Lateolabrax Japonicus Research Articles

Growth performance, digestive capacity and intestinal health of juvenile spotted seabass (Lateolabrax maculatus) fed dietary laminarin supplement

Laminarin has antioxidant and immunomodulatory properties and favorably impacts gut microbial composition, providing a potential solution for the treatment of intestinal diseases in fish. The aim of this study was to investigate the effects of laminarin on the growth and intestinal health of juvenile spotted seabass, Lateolabrax maculatus. A total of 450 juveniles (initial body weight: 7.14 ± 0.10 g) were randomly divided into 6 groups with 3 replicates per group and 25 fish per replicate. Six diets were prepared with laminarin supplementation at doses of 0% (Control), 0.4% (P0.4), 0.8% (P0.8), 1.2% (P1.2), 1.6% (P1.6), and 2% (P2). Each group was fed the corresponding diet for 8 weeks. The results indicated that dietary laminarin supplementation of 0.4-1.6% enhanced the specific growth rate (SGR), weight gain rate (WGR), and feed conversion ratio (FCR) of juvenile spotted seabass, and the difference was significant in the P0.8 group (P<0.05). Significantly higher intestinal amylase activity was measured in P0.8 compared with the control group. Trypsin activity was significantly increased in P0.4 and P0.8 groups in contrast to the control (P<0.05). Lipase activity was significantly increased in P0.4, P0.8, P1.6, and P2 groups in contrast to the control (P<0.05). Total antioxidant capacity was significantly increased in the P0.8, P1.2, and P1.6 groups compared to the control group (P<0.05). The P0.8 group exhibited significant increases in reduced glutathione, alkaline phosphatase, and lysozyme levels (P<0.05), whereas the concentrations of diamine oxidase and D-lactate were significantly decreased (P<0.05). Furthermore, intestinal villus height, villus width, and crypt depth were significantly increased in P0.8 and P2 groups (P<0.05), and muscular thickness was significantly increased in the P1.2 group (P<0.05). Intestinal microbial analysis revealed that the alpha diversity of the laminarin supplemented groups was significantly higher than that of the control group. Moreover, the abundance of intestinal beneficial bacteria Lactobacillus and Klebsiella in P0.4 and P0.8 groups was significantly increased (P<0.05), indicating that laminarin altered the composition of intestinal flora and the abundance of dominant bacteria, with a low dose being more conducive to the formation of beneficial bacteria. In conclusion, dietary laminarin supplementation can improve the growth performance and intestinal function of juvenile spotted seabass. Based on the regression analyses of weight gain rate and specific growth rate, the optimal supplemental level of laminarin was estimated to be 0.97% and 0.98%, respectively.

The Effects of Porphyra yezoensis Polysaccharides on Intestinal Health of Spotted Sea Bass, Lateolabrax maculatus

Porphyra yezoensis polysaccharides (PPs) have biological activities such as promoting digestion, functioning as antioxidants, and improving intestinal health. The aim of this study was to investigate the effects of PPs on the intestinal health of spotted sea bass (Lateolabrax maculatus). A total of 360 spotted sea bass (10.53 ± 0.02 g) were randomly divided into six groups. Fish in each group were fed with varying PP concentrations (0, 3, 6, 9, 12, 15 g/kg) for 52 days. The results showed that 12 g/kg PPs significantly increased the body weight gain, specific growth rate, and condition factor, while there was no significant change in the feed conversion ratio. A supplementation dosage of 9 g/kg PPs significantly increased intestinal amylase activity, and 12 g/kg PPs supplementation significantly increased intestinal trypsin activity. In addition, compared with the control group, there was no difference in lipase in the experimental groups. When fed 9 g/kg, the intestinal glutathione content was significantly increased, and the malondialdehyde content was significantly decreased; the effect of PPs on the catalase activity was not significant. PPs improved intestinal morphology, specifically by improving the intestinal villus morphology and increasing the intestinal lining surface area. Compared with the control group, PPs increased the abundance of Firmicutes and Bacteroides. At the genus level, Cyanobacteria, Muribaculaceae, and Lachnospiraceae were the main flora in the intestinal tract of spotted sea bass. In addition, PPs increased ACE and Chao1 indices of the intestinal microorganisms, while the Simpson index and Shannon index did not change significantly, indicating that intestinal microbial composition and abundance had increased to a certain extent. The results indicated that different levels of PPs in feed can improve the intestinal physiological and biochemical indexes, intestinal morphology, and microbial composition, and thus improve the intestinal health of spotted sea bass.

