Volume 76, Issue 2, 2024
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ItemComparative analysis of the structural and compositional change of spotted sea bass (Lateolabrax maculatus) gut microflora following Aeromonas veronii infection and the effects of Lactobacillus plantarum on these changes( 2024)Growing evidence suggests a close relationship between gut microbiota and infectious diseases. However, the specific role of gut microbiota in host-pathogen interactions during aquaculture-related infections remains poorly understood. This study investigated the diversity and composition of gut microbiota communities in Aeromonas veronii-infected Lateolabrax maculatus using high-throughput sequencing. The results revealed significant changes in the structure and composition of L. maculatus gut microbiota after A. veronii infection. Over time, Bacteroidetes and Firmicutes decreased significantly, while Proteobacteria increased significantly after A. veronii infection. Most intestinal bacteria showed a decline in abundance over time, with probiotics (such as Lactobacillus) experiencing a significant decrease and pathogens (such as Aeromonas) showing a significant increase. Conversely, no differences were observed in the structure and composition of gut microbiota between healthy L. maculatus and those infected with A. veronii after treatment with Lactobacillus plantarum; no changes in relative abundances of other bacterial phyla or genera except for Aeromonas. Furthermore, intestinal flora's structural diversity and composition differed significantly from untreated L. maculatus infected with A. veronii. These findings suggest alterations in the structure and composition of gut microbiota following A. veronii infection. L. plantarum can maintain a dynamic balance within the intestinal flora, reducing the potential risk of pathogen infections.
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ItemRice-fish symbiosis improves the muscle nutrition and intestinal flora diversity of tilapia( 2024)Rice-fish symbiosis is an ecological farming model that can improve fish's muscle nutrient profile and intestinal flora. We investigated the effect of rice-fish symbiosis on tilapia's intestinal flora and muscle nutrients. We used 16S rDNA technology to analyze the intestinal flora of tilapia in pond culture and rice-fish symbiosis. Furthermore, spearman correlation analysis was performed on tilapia intestinal flora and muscle nutrients. The results showed that the contents of Valine, Phenylalanine, and Docosahexaenoic acid were significantly higher in the rice-fish symbiosis than those in the pond culture (p<0.05). Intestinal flora analysis showed that the diversity in rice-fish symbiosis was significantly higher than in pond culture (p<0.05). Meanwhile, the abundance of Brevundimonas, Pseudomonas, and Ralstonia in rice-fish symbiosis was significantly higher than those in pond culture (p<0.05), but Pirellulaceae unclassified and Cyanobium_PCC-6307 were opposite. The number of 8 predictive functional tilapia genes in the rice-fish symbiosis was higher than in the pond culture. Correlation analysis showed that the abundance of Ralstonia was positively correlated with the contents of Valine, Phenylalanine, and Docosahexaenoic acid, respectively. Our study shows that the rice-fish symbiosis could improve muscle nutrient profile and intestinal flora diversity in tilapia. This study will help to improve the rice-fish symbiosis model and provide a scientific basis for ecological aquaculture and healthy fish production.
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ItemFish Welfare – A Case Study: Reviling for the first-time side effects of vaccination in European sea bass (Dicentrarchus labrax) and barramundi (Lates calcarifer) in the Israeli fish farming( 2024)Vaccination is an effective way to control many infectious diseases in fish. Israeli fish farming has successfully used two vaccines over the last 30 years and has no problem with the side effects of vaccination. However, after introducing new species, a new problem emerged: these fish, after vaccination, demonstrated peritoneal lesions such as granulomas. At the same time, the fish did not show retarded growth or suffering during the fattening period. This study was conducted to establish the connection between vaccination and the appearance of granulomas. Evidence drawn from this research work and comparing vaccinated and non-vaccinated fish confirms that intraperitoneal granulomas do not impact the growth, performance, or fish fillet quality at harvest.
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ItemIsolation of Lactobacillus plantarum CMT1 from shrimp intestine and its effects on growth and survival of the whiteleg shrimp, Litopeneaus vannamei( 2024)Probiotics are widely applied in aquaculture, which can improve the growth, survival and health of aquatic animals. The aim of this study was to isolate and evaluate a Lactobacillus strain from the intestine of healthy whiteleg shrimp, Litopenaeus vannamei. A total of 20 Lactobacillus isolates showed rod-shaped morphology, gram-positive, non-motile, non-spore forming, and catalase and oxidase negative. Among the isolates, strain CMT1 exhibited the highest antibacterial activity against Vibrio parahaemolyticus and extracellular enzyme activity, which was selected and identified as Lactobacillus plantarum CMT1 based on 16S rDNA gene sequencing. This strain was also chosen to evaluate its effects on growth and survival of the whiteleg shrimp as a feed supplement. Four different diets were prepared, including the control (a commercial diet without L. plantarum CMT1) and three different concentrations of L. plantarum CMT1, viz. T1 (10^6 CFU kg diet^-1), T2 (10^7 CFU kg diet^-1), and T3 (10^8 CFU kg diet^-1). After a 56-day feeding trial, the growth parameters in the T3 group had the highest values and showed a significant difference compared to the other groups. The survival rates of shrimp fed T2 and T3 diets were significantly higher than those in the control diet (p < 0.05). The lowest FCR value was recorded in the T3 group and showed a significant difference compared to the control group (p < 0.05). In addition, Lactobacillus counts in T2 and T3 groups increased significantly from day 28, which indicated that L. plantarum CMT1 could sustain its population in the intestine of shrimp. However, the total Vibrio sp. count in the T2 and T3 groups was significantly lower than that in the control group (p < 0.05). In conclusion, L. plantarum CMT1 could be used as a potential probiotic for shrimp aquaculture, and the recommended level of the probiotic strain CMT1 is 10^8 CFU kg diet^-1.
