This study characterized Aeromonas veronii isolates recovered from diseased Micropterus salmoides , Procambarus clarkii , and Ctenopharyngodon idella in Guangxi, China. The objective was to assess genetic diversity, virulence gene profiles, and antimicrobial resistance patterns to support effective disease control. Seven strains were confirmed as A. veronii using morphological, physiological, biochemical, and molecular methods. Virulence gene screening showed that all isolates carried GcaT, OmpAI, Hly, Fla, and Exu. Artificial challenge tests demonstrated strong pathogenicity, with median lethal dose (LD₅₀) values ranging from 1.43×10⁶ to 3.58×10⁶ CFU/individual. Antimicrobial susceptibility testing indicated sensitivity to ceftriaxone, cefepime, and fosfomycin, but resistance to amoxicillin, teicoplanin, and sulbactam. Multilocus sequence typing (MLST) identified seven novel sequence types (ST2742, ST2740, ST2765, ST2760, ST2770, ST2774, and ST2775). These results confirm that A. veronii isolates from Guangxi exhibit high genetic diversity, carry multiple virulence genes, and display multidrug resistance. The findings provide a basis for epidemiological surveillance and targeted control of this pathogen.

Chinese herbal medicine is rich in active ingredients that can promote growth and enhance immune function. In this study, Lycium barbarum, Panax ginseng, Astragalus membranaceus and Phragmitis rhizoma were crushed and mixed to prepare a compound Chinese herbal medicine. The basic feed of Megalobrama amblycephala was supplemented with 0 (control group), 1% (T1), 2% (T2) and 4% (T3) of this compound medicine. After raising for 90 days, in the T1 and T2 experimental groups, the length and width of intestinal villi and the activities of amylase, trypsin and lipase in the intestine were significantly higher than those in the control group. The weight gain rate and specific growth rates were highest and the feed coefficient was lowest in the T2 experimental group. In the control group, a large number of dilated hepatic sinusoids were detected, while this number significantly decreased in the T1 experimental group and they were not detected at all in the T2 and T3 experimental groups. The spleen and liver body indices were highest in the T2 experimental group. In all experimental groups, the Lys content and the activities of T-SOD, CAT, ACP, AKP and GSH-PX in serum were significantly higher than those of the control group. The expression of IgM, C3, TNF-ɑ and IL-1β in the head kidney; C3, TNF-ɑ and IL-1β in the spleen; C3 and IL-1β in the gills; IgM, C3 and IL-1β in liver; and IL-1β in the intestine was highest in the T2 experimental group. After challenge with Aeromonas hydrophila, the cumulative mortality rate of M. amblycephala was lowest in the T2 experimental group. The results of this study indicated that this compound Chinese herbal medicine could significantly enhance immunity, increase the activity of intestinal digestion-related enzymes and promote the growth of M. amblycephala. The appropriate addition amount of this compound Chinese herbal medicine in the basic feed of M. amblycephala was 2%.

Nonspecific cytotoxic cell receptor protein type I (NCCRP1), as an important type of receptor protein, plays a key role in the immune process of teleost, which triggers cytotoxic reactions by recognizing and binding to multiple target cells. In this study, the NCCRP1 gene sequence of Megalobrama amblycephala was cloned by PCR technology. Its length was 726 bp and the open reading frame (ORF) was 702 bp, which encoded 233 amino acids, with a relative molecular weight of 26.87 kD. Through homologous sequence retrieval in NCBI, the amino acid sequence of Megalobrama amblycephala NCCRP1 was compared with other fish NCCRP1, and the similarity was as follows: Labeo rohita (87.12%), Carassius auratus (85.84%), Danio rerio (83.26%) and Cyprinus carpio (82.05%). The genetic phylogenetic tree was constructed using the adjacency method. The NCCRP1 gene of Megalobrama amblycephala was clustered into one branch with that of Cyprinidae fish. Megalobrama amblycephala NCCRP1 had the closest genetic relationship with that of Ctenopharyngodon idellus. The NCCRP1 expression in different tissues was detected by qPCR. It was found that the expression level of the NCCRP1 gene was highest in the head kidney, followed by the spleen, liver and posterior kidney. After infection with Aeromonas hydrophila, the expression level of NCCRP1 gene in head kidney, spleen, gill and intestine first increased and then decreased during 21 days. The NCCRP1 expression was reached the peak at 5d in head kidney, spleen and gill, and reached its maximum at 7 d in intestine after infection, which indicated that the NCCRP1 expression could be significantly induced after infection with Aeromonas hydrophila. The maximum relative expression of NCCRP1 gene in head kidney and spleen were 19.84 folds and 7.82 folds, respectively, which were significantly higher than those in intestine (5.32 folds) and gill (6.35 folds). It indicated that Megalobrama amblycephala NCCRP1 might play an important role in the systemic immune tissues of the head kidney and spleen in the process of resisting Aeromonas hydrophila infection.