Evaluating Kinetics of Convection Drying and Microstructure Characteristics of Asian Seabass Fish Skin without and with Ultrasound Pretreatment.

Convection drying in combination with ultrasound pretreatment has emerged as a promising technology for seafood manufacturing. The primary objective of this research was to model the mass transfer process of Asian seabass (Lates calcarifer) fish skin without and with ultrasound pretreatment during convection drying at different temperatures (45, 55, and 65 °C). Additionally, the study aimed to examine the impact of ultrasound pretreatment and temperatures on the drying characteristics and specific energy consumption for drying of Asian seabass fish skin. Seven semi-theoretical models, namely Lewis, Page, modified Page, Vega-Lemus, Verma, Henderson and Pabis, and two-term models, were employed to characterize the moisture transfer process. The results of the study indicated a decrease in the moisture content as the drying time increased at different drying temperatures. Higher drying temperatures were associated with an increased drying rate. Among the mathematical models tested, the modified Page model provided a satisfactory description of the thin-layer drying characteristics of fish skin. Fick's law of diffusion was utilized to determine the effective moisture diffusivities. Comparing the drying of fish skin without (SS) and with ultrasound pretreatment (US-SS), the drying of the latter generally showed higher Deff values. The temperature dependence of the effective diffusivity coefficient was well described by the Arrhenius-type model. An increase in the drying temperature resulted in an increment of the effective moisture diffusivity. In general, the skin pretreated using ultrasound had a reduced drying time, by up to 28%. Additionally, this approach contributed to an approximate 22% reduction in the specific energy consumption, concurrently enhancing the energy efficiency. The microstructure analysis showed that fresh and dried US-SS samples had a more open structure and higher porosity, in comparison to the corresponding SS samples. These findings contribute to the knowledge on the application of ultrasound as the pretreatment of fish skin before drying and provide valuable insights for the development of potential drying techniques in the seafood industry.

Mapping of a major QTL for increased robustness and detection of genome assembly errors in Asian seabass (Lates calcarifer)

BackgroundFor Asian seabass (Lates calcarifer, Bloch 1790) cultured at sea cages various aquatic pathogens, complex environmental and stress factors are considered as leading causes of disease, causing tens of millions of dollars of annual economic losses. Over the years, we conducted farm-based challenges by exposing Asian seabass juveniles to complex natural environmental conditions. In one of these challenges, we collected a total of 1,250 fish classified as either ‘sensitive’ or ‘robust’ individuals during the 28-day observation period.ResultsWe constructed a high-resolution linkage map with 3,089 SNPs for Asian seabass using the double digest Restriction-site Associated DNA (ddRAD) technology and a performed a search for Quantitative Trait Loci (QTL) associated with robustness. The search detected a major genome-wide significant QTL for increased robustness in pathogen-infected marine environment on linkage group 11 (ASB_LG11; 88.9 cM to 93.6 cM) with phenotypic variation explained of 81.0%. The QTL was positioned within a > 800 kb genomic region located at the tip of chromosome ASB_LG11 with two Single Nucleotide Polymorphism markers, R1-38468 and R1-61252, located near to the two ends of the QTL. When the R1-61252 marker was validated experimentally in a different mass cross population, it showed a statistically significant association with increased robustness. The majority of thirty-six potential candidate genes located within the QTL have known functions related to innate immunity, stress response or disease. By utilizing this ddRAD-based map, we detected five mis-assemblies corresponding to four chromosomes, namely ASB_LG8, ASB_LG9, ASB_LG15 and ASB_LG20, in the current Asian seabass reference genome assembly.ConclusionAccording to our knowledge, the QTL associated with increased robustness is the first such finding from a tropical fish species. Depending on further validation in other stocks and populations, it might be potentially useful for selecting robust Asian seabass lines in selection programs.

