Search Results (56)

Siniperca chuatsi is an important high-quality freshwater aquaculture species in China. In nature, it feeds exclusively on live food. In this study, domesticated juvenile S. chuatsi were divided into three groups and fed live food (group L), compound feed (group C), or a mixed diet (group M) for three months to investigate the molecular mechanisms underlying adaptation to compound feed. Histopathological examination revealed that compound feed consumption induced looser liver cell arrangement, hepatocyte morphological irregularities, and vacuolization. A total of 1033 and 1428 differentially expressed genes (DEGs), and 187 and 184 differential metabolites (DMs), were identified in the C vs. L and C vs. M groups, respectively. Transcriptomic analysis revealed that the significantly and commonly enriched metabolic pathways shared by both comparison groups were predominantly involved in amino acid, carbohydrate, and lipid metabolisms. Metabolomic analysis demonstrated that the significantly and commonly enriched metabolic pathways shared by both comparison groups were the arachidonic acid metabolism, linoleic acid metabolism, oxidative phosphorylation, and PPAR signalling pathways. Integrated omics analysis showed that the PPAR signalling pathway was the only significantly co-enriched pathway across both omics datasets. This study provides new insights into the molecular mechanisms of compound feed adaptation and provides theoretical support for selecting feed traits in S. chuatsi. Full article

A 56-day trial was conducted to assess the effects of rice straw (RS) and bamboo flour (BF) on growth performance, water quality, gill histology, and the bacterial community of water and the intestine of mandarin fish (Siniperca chuatsi) in biofloc technology systems. The results showed that mandarin fish in the RS and BF groups had comparable survival rates of 100.00 ± 0.00 and 93.33 ± 3.85%; feed conversion ratios of 1.13 ± 0.02 and 1.40 ± 0.15; and weight gain rates of 112.21 ± 1.56 and 100.92 ± 6.45%, respectively. From days 11 to 56 of the farming period, the BF group was more effective than the RS group in removing total ammonia nitrogen (TAN) and NO₂⁻-N, maintaining TAN levels below 0.24 ± 0.05 mg/L. During the early stage of the experiment, the TAN level in the RS group was higher; however, with the supplementation of a carbon source, it gradually decreased and eventually stabilized at 0.13 ± 0.03 mg/L later in the farming period. The secondary gill lamella in the RS group was curved and showed hyperplasia, and the basal gill lamellae showed an increase in the volume of interlamellar cell mass in the BF group. Genes related to denitrification (narG, napA, nirS, nirK, and nosZ) and anammox showed higher expression levels in the BF group than in the RS group, although the differences were not statistically significant (p > 0.05). The results of 16S rRNA sequencing research showed that both treatment groups’ intestinal and water bacterial communities had comparable levels of richness and diversity. Pseudomonas mosselii was the dominant bacterial species in the water. In the BF group, the dominant intestinal species were Bacillus halodurans and Caldalkalibacillus thermarum, while in the RS group, the dominant species was Plesiomonas shigelloides. In conclusion, rice straw and bamboo flour are applicable in BFT systems for mandarin fish culture, with good growth performance and water quality. The BF group showed higher nitrogen removal efficiency and denitrification gene expression than the RS group. Full article

Mandarin fish (Siniperca chuatsi) are known to exhibit distinct physiological and immunological adaptations to environmental stressors, but the underlying molecular and microbial mechanisms remain unclear. In this study, we integrated transcriptome and microbiome analyses to investigate adaptations across three geographically distinct mandarin fish groups: Guangdong (G), Qiupu (Q), and native Taihu (T). Liver RNA sequencing revealed 5339 differentially expressed genes (DEGs) between T and G and 1531 DEGs between T and Q. Functional enrichment analysis revealed group-specific responses. Specifically, DEGs from T vs. G were linked to small-molecule metabolism and innate immunity whereas the DEGs from T vs. Q were related to immune regulation and chromatin organization. The concurrent 16S rRNA sequencing of the intestinal microbiota identified 2680 amplicon sequence variants, with principal coordinate analysis showing distinct clustering (31.77% variance). Group T had higher Firmicutes abundance whereas groups G and Q had a higher relative abundance of Fusobacteriota. Correlation networks revealed key microbe–gene interactions, including positive links between Lactobacillus and immune genes in group T and negative associations with Romboutsia. These findings suggest that enhanced immune homeostasis and metabolic flexibility in group T may result from coordinated host gene expression and Lactobacillus-driven microbiome modulation. We provide new insights into the mechanisms of adaptation in mandarin fish and identify potential biomarkers for enhancing aquaculture resilience. Full article

