Yan Cai

为明确多纹钱蝶鱼烂身病的病原，从患病鱼体表病灶与内脏组织中分离获得一株优势菌，编号为5-2。通过形态观察、生理生化鉴定及16S rRNA基因序列分析对菌株进行鉴定；采用人工回归感染实验和7 d半数致死浓度测定评估其致病性。同时，通过不同攻毒途径探究其感染特性，进行药物敏感性试验。结果表明：分离菌株5-2为革兰氏阴性菌，菌体呈弧状和杆状等多种形态。经系统鉴定，该菌为哈维氏弧菌（Vibrio harveyi）。人工回归感染实验中，受试鱼出现突眼、体表溃烂、烂尾、肝肿大和脾充血等症状，与自然发病鱼症状一致；7 d半数致死浓度测定显示，菌株5-2对多纹钱蝶鱼的7 d半数致死浓度为5×10⁶ CFU·mL^－1。不同感染途径中，腹腔注射、肌内注射和高密度浸泡组受试鱼累计死亡率显著高于其他途径。药物敏感性试验显示，菌株5-2对多西环素、复方新诺明和氟苯尼考等8种抗菌药物敏感，对卡那霉素、头孢氨苄、头孢拉定和头孢呱酮等4种药物耐药。研究证实了哈维氏弧菌可感染多纹钱蝶鱼并引起烂身病，其结果可为该病的防控提供理论依据。

Lactobacillus plantarum 58 (lactic acid bacteria [LAB] 58), isolated from vinegar dregs, was incorporated at 1 × 10 ⁸ CFU/g diet into the feeds of hybrid groupers to assess its lipid‐lowering efficacy under normal (7.52 % lipid) or high‐fat (14.83 % lipid) regimens. A 2 × 2 factorial design generated four diets: C (normal), H (high‐fat), C58 (normal + LAB 58), and H58 (high‐fat + LAB 58). Serum biochemical parameters tests, histological section, and Oil Red O staining results indicated that in both LAB 58‐supplemented groups (C58 and H58), serum triglycerides and total cholesterol (T‐CHO) declined regardless of basal lipid content, and hepatic fat vacuolation and lipid‐droplet accumulation were markedly curtailed. The qPCR data revealed that LAB 58 elevated the levels of hepatic lipolysis genes (adipose triglyceride lipase [ATGL], carnitine palmitoyltransferase 1 [CPT‐1], farnesoid X receptor [FXR], and lipoprotein lipase [LPL]) while simultaneously suppressing lipid synthesis gene expressions (fatty acid synthase [FAS] and stearoyl‐CoA desaturase 1 [SCD‐1]) in the H58 group compared with the H group. Gut‐microbiota profiling showed a pronounced Firmicutes‐to‐Bacteroidetes shift, driven by increased Bacteroides, Faecalibacterium, and Lachnospiraceae‐UCG‐004; the relative abundance of Lactobacillus spp. surged, especially in the H58 group. Metabolomic analysis of intestinal contents further disclosed elevated levels of beneficial fatty acids—linoleic and α‐linolenic acids in H58 group. In conclusion, these findings demonstrate that LAB 58 alleviates lipid metabolic disorders by modulating hepatic gene expression, restructuring the gut microbiota, and enhancing beneficial metabolites.

本研究系统评估了丁香酚、芳樟醇和MS-222三种麻醉剂对点带石斑鱼（Epinephelus coioides）幼鱼的麻醉效果及生理影响。结果表明麻醉剂浓度与麻醉诱导时间呈负相关，深度麻醉会延长复苏时长。以维持幼鱼深度镇静的浓度（5 mg/L 丁香酚、18 mg/L 芳樟醇、30 mg/L MS-222）开展运输试验，麻醉运输18 h后，丁香酚组幼鱼复苏72 h存活率仅10.34%，其余组存活率均达100%。MS-222可通过抑制肌肉乳酸积累、减缓糖原消耗维持能量代谢稳定，且能降低肝脏超氧化物歧化酶（SOD）活性、缓解氧化应激，对机体抗氧化系统干扰较小。三种麻醉剂均未造成肝脏脂质过氧化损伤；但丁香酚与芳樟醇易引发鱼体无氧代谢应激，表现为肌肉乳酸含量显著升高。研究结果为点带石斑鱼幼鱼的麻醉运输优化及后续研究提供了科学参考。

This study aims to investigate the response of surface bacterial communities in Trachinotus ovatus to Cryptocaryon irritans infection at different stages of a single infection cycle (0~168 h). These samples were analyzed using high-throughput 16S rRNA sequencing. Alpha diversity analysis showed a reduction in the richness and diversity of skin microbiota during infection, with partial recovery post-detachment. Beta diversity analysis revealed distinct structural shifts in skin microbiota at early (24 h) and post-detachment (168 h) stages compared to other phases, while gill microbiota remained stable except during detachment. At the phylum level, Proteobacteria, Actinobacteriota, Bacteroidetes, and Firmicutes were dominant on the skin at different stages, whereas the gill microbiota was predominantly Proteobacteria (>90%). At the genus level, opportunistic pathogens, such as Vibrio and Nautella, increased in relative abundance on the skin with the infection progression, while gill microbiota composition barely changed. The hepatic bacterial load continued to increase with infection duration. These findings indicate that C. irritans alters microbiota composition on skin, facilitating pathogen invasion, thereby elevating the risk of secondary bacterial infections in T. ovatus.

During a suspension of a GIFT tilapia broodstock recirculating aquaculture system (RAS), a significant fish mortality event occurred. To determine the cause, four bacterial strains were isolated from affected fish and identified as Vibrio vulnificus through 16S rDNA sequencing. Virulence assays confirmed the pathogenicity of these strains, with the most virulent, CS-4, selected for a further analysis. Antimicrobial testing revealed CS-4’s sensitivity to 19 antibiotics, including meloxicillin and Gentamicin. Challenge tests indicated varied 7-day Lethal Dose 50 (LD₅₀) values for CS-4 depending on the infection route, with immersion after skin injury being the most lethal. Additionally, the effects of salinity, crowding with air exposure, and nitrite on tilapia mortality were evaluated. The results showed that salinity stress increased the mortality rate of tilapia infected with V. vulnificus through immersion, and that salinity stress and V. vulnificus infection had a synergistic effect. A 20 min crowding with air exposure stress reduced the mortality rate of Nile tilapia infected with V. vulnificus. Nitrite stress had little effect on the mortality rate of tilapia infected with V. vulnificus. The results of the risk factor analysis indicated that salinity was the main factor affecting tilapia mortality caused by V. vulnificus infection. This study will serve as a valuable reference for the future management of similar RAS.

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.

In the realm of modern aquaculture, the utilization of probiotics has gained prominence, primarily due to their ability to enhance growth, boost immunity, and prevent diseases in aquatic species. This study primarily investigates the efficacy of Bacillus subtilis strains, both host-derived and from other sources, in influencing fish growth, immunity, lipid metabolism, and disease resistance. Employing a 42-day feeding trial, we divided hybrid grouper into four distinct groups: a control group on a basal diet and three experimental groups supplemented with 1 × 10⁸ CFU/g of different Bacillus subtilis strains-BS, 6-3-1, and HAINUP40. Remarkably, the study demonstrated that the 6-3-1 and HAINUP40 groups exhibited significant enhancements across key growth parameters: final body weight (FBW), weight gain rate (WGR), feed intake (FI), feed efficiency ratio (FER), and feed conversion ratio (FCR). The investigation into lipid metabolism revealed that the 6-3-1 strain upregulated seven metabolism-related genes, HAINUP40 affected four metabolism-related genes, and the BS strain influenced two metabolism-related genes, indicating diverse metabolic impacts by different strains. Further, a notable reduction in liver enzymes AST and ALT was observed across all supplemented groups, implying improved liver health. Noteworthy was the BS strain’s superior antioxidative capabilities, positively affecting all four measured parameters (CAT, GSH-Px, MDA). In the sphere of immune-related gene expression, the BS strain significantly decreased the expression of both inflammation and apoptosis-related genes, whereas the HAINUP40 strain demonstrated an upregulation in these genes. The challenge test results were particularly telling, showcasing improved survival rates against Vibrio harveyi infection in the BS and 6-3-1 groups, unlike the HAINUP40 group. These outcomes highlight the strain-specific nature of probiotics and their varying mechanisms of action within the host. In conclusion, this study reveals that probiotic strains, varying by source, demonstrate unique, strain-specific effects in promoting growth and modulating immunity in hybrid grouper. This research highlights the promise of tailored probiotic applications in improving aquaculture practices. Such advancements contribute to more sustainable and efficient fish farming methods.

