Lateolabrax Japonicus Research Articles

Chemical Compositions and Characteristics of Biocalcium from Pre-Cooked Tuna Bone as Influenced by Sodium Chloride Pretreatment and Defatting by Asian Seabass Lipase.

Pre-cooked bone is a waste product generated during tuna processing and can serve as a potential source of biocalcium (BC). Generally, non-collagenous protein and fat must be removed properly from bone. A NaCl solution can be used to remove such proteins, while fish lipase can be used in a green process, instead of solvent, for fat removal. Thus, this study aimed to investigate the impact of NaCl pretreatment at different concentrations in combination with heat to eliminate non-collagenous proteins, and to implement fish lipase treatments at varying levels for fat removal, for BC production from pre-cooked tuna bone. Optimal NaCl pretreatment of bone was achieved when a 5% NaCl solution at 80 °C was used for 150 min. The lowest lipid content was obtained for bone defatted with crude lipase extract (CLE) at 0.30 Unit/g of bone powder for 2 h. BC powder from bone defatted with CLE (DF-BC) possessed greater contents of ash, calcium, and phosphorus and smaller particle sizes than the control BC powder. X-ray diffractograms suggested that both BC powders consisted of hydroxyapatite as a major compound, which had a crystallinity of 62.92-63.07%. An elemental profile confirmed the presence of organic and inorganic matter. Thus, BC powder could be produced from pre-cooked tuna bone using this 'green process'.

Molecular characterization of vascular endothelial growth factor b from spotted sea bass (Lateolabrax maculatus) and its potential roles in decreasing lipid deposition

Vascular endothelial growth factor B (VEGFB), a member of the VEGF family, exhibits limited angiogenic activity in mammals but plays an unexpected role in targeting lipids to peripheral tissues. However, its role in lipid metabolism in fish is unknown. In this study, the vegfb gene was cloned and characterized from spotted sea bass (Lateolabrax maculatus). It encodes 254 amino acids and possesses the typical characteristics of the Vegfb family, demonstrating high homology with those from other vertebrate species. The vegfb gene exhibits the highest expression levels in the liver, followed by the gills, intestine, and adipose tissues in spotted sea bass. In vivo, high-lipid diets decreased vegfb expression and increased lipid deposition in liver of fish. In vitro, palmitic acid + oleic acid treatment or vegfb knockdown significantly increased TG and TC contents, promoting lipid droplet deposition in hepatocytes. Vegfb overexpression has the opposite effects, inhibiting lipid deposition and downregulating fatty acid transport and adipogenesis genes. In contrast, the vegfb knockdown significantly upregulated the expression levels of c/ebpα, plin2, and dgat1 (P < 0.05). These results demonstrate that Vegfb may play an important role in reducing lipid deposition by regulating fatty acid transport and adipogenesis in the hepatocytes of spotted sea bass.

A novel vaccination strategy against Vibrio harveyi infection in Asian seabass (Lates calcarifer) with the aid of oxygen nanobubbles and chitosan

Immersion vaccination, albeit easier to administer than immunization by injection, sometimes has challenges with antigen uptake, resulting in sub-optimal protection. In this research, a new strategy to enhance antigen uptake of a heat-inactivated Vibrio harveyi vaccine in Asian seabass (Lates calcarifer) using oxygen nanobubble-enriched water (ONB) and positively charged chitosan (CS) was explored. Antigen uptake in fish gills was assessed, as was the antibody response and vaccine efficacy of four different combinations of vaccine with ONB and CS, and two control groups. Pre-mixing of ONB and CS before introducing the vaccine, referred to as (ONB + CS) + Vac, resulted in superior antigen uptake and anti-V. harveyi antibody (IgM) production in both serum and mucus compared to other formulas. The integration of an oral booster (4.22 × 108 CFU/g, at day 21–25) within a vaccine trial experiment set out to further evaluate how survival rates post exposure to V. harveyi might be improved. Antibody responses were measured over 42 days, and vaccine efficacy was assessed through an experimental challenge with V. harveyi. The expression of immune-related genes IL1β, TNFα, CD4, CD8, IgT and antibody levels were assessed at 1, 3, and 7-day(s) post challenge (dpc). The results revealed that antibody levels in the group (ONB + CS) + Vac were consistently higher than the other groups post immersion immunization and oral booster, along with elevated expression of immune-related genes after challenge with V. harveyi. Ultimately, this group demonstrated a significantly higher relative percent survival (RPS) of 63 % ± 10.5 %, showcasing the potential of the ONB-CS-Vac complex as a promising immersion vaccination strategy for enhancing antigen uptake, stimulating immunological responses, and improving survival of Asian seabass against vibriosis.