Mandarin fish (Siniperca chuatsi), golden mandarin fish (Siniperca scherzeri), and Coreoperca whiteheadi are three important aquaculture species in China facing several threats to their production. Genetic diversity was assessed by sequencing the mitochondrial D-loop and cox1 regions in 207 individuals across nine populations. The genetic diversity analysis, based on the concatenated sequences, revealed that the total haplotype diversity was high across all sinipercine fish populations. Population differentiation analysis revealed that most genetic variation was within populations: 74.5% in S. chuatsi (p < 0.001) and 83.0% in S. scherzeri (p < 0.001). All five S. chuatsi populations showed moderate and significant genetic differentiation, and moderate genetic differentiation was observed between the Beijiang and Wujiang populations in S. scherzeri. Phylogenetic and nested clade analysis indicated that artificially bred and wild S. chuatsi populations shared haplotypes, and close phylogenetic relationships were observed between the Beijiang and Dongjiang populations in S. scherzeri. These findings could be useful for the conservation management, artificial breeding, and hybridization of these three sinipercine fish species. Full article

Background: Birnaviruses infect a wide range of aquatic and terrestrial hosts, including several economically important fish species. This study aimed to isolate and characterize a novel birnavirus strain from mandarin fish (Siniperca chuatsi), a high-value freshwater species in Chinese aquaculture. Methods: A novel strain, designated mandarin fish birnavirus (MFBV), was isolated from diseased fish and propagated in SCK cells. The complete genome was determined using high-throughput sequencing and RACE. Viral replication kinetics, tissue distribution, and pathogenicity were assessed through in vitro infection, RT-qPCR, histopathology, and experimental challenges. In addition, disinfectant sensitivity and environmental stability were evaluated. Results: The MFBV genome comprises two segments (A: 3539 bp; B: 2719 bp), and phylogenetic analysis revealed close relatedness to largemouth bass birnavirus (LBBV) and Lates calcarifer birnavirus (LCBV). MFBV displayed rapid replication in SCK cells, completing a replication cycle in 8–10 h. In juvenile and fry fish, an experimental infection caused acute disease with cumulative mortality ranging from 41.8% to 83.6%, with fry showing higher susceptibility. Viral RNA was detected in multiple tissues (7.9 × 10⁶–7.9 × 10⁷ copies/μg RNA), and histopathological lesions were observed in the intestine, spleen, and kidney. MFBV was highly sensitive to glutaraldehyde (20 ppm), while other disinfectants showed reduced efficacy. Viral half-life ranged from 36.5 to 144.5 h at room temperature. Conclusions: These findings demonstrate that MFBV can induce acute systemic infection in mandarin fish. The results offer new insights into the genomic and biological features of birnaviruses, contributing to improved disease management and viral taxonomy. Full article

Scale drop disease virus (SDDV) poses an escalating threat to global aquaculture, prompting an urgent need for research. Our study found that SDDV infection upregulates genes related to iron, oxidative stress, and lipid metabolism, causing iron overload, reactive oxygen species (ROS) accumulation, and ultimately ferroptosis. Among the tested antioxidants, vitamin C (VC) demonstrated the most potent inhibitory effect in mandarin fish, reducing SDDV-induced mortality by 37.5%. qPCR and IFA results showed that VC effectively suppressed SDDV infection; decreased ROS, lipid peroxidation (LPO), and iron levels; and enhanced glutathione peroxidase 4 (GPX4) expression in infected cells. Mechanistically, VC’s inhibitory effect was reversed by the nuclear factor erythroid 2-related factor 2 (Nrf2) inhibitor ML-385, indicating an Nrf2-dependent pathway. VC promoted Nrf2 nuclear translocation and activated downstream antioxidant genes. Moreover, VC modulated inflammation by regulating pro- and anti-inflammatory factors. These findings suggest VC as a promising therapeutic for SDDV infection. Full article

The objective of this research was to prepare robust edible films possessing antioxidant properties by utilizing konjac glucomannan (KGM), sodium alginate (SA), and epigallocