Immune response for acute Aeromonas hydrophila infection in two distinct color morphs of northern snakehead, Channa argus.

To compare and analyze the differences in immunological response between the two color morphs of Channa argus, a fish cohort was divided into four groups: black C argus + PBS (B-PBS), black C argus + Aeromonas hydrophila (B-Ah), white C. argus + PBS (W-PBS), and white C. argus + A hydrophila (W-Ah). The B-PBS and W-PBS groups received 100 µL PBS, while the B-Ah and W-Ah groups received 3.6 × 105 CFU/mL A. hydrophila in the same volume. The death rate in each group was noted, changes in plasma biochemical indicators and the expression of liver immune-related genes were examined, and transcriptome techniques were used to compare the differences between the two colors of C. argus following stress. No mortality occurred in the B-PBS and W-PBS groups. Mortality in the W-Ah and B-Ah groups showed an upward and then downward trend after A. hydrophila injection. The highest mortality occurred within 24 h and was higher in the W-Ah group than in the B-Ah group. MDA levels in the B-Ah and W-Ah groups increased and then decreased, while SOD and T-AOC showed the reverse tendency. The W-Ah and W-PBS groups differed significantly in MDA at 3, 12, and 24 h, SOD from 6 to 96 h, and T-AOC between 6 and 48 h. Plasma MDA and T-AOC levels at 12 h and SOD levels at 24 and 48 h differed significantly between the B-PBS and B-Ah groups. In both the W-Ah and B-Ah groups, the expression levels of IL-1ß and IL-8 in the liver showed a temporal pattern with an initial increase followed by a decrease, reaching peak levels after 24 h, while IL-10 showed the reverse pattern. Transcriptome analysis of the liver revealed significant differences between the two C. argus colors. Differential genes in black C. argus were mainly enriched in steroid biosynthesis, glycolysis/gluconeogenesis, and glutathione and propanoate metabolism pathways 24 h after infection. In contrast, differential genes in white C. argus were mainly enriched in pathways such as oxidative phosphorylation, pancreatic secretion, and protein digestion and absorption 24 h after infection. After A. hydrophila infection, white C. argus had higher mortality, more severe oxidative stress and inflammatory responses, and lower antioxidant capacity than black C. argus.

Multiple effects of dietary supplementation with Lactobacillus reuteri and Bacillus subtilis on the growth, immunity, and metabolism of largemouth bass (Micropterus salmoides).

Probiotics play an essential role in the largemouth bass (Micropterus salmoides) aquaculture sector. They aid the fish in sickness prevention, intestinal structure improvement, food absorption, and immune system strengthening. In this experiment, Bacillus subtilis (BS, 107 CFU/g) and Lactobacillus reuteri (LR, 107 CFU/g) were added to the feed and then fed to M. salmoides for 35 days. The effects of two probiotics on the growth, immunity, and metabolism of M. salmoides organisms were studied. The results revealed that the BS group significantly increased the growth rate and specific growth rate of M. salmoides, while both the BS and LR groups significantly increase the length of villi M. salmoides intestines. The BS group significantly increased the levels of AKP, T-AOC, and CAT in the blood of M. salmoides, as well as AKP levels in the intestine. Furthermore, the BS group significantly increased the expression of intestinal genes Nrf2, SOD1, GPX, and CAT, while significantly decreasing the expression of the keap1 gene. M. salmoides gut microbial analysis showed that the abundance of Planctomycetota was significantly different in both control and experimental groups. Analyzed at the genus level, the abundance of Citrobacter, Paracoccus, Luedemannella， Sphingomonas, Streptomyces and Xanthomonas in the both control and experimental groups were significantly different. The BS group's differentially expressed genes were predominantly enriched in oxidative phosphorylation pathways in the intestine, indicating that they had a good influence on intestinal metabolism and inflammation suppression. In contrast, differentially expressed genes in the LR group were primarily enriched in the insulin signaling and linoleic acid metabolism pathways, indicating improved intestine metabolic performance. In conclusion, B. subtilis and L. reuteri improve the growth and health of M. salmoides, indicating tremendous potential for enhancing intestinal metabolism and providing significant application value.

MPs and PFOS single and combined exposure significantly alter genetic expressions of growth hormone and insulin growth factor-related biomarkers during zebrafish embryonic development.

Microplastics (MPs) and perfluorooctane sulfonate (PFOS) are emerging pollutants that are ubiquitously present in the environment and can cause series of ecotoxicological effects on aquatic animals. This study examined how the expression of genes related to insulin growth factor (igf1, igf2a, igf2b, igfra, and igfrb) and growth hormone (ghrh, gh1, ghra, and ghrb) changes during the development of zebrafish embryos exposed to 8 µm polyethylene microplastics (PE-MPs) and perfluorooctane sulfonate (PFOS) individually and in combination for 72 h. Our findings revealed that both low-concentrations of MP (50 µg/L) and PFOS (0.02 µg/L) treatments could significantly activate gene expression within a short period. High concentrations of MPs (500 µg/L) and PFOS (0.1 µg/L) not only rapidly activated gene expression but also sustained high expression levels for a longer duration. During combined exposures, peak gene expression in the low concentration groups (50 µg/L MPs and 0.02 µg/L PFOS; 50 µg/L MPs and 0.1 µg/L PFOS) primarily occurred within 12 h after treatment. In the high concentration groups (500 µg/L MPs and 0.02 µg/L PFOS), peak expression was also observed within 12 h. Notably, the combined exposure groups exhibited more pronounced effects on gene expression than the individual exposure groups. The activation of gene expression was both more significant and longer-lasting in the combined exposure, indicating a synergistic regulatory effect of MPs and PFOS. Overall, our study suggests that zebrafish embryo development can be significantly impacted by exposure to MPs, PFOS, and their combination, with combined exposures having a more lasting and profound effect on gene regulation compared to single exposures.

Transcriptomics reveals that NAD(P)H affects the development of the Zig-zag eel (Mastacembelus armatus ♀) × Spiny eel (Sinobdella sinensis ♂) hybrid offspring leading to low hatching rates.

Zig-zag eel (Mastacembelus armatus (2 n = 48)) and Spiny eel (Sinobdella sinensis (2 n = 48)) are two species of the Mastacembelidae family commonly found in southern China. Hybridization between the two has a very high deformity rate and a very low hatching rate. In order to investigate the reasons for this, the first hybridization between M. armatus and S. sinensis was carried out using artificial insemination, and the embryonic development of the hybrid offspring was examined using microphotography, and the malformations of the hybrid offspring were investigated by transcriptomics. The experiments showed that the average egg production was 4265.7 ± 322.94 (Mean ± SD), the average fertilization rate of hybrid offspring was 98.67 ± 0.58 % (Mean ± SD), the hatching rate was 12.06 ± 3.44 % (Mean ± SD), the deformity rate was 98.15 ± 3.21 % (Mean ± SD), and the embryonic development successively went through the five main stages of fertilized egg, egg cleavage, embryo formation, organogenesis, and exertion of membranes. Transcriptomics showed that the expression of NAD(P)H-related enzyme activity DEGs was increased, and many DEGs related to cell signaling molecule transmission and metabolic regulation are enriched in KEGG pathways, such as IL-17 signaling pathway, Osteoclast differentiation, TNF signaling pathway and MAPK signaling pathway. etc. The major types of DEGs corresponded to those coding for proteins. This study suggests that the high malformation rate in hybrid offspring may be caused by impaired synthesis of proteins during embryonic development.

Multi-Omics Reveals the Effects of Spirulina platensis Powder Replacement of Fish Meal on Intestinal Metabolism and Stress in Zig-Zag Eel (Mastacembelus armatus).

The booming aquaculture industry has created a strong demand for fishmeal and increased environmental pressures. Spirulina, as a potential alternative to fishmeal, has been shown to have growth-promoting and animal health-enhancing properties. In this study, 600 large spiny loaches, divided into five experimental groups, F0, F1, F2, F3, and F4, were reared for 10 weeks using Spirulina platensis powder (SPP) as a substitute for 0%, 5%, 10%, 15%, and 20% of fishmeal, respectively. The results of intestinal physiological indexes showed that superoxide dismutase was lower than F0 in all treatment groups, and the activity of F3 was significantly lower than F0 (p < 0.05). The activity of malondialdehyde was significantly higher than that of F0 in all groups except F3 (p < 0.05). The addition of SPP also led to a decrease in the activity of acid phosphatase in the intestine, which was significantly lower in all treatment groups compared to the F0 group (p < 0.05). The results of serum physiology showed that the activity of superoxide dismutase in serum gradually increased with the increase in the percentage of SPP addition, and the F3 group produced a significant difference from the F0 group (p < 0.05). The transcriptomics results showed that DEGs in the low percentage substitution group (<15%) were mostly enriched in metabolism-related pathways, such as bile secretion; DEGs in the high percentage substitution group (>15%) were mostly enriched in inflammation-related pathways, such as complement p and coagulation cascades. Metabolomics confirmed that nicotinate and nicotinamide metabolism and glycerophospholipid metabolism were the two pathways that were significantly enriched in the treatment groups of fishmeal replacement by SPP. The present study demonstrated that a low percentage (<15%) of fishmeal replacement by SPP in feed mobilized MA digestive metabolism, whereas a high percentage (>15%) of replacement induced intestinal stress. Considering the health and farm efficiency aspects, the proportion of SPP in feed formulation for MA should be less than 15%.

Dietary kelp meal improves serum antioxidants, intestinal immunity, and lipid metabolism in hybrid snakehead (Channa maculata ♀ × Channa argus ♂).

BACKGROUND: Dietary kelp possesses a variety of useful biological qualities but does not have a toxic effect on the host. In this study, we examine how kelp dietary supplementation enhances the serum biochemistry, intestinal immunity, and metabolism of hybrid snakehead. A total of 810 juvenile hybrid snakeheads (Channa maculata ♀ × Channa argus ♂), with an initial average weight of 11.4 ± 0.15 g, were allocated randomly to three treatment groups (three replicates per group). The fish were fed for 60 days with isonitrogenous and isolipidic diets. The groups were the control group (C) (20% high-gluten flour), the medium replacement group (MR) (10% high-gluten flour and 10% kelp meal), and the full replacement group (FR) (0% high-gluten flour and 15% kelp meal). RESULTS: The results showed that dietary kelp increased the activity of serum antioxidant enzymes significantly and decreased the content of serum malondialdehyde (MDA) in hybrid snakeheads, with significant changes in the FR group (P < 0.05). The intestinal morphology results showed that dietary kelp helped to increase the specific surface area of intestinal villi, which was beneficial for intestinal digestion and absorption. According to transcriptome and quantitative real-time polymerase chain reaction (qRT-PCR) analysis, dietary kelp can improve the expression of intestinal immunity and metabolism-related pathways. Among them, immune-related genes MHC1 and HSPA1 were significantly up-regulated, and IGH, MHC2, and IL-8 were significantly down-regulated (P < 0.05). Lipid metabolism-related genes DGAT2, FABP2, RXRα, and PLPP1 were all significantly up-regulated (P < 0.05). CONCLUSION: Dietary kelp can effectively improve the antioxidant function of hybrid snakeheads, improve intestinal morphology, reduce intestinal inflammation, and promote intestinal lipid synthesis and transportation, thereby improving intestinal immunity and metabolic functions. © 2024 Society of Chemical Industry.

Effect of aqueous extract of Millettia speciosa Champ on intestinal health maintenance and immune enhancement of Cyprinus carpio.