Largemouth bass (Micropterus salmoides) is an economically important freshwater fish species in China that is frequently affected by disease outbreaks caused by Aeromonas hydrophila. This study employed an integrated transcriptomic and proteomic approach to investigate the response of the liver in largemouth bass at 72 h post-infection with A. hydrophila via intraperitoneal injection. We identified differentially expressed genes (DEGs; 2136 upregulated and 200 downregulated) and differentially expressed proteins (DEPs; 1683 upregulated and 1817 downregulated). Functional enrichment analysis indicated that the upregulated DEGs/DEPs were significantly involved in immune and inflammatory responses, encompassing pathways, such as TNF signalling, NF-kappa B signalling, complement and coagulation cascades and B cell receptor signalling, while the downregulated DEGs/DEPs were primarily associated with metabolic processes, especially lipid metabolism. Integrated transcriptomic and proteomic analysis identified 420 correlated DEG/DEP pairs, among which 154 were consistently upregulated and 19 consistently downregulated. The upregulation of eight key immune-related DEG/DEPs, including complement components (C1q, C7b, C1r-A), MYD88 and BCL10, was verified by RT-qPCR. Collectively, these findings provide valuable insights into the molecular basis of immune defence against A. hydrophila in largemouth bass and identify potential immune-related biomarkers that may be useful in the development of effective prevention and control strategies.

This study investigates the effects of compound Chinese herbal medicine (CCHM) on growth performances, antioxidation activities, immune-related enzymes, and digestive enzymes of dongtingking crucian carp ( Carassius auratus indigentiaus) . Lycium barbarum L., Panax ginseng C.A. Mey, Astragalus membranaceus and Phragmites communis Trin were ground and prepared into CCHM at the ratio of 4.5:3:1.5:1. The one-factor experiments were designed, in which different gradients of CCHM (0%, 1%, 2% and 4%) were added to basal feeds for C. auratus indigentiaus , which were fed for 90 d. The weight gain rate (WGR) and specific growth rate (SGR) in the experimental groups with CCHM addition were significantly higher than those of the control group (0%, without CCHM), the feed coefficient (FCR) was significantly lower in the experimental groups compared to the control group. In the experimental group with 4% of CCHM, WGR, and SGR of C. auratus indigentiaus were the highest (73.87±7.20 % and 0.63±0.15 %, respectively), while the FCR was the lowest (0.24±0.07 %). In the experimental group with 1% CCHM, the spleen index (SPI) increased significantly. However, the SPI of experimental groups, with 2% and 4% CCHM, showed no significant difference from that of the control group. The hepatosomatic index (HSI) of both experimental groups, with 2% and 4% of CCHM, was lower than that of the control group. However, there was no significant difference between the experimental group, which had 1% CCHM, and the control group. Activities of immune-related enzymes like lysozyme, acid phosphatase, and alkaline phosphatase (AKP) in the experimental groups with 1%, 2%, and 4% of CCHM were all higher than those of the control group. The lysozyme activity reached the highest in the experimental group with 1% of CCHM, the alkaline phosphatase (AKP) activity reached the peak in the experimental group with 2% of CCHM, and the acid phosphatase activity reached the highest in the experimental group with 2% of CCHM. Activities of antioxidant-related enzymes like catalase and glutathione peroxidase (GSH-PX) in C. auratus indigentiaus were all higher than those of the control group and reached the highest in the experimental group with 1% of CCHM. The total superoxide dismutase activity was highest in the experimental group with 4% of CCHM. Activities of intestinal digestive enzymes such as lipase, amylase, and trypsin in the experimental groups with 1%, 2%, and 4% of CCHM were higher than in the control group. Specifically, lipase and amylase activities were highest in the experimental group, with 1% of CCHM. In comparison, trypsin activity reaches the highest in the experimental group with 4% of CCHM. The results of this study show that adding CCHM into feed can increase the activity of immune-related enzymes and antioxidant-related enzymes in the serum of C. auratus indigentiaus , improve the activity of intestinal digestive enzymes, and promote growth. The appropriate CCHM content in basal feed for C. auratus indigentiaus is 1%.