Single-Cell Transcriptome Profiling of Scale Drop Disease Virus-Infected Asian Seabass (Lates calcarifer)

The study aims to characterize the immune cell landscape in convalescent Asian seabass (Lates calcarifer) blood samples after exposure to scale-drop disease virus (SDDV). Traditional immunophenotyping approaches used in human and mouse studies are impractical for non-model organisms like the Asian seabass due to the lack of specific antibody-based reagents. To overcome this challenge, 10x Genomics single-cell RNA sequencing was employed. The analysis of blood samples revealed 24 distinct leukocyte clusters, with elevated proportions of B cells, granulocytes, and T cells in the convalescent group compared to the uninfected group. While distinguishing granulocyte and macrophage subsets was challenging, the analysis of differential gene expression in the macrophage population indicated that the upregulated genes were linked to inflammatory processes. Specific T cell clusters showed notable expressions of cd4-1, cd8a, perforin-1 and il-2rβ, suggesting the presence of CD4+ T helper (Th), CD8+ cytotoxic T (Tc) cells, immature T cells, and naive T cells. Attempts to categorize CD4+ T cells into Th subtypes lacked clear distinctions, while CD8+ T cells exhibited three clusters, predominantly Tc1 cells. Furthermore, comparisons between convalescent and uninfected groups revealed increased percentages of activated and antibody-secreting B cells in the convalescent group. This single-cell analysis provides vital insights into the immune cell dynamics in convalescent and uninfected Asian seabass, providing valuable information on potential immune responses to SDDV infection.

Comparisons on Growth Performance, Survivability, Organoleptic Qualities and Economic Feasibility of Asian Seabass (Lates calcarifer) Reared in Different Salinities

Asian seabass, Lates calcarifer is among the most cultured aquaculture species in the Southeast Asian region due to its remarkable tolerance for a diverse environmental fluctuation. In aquaculture, salinity has a direct influence on many biological, physiological and market value of any cultured fish. This study investigated the impacts of different salinities (0, 15, &amp; 30 ppt) on Asian seabass growth, body indices, feeding performance, organoleptic qualities, and production cost for 85 days. Ninety fish were reared in 700-liter tanks equipped with recirculation system with 10 fish each tank. They were fed with commercial marine feed. The findings revealed Asian seabass in 15 ppt attained significantly higher (p&gt;0.05) body weight (470.40 ± 41.16 g), total length (31.51 ± 0.81 cm), total feed intake (309.28 ± 35.66 g/fish) and daily feed intake (3.64 ± 0.42 g/fish/day) compared to 30 ppt but remained insignificant with 0 ppt. Meanwhile, there was no significant difference (p&lt;0.05) in terms of body weight gain, specific growth rate, body indices, and feed conversion ratio of Asian seabass when reared in different salinities. The organoleptic qualities showed that rearing Asian seabass in different salinities has no significant effect (p&lt;0.05) on odour, appearance, texture, and flavour score. However, the overall acceptance score of Asian seabass reared in 30 ppt (3.53 ± 0.22) was significantly higher (p&gt;0.05) compared to 15 ppt but remained insignificant with 0 ppt. Economically, Asian seabass cultured in 15 ppt yielded the most optimal conditions for profitable production. The findings conclude 15 ppt can promotes enhanced growth performance and profitability, while 0 ppt and 30 ppt can promote consumer acceptance positively.