Effects of LPS, Poly (I:C) and Edwardsiella tarda on the Expression Patterns of IL-17 Family Members and Their Receptors in Spotted Sea Bass (Lateolabrax maculatus)

In fish, the immune system plays a crucial role in defending against pathogen-induced infections. The interleukin 17 (IL-17) family, which is a well-studied class of cytokines, serves as a key component of the immune response against external pathogens. In this research, four IL-17 ligands (IL-17A/F1, IL-17B, IL-17C and IL-17D) and one receptor (IL-17RB) genes were identified from spotted sea bass (Lateolabrax maculatus). Alignment analysis showed that the C-terminal region of IL-17 ligands in spotted sea bass was highly conserved. The expression of the IL-17 ligand and receptor genes differed in unstimulated tissues. To investigate the impact of various factors on the immune response of spotted sea bass, we assessed the effect of lipopolysaccharide (LPS), polyinosinic–polycytidylic acid [poly (I:C)] and Edwardsiella tarda treatment on the IL-17 ligands and receptor responses. Our results reveal that the expression of the IL-17 ligand and receptor transcripts is modulated by LPS, poly (I:C) and E. tarda, indicating their significant role in the immune system.

Effects of dietary zinc levels on growth, intestinal health, antioxidant and non-specific immunity of spotted seabass (Lateolabrax maculatus) reared at two temperatures

This study investigated effects of dietary zinc levels and water temperature on growth, feed utilization, intestinal health, antioxidant and non-specific immunity of spotted seabass. Six experimental diets were formulated to contain 30, 53, 77, 98, 116, or 145 mg Zn/kg. Each diet was fed to two different groups of fish reared at low temperature (27 °C; LT) or high temperature (33 °C; HT). Triplicate groups of fish were fed the test diets to apparent satiation two times daily for 8 weeks. Results showed that fish under HT showed the lower weight gain (WG) and higher feed conversion rate (FCR) comparing to the LT treatment (P < 0.05). Also, the growth and feed utilization were significantly (P < 0.05) influenced by dietary Zn levels and broken-line regression analysis showed the optimal dietary Zn level for spotted seabass reared at 27 °C and 33 °C are 77.69 mg/kg and 93.61 mg/kg, respectively. Apparent digestibility coefficients (ADCs) of protein and lipid in HT treatment were significantly lower than those of LT treatment (P < 0.05), and ADCs significantly increased with the increase of dietary Zn levels. The histology showed HT and Zn-deficiency can cause the damage of intestine, while fish fed 77 mg Zn/kg diets presented normal structure. Serum LZM activity, C3 and IgM contents of HT treatments were lower than those of the LT treatments. Further, LZM activity, C3, and IgM contents can be significantly elevated by the increasing of dietary Zn levels. MDA content of HT treatments were significantly higher than that of LT treatments, while MDA content decreased with the increase of dietary Zn levels as SOD activity and T-AOC increased. Overall, the optimum dietary Zn level alleviated heat stress via enhancing immunity, antioxidant capacity and intestine health.

Trypsin from Pyloric Caeca of Asian Seabass: Purification, Characterization, and Its Use in the Hydrolysis of Acid-Soluble Collagen.

The study aimed to purify trypsin from the pyloric caeca of Asian seabass (Lates calcarifer), and investigate its proteolytic capability toward acid-soluble collagen (ASC) in comparison with commercial porcine trypsin (CPT). Trypsin was purified from pyloric caeca, a leftover from the evisceration process, via ammonium sulphate (40-60% saturation) precipitation, and a soybean trypsin inhibitor (SBTI)-Sepharose 4B column. A 18.5-fold purification and a yield of 15.2% were obtained. SDS-PAGE analysis confirmed a single band of trypsin with a molecular weight of 23.5 kDa. Purified trypsin also showed the single band in native-PAGE. The optimal pH and temperature of trypsin for BAPNA (the specific substrate for amidase) hydrolysis were 8.5 and 60 °C, respectively. The trypsin was stable within the pH range of 7.0-9.5 and temperature range of 25-55 °C. Protease inhibition study confirmed that the purified enzyme was trypsin. The purified trypsin had a Michaelis-Menten constant (Km) and catalytic constant (kcat) of 0.078 mM and 5.4 s-1, respectively, when BAPNA was used. For the hydrolysis of TAME (the specific substrate for esterase), the Km and Kcat were 0.09 mM and 4.8 s-1, respectively. Partially purified seabass trypsin (PPST) had a slightly lower hydrolysis capacity toward ASC than CPT, as evidenced by the lower degree of hydrolysis and protein degradation when the former was used. Both the α-chain and β-chain became more degraded as the hydrolysis time increased. Based on MALDI-TOP, peptides with MW of 2992-2970 Da were dominant in the hydrolysates. Therefore, seabass trypsin could be used in the production of hydrolyzed collagen. It could have economic importance to the market, by replacing some commercial proteases, which have religious constraints.

