basic nitrogen. This study confirmed that an active gelatin coating containing eugenol and vacuum could reduce the species of bacteria, inhibit the growth and reproduction of the main dominant spoilage bacteria, and delay the spoilage of seabass.

Molecular cloning and functional analysis of type I IFNd of Chinese sea bass (Lateolabrax maculatus) under immune stimulation

Chinese sea bass (Lateolabrax maculatus) is an economically important marine cultured species in China. Interferons (IFNs) play an essential role in innate antiviral immunity. The study on IFN immune system helps prevent and control viral diseases of L. maculatus. We have obtained cloning and characterization of the type I IFNd gene from L. maculatus (LmIFNd) in the present study. The full length of cDNA was 1190 bp, including 5’UTR (untranslated region) of 354 bp, 3’UTR of 278 bp, and an open reading frame (ORF) of 558 bp. It encodes 185 amino acids, and the first 20 amino acids are hypothetical signal peptides. The results of amino acid multiple sequence alignment and phylogenetic tree analysis showed that LmIFNd and mandarin fish (Siniperca chuatsi) IFNd were clustered into one branch, and the gene sequence similarity was as high as 88.9%. The expression of LmIFNd was tissue-specific and highly expressed in the head kidney, spleen, and gill. After infection with Rana grylio virus (RGV), and polyinosinic-polycytidylic acid [Poly(I:C)], the expression of LmIFNd in gill, spleen, and head-kidney was up-regulated significantly. Besides, the expression level of LmIFNd has increased significantly under the stimulation of Vibrio harveyi and Streptococcus iniae. The results show that LmIFNd may play a protective role in both viral and bacterial infections.