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ItemBehavioral characteristics and transcriptome analysis of Mizuhopecten yessoensis in response to Neptunea arthritica cumingii predation during laboratory bottom-sowing culture( 2024)In this study, we investigated the effects of predation by the whelk Neptunea arthritica cumingii on the culture and survival of scallops (Mizuhopecten yessoensis) during bottom culture. The behavioral characteristics of three sizes (small, medium, and large) of scallops were assessed in response to exposure to N. cumingii. We also measured the activities of superoxide dismutase, catalase, arginine kinase, and octopine dehydrogenase in the gill, adductor muscle, and mantle tissues of scallops before and after exposure to predation. We found that scallops escaped from N. cumingii predation by continuous shell closure or movement. The shell closure force increased with the scallop size, and scallops of the same size that were stimulated by the presence of N. cumingii closed their shells more frequently than control scallops. The shell closure ability of scallops of all sizes decreased as the duration of the experiment continued. The enzyme activities in the three scallop tissues changed significantly after continuous stimulation, and the trend was particularly obvious for the enzyme activities in the adductor muscles of medium-sized scallops. Transcriptome analysis of the adductor muscles from medium-sized scallops detected 405 differentially expressed genes (172 upregulated and 233 downregulated), where the expression levels of RYK, APC, BAMBI, WNT16, CACYBP, and RUVBL1 changed after stimulation by N. cumingii. The sequencing results were verified by quantitative real-time PCR. We hypothesize these genes may be related to muscle movement and regulation in M. yessoensis after stimulation.
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ItemImproved breeding and seed production of climbing perch (Anabas testudineus) in controlled tanks and cage systems( 2024)The climbing perch (Anabas testudineus) is a valuable fish species with significant potential for aquaculture. However, a low survival rate was observed at its early development stages, requiring an optimized protocol for sustainable aquaculture production. This paper presents an improved breeding and seed production technology for climbing perch. Mature climbing perch were induced to spawn using salmon gonadotropin-releasing hormone analog (sGnRHa) at a dose of 30 µg/kg-1 body weight of the breeder. The female broodfish spawn 9–10 hours after hormone injection. Developmental stages were defined based on the morphological features of the embryos from the first cleavage to the hatching stage. The first cleavage began at approximately 18–20 minutes after fertilization. Newly hatched larvae were observed within 18–20 h at 30°C, having an average larval size of 0.389±0.042 mm (total length). Successful breeding entails a selection of suitable algal species, an optimal aquaculture environment, regular feeding rates, consistent monitoring of larval development, and effective management of water quality. Survival rates from the larval stage to fry were achieved at 84.69% and 77.60%, respectively, while the survival rate to the fingerlings stage was 72.51%. Therefore, by implementing an optimized protocol, aquaculture practitioners can maximize the production potential of climbing perch while ensuring sustainable cultivation practices. The findings from this research contribute to the advancement of climbing perch aquaculture by providing valuable insights for the successful cultivation and increased economic profitability of A. testudineus species in hatchery productions.
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ItemAnalysis of bacterial community of Labidochromis caeruleus reared in RAS with various feeds( 2024)The electric yellow cichlid (Labidochromis caeruleus), renowned for its exceptional ornamental value, enjoys widespread popularity among aquarium enthusiasts and holds significant economic value in the market. This study employed high-throughput sequencing technology to analyze the microorganisms in the circulating water of the electric yellow cichlid cultivated with six different types of feeds. Statistical results showed that the compound feed group exhibited the highest specific growth and mass gain rates. In contrast, the water flea and brine shrimp groups showed lower rankings with significant differences. 51,084 to 64,626 effective sequences were obtained and clustered into 127 to 848 operational taxonomic units (OTUs). The research findings indicate a remarkable bacterial diversity in the breeding environment of electric yellow cichlids with higher levels in the water flea and brine shrimp groups, and the lowest level in the compound feed group; the dominant bacterial phyla in all six experimental groups include Proteobacteria, Actinobacteria, Parcubacteria, and Cyanobacteria; Comparative analysis using the COGs database revealed significant differences (P<0.05) in the metabolic pathways of 24 functional microbial genes among the experimental groups.
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ItemDietary supplementation of Astragalus fermentation products improves the growth performance, immunological characteristics, and disease resistance of crucian carp (Carassius auratus)( 2024)The fermentation products of Astragalus have been acknowledged for their ability to enhance immune functions. This study assessed the impact of incorporating Astragalus, fermented with Lactobacillus plantarum and Bacillus coagulans, on crucian carp's growth, disease resistance, and immunological characteristics. The experimental groups were fed with common feed (C), C + Astragalus (A), A + Lactobacillus plantarum (AL), A + Bacillus coagulans (AB), and AL + Bacillus coagulans (ALB). The fermented products were mixed with common feed at a 1:99 ratio, and crucian carp were fed 2% of their body weight for four weeks, with sampling conducted on days 3, 7, 14, 21, and 28. Disease resistance was evaluated using Aeromonas hydrophila (A. hydrophila) at a concentration of 0.2 mL (1.0×10^7 CFU/mL). The final weights in the AL, AB, and ALB groups significantly increased compared to the C group. The ALB group exhibited elevated serum albumin levels, alkaline phosphatase, intestinal lipase, protease enzyme, C3, and IgM gene expression compared to the C group. At the same time, alanine aminotransferase, aspartate aminotransferase, and glucose contents were significantly reduced. The survival rate significantly increased in all experimental groups after treatment with A. hydrophila. In conclusion, Astragalus products fermented with Lactobacillus plantarum and Bacillus coagulans could effectively improve crucian carp's growth, disease resistance, and immune response.
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ItemEffects of dietary β-sitosterol supplementation on growth performance, antioxidant ability, and disease resistance in largemouth bass Micropterus salmoides( 2024)β-sitosterol, as the most abundant phytosterol, has been shown to exert multiple biological roles in in vitro and in vivo animal studies. Largemouth bass (Micropterus salmoides) is an economical freshwater-farmed species widely cultivated in China due to its nutritious and delicious meat. This study investigated the effects of dietary β-sitosterol supplementation on largemouth bass farming. In the study, largemouth bass were fed with five levels of β-sitosterol (0, 20, 40, 80, and 160 mg/kg) supplementation in a commercial feed for four weeks. The growth performance, antioxidant ability, intestinal structure, immune-related gene expression, and resistance to pathogens such as Aeromonas hydrophila and largemouth bass virus (LMBRaV) were detected. The results revealed that β-sitosterol supplementation in feed increased the weight gain rate of largemouth bass, with 40 mg/kg supplementation displaying the best effect. The serum biochemical indices all showed an increase, including glucose and alkaline phosphatase. The intestinal villus length and muscularis propria thickness also increased, accompanied by elevated digestive enzyme activities, which promoted digestion and absorption of nutrients. Meanwhile, the levels of total cholesterol, aspartate aminotransferase, and alanine aminotransferase in serum decreased, indicating reduced liver damage. In addition, β-sitosterol supplementation effectively enhanced the antioxidant capacity of largemouth bass by decreasing malondialdehyde and elevating superoxide dismutase. Immune-related gene expression also changed. Pathogen infection tests revealed that β-sitosterol supplementation in feed had a certain protective effect against infection in largemouth bass, with the protection rate against A. hydrophila being higher than LMBRaV. The 40 mg/kg β-sitosterol supplementation group exhibited the best results. Collectively, the results revealed that the β-sitosterol can promote growth, improve enzyme activity, stimulate intestinal digestion, increase immune gene expression, and induce disease resistance in largemouth bass, with the optimal supplementation dosage being 40 mg/kg. β-sitosterol might be an excellent feed additive in aquaculture.
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ItemMannan oligosaccharide improves antioxidant capacity, non-specific immunity and protection against Vibrio disease and Typhoon stress in Trachinotus ovatus juveniles( 2024)This study examined the impact of varying doses of mannan oligosaccharide (MOS) supplementation on antioxidant defense, non-specific immunity, resistance to typhoon stress, and resistance to disease in Trachinotus ovatus. Fish groups C, M1, M2, and M3 were fed 1%, 0.3%, 0.6%, and 1% MOS-supplemented feed, respectively. On the 28th and 56th day of the feeding trial, samples from all groups were taken to measure the antioxidant and non-specific immunity parameters and challenged with Vibrio harvey. On the 32nd day, a typhoon hit the experimental site, and the survival rates of all groups were calculated. Results showed that on the 28th day, groups M2 and M3 showed considerably higher levels of antioxidant abilities (T-AOC), and groups M1 and M2 showed significantly enhanced non-specific immunity (AKP, LZM, and TP) levels than those of group C (p < 0.05). All MOS groups had significantly lower cumulative mortality following the challenge test and typhoon stress than the control group (p < 0.05). On the 56th day, groups M2 and M3 showed significantly enhanced antioxidant ability (CAT) compared to the control group. Only one non-specific immunity parameter increased significantly in groups M2 and M3 (p < 0.05). After the challenge test, only group M3 exhibited a significantly declined cumulative mortality rate compared to the control groups (p < 0.05). In summary, supplementation of MOS at dose 0.6% (M2) for 28 days showed the best overall improving effects on the antioxidant capacity, non-specific immunity, disease resistance, and typhoon stress resistance in T. ovatus juveniles.