Synthetic peptides derived from predicted B cell epitopes of nervous necrosis virus (NNV) show antigenicity and elicit immunogenic responses in Asian seabass (Lates calcarifer).

Nervous necrosis virus (NNV) has spread throughout the world, affecting more than 120 freshwater and marine fish species. While vaccination effectively prevents disease outbreaks, the difficulty of producing sufficient viruses using cell lines continues to be a significant disadvantage for producing inactivated vaccines. This study, therefore, explored the application of synthetic peptides as potential vaccine candidates for the prevention of NNV in Asian seabass (Lates calcarifer). Using the epitope prediction tool and molecular docking, three predicted immunogenic B cell epitopes (30-32 aa) derived from NNV coat protein were selected and synthesised, corresponding to amino acid positions 5 to 34 (P1), 133 to 162 (P2) and 181 to 212 (P3). All the predicted peptides interact with Asian sea bass's MHC class II by docking. The antigenicity of these peptides was determined through ELISA and all peptides were able to react with NNV-specific antibodies. Subsequently, the immunogenicity of these synthetic peptides was investigated by immunisation of Asian seabass with individual peptides (30 μg/fish) and a peptide cocktail (P1+P2+P3, 10 μg each/fish) by intraperitoneal injection, followed by a booster dose at day 28 post-primary immunisation. There was a subset of immunised fish that were able to induce upregulation of immune genes (IL-1β, TNFα, MHCI, MHCII β, CD4, CD8, and IgM-like) in the head kidney and spleen post immunization. Importantly, antibodies derived from fish immunised with synthetic peptides reacted with whole NNV virions, and sera from P1 group could neutralise NNV in an in vitro assay. Taken together, these findings indicate that synthetic linear peptides based on predicted B cell epitopes exhibited both antigenic and immunogenic properties, suggesting that they could be potential vaccine candidates for the prevention of NNV in fish.

Molecular characterization, transcriptional regulation of sea perch Moloney leukemia virus 10 and its antiviral function against VHSV.

Moloney leukemia virus 10 (MOV10) is a conserved RNA helicase and has multiple biological functions in mammals, but its role remains poorly understood in bony fish. Here, we cloned a MOV10 homolog from sea perch (Lateolabrax japonicus), which contained 23 exons and 22 introns, with an open reading frame of 3000 bp encoding 1000 amino acids. Tissue distribution analysis showed that MOV10 was high expressed in blood of sea perch. Promoter analysis revealed several putative multiple transcription factors binding sites, including upstream transcription factor 1, GATA-box, transcription initiation factor IIB, activator protein 1 and two interferon (IFN) stimulated response elements. Further analysis found that IFNc, IFNh, and IFNγ could not only activate IFN regulatory factor (IRF) 1 expression which in turn led to the induction of MOV10, but also prompted the expression of IRF10 to hinder excessive MOV10 expression. Moreover, IRF2 also suppressed MOV10 expression that was initiated by IRF1. Viral hemorrhagic septicemia virus (VHSV) infection upregulated MOV10 expression in vivo and in vitro, which in turn, enhanced IFNh expression and exhibited strong antiviral activity against VHSV proliferation. This study provides a basis to investigate the immune escape of VHSV by affecting the biological function of transcription factors in the signaling pathways associated with antiviral molecules.