Millettia speciosa Champ (MSP) is a natural Chinese herb that improves gastrointestinal health and enhances animal immunity. An 8-week feeding trial with different MSP levels (0, 150, 300, and 600 mg/kg) was conducted to evaluate the promotive effects of MSP in Cyprinus carpio. Results indicate that MSP improved intestinal immunity to some extent evidenced by the immuno-antioxidant parameters and the 16S rRNA in the Illumina MiSeq platform. With the analysis of transcriptome sequencing, 4685 differentially expressed genes (DEGs) were identified, including 2149 up-regulated and 2536 down-regulated. According to the GO and KEGG enrichments, DEGs were mainly involved in the immune system. Transcriptional expression of the NOD-like signaling pathway and key genes retrieved from the transcriptome database confirmed that innate immunity was improved in response to dietary MSP administration. Therefore, MSP could be used as a feed supplement that enhances immunity. This may provide insight into Chinese herb additive application in aquaculture production.

Effects of different combinations of koumine and gelsemine on growth performance, intestinal health, and transcriptome of Cyprinus carpio.

Koumine (KM) and gelsemine (GS) have shown significant benefits in livestock production, but their potential in aquaculture remains largely unexplored. This study examined the impact of different KM and GS combinations as feed additives on C. carpio (90 fish per group, initial weight 1.95 ± 0.08 g). KM and GS were introduced in ratios of 2:2 (mg/kg), 2:1 (mg/kg), and 2:0.67 (mg/kg) over a 10-week aquaculture experiment. The results demonstrate that the 2:1 (mg/kg) group increases the villus length, muscular layer thickness, crude protein, and crude fat content. Regarding fatty acid content, KM and GS enhance the levels of various fatty acids, including the total saturated fatty acid and total monounsaturated fatty acid. Additionally, KM and GS improve the composition and function of the intestinal microbiota. The 2:1 (mg/kg) group significantly elevates the enzymatic activities of SOD, MDA, CAT and upregulates the expression of immune-related genes such as toll-like receptor 2, transforming growth factor ß, and glutathione S-transferase. Transcriptomic analysis suggests that KM and GS may have potential benefits for nutrient utilization and immune regulation in C. carpio. In summary, this study provides valuable insights into the use of KM and GS as feed additives in aquaculture.

Effect of dietary koumine on the immune and antioxidant status of carp (Cyprinus carpio) after Aeromonas hydrophila infection.

Koumine (KM) has anxiolytic, anti-inflammatory and growth-promoting effects in pigs and sheep. Based on the growth-promoting and immunological effects of koumine, the present study was conducted on Cyprinus carpio (C. carpio) with four KM concentrations: 0 mg/kg, 0.2 mg/kg, 2 mg/kg, and 20 mg/kg for 10 weeks, followed by a 1-week Aeromonas hydrophila (A. hydrophila) infection experiment. The effect of KM on the immunity of A. hydrophila infected carp was analyzed by histopathology, biochemical assay, and qRT-PCR to assess the feasibility of KM in aquaculture. The results showed that the presence of KM alleviated pathogen damage to carp tissues. At 2 mg/kg and 20 mg/kg concentrations of KM successively and significantly elevated (p < 0.05) the SOD activities in the intestinal tract, hepatopancreas and kidney of carp. The expression levels of hepatopancreatic antioxidant genes Nrf2 and IGF-1 were significantly up-regulated in the same group (p < 0.05), while the expression levels of immune genes IL-8 and IL-10 were down-regulated. In summary, KM at concentrations of 2 mg/kg and 20 mg/kg could regulate the expression of antioxidant and immune genes in various tissues in an orderly and rapid manner, and significantly improve the antioxidant and immune abilities of carp, which is conducive to the improvement of the resilience of carp.

Characterization, Expression, and Functional Analysis of the Northern Snakehead (Channa argus) Hepcidin.