【Objective】In order to establish a scientific foundation for the prevention and management of diseases in largemouth bass (Micropterus salmoides) culture, the objective of this study is to examine the in vitro antibacterial effects of 59 Chinese medicines and their combinations on the pathogenic bacteria of largemouth bass and to identify the Chinese medicines that have effective bacteriostatic effects.【Method】The agar plate diffusion method and Oxford cup perforation method were used to screen the single Chinese medicines with bacteriostatic effect in a preliminary manner. In order to screen the single and compounded Chinese medicines with better bacteriostatic effect, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the single and compound Chinese medicines against the pathogenic bacteria from largemouth bass were determined using the two-fold dilution method.【Result】Both Edwardsiella tarda and Aeromonas hydrophila were shown to be extremely sensitive to eight Chinese medicines, including Caesalpinia sappan, Terminalia chebula, Scutellaria baicalensis, Galla chinensis, Syzygium aromaticum, Euphorbia humifusa, Sanguisorba officinalis and Punica granatum. Of these, the diameters of inhibition circles of G. chinensis and S. aromaticum against A. hydrophila were 21.20 mm and 26.19 mm, respectively, with MICs of 7.81 mg/mL and MBCs of 15.63 mg/mL; the inhibition circle of G. chinensis against E. tarda reached 30.33 mm in diameter, with MICs of 3.91 mg/mL and MBCs of 7.81 mg/mL, respectively; the two pathogens were highly sensitive to M. officinalis, P. vulgaris, A. argyi, and V. yedoensis with diameters ranging from 15.84 mm to 19.47 mm respectively. The most pronounced bacteriostatic effect on A. hydrophila was recorded with C. sappan+G.chinensis and S. aromaticum+T. chebula exhibiting MIC and MBC of 3.91 mg/mL. Additionally, C. sappan+G. chinensis, S. aromaticum+S. baicalensis, C. sappan+T. chebula, G. chinensis+S. baicalensis, and G. chinensis+P. granatum demonstrated efficacy against E. tarda, with MIC and MBC of 3.91 mg/mL. C. sappan+T. chebula, S. aromaticum+T. chebula, and S. aromaticum+S. baicalensis exhibited additive effects on the two pathogenic bacteria. The inhibitory effects among the combinations of C. sappan+C. chinensis, S. aromaticum+P. granatum, and C. sappan+P. granatum demonstrated unrelated inhibitory effects on the two pathogens. Conversely, the combinations of S. aromaticum+G. chinensis, G. chinensis+C. chinensis exhibited antagonistic effects on the two pathogenic bacteria.【Conclusion】In conclusion, six single Chinese medicines including C. sappan, T. chebula, S. baicalensis, G. chinensis, S. aromaticum and P. granatum, exhibit superior antibacterial properties against A. hydrophila and E. Tarda. Specifically, C. sappan+G. chinensis had the strongest inhibitory effects on the two pathogens.