The nutritional characteristic of spotted seabass (Lateolabrax maculatus) flesh

Spotted seabass (Lateolabrax maculatus) is a popular food fish in Asian countries. Not only does the fish tasted well, but it is also widely utilized as nutraceuticals. However, the knowledge about the composition of the fish is lack. In this work, the proximate composition of spotted seabass flesh was determined. The content of proximate composition (moisture, proteins, fat, and ash) of spotted seabass flesh was fell within the range of other reported fish species, while it was a high-quality food fish with low oil-very high protein. The ratio of essential amino acids (EAAs) to nonessential amino acids (NEAAs) was 0.74, and the amount of EAAs accounted for approximately 42.34% of the total amino acids. Unsaturated fatty acids composed the majority of the fatty acid components, with linoleic acid was the predominate one. The content of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were abundant in spotted seabass flesh. The proximate composition of the dorsal, ventral, lateral, and tail flesh was similar, except for the ventral flesh exhibited a higher content of fatty acids and lower content of moisture. Our research will be helpful for the general population to know the nutritional traits of spotted seabass.

Effect of starch content and ultrasonic pretreatment on gelling properties of myofibrillar protein from Lateolabrax japonicus

AbstractTo investigate the protein–starch interactions in myofibrillar protein gels under the ultrasonic pretreatment, the effect of cassava starch content and ultrasonic pretreatment on gelling properties of myofibrillar protein from Lateolabrax japonicus was studied. For the myofibrillar protein–starch (MPS) solutions, the turbidity and elastic modulus increased when the starch content increased from 0% to 8%. For the MPS gels, the hardness, chewiness, gumminess, and water holding capacity increased with the starch content, whereas the cooking loss and whiteness decreased. Starch incorporation promoted the conversion of free water to immobilized water and bound water. The active sulfhydryl content decreased with the starch content, whereas the hydrogen bond and hydrophobic interaction content increased. Fine network structure containing pores at uniform size was formed in the MPS gel at an increased starch content, as shown in the scanning electron microscope images. When the ultrasonic pretreatment was introduced, the elastic modulus of MPS solutions and hardness, chewiness, gumminess, hydrophobic interaction, β‐sheet content, and microstructural compactness of the MPS gels increased, whereas the turbidity of the MPS solutions and cooking loss, whiteness, free water content, active sulfhydryl content, and random coil content of the MPS gels decreased. The MPS gel containing 8% of starch and subjected to ultrasonic pretreatment showed the highest hardness, chewiness, and gumminess of 220, 150, and 160 g, while the lowest cooking loss of 2.5% among all samples. Therefore, the gelling properties of myofibrillar protein from L. japonicus could be enhanced by the starch incorporation, ultrasonic pretreatment, and their synergistic effect.

Characteristics and Application of Lipase from Asian Seabass Liver Fractionated Using Aqueous Two-phase Partition Technique for Defatting Fish Skin before Collagen Extraction

Lipase, from crude extract of fish viscera including liver, is highly contaminated with other hydrolytic enzymes such as proteases that would cause severe degradation of native collagen during defatting. Asian seabass liver lipase was therefore subjected to fractionation with the aqueous two-phase system (ATPS) to remove proteases from lipase. ATPS was carried out using various salts and polyethylene glycol (PEG) having various molecular weights at different concentrations. The concentration of 20% ammonium sulfate (w/v) and 50% PEG-6000 (w/w) could reduce protease by 85%. Lipase-rich fraction showed a specific activity of 68 U/mg protein, purification fold of 9, selectivity of 167, and yield of 48%. When pulse electric field (PEF) was treated Asian seabass fish skin was defatted, and the acid-soluble collagen was extracted and characterized. The ATPS fractionated lipase could remove more than 92% of lipid contents. Polyunsaturated and monounsaturated fatty acids were mainly eliminated. The extracted collagen from defatted skin showed typical type Ⅰ collagen with negligible degradation. FTIR spectra substantiated the presence of amide groups in resulting skin collagen. Thus, the fractionation of Asian seabass liver crude extract with ATPS could significantly remove the contaminated proteases. The obtained fraction could be used to defat Asian seabass skin without drastic damage to the extracted native collagen.