Gut microbiota-bile acid crosstalk and metabolic fatty liver in spotted seabass (Lateolabrax maculatus): The role of a cholesterol, taurine and glycine supplement

The prevalent practice of substituting fishmeal with plant protein frequently leads to disturbances in bile acid metabolism, subsequently increasing the incidence of metabolic liver diseases. Bile acid nutrients such as cholesterol, taurine and glycine have been shown to enhance bile acid synthesis and confer beneficial effects on growth. Therefore, this study aimed to investigate the effects of cholesterol-taurine-glycine (Ch-Tau-Gly) supplement on bile acid metabolism and liver health in spotted seabass (Lateolabrax maculatus) fed a plant-based diet. Two isonitrogenous and isolipidic diets were formulated: (1) plant protein-based diet (PP); (2) PP supplemented 0.5% cholesterol, 0.5% taurine and 1.3% glycine (CTG). Each experimental diet was randomly fed to quadruplicate groups of 30 feed-trained spotted seabass in each tank. The results revealed that supplementing plant-based diet with Ch-Tau-Gly supplement led to an increase in carcass ratio (meat yield) in spotted seabass (P < 0.05), indirectly contributing positively to their growth. The dietary supplement effectively suppressed endogenous cholesterol synthesis in the liver, promoted the expression of bile acid synthesis enzyme synthesis, and simultaneously the expression of intestinal fxr and its downstream genes, including hnf4α and shp (P < 0.05). The reduction in Lactobacillus_salivarius and bile salt hydrolase (BSH) were observed in CTG group with concurrently increased conjugated chenodeoxycholic acid (CDCA) bile acids (P < 0.05), suggesting the enhancement of the hydrophilicity of the bile acid pool. In CTG group, fatty liver was alleviated with a corresponding increase in lipid metabolism, characterized by a downregulation of genes associated with lipogenesis and lipid droplet deposition, along with an upregulation of genes related to lipolysis. Our study underscored the ability of Ch-Tau-Gly supplement to influence the gut microbiota, leading to an increase in the levels of conjugated CDCA (P < 0.05) in the bile acid pool of spotted seabass. The interplay between the gut microbiota and bile acids might constitute a crucial pathway in the promotion of liver health. These findings offer a promising solution, suggesting that Ch-Tau-Gly supplement have the potential to promote the growth of aquatic species and livestock fed on plant-based diets while addressing issues related to metabolic fatty liver.

Comparative pathogenicity of Nocardia seriolae in Nile tilapia (Oreochromis niloticus), milkfish (Chanos chanos) and Asian seabass (Lates calcarifer).

Nocardiosis, caused by Nocardia seriolae, has been a prominent disease in Southeast Asian aquaculture in the last three decades. This granulomatous disease reported in various fish species is responsible for significant economic losses. This study investigated the pathogenicity of N. seriolae in three cultured species in Taiwan: Nile tilapia (omnivore), milkfish (herbivore) and Asian seabass (carnivore). Administration of an infective dose of 1 × 106 CFU/ fish in tilapia, seabass and milkfish demonstrated mortalities of 100%, 90% and 75%, respectively. Additionally, clinical signs namely, granuloma and lesions displayed varying intensities between the groups and pathological scores. Polymerase chain reaction (PCR) amplification specific for N. seriolae was confirmed to be positive (432 bp) using NS1/NG1 primers. Post-mortem lesions revealed the absence of granulomas in tilapia and milkfish and their presence in the seabass. Interestingly, the gut in tilapia showed an influx of eosinophils suggesting its role during the acute stages of infection. However, post-challenge, surviving milkfish exhibited granulomatous formations, while surviving seabass progressed toward healing and tissue repair within sampled tissues. Overall, in conclusion, these results demonstrate the versatility in the immunological ability of individual Perciformes to contain this pathogen as a crucial factor that influences its degree of susceptibility.

Cloning and expression analysis of Janus activated kinase family genes from spotted seabass (Lateolabrax maculatus)