Hepcidin, an antimicrobial peptide (AMP), is a well-conserved molecule present in various species such as fish, amphibians, birds, reptiles, and mammals. It exhibits broad-spectrum antimicrobial activity and holds a significant role in the innate immune system of host organisms. The northern snakehead (Channa argus) has become a valuable freshwater fish in China and Asia. In this investigation, the cDNA encoding the hepcidin gene of northern snakehead was cloned and named caHep. The amino acid sequences and protein structure of caHep are similar to those of hepcidins from other fish. The eukaryotic expression product of the caHep gene showed broad-spectrum antibacterial activity. Scanning electron microscope analysis indicated that the caHep peptide inhibited bacterial growth by damaging their cell membranes. Lipopolysaccharide (LPS) injection induced significant expression of caHep, implying the involvement of caHep in the innate immune response of northern snakeheads. This investigation showed that the caHep peptide is potentially a robust antibacterial drug against bacterial diseases in aquaculture animals.

Toxic Effects of Koumine on the Early-Life Development Stage of Zebrafish.

Koumine is one of the most abundant alkaloids found in Gelsemium elegans, and it has a wide range of pharmacological effects including antitumor, anti-inflammatory, analgesic treatment effects, and antianxiety. However, its high toxicity and unclear mechanism of action have greatly limited the medicinal development and use of koumine. We investigated the toxic effects of koumine on the developmental toxicity and behavioral neurotoxicity of zebrafish embryos and larvae. Embryos at 6 h postfertilization (hpf) were exposed to 12.5, 25, 50, 75, and 100 mg/L of koumine until 120 hpf. Koumine affected the hatching and heartbeats of the embryos. The morphological analysis also revealed many abnormalities, such as shortened bodies, yolk sac edemas, tail malformations, and pericardial edemas. To identify the neurotoxicity of koumine, the behavior of the larvae was measured. Koumine at 50 and 100 mg/L affect the escape response. The embryos exhibited uncoordinated muscle contractions along the body axis in response to touch at 36 hpf. More importantly, we found that the neurotoxicity of koumine is mainly caused by influencing the ACh content and the activity of AChE without impairing motor neuron development. A comprehensive analysis shows that a high concentration of koumine has obvious toxic effects on zebrafish, and the safe concentration of koumine for zebrafish should be less than 25 mg/L. These results will be valuable for better understanding the toxicity of koumine and provide new insights into the application of koumine.

Generation and application of a novel transgenic zebrafish line Tg(GAcyp1a:eGFP/Luc) as an in vivo assay to sensitive and specific monitoring of DLCs in the environment.

CYP1A is the most commonly used biomarker and transgenic fish which carrying a cyp1a promoter to drive a reporter gene can be used as reliable way to monitor dioxin/dioxin-like compounds (DLCs) in the environment. Here, we cloned the cyp1a promoter of Gambusia affinis and this promoter showed stronger transcriptional activity than that of zebrafish. Then, a Tg(GAcyp1a:eGFP/Luc) transgenic zebrafish line was first constructed with the G. affinis cyp1a promoter driving eGFP expression using meganuclease I-SceI mediated transgenesis technology. The Tg(GAcyp1a:eGFP/Luc) larvae at 72 h post-fertilization (hpf) were tested by exposing to TCDD for 72 h, and induced GFP was mainly expressed in the liver with low background. The Tg(GAcyp1a:eGFP/Luc) zebrafish showed high sensitivity (limit of detection of 0.322 ng/L TCDD and 0.7 TEQ-ng/L PCDD/Fs) and specificity (insensitive to responses to PAHs and PCBs). In addition, the transgenic line showed a low detection concentration of the DLCs contaminated environmental samples (as low as 1.8 TEQ-ng/L), and the eGFP fluorescence intensity and the chemical-TEQ values were closely correlated. In conclusion, a sensitively and specifically transgenic zebrafish line was established to convenient and effective to detect DLCs in the environment.

Microbiome-Metabolomic Analysis Reveals Beneficial Effects of Dietary Kelp Resistant Starch on Intestinal Functions of Hybrid Snakeheads (Channa maculata ♀ × Channa argus ♂).

The benefits of resistant starch on hypoglycemia, obesity prevention, antioxidant status and the alleviation of metabolic syndrome have received considerable attention. In this study, we explored how dietary kelp resistant starch (KRS) enhances intestinal morphology and function through a microbiome-metabolomic analysis. Hybrid snakeheads (initial weight: 11.4 ± 0.15 g) were fed experimental diets for 60 days. Fish were fed a basic wheat starch diet and the KRS diet. Dietary KRS improved intestinal morphology and enhanced intestinal antioxidant and digestive capabilities, as evidenced by decreased intestinal damage and upregulated intestinal biochemical markers. The microbiome analysis showed that KRS administration elevated the proportion of butyrate-producing bacteria and the abundance of beneficial bacteria that increases insulin sensitivity. Furthermore, significant alterations in metabolic profiles were observed to mainly associate with the amino acid metabolism (particularly arginine production), the metabolism of cofactors and vitamins, fat metabolism, glutathione metabolism, and the biosynthesis of other secondary metabolites. Additionally, alterations in intestinal microbiota composition were significantly associated with metabolites. Collectively, changes in intestinal microbiota and metabolite profiles produced by the replacement of common starch with dietary KRS appears to play an important role in the development of intestinal metabolism, thus leading to improved intestinal function and homeostasis.

Species-specific effects of microplastics on juvenile fishes.

Microplastics contamination have been extensively reported in aquatic ecosystem and organisms. It is wildly acknowledged that the ingestion, accumulation and elimination of microplastics in fishes are species-specific, which mainly depending on the feeding behavior. This study aimed to investigate the effects of microplastics on the morphology and inflammatory response in intestines of fishes with different feeding types. Largemouth bass (carnivorous fish), grass carp (herbivorous fish) and Jian carp (omnivorous fish) were used as organism model. The contributing concentration and size of microplastics were explored as well as the response time and legacy effect in fishes. Two different sizes of polystyrene microplastics (80 nm and 8 µm) were set at three concentrations. And samples were analyzed at different exposure times and depuration times. Histological analysis indicated that multiple abnormalities in intestines were presented in three species fishes after acute exposure microplastics. The mRNA abundance of immune-related genes in the intestine tissues of fishes were significantly fluctuant. There were differential expressions of genes coping with differential sizes and concentrations of microplastics exposure in different fishes. The reason for the difference effects of microplastics on fishes was still unclear but could be due to the difference in the structure and function of the digestive system. These results provided a theoretical basis to further analysis of the mechanism of fish intestinal pathology caused by microplastics.

An effect assessment of microplastics and nanoplastics interacting with androstenedione on mosquitofish (Gambusia affinis).

An increasing number of microplastics have been detected in aquatic environments, causing various damage to organisms. The size of microplastics affects the toxicity once they enter the organisms. Meanwhile, there is an increasing variety of Endocrine-disrupting chemicals (EDCs) present in aquatic environments. Androstenedione (AED) is a typical EDC. In this study, we used polystyrene microspheres of 80 nm (NPs) and 8 µm (MPs) as materials to simulate environmental contaminants in the aquatic environment with AED. We used female mosquitofish (Gambusia affinis) as the research object to investigate the effects of microplastics on fish in waters containing AED. We compared different sizes of particles accumulation in some tissues of fish and variation of enzyme activities (SOD, LDH, CAT), and the content of MDA in the gut. MPs, NPs, and AED combined exposure test investigated mRNA profiles of immune-related genes (IL-1ß, IL-6, IL-8, IL-10) and hormone receptor genes (ARα, ARß, ERα, ERß) in the liver of fish. Our results indicated that MPs emerged in various tissues (gill, gut, and liver) of mosquitofish. Besides, NPs and MPs caused enteric abnormal enzyme activity after 48 h of exposure, which was particularly pronounced in the MPs-AED group. MPs induced significant upregulation of inflammatory factors and gonadal factor genes after 96 h of exposure, which was more pronounced when co-exposed with AED. In conclusion, NPs and MPs caused mechanisms of immune damage and inflammatory response. MPs were found to be more likely to cause adverse reactions than NPs, and these responses were enhanced by the combined effects of AED. This study demonstrated that AED can exacerbate the negative effects of MPs and NPs on mosquitofish. It provided an important basis for the effective assessment of MPs and NPs on bioaccumulation and biochemical status of mosquitofish. Additionally, it serves as a foundation to investigate the interactive effects of microplastics and EDCs in living organisms.

Effect of kelp powder on the resistance of Aeromonas hydrophila in the gut of hybrid snakeheads (Channa maculata ♀ × Channa argus ♂).

To assess the level of oxidative stress, expression of immune-related genes, histomorphology, and changes in the intestinal tract of hybrid snakeheads(Channa maculata ♀ × Channa argus ♂) under stress from kelp powder in place of flour against Aeromonas hydrophila. We set up experimental diets: a control (C) diet of 20% flour, an experimental (MR) diet of 10% kelp powder and 10% flour, and an experimental (FR) diet of 0% starch and 15% kelp powder. The experimental fish in each group were infected with Aeromonas hydrophila after 60 days of feeding. For this experiment, some of the experimental fish in group C were injected with PBS as a negative control group (PBS). The results showed that the C group had significantly higher SOD, CAT, and T-AOC activity and expression of TAK1, IKKß, IL-1ß, and TNF-α genes in the MyD88 pathway than the PBS group. CAT activity and the expression of TAK1, IL-1ß and TNF-α genes in the MyD88 pathway were significantly lower in the MR group than in the C group. Furthermore, the number of goblet cells in the MR group was significantly higher than in the C group. Furthermore, microorganisms such as Bacteroidota and Actinobacteriota were significantly lower in the C group than in the PBS and FR groups, as were beneficial bacteria such as Clostridium_sensu_stricto_1 and Sphingomonas. Replacing flour with kelp powder increases hybrid snakehead gut resistance to Aeromonas hydrophila.

Effects of tidal action on the stability of microbiota, antibiotic resistance genes, and microplastics in the Pearl River Estuary, Guangzhou, China.

In this study, the 16S rRNA gene amplicon sequencing technique was used to explore the microbial diversity and differences in the water environment of the Pearl River Estuary in Nansha District with various land use types such as the aquaculture area, industrial area, tourist area, agricultural plantation, and residential area. At the same time, the quantity, type, abundance, and distribution of two types of emerging environmental pollutants, antibiotic resistance genes (ARGs) and microplastics (MPs), are explored in the water samples from different functional areas. The results show that the dominant phyla in the five functional regions are Proteobacteria, Actinobacteria and Bacteroidetes, and the dominant genera are Hydrogenophaga, Synechococcus, Limnohabitans and Polynucleobacter. A total of 248 ARG subtypes were detected in the five regions, belonging to nine classes of ARGs (Aminoglycoside, Beta_Lactamase, Chlor, MGEs, MLSB, Multidrug, Sul, Tet, Van). Blue and white were the dominant MP colors in the five regions; 0.5-2 mm was the dominant MP size, and cellulose, rayon, and polyester comprised the highest proportion of the plastic polymers. This study provides the basis for understanding the environmental microbial distribution in estuaries and the prevention of environmental health risks from ARGs and microplastics.

Replacing starch with resistant starch (Laminaria japonica) improves water quality, nitrogen and phosphorus budget and microbial community in hybrid snakehead (Channa maculata ♀ × Channa argus ♂).