Enhanced intestinal microflora composition and phosphorus-transportation efficiency in fast-growing spotted seabass (Lateolabrax maculatus) fed a low-phosphorus diet

This study examined differences in the intestinal microflora composition and phosphorus-transportation efficiency between fast- and slow-growing spotted seabass (Lateolabrax maculatus) fed a low-phosphorus diet. A total of 60 spotted seabass (9.48 ± 0.19 g) were randomly distributed into three tanks at a density of 20 fish per tank and fed a low-phosphorus diet for eight weeks. At the end of the experiment, the four heaviest and four lightest individuals from each tank were sampled as the fast-growing spotted seabass (FGS) and slow-growing spotted seabass (SGS), respectively. FGS had significantly higher weight gain (WG) than those in SGS. Higher whole-body phosphorus deposition, serum phosphorus content and the mRNA expression of genes associated with phosphorus transportation (NaPIiib, PiT1, and PiT2) were observed in FGS compared to SGS. Moreover, lower serum alkaline phosphatase (AKP) activity was found in FGS compared to SGS. However, no significant differences were found in liver phosphorus deposition or serum parathyroid hormone (PTH) levels between FGS and SGS. Compared to SGS, higher relative abundances of operational taxonomic units (OTUs) and potential probiotics, including Lactobacillus and Cetobacterium, and lower relative abundances of potentially pathogenic bacteria, including Enhydrobacter and Chryseobacterium, were observed in the intestinal microflora of FGS. Overall, these findings suggested that higher growth rates in spotted seabass fed a low-phosphorus diet were associated with enhanced phosphorus-transportation efficiency and intestinal microflora composition.

Molecular Characterization and Expression Analysis of NLRC3-like, ASC, and Caspase1 in Spotted Sea Bass (Lateolabrax maculatus)

Nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family members are innate immune sensors involved in the recognition of highly conserved pathogen-associated molecular patterns (PAMPs). Apoptosis-associated speck-like protein (ASC) is a critical adaptor molecule in multiple inflammasome protein complexes, mediating inflammation and host defense. Caspase1, an inflammatory caspase, has been documented to play important roles in the innate immune system. In this study, we identified and characterized NLRC3-like, ASC, and Caspase1 (referred to as LmNLRC3L, LmASC, and LmCaspase1) from the spotted sea bass (Lateolabrax maculatus). A sequence analysis revealed that LmNLRC3L, LmASC, and LmCaspase1 shared similar features with their fish counterparts. LmNLRC3L contained a FISNA domain, a NACHT domain, and four LRR motifs, followed by a C-terminal fish-specific B30.2 domain. LmASC possessed a PYRIN domain for interacting with inflammasome sensor proteins, as well as a CARD domain. LmCaspase1 had a CARD domain at its N-terminus and a CASC domain at its C-terminus. These three genes were ubiquitously distributed in the liver, spleen, head kidney, gill, intestine, skin, muscle, and brain. They share similar expression patterns, and all demonstrate the highest level of expression in the gill. We analyzed the expression changes in genes in the spleen, gill, and head kidney after stimulation experiments in vivo. After lipopolysaccharide (LPS) stimulation, the expression levels of these three genes were significantly upregulated in the short term, followed by significant downregulation at 48 and 72 h in some examined tissues. Following Edwardsiella tarda infection, these three genes were upregulated in various tissues. However, the expressions of these three genes were not affected by polyinosinic-polycytidylic acid (poly (I:C)) stimulation. Overall, our results indicate that these three genes are involved in the immune response against bacterial infection in the spotted sea bass, providing the foothold for understanding the immune function and mechanism of the fish inflammasome.

Effects of dietary seaweeds (Gracilaria spp. and Sargassum spp.) on growth, feed utilization, and resistance to acute hypoxia stress in juvenile Asian seabass (Lates calcarifer)