Janus kinases (JAKs) are important components of the JAK-STAT signaling pathway and play vital roles in innate immunity, autoimmune diseases, and inflammation. However, information about JAKs remains largely unknown in the spotted seabass, a fish species of Perciformes with great commercial value in the aquaculture industry. The aims of this study are to obtain the complete cDNA sequences of JAKs (JAK1, JAK2A, JAK2B, JAK3 and TYK2) from spotted seabass and to investigate their roles upon stimulation with lipopolysaccharides (LPS) and Edwardsiella tarda, using RT-PCR, PCR and qRT-PCR methods. All five JAK genes from the spotted seabass, each encode more than 1100 amino acids residues. JAK1 and JAK3 consist of 24 exons and 23 introns, whereas JAK2A, JAK2B and TYK2 consist of 23 exons and 22 introns. Furthermore, these five spotted seabass JAKs share high sequence identities with those of other fish species in protein domain analysis, synteny analysis, and phylogenetic analysis. Moreover, these five JAK genes were ubiquitously expressed in all tissues examined from healthy fish, and inducible expressions of JAKs were observed in the intestine, gill, head kidney, and spleen following LPS treatment or E. tarda infection. These findings indicate that all these JAK genes are involved in the antibacterial immunity of the spotted seabass and provide a basis for further understanding the mechanism of JAKs antibacterial response in the spotted sea bass.

Influence of ultrasonic pretreatment on drying and thermodynamic characteristics of Asian seabass fish skin during air-frying process

Influence of ultrasonic pretreatment on drying and thermodynamic characteristics of Asian seabass fish skin during air-frying process

Lipidomics‐based study of lipid quality of fish by‐products: a case study of sea bass (Lateolabrax japonicus)

SummaryBy‐products of sea bass are a good source of lipids, among which viscera was the best lipid source containing 66% total lipids. Acid value, peroxide value (POV), p‐anisidine value (p‐AV), and conjugated diene value (CDV) were used to monitor oxidation. Visceral oil has a relatively higher level of POV, AV and CDV than head and belly. Radical production detected by ESR spectroscopy was also high in viscera. Fatty acid analysis showed that visceral oil of sea bass has a very high ratio of monounsaturated fatty acid, which includes oleic acid (C18:1n9), and palmitoleic acid (C16:1n9) accounting for 28.45% and 3.25% of total visceral oil and are rich in omega‐6 polyunsaturated fatty acids accounting for 34.78% of total lipids. Volatile compounds in visceral oil were low with flora and spicy oil wax aroma. Low amounts of aldehydes, ketones and alcohols indicated a low level of oxidation in the early stage of storage. ESR results indicated higher free radical level in visceral oil, which might result in the Inside‐Out quality deterioration.

Storage stability of Asian seabass oil-in-water Pickering emulsion packed in pouches made from electrospun and solvent casted bilayer films from poly lactic acid/chitosan-gelatin blend containing epigallocatechin gallate

Bilayer pouches were fabricated with chitosan (CS)-fish gelatin (FG) mixture containing epigallocatechin gallate (EGCG) deposited over the poly lactic acid (PLA) film through solvent casting and electrospinning techniques. Pickering emulsions (PE) of Asian seabass depot fat oil stabilized by zein colloidal particles were packed in bilayer pouches and stored at 28 ± 2 °C. The PE packed in pouch containing EGCG had higher emulsion and oxidative stability after 30 days of storage as witnessed by the smaller droplet size and lower values of thiobarbituric acid reactive substances, peroxide, conjugated diene and volatile compounds in comparison with control (PE packed in monolayer PLA pouch) (P < 0.05). EGCG incorporated pouch retained more linoleic acid (C18:2 n-6) and linolenic acid (C18:3 n-9) in emulsion than PLA pouch. Therefore, pouch from bilayer PLA/CS-FG films comprising EGCG could serve as active packaging and extended the shelf life of Pickering emulsion.

Immuno-protective response of Asian seabass (Lates calcarifer) to inactivated vaccines against Streptococcus iniae and Vibrio harveyi

BackgroundIn this study, the protective immunity and immunogenicity of the monovalent and bivalent Streptococcus iniae and Vibrio harveyi vaccine were evaluated in Asian seabass. To analyze immune responses, 1200 Asian seabass with an average weight of 132.6 ± 25.4 g were divided into eight treatments in triplicates (50 fish per tank) as follows: S. iniae immunized by injection (SI), V. harveyi immunized by injection (VI), bivalent S. iniae and V. harveyi (SVI) immunized by injection, S. iniae immunized by immersion (SIM), V. harveyi (VIM) immunized by immersion, bivalent S. iniae and V. harvei (SVIM) immunized by immersion, phosphate-buffered saline (PBS) by injection (PBSI) and control group without vaccine administration (CTRL). Blood and serum samples were taken at the end of the 30th and 60th days. Then the vaccinated groups were challenged with two bacteria (S. iniae) and (V. harveyi) separately and mortality was recorded for 14 days.ResultsThis study reveals that there is no significant difference in the hematological parameters on the 30th and 60th days of the experiment in the vaccine-immunized groups compared to the CTRL group (P > 0.05). Meanwhile, there was no significant difference in the amount of serum albumin level, respiratory burst activity, and serum bactericidal activity in the vaccine-immunized groups compared to the CTRL group on the 30th and 60th days of the experiment (P > 0.05). Total protein on the 60th day (in the VI and SVI groups), globulin on the 30th day (in the VI and SVI groups) and the 60th day (in the VI group) compared to the CTRL and PBSI groups had a significant increase (P < 0.05). Complement activity (in the VI and SVI groups) and lysozyme (in the SI and SVI groups) increased significantly compared to the control group (P < 0.05). Serum antibody titer against S. iniae had a significant increase in the SI, VI, SVI and SVIM groups compared to the CTRL and PBSI groups (P < 0.05). Serum antibody titer against V. harveyi had a significant increase in the groups immunized with the vaccine compared to the CTRL and PBSI groups (P < 0.05). A significant increase in the relative percentage survival (RPS) following challenge with S. iniae in the SVI (86.6%), SI (83.3%,) and VI (73.3%) groups were observed compared to the CTRL (43.3%) and PBSI (40%) groups (P < 0.05). Also, a significant increase in the RPS after challenge with V. harveyi in the SVI group, VI 86.6%, SVI 83.3%, VIM 80% and SVIM 76.6% were observed compared to the CTRL (46.6%) and PBSI (50%) groups (P < 0.05).ConclusionOverall, the results demonstrated that the bivalent vaccine of S. iniae and V. harveywas able to produce significant immunogenicity and RPS in Asian seabass

Effects of chronic nitrite exposure on hematological parameters, oxidative stress and apoptosis in spotted seabass (Lateolabrax maculatus) reared at high temperature

The effects of nitrite stress on blood biochemistry, antioxidant capacity, and apoptosis of spotted seabass (Lateolabrax maculatus) under high-temperature conditions were investigated. Fish were subjected to varying levels of nitrite concentrations for 28 days, specifically 0, 8, and 16 mg/L. Blood and gill samples were collected at the 1st, 3rd, 7th, 14th, 21st and 28th of the exposure for index determination, respectively. Results showed that as the concentration of nitrite increased, blood hemoglobin (Hb) and serum chloride ion (Cl-) levels decreased. In addition, compared to the control group, methemoglobin (MetHb), hematocrit (HCT), red blood cells (RBCs), white blood cells (WBCs), and serum potassium ion (K+) were significantly increased in the nitrite-stressed group. In terms of antioxidants, catalase (CAT) and superoxide dismutase (SOD) activities in the gill were significantly decreased with increasing nitrite concentration. Additionally, malondialdehyde (MDA) content was significantly increased with increasing nitrite concentration. Regarding genes related to apoptosis, as nitrite concentration increased, the expressions of hypoxia-inducible factor (Hif-1α) and cytochrome C (Cyt-c) genes in the gill were significantly up-regulated on the 1st and 3rd day of exposure. The expressions of P53, Bax, Caspase-3, Caspase-8, and Caspase-9 genes in the gill were significantly up-regulated in stress groups at different exposure time intervals compared to the control group. In summary, nitrite caused disruption in the balance of blood ions, decreased antioxidant capacity in the gills, increased expression of genes associated with apoptosis, ultimately resulting in gill injury in the spotted seabass.

Effects of active film based on chitosan/polyvinyl alcohol on the quality of refrigerated sea bass (Lateolabrax Japonicus) fillets

There has been a growing interest in employing active films for fish preservation due to the environmental concern of plastic packaging and the high perishability of fish. This work aimed to develop active films (CPB0.8) based on chitosan/polyvinyl alcohol integrated with ginger essential oil (GEO) -loaded bacterial cellulose, and to evaluate the preservation effect of the films on refrigerated sea bass fillets. Different active films were obtained by the solution blending method. It was evaluated by measuring microbiological indicators, physicochemical indexes, and water loss of sea bass fillets. The sample wrapped by CPB0.8 film had a lower microbial load after 12 days of storage. The results showed that the sample wrapped by CPB0.8 film had a lower microbial load after 12 days of storage compared to the active film sample without GEO and the control sample. Besides, the reduction of hardness and springiness of fillets packaged with CPB0.8 film was markedly inhibited. Additionally, the fillets wrapped by CPB0.8 film indicated a lower K-value (56.54%) under the rejection limit (60%) on the 10th day, which confirmed that CPB0.8 films extended the shelf-life of fillets to 10 days. Also, the active packaging could preserve fish quality by controlling water migration and lipid oxidation. Overall, these findings indicate that CPB0.8 films can be useful for the preservation of fish and effectively reduce petroleum-based plastics.

Effects of dietary supplementation with mannan-rich oligosaccharides and solid-state fermented Aspergillus niger on the growth performance of juvenile Asian seabass, Lates calcarifer

Effects of dietary supplementation with mannan-rich oligosaccharides and solid-state fermented <i>Aspergillus niger</i> on the growth performance of juvenile Asian seabass, <i>Lates calcarifer</i>

Coinfection of Cage-Cultured Spotted Sea Bass (Lateolabrax maculatus) with Vibrio harveyi and Photobacterium damselae subsp. piscicida Associated with Skin Ulcer.

Spotted sea bass (Lateolabrax maculatus) is a high-economic-value aquacultural fish widely distributed in the coastal and estuarine areas of East Asia. In August 2020, a sudden outbreak of disease accompanied by significant mortality was documented in L. maculatus reared in marine cage cultures located in Nanhuang island, Yantai, China. Two coinfected bacterial strains, namely, NH-LM1 and NH-LM2, were isolated from the diseased L. maculatus for the first time. Through phylogenetic tree analysis, biochemical characterization, and genomic investigation, the isolated bacterial strains were identified as Vibrio harveyi and Photobacterium damselae subsp. piscicida, respectively. The genomic analysis revealed that V. harveyi possesses two circular chromosomes and six plasmids, while P. damselae subsp. piscicida possesses two circular chromosomes and two plasmids. Furthermore, pathogenic genes analysis identified 587 and 484 genes in V. harveyi and P. damselae subsp. piscicida, respectively. Additionally, drug-sensitivity testing demonstrated both V. harveyi and P. damselae subsp. piscicida exhibited sensitivity to chloramphenicol, ciprofloxacin, ofloxacin, orfloxacin, minocycline, doxycycline, tetracycline, and ceftriaxone. Moreover, antibiotic resistance genes were detected in the plasmids of both strains. Extracellular product (ECP) analysis demonstrated that both V. harveyi and P. damselae subsp. piscicida can produce hemolysin and amylase, while V. harveyi additionally can produce caseinase and esterase. Furthermore, infected fish displayed severe histopathological alterations, including infiltration of lymphocytes, cellular degeneration and necrosis, and loose aggregation of cells. Artificial infection assays determined that the LD50 of P. damselae subsp. piscicida was 3 × 105 CFU/g, while the LD50 of V. harveyi was too low to be accurately evaluated. Furthermore, the dual infection of V. harveyi and P. damselae subsp. piscicida elicits a more rapid and pronounced mortality rate compared to single challenge, thereby potentially exacerbating the severity of the disease through synergistic effects. Ultimately, our findings offer compelling evidence for the occurrence of coinfections involving V. harveyi and P. damselae subsp. piscicida in L. maculatus, thereby contributing to the advancement of diagnostic and preventative measures for the associated disease.

Effects of microgels fabricated by microfluidic on the stability, antioxidant, and immunoenhancing activities of aquatic protein

Aquatic products are considered a potential source of novel bioactive proteins, which are used as therapeutic drugs for the treatment of different diseases (such as oxidative stress, immunocompromised, and inflammation), as well as nutraceuticals and cosmetics. However, the physical and chemical properties of proteins are unstable, and they are easily denatured by the influence of external high temperature and polar pH during processing, resulting in the loss of their functional activity. Herein, Fenneropenaeus chinensis water-soluble protein (FCWP) and Lateolabrax japonicus water-soluble protein (LJWP) were encapsulated within spherical biopolymer microgels composed of pectin and chitosan produced by the microfluidic device. The encapsulated samples remained inside the microgels when they were exposed to upper gastrointestinal but were released when they were exposed to simulated colonic fluid due to the hydrolysis effect by enzymes secreted by the colonic microflora. The results showed that microgels improve the thermal stability of FCWP and LJWP due to the interaction between polysaccharides and proteins in the microgels. In addition, microgels encapsulation did not affect the antioxidant and immunoenhancing activities of FCWP and LJWP. In summary, these microgels are suitable for oral colon-specific delivery in functional foods and supplements.