Cyclophilin A (CypA) is a cell’s primary receptor of Cyclosporin A (CsA). It is essential for biodiversity and plays an important role in the immune system. In this study, the full-length cDNA sequence (GenBank ID: PV256473) of Megalobrama amblycephala CypA was acquired by PCR and RACE technology. The complete cDNA sequence of M. amblycephala CypA is 901 bp. The lengths of the 5′ untranslated region (UTR), the 3′ untranslated region, and the open reading frame (ORF) are 77 bp, 329 bp, and 495 bp, respectively. It encodes a total of 164 amino acids. The theoretical isoelectric point of M. amblycephala CypA is 8.6, and the relative molecular weight is 17.43 KDa. According to homologous sequence retrieval in GenBank, the similarity between CypA amino acid sequence of M. amblycephala and other fish was Cyprinus carpio (94.51%), Ctenopharynodon idellus (92.07%), Carassius gibelio (92.07%), Labeo rohita (92.07%), Danio rerio (91.46%), and Onychostoma macrolepis (91.46%). ESyPred3D predicted that the CypA of M. amblycephala contained 8 β-pleated sheets and double α-helixes, which might form the active central region of CypA. MEGA 5.1 software was used for multiple sequence comparison analysis, and the adjacency method constructed the genetic phylogenetic tree. It was found that the CypA gene of M. amblycephala was clustered into one branch of Cyprinidae fish CypA, and CypA of M. amblycephala was closely related to CypA of Cyprinus carpio . Expressions of CypA in different tissues of M. amblycephala were detected through qPCR; it was found that the expression level of the CypA gene was highest in the head kidney, followed by liver, kidney, and spleen. The M. amblycephala was immersed in Aeromonas hydrophila for infection; it was found that expression levels of CypA in head kidney, liver, gills, and intestines first increased, then decreased in the first 72 h of infection. Specifically, the expression levels reached a peak at 6h in the head kidney, at 12 h in the liver and gills, and at 24h in the intestines. It indicated that the expression of M. amblycephala CypA gene could be significantly induced after A. hydrophila infection—expression levels of CypA in the head kidney peak earlier than in the liver and intestines. Moreover, the relative expression level of CypA in the head kidney at peak (15.02-fold) is significantly higher than that in the liver (6.89-fold), intestines (9.92-fold), and gills (7.42-fold). It is suggested that CypA might play an essential role in the head kidney of M. amblycephala in defense against bacterial infection.

This study investigates the immune responses of largemouth bass ( Micropterus salmoides) to infection by Aeromonas hydrophila, a pathogen responsible for significant economic losses in freshwater aquaculture due to bacterial enteritis. We employed transcriptomic sequencing, label-free LC-MS/MS quantitative proteomics, and 16S RNA sequencing to evaluate the transcriptomic, proteomic, and intestinal microbiota changes in infected fish compared to healthycontrols. Each fish (approximately 60 g) in the infection group was injected with 0.5 ml of an A. hydrophila suspension (1.0 x 108 CFU/mL), while the control group received 0.5 ml of phosphate buffer. Samples were collected 72 h post-injection, with three biological replicates made from an equal mix of tissue samples from six fish each. A total of 1666 differentially expressed genes (DEGs) and 2477 differentially expressed proteins (DEPs) were identified. Integrated analysis revealed that the up-regulated DEGs/DEPs in the intestines of infected largemouth bass were primarily associated with immune-related pathways including "antigen processing and presentation", "MAPK signaling pathway", "ECM-receptor interaction", and "leukocyte transendothelial migration". Notable upregulated immune-related proteins included complement or antigen- presenting proteins like complement C1, complement C3, complement C6, alpha-2-macroglobulin, laminin, serotransferrin, leukocyte cell-derived chemotaxin-2, immunoglobulin C1-set domain-containing protein, and the MHC class I alpha antigen. 16S RNA sequencing indicated a significant increase in Proteobacteria and a decrease in Fusobacteria in the intestines of infected fish compared to controls. Collectively, these findings demonstrate that A. hydrophila infection significantly alters gene and protein expression as well as intestinal microbiota in largemouth bass, providing insights into their immune defense mechanisms against infection.

A bacterial strain (No. 20230510) was isolated from the kidneys of diseased Siniperca chuatsi in Guangxi, China, since 2023. Artificial infection experiments demonstrated that this strain caused the observed disease in S. chuatsi. The isolate underwent morphological, pathological, genomic (whole-genome sequencing, WGS), and antibiotic susceptibility analyses. Infection trials revealed 100% mortality in high-concentration groups, with an LD50 of 3.89 × 104 CFU/mL, indicating high virulence. WGS results showed a circular chromosome of 8,123,106 bp (GC content: 68.14%), containing 7,638 CDSs, 72 tRNAs, and 12 rRNAs. Phylogenomic analysis revealed that strain 20230510 (CP130742) clusters with three N. seriolae strains with 98% bootstrap supporting, confirming its identification as N. seriolae. Further analysis identified 403 potential virulence genes linked to nutrient metabolism, regulatory factors, immune modulation, effector delivery systems, and exotoxins. Chromosomal comparisons also detected multiple antibiotic resistance genes. Susceptibility testing confirmed sensitivity to nine antibiotics, including enrofloxacin, doxycycline, florfenicol, and sulfamethoxazole. Histopathology revealed chronic granulomatous lesions, most severe in the kidneys, with similar but milder damage in the liver, spleen, gills, and intestines. These results confirm N. seriolae strain 20230510 as the pathogenic agent behind S. chuatsi mortality, offering key insights for developing control strategies.

Cadmium (Cd) is one of the main pollutants in the water environment, exhibiting bioaccumulation and toxicological effects on fish. In this study, dongtingking crucian carp (Carassius auratus indigentiaus) were exposed to 0 (control group), 0.1, 0.5 and 1.0 mg/L Cd for 30 days. The results showed that the liver body index and spleen body index increased gradually with increases in the Cd concentration, and morphological changes were observed in the spleen and liver. The level of accumulation of Cd in the tissues was as follows: gut > middle kidney > liver > spleen > gills > heart > brain > muscles. With increases in the concentration, the Cd enrichment concentration increased gradually in the spleen and middle kidney. Pathological features were observed in the intestines, gills, spleen and liver of C. auratus indigentiaus after 1.0 mg/L Cd exposure. The Lys content and the AKP, ACP, CAT, GSH-PX and SOD activities were significantly increased in the low concentration Cd exposure group (0.1 mg/L), and dramatically decreased in the high concentration Cd exposure group (1.0 mg/L). The expression levels of the IL-6 and IL-1 beta genes in the intestines, gills, spleen and liver, TNF-alpha gene expression in the gills, spleen and liver, IgM, IgZ and C3 genes expression in the liver decreased gradually with increases in the Cd concentration, while the expression of TNF-alpha gene in intestine, IgM, IgZ and C3 genes expression in intestine and gill increased with increasing Cd concentration. The expression of IgM, IgZ and C3 genes in the spleen were significantly increased in the 0.1 mg/L Cd exposure group, but significantly decreased in the 0.5 mg/L and 1.0 mg/L Cd exposure groups. These results indicate that low concentration of Cd (0.1 mg/L) might induce toxic excitability, but higher concentration of Cd (1.0 mg/L) inhibit the antioxidant and immune systems.

The escalating problem of copper (Cu) and cadmium (Cd) pollution in aquatic environments poses a significant threat to the ovarian tissue and reproductive capacity of fish, hindering the development of the aquaculture industry. However, the combined effects of Cu and Cd on fish gonadal development remain unclear. In this study, the fish species Nile tilapia was stressed with rearing water containing 300 μg/L Cu2+ and 100 μg/L Cd2+ for 30 days, followed by an intraperitoneal injection of luteinizing hormone-releasing hormone (LHRH-α) and human chorionic gonadotropin (HCG) at various concentrations. We investigated the ovarian transcriptome profiles before and after injection. Prior to injection, combined treatment with Cu and Cd resulted in reproductive dysfunction and metal ion imbalance in tilapia. Transcriptomic profiling revealed differential gene annotation concentrated in the MAPK signaling pathway and regulation of GTPase activity. Post-injection, all concentrations of LHRH-α and HCG groups showed an upregulated gonadosomatic index (G.S.I) and higher levels of vitellogenin (VTG), gonadotropin-releasing hormone (GnRH), gonadotropin (GTH), and estrogen (E2) in serum compared to the negative control group. Transcriptomic analysis revealed alterations in various ovarian signaling pathways, preliminarily revealing the in vivo molecular mechanisms and differences in LHRH-α and HCG. The findings from this study could help us better understand how to counteract the effects of combined Cu and Cd exposure on tilapia ovarian development, which has significant implications for the Nile tilapia aquaculture industry.