The aim of this work was to evaluate the impact of adding Gracilaria spp. and Sargassum spp. to diets on growth performance and resistance to hypoxia stress in Asian seabass. The fish (36.06 ± 0.05 g) were stocked in 18 tanks (200 L), divided into six experimental groups and fed diets containing 0 (control), 3 % (SW3), 6 % (SW6), 9 % (SW9), 12 % (SW12) and 15 % (SW15) Gracilaria and Sargassum mixture in equal proportions for 56 days. Each group consisted of three tanks. Fish were exposed to air for 1 min (hypoxia) and the recovery rate of fish was monitored for 24 h. Results showed that final weight, weight gain, and specific growth rate (SGR) of fish fed the dietary seaweed mixture up to 12 % were significantly higher than fish fed 15 % seaweed powder. Fish fed the 9 % and 12 % seaweed mixture also showed a significantly lower feed conversion ratio (FCR) than the SW15 group. Serum cortisol was significantly higher in the control and lowest in the 12 % seaweed group 6 h post-stress. Hypoxia stress led to significant increases in cortisol values in all fish, but the dietary Gracilaria and Sargassum mixture significantly reduced cortisol values in the SW9 and SW12 groups at 24 h post-stress. Before and 1 h and 24 h after hypoxia, fish fed the 9 % and 12 % seaweed mixture showed significantly lower glucose than the SW15 and control groups. Moreover, serum lactate in the 6–12 % seaweed groups was significantly lower than the control fish at 24 h post-stress. Overall, dietary seaweed showed anti-stress properties and the dietary Gracilaria and Sargassum mixture at levels of 9–12 % increased resistance to hypoxia stress in fish. The present results showed that seaweed (Gracilaria and Sargassum mixture) up to 12 % level is useful in the diet of juvenile Asian seabass.

Effects of dietary Clostridium butyricum on the growth performance, digestion, and intestinal health of spotted sea bass (Lateolabrax maculatus).

Clostridium butyricum (CB) is known to promote growth, enhance immunity, promote digestion, and improve intestinal health. In this study, we investigated the effects of CB in the feed on growth performance, digestion, and intestinal health of juvenile spotted sea bass. To provide a theoretical basis for the development and application of CB in the feed of spotted sea bass, a total of 450 spotted sea bass with an initial body weight of (9.58 ± 0.05) g were randomly divided into six groups. Gradient levels with 0, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% of CB (1×109 cfu/g) were supplemented into diets, designated as CC, CB1, CB2, CB3, CB4, and CB5, respectively. Each group was fed for 54 days. Our results suggest that dietary 0.2% and 0.3% of CB can significantly increase the weight gain (WG) and specific growth rate (SGR) of spotted sea bass. The addition of CB significantly increased intestinal amylase activity, intestinal villus length, intestinal villus width, and intestinal muscle thickness. Similarly, CB supplementation increased the expression of tumor necrosis factor-α (TNF-α) and interleukin-8 (IL-8). Sequence analysis of the bacterial 16S rDNA region showed that dietary CB altered the intestinal microbiota profile of juvenile spotted sea bass, increasing the dominant bacteria in the intestine and decreasing the harmful bacteria. Overall, dietary addition of CB can improve growth performance, enhance intestinal immunity, improve intestinal flora structure, and comprehensively improve the health of spotted sea bass.

The haematology of clinically healthy, farmed juvenile Asian seabass (Lates calcarifer Bloch)-reference intervals, and indicators of subclinical disease.

This study establishes the blood reference intervals (RIs) for clinically healthy and farmed juvenile Asian seabass (Lates calcarifer), within 4-6 weeks after stocking into flow-through, marine aquaculture systems. The 90% percentile RIs (n = 156, mean bodyweight 41.8 g) are as follows: glucose (GLU) 2.4-11.3 mmol/L, haematocrit (Hct) 18.9%-39.2%, haemoglobin concentration (Hb) 56.0-85.0 g/L, total plasma protein (TPP) 56.0-77.0 g/L, total red blood cell (RBC) count 4.1-11.2 × 1012 /L, total white blood cell (WBC) count 5.3-69.9 × 109 /L, total lymphocytes 4.7-51.4 × 109 /L, monocytes 0.3-16.2 × 109 /L and heterophils count 0.6-8.4 × 109 /L. Pearson's method analysis showed weak but significantly positive correlations between fish bodyweight and Hct, Hb, TPP and total RBC count (p < 0.05). Histopathology of 42 of the 156 clinically healthy fish used to derive the RIs, with blood values within the 90% percentile range, did not exhibit any abnormal pathology. In contrast, histopathology from a different group of clinically healthy L. calcarifer (n = 72, mean bodyweight 31.3 g) with blood values falling outside of these established 90% percentile RIs showed that 25% of these fish had severe, chronic granulomatous enteritis, and 13% had severely depleted lipid stores in their liver. Point biserial correlation analysis of blood values from this second group of 72 fish showed that elevated total WBC, monocyte and heterophil counts and reduced Hct levels are significantly associated (p < 0.05) with the occurrence of severe, chronic granulomatous enteritis and depleted lipid stores in their liver. Reduced blood GLU and TPP levels in the second group of fish were significantly associated with fish that had depleted lipid stores in liver (p < 0.05), corroborating a period of malnutrition. This study is among the first to establish blood RIs for clinically healthy, farmed juvenile L. calcarifer and detection of subclinical diseases in fish to support early intervention.