Characterization of sperm quality in captive-bred barramundi (Lates calcarifer): Effect on spawning performance and paternal contribution in mass-spawning events

Barramundi (Asian sea bass, Lates calcarifer) is a species with a mass-spawning reproductive strategy whereby adults synchronously release their gametes into the water column. In captivity, this reproductive strategy usually results in uneven paternal contributions to each cohort of progeny, creating skews in family size that hinder the effectiveness of selective breeding programs. As sperm quality influences fertilization success and early larval development, we investigated the relationship between sperm quality and spawning performance. Accordingly, we assessed three established breeding cohorts. Sperm samples (n = 22) were collected by cannulation. Sperm motility was assessed using CASA, and sperm viability and DNA integrity were evaluated using dual-fluorescence stains by flow cytometry. Broodstock were induced to spawn across two consecutive nights, and offspring were collected at 2.5 h and 12 h post-fertilization (hpf) and 24 h and 48 h post-hatching (hph). Offspring were assessed for morphological abnormalities, and key morphological parameters were recorded. Offspring collected at 2.5 hpf and 24 hph were genotyped to determine their parentage and examine the relationship between sperm quality of individual males and offspring survival. Results highlighted that male condition factor (K) and sperm quality were highly variable within each breeding cohort. Males with a lower condition factor showed lower sperm motility and velocity. In contrast, males with a higher condition factor showed higher sperm motility and velocity but also higher levels of sperm DNA damage. While all males were capable of fertilization, males with a lower condition factor had greater paternal contribution. In this study, a reduction in skewed paternity was also found on Night 2 of spawning compared to Night 1. Moreover, males from Tank B, which had the lowest level of sperm DNA damage, had the most even paternal contribution. Conversely, highly skewed maternal contributions were reported across all spawning events. The results of this study suggest that additional complex dynamics and further unmeasured variables, such as spawning behavior, social hierarchy, and the spawning induction procedure, may also skew family sizes. Therefore, further development of artificial reproductive technology is recommended to gain greater control over individual contribution and overcome current breeding bottlenecks.

Deletion of speA and aroC genes impacts the pathogenicity of Vibrio anguillarum in spotted sea bass

Vibrio anguillarum is one of the major pathogens responsible for bacterial infections in marine environments, causing significant impacts on the aquaculture industry. The misuse of antibiotics leads to bacteria developing multiple drug resistances, which is detrimental to the development of the fisheries industry. In contrast, live attenuated vaccines are gradually gaining acceptance and widespread recognition. In this study, we constructed a double-knockout attenuated strain, V. anguillarum ΔspeA-aroC, to assess its potential for preparing a live attenuated vaccine. The research results indicate a significant downregulation of virulence-related genes, including Type VI secretion system, Type II secretion system, biofilm synthesis, iron uptake system, and other related genes, in the mutant strain. Furthermore, the strain lacking the genes exhibited a 67.47% reduction in biofilm formation ability and increased sensitivity to antibiotics. The mutant strain exhibited significantly reduced capability in evading host immune system defenses and causing in vivo infections in spotted sea bass (Lateolabrax maculatus), with an LD50 that was 13.93 times higher than that of the wild-type V. anguillarum. Additionally, RT-qPCR analysis of immune-related gene expression in spotted sea bass head kidney and spleen showed a weakened immune response triggered by the knockout strain. Compared to the wild-type V. anguillarum, the mutant strain caused reduced levels of tissue damage. The results demonstrate that the deletion of speA and aroC significantly reduces the biosynthesis of biofilms in V. anguillarum, leading to a decrease in its pathogenicity. This suggests a crucial role of biofilms in the survival and invasive capabilities of V. anguillarum.

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.