With the rapid development of industrialization and urbanization, the issue of copper (Cu) and cadmium (Cd) pollution in aquatic ecosystems has become increasingly severe, posing threats to the ovarian tissue and reproductive capacity of aquatic organisms. However, the combined effects of Cu and Cd on the ovarian development of fish and other aquatic species remain unclear. In this study, female Nile tilapia (Oreochromis niloticus) were individually or co-exposed to Cu and/or Cd in water. Ovarian and serum samples were collected at 15, 30, 60, 90, and 120 days, and the bioaccumulation, ovarian development, and hormone secretion were analyzed. Results showed that both single and combined exposure significantly reduced the gonadosomatic index and serum hormone levels, upregulated estrogen receptor (er) and progesterone receptor (pr) gene transcription levels, and markedly affected ovarian metabolite levels. Combined exposure led to more adverse effects than single exposure. The data demonstrate that the Cu and Cd exposure can impair ovarian function and structure, with more pronounced adverse effects under Cu and Cd co-exposure. The Cu and Cd affect the metabolic pathways of nucleotides and amino acids, leading to ovarian damage. This study highlights the importance of considering combined toxicant exposure in aquatic toxicology research and provides insights into the potential mechanisms underlying heavy metal-induced reproductive toxicity in fish.

Polymeric immunoglobulin receptor (pIgR) is an important immune factor in the mucosal immune system of fish, which plays a key role in mediating the secretion and transport of immunoglobulin into mucus. In this study, the full-length cDNA sequence of Megalobrama amblycephala pIgR gene was firstly cloned and the immune response to Aeromonas hydrophila was detected. After being challenged by Aeromonas hydrophila at 3 d, significantly pathological features were observed in intestine, head kidney, spleen, liver and gill of Megalobrama amblycephala. The content of lysozyme (Lys) and the activities of acid phosphatase (ACP) and alkaline phosphatase (AKP) increased significantly at 1 d and reached the peak at 3 d, and the activities of total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-PX) and catalase (CAT) in serum reached the peak at 5 d and 7 d after infection, respectively. The expression level of IL-1β gene reached the peak at 3 d in intestine, 5 d in gill and spleen, 7 d in head kidney and liver of Megalobrama amblycephala after infected by Aeromonas hydrophila, respectively. The TNF-α gene expression reached the peak at 3 d in intestine and gill, 5 d in head kidney and spleen, 7 d in liver after infection, respectively. The experimental results showed that the infection of Aeromonas hydrophila caused the pathological changes of immune-related tissues and triggered the inflammation responses. The full-length cDNA sequence of Megalobrama amblycephala pIgR was 1828 bp, and its open reading frame (ORF) was 1023 bp, encoding 340 amino acids. The pIgR of Megalobrama amblycephala has a signal peptide sequence, followed by extracellular region, transmembrane region and intracellular region. The extracellular region includes two Ig-like domains (ILDs), and its tertiary structure is twisted "L". The phylogenetic tree was constructed using the adjacency method, and the pIgR genes of Megalobrama amblycephala and cyprinidae fish were clustered into a single branch. Quantitative real-time PCR (qRT-PCR) was used to detect the expression of pIgR gene in different tissues of Megalobrama amblycephala. The expression level of pIgR gene was the highest in liver, followed by intestine, head kidney, skin, middle kidney and spleen, lower in heart, gill and brain, and the lowest in muscle. After being infected by Aeromonas hydrophila, the expression level of Megalobrama amblycephala pIgR gene in intestine, head kidney, spleen, liver and gill showed a trend of increasing first and then decreasing within 28 d. The pIgR gene expression reached the peak in mucosal immune-related tissues (gill and intestine) was earlier than that in systemic immune-related tissues (head kidney and spleen), and the relative expression level of pIgR gene at peak in intestine (12.3 fold) was higher than that in head kidney (3.73 fold) and spleen (7.84 fold). These results suggested that Megalobrama amblycephala pIgR might play an important role in the mucosal immune system to against Aeromonas hydrophila infection.