In the dynamic field of intensive aquaculture, the strategic application of probiotics has become increasingly crucial, particularly for enhancing resistance to environmental stressors such as ammonia-nitrogen. Over a 42-day period, this study investigated the effects of different probiotic strains—Bacillus subtilis (BS, 6-3-1, and HAINUP40)—on the health and resilience of hybrid groupers. Each strain, distinct in its origin, was assessed for its influence on growth performance, antioxidant capacity, immune gene expressions, and ammonia-nitrogen stress response in the hybrid grouper. The experimental design included a control group and three experimental groups, each supplemented with 1 × 10⁸ CFU/g of the respective probiotic strains, respectively. Our results demonstrated notable differences in growth parameters, including final body weight (FBW) and feed conversion ratio (FCR). The 6-3-1 strain, originating from grouper, exhibited significant improvements in growth, oxidative capacity, and intestinal health. Conversely, the BS strain achieved the highest survival rates under ammonia-nitrogen stress, indicating its superior ability to regulate inflammatory responses despite its less pronounced growth-promoting effects. The HAINUP40 strain was distinguished for its growth enhancement and improvements in intestinal health, though it also showed significant activation of inflammatory genes and decreased resistance to ammonia-nitrogen stress after extended feeding. The uniqueness of this study lies in its detailed examination of the strain-specific effects of probiotics on fish in the context of ammonia-nitrogen stress, a significant challenge in contemporary aquaculture. The research revealed that host-derived probiotics, particularly the 6-3-1 strain, provided more comprehensive benefits for growth performance and stress resilience. In contrast, the BS and HAINUP40 strains exhibited varying efficiencies, with BS excelling in stress resistance and HAINUP40 promoting growth and gut health. In conclusion, this study underscores the complex roles of different probiotic strains in aquaculture, contributing to the understanding of probiotic applications and presenting new approaches to address the challenges of intensive farming.

The tiger grouper (Epinephelus fuscoguttatus), an important mariculture fish in Southeast Asia, faces increasing health issues in recent years. Phellodendri Cortex (PC) is a traditional Chinese herbal medicine that exhibits a variety of beneficial effects on tiger groupers. The effects of PC, however, varies with the period of dietary intervention. This study aims to investigate the long-term effects of 1% PC supplementation on tiger groupers, focusing on growth, immunity, disease resistance, and intestinal gene expression. The tiger groupers (with an initial mean weight of 27.5 ± 0.5 g) were fed with a diet of Phellodendri Cortex supplementation and a control diet for 8 weeks. Our results indicate that the long-term PC supplementation did not affect growth or Vibrio disease resistance in tiger groupers. However, the transcriptome analysis revealed potential damage to the structural and functional integrity of the groupers’ intestines. On the other hand, anti-inflammatory and cathepsin inhibition effects were also observed, offering potential benefits to fish enteritis prevention and therapy. Therefore, long-term PC supplementation in grouper culture should be applied with caution.