It is essential to increase the use of carbohydrates as an energy source and improve protein synthesis and utilization to reduce ammonia nitrogen emissions. A 60-day cultural experiment was conducted to assess the impact of resistant starch (kelp meal, Laminaria japonica) replacing starch on water quality, nitrogen and phosphorus budget and microbial community of hybrid snakehead. Approximately 1350 experimental fish (11.4 ± 0.15 g) were randomly divided into control group (C, 20% starch) and four resistant starch groups: low replacement group (LR, 15% starch), medium replacement group (MR, 10% starch), high replacement group (HR, 5% starch) and full replacement group (FR, 0% starch). The crude protein and crude fat content of hybrid snakehead fish fed with the FR diet had the most significant improvement (P < 0.05). However, resistant starch also increased the effectiveness of nitrogen and phosphorus utilization in hybrid snakeheads, which decreased the proportion of total nitrogen and total phosphorus in tail water. The minimum nitrogen and phosphorus emission rate was when the starch level was 6.1%. Denitrifying microbes including Gemmobacter, Rhodobacter, Emticicia and Bosea have become much more prevalent in group FR (P < 0.05). In general, replacing starch with resistant starch can enhance the rate at which nitrogen and phosphorus are used in feeding, lessening water pollution and altering environmental microbial composition. PRACTITIONER POINTS: Resistant starch (RS) improves whole fish nutritional content. Resistant starch improves dietary nitrogen and phosphorus utilization. Resistant starch acts as a carbon source and encourages the colonization of denitrifying bacteria in water.

Effects of TLR2/4 signalling pathway in western mosquitofish (Gambusia affinis) after Edwardsiella tarda infection.

Gambusia affinis is regarded as an important animal model. Edwardsiella tarda is one of the most serious pathogens affecting aquaculture. The study explores the effects of TLR2/4 partial signalling pathway in G. affinis of E. tarda infection. The study collected the brain, liver, and intestine after E. tarda LD50 and 0.85% NaCl solution challenge at different times (0 h, 3 h, 9 h, 18 h, 24 h, and 48 h). In these three tissues, the mRNA levels of PI3K, AKT3, IRAK4, TAK1, IKKß, and IL-1ß were substantially enhanced (p < .05) then returned to normal levels. Additionally, Rac1 and MyD88 in liver had different trend with other genes in brain and intestine, which displayed significantly indifference. The overexpression of IKKß, and IL-1ß indicated that E. tarda also caused immune reaction in intestine and liver, which would be consistent with delayed edwardsiellosis, which causes intestinal lesions and liver and kidney necrosis. Additionally, MyD88 plays a smaller role than IRAK4 and TAK1 in this signalling pathways. This study could enrich the understanding of the immune mechanism of the TLR2/4 signalling pathway in fish and might help to prescribe preventive measures against E. tarda to prevent infectious diseases in fish.

Koumine induces apoptosis in Cyprinus carpio liver cells by regulating JAK-STAT and p53 signaling pathways.

Koumine is an alkaloid with significant anti-anxiety, anticancer cell proliferation, and analgesic activities, and our previous studies have shown that koumine can be used as an immunostimulant in aquaculture, but the molecular mechanism of its effect remains unclear. We fed a basal diet with 0, 0.2, 2, and 20 mg/kg koumine to C. carpio for 10 weeks, and comprehensive studies of the histological and biochemical parameters and transcriptomes of the four groups were performed. Histological results indicated that the number of apoptotic cells in the liver increased with increasing koumine concentration. Compared with those of the control group, the malondialdehyde, superoxide dismutase, catalase, acid phosphatase, alkaline phosphatase, and lactate dehydrogenase levels of the treatment group increased to varying degrees. In total, 100.11 GB of clean data, 4774 DEGs, and 138 differentially expressed genes were obtained from the transcriptome data. Differentially expressed genes were classified into 187 signalling pathways, and the circadian rhythm signalling pathway, the JAK-STAT signalling pathway, the p53 signalling pathway and the PPAR signalling pathway were the top enriched pathways. The qRT-PCR results confirmed that the key genes ifnar1, socs3l, epoa, ghra, cMyc, mcl-1, shisa4, and gtse1 involved in balancing cell proliferation and apoptosis were enriched in these pathways. We discovered that the JAK-STAT and p53 pathways are important targets of koumine. Such information contributes to a better understanding of the potential mechanism by which koumine regulates hepatic immunity as well as to lays the theoretical foundation for its application.