Complement (C) is a serum protein with immunity-related functions and enzymatic activities. It can induce inflammatory responses and antibody formation following activation by substances such as pathogens. Moreover, it is a crucial molecule in the congenital immune defense system. Complement manifests earlier than immunoglobulin in the evolutionary process of fish’s immune system. Therefore, the complement system of fish is vital for congenital and acquired immunities. A complement system is a polymolecule system comprising more than 30 soluble proteins, membrane-bound proteins, and complement receptors. It can be activated through three pathways for immunoregulation, the clearance of the immune complex, etc. The liver primarily produces the fish complement C3, which is a significant component of the complement system of fishes. C3 is the hub of three activation pathways. Research works concerning the structure, generation process, expression, and functions of C3 in fishes are reviewed in this study.

Immunoglobulin (Ig) is a type of globulin produced by B lymphocytes during pathogenic infection of vertebrates. It has immune functions and can realize specific recognition and neutralization of corresponding antigens. As IgM is reported first in fish, IgM is the first antibody produced during immune responses and plays a vital role in systemic and mucosal immune tissues. IgM molecules have two forms: membrane-bound IgM (mIgM) and secreted IgM (sIgM). The latter is produced by plasmacytes and secreted into body fluid, existing as immunological effect molecules. The former embeds into B cytomembrane and exists as an antigen receptor. It binds with assistant molecules to form cell receptor compounds. This study reviews research progress on the structures and production processes of IgM genes in different fish species and the distribution characteristics of IgM on B cells, mediated signal pathways, and functions. It aims to enrich basic theoretical knowledge of fish immunology and provide some scientific references for disease control in fishes.

Female tilapia of the Genetic Improvement of Farmed Tilapia (GIFT) strain were selected as an animal model to study the effects of four hormonal drugs in mitigating ovarian damage following exposure to copper and cadmium. After combined exposure to copper and cadmium in aqueous phase for 30 d, tilapia were randomly injected with oestradiol (E2), human chorionic gonadotropin (HCG), luteinizing hormone releasing hormone (LHRH), or coumestrol and raised in clear water for 7 d Ovarian samples were collected after combined exposure to heavy metals for 30 d and after recovery for 7 d Gonadosomatic index (GSI), copper and cadmium levels in the ovary, reproductive hormone levels in serum, and mRNA expression of key reproductive regulatory factors were determined. After 30 d of exposure to the combined copper and cadmium in aqueous phase, the Cd2+ content in tilapia ovarian tissue increased by 1,242.46% (p < 0.05), whereas the Cu2+ content, body weight, and GSI decreased by 68.48%, 34.46%, and 60.00% (p < 0.05), respectively. Additionally, E2 hormone levels in tilapia serum decreased by 17.55% (p < 0.05). After drug injection and recovery for 7 d, compared to the negative control group, the HCG group exhibited an increase of 39.57% (p < 0.05) in serum vitellogenin levels. Increases of 49.31%, 42.39%, and 45.91% (p < 0.05) in serum E2 levels were observed, and mRNA expression of 3β-HSD increased by 100.64%, 113.16%, and 81.53% (p < 0.05) in the HCG, LHRH, and E2 groups, respectively. The mRNA expression of CYP11A1 in tilapia ovaries increased by 282.26% and 255.08% (p < 0.05) and mRNA expression of 17β-HSD increased by 109.35% and 111.63% in the HCG and LHRH groups, respectively (p < 0.05). All four hormonal drugs, particularly HCG and LHRH, promoted the restoration of tilapia ovarian function to varying degrees after injury induced by combined exposure to copper and cadmium. This study presents the first hormonal treatment protocol for the mitigation of ovarian damage in fish exposed to combined aqueous phases of copper and cadmium as a strategy to prevent and treat fish ovarian damage induced by heavy metals.

为了探索一种安全、高效的罗非鱼养殖模式,减少病害发生,试验采用定期投喂EM菌的养殖模式,分析其对池塘水质以及罗非鱼的生长性能、血清抗氧化和非特异免疫指标的影响.结果表明,定期投喂EM菌,有助于增加池塘溶解氧(DO),降低氨氮(NH4+-N)和亚硝酸盐氮(NO2--N)浓度,维持较稳定的pH值;促进罗非鱼生长,提高成活率;提高总抗氧化能力(T-AOC),增强过氧化氢酶(CAT)、超氧化物歧化酶(SOD)和溶菌酶(LZM)的活力,降低丙二醛(MDA)含量.

[目的]分离鉴定双棘黄姑鱼(Protonibea diacanthus)源致病发光杆菌,为查明引起双棘黄姑鱼出现大批量死亡的病因及科学指导防控该病的规范用药提供参考依据.[方法]对从广西北海市铁山港网箱养殖发病双棘黄姑鱼肾脏中分离到的菌株(编号20210120)进行人工感染试验,确定其是否为双棘黄姑鱼致病菌;并对该菌株进行形态学观察、多基因(gapA、topA、mreB、ftsZ、gyrB和16S rRNA)序列分析及药敏试验.[结果]分离菌株与托鲁尼发光杆菌(Photobacterium toruni)16SrRNA序列在系统发育进化树上聚类为一支,其序列相似性达99.93％,与5个管家基因(gyrB、gapA、topA、ftsZ和mreB)序列的相似性分别为99.50％、99.86％、100.00％、99.83％和99.44％,因此确定菌株20210120为托鲁尼发光杆菌.人工感染双棘黄姑鱼病鱼出现与 自然发病相同的病症,且再次从其肾脏中分离到与 自然发病相同的细菌.药敏试验结果表明,菌株20210120对恩诺沙星、氧氟沙星、环丙沙星、复方新诺明、头孢氨苄、链霉素和庆大霉素7种药物敏感.结合农业农村部《水产养殖用药明白纸》文件中批准使用的药物目录,建议选用恩诺沙星对双棘黄姑鱼托鲁尼发光杆菌进行防治.[结论]托鲁尼发光杆菌是引起广西北海双棘黄姑鱼发病死亡的病原菌,实际生产中可考虑将恩诺沙星、氧氟沙星、环丙沙星、复方新诺明、头孢氨苄、链霉素和庆大霉素7种药物(尤其是恩诺沙星)作为托鲁尼发光杆菌引起双棘黄姑鱼相关疾病的防治用药.

鳗鲡是经济价值较高的鱼类,也是我国出口创汇最多的水产养殖品种之一.近几年来,养鳗界把鳗业发展目光投向广西,现在已经呈现出"东鳗西移"的趋势.至2021年广西已建设鳗鲡陆基养殖工厂26座,产量超6000t,2022年预计超过10000t.为进一步促进广西鳗鲡养殖业健康发展,并与广西国家战略储备资源——蔗糖产业融合,本团队开展了以水蚯蚓为饵料的美洲鳗鲡工厂化养殖试验,由甘蔗制糖副产品滤泥养殖水蚯蚓,为鳗鲡提供高质量饵料,以期促进"东鳗西移"及甘蔗产业链的延伸,推动广西现代农业高质量发展.

为探究乙醇假丝酵母(Candida ethanolica GXU01)在罗非鱼养殖中的益生潜能,为罗非鱼可持续养殖寻找生态友好的饲用添加菌,该研究将乙醇假丝酵母作为饲料添加菌饲喂尼罗罗非鱼(Oreochroms niloticus),通过测定罗非鱼的生长性能、肠道消化酶、血清非特异性免疫指标、肠道微生物群落结构以及用无乳链球菌(Strepto-coccus agalactiae)对罗非鱼进行攻毒试验,全面评价了乙醇假丝酵母对罗非鱼生长及其免疫力的影响.结果 表明,摄食乙醇假丝酵母可以使罗非鱼的生长性能、消化酶活性、血清溶菌酶活性和补体C3含量显著提高(P＜0.05).投喂乙醇假丝酵母后,罗非鱼肠道中梭杆菌门、鲸杆菌属(Cetobacterium)和艾克曼菌属(Akkermansia)等有益菌群的丰度显著上调,蓝细菌门大幅减少.攻毒试验中,摄食酵母饲料的罗非鱼成活率增加26.66％.研究表明乙醇假丝酵母对罗非鱼肠道消化能力和免疫抗病能力均有促进作用.