PCR detection and phylogenetic analysis of the major capsid protein gene of Lymphocystis disease virus from cultured Asian seabass (Lates calcarifer Bloch, 1790) along the west coast of Kerala, India

PCR detection and phylogenetic analysis of the major capsid protein gene of Lymphocystis disease virus from cultured Asian seabass (Lates calcarifer Bloch, 1790) along the west coast of Kerala, India

Chemical Compositions and Characteristics of Biocalcium from Asian Sea Bass (Lates calcarifer) Scales as Influenced by Pretreatment and Heating Processes.

Asian sea bass scales discarded from the fish processing industry contain collagen and calcium. The production of biocalcium can increase their value. The effect of alkaline pretreatment on non-collagenous protein removal from scales was investigated. The alkaline pretreatment of scales was optimal when 2 M NaOH solution was used for 10 min. The impacts of heating processes of varying times on chemical compositions and characteristics of biocalcium (BC) powder from alkali-pretreated scales were also studied. A lower loss of hydroxyproline (HYP) and decreased hardness of scales were obtained when the scales were treated with a boiling process. BC powders from the scales subjected to boiling (B-BC) had higher yield and HYP content than BC powders using a high-pressure heating (HP-BC) process. An augmented heating time (10-30 min) lowered yield, HYP, moisture, and protein contents in BC powder regardless of the heating processes. HP-BC powder had higher ash, calcium, and phosphorus contents than B-BC powder. A whiter color and larger mean particle size were attained for the B-BC powders. X-ray diffractograms revealed that all BC powders had hydroxyapatite, which had a crystallinity of 53.60-66.54%, as a major component. FTIR spectra confirmed that all BC powders comprised proteins and inorganic matter. BC powder from scales with high yield and satisfactory characteristics could be used in calcium supplements.

Development of leather from the skin of yellowfin tuna (&lt;em&gt;Thunnus albacares&lt;/em&gt;) and Asian sea bass (&lt;em&gt;Lates calcarifer&lt;/em&gt;) using an environmentally friendly tanning technique

Yellowfin tuna (Thunnus albacares) and Asian sea bass (Lates calcarifer) are highly demanded export fish species in Sri Lanka. The objective of the present study was to prepare leather from the skin of T. albacares and L. calcarifer using tanning media prepared with black tea (Camellia sinensis) powder and table salt (NaCl). Black tea powder and table salt concentrations were increased by 10 grams (initial weight; 10 gL-1) and 1 gram (initial weight; 1 gL-1), respectively each day for 12 d. Skins were dipped in each concentration for 24 hrs. After additional water was removed, vegetableoil-applied skins were stretched and air-dried at room temperature. The percentage of ash, fat,protein, and tensile strength of the leather prepared from L. calcarifer skin was significantly higher(P&lt;0.05) compared to leather prepared from T. albacares skin. The percentage of moisture, averagethickness, and tear strength of the leather prepared from the T. albacares skin were significantlyhigher (P&lt;0.05) than the leather prepared from L. calcarifer skin. According to the ΔL*, Δa*, andΔb* values, leather prepared from T. albacares skin has lighter, greener, bluer and L. calcarifer skinhas darker, greener, yellower colours respectively. There are no significant colour differences betweenprepared leathers (P&gt;0.05). Sensory evaluation results indicated that, finishing, appearance,handling, and overall acceptability, of leather wallet prepared from T. albacares has higherconsumer acceptance. The study demonstrated the effectiveness of this novel method for preparationof leather from T. albacares and L. calcarifer skin. In conclusion, T. albacares skin is more suitablefor fish leather preparation using the above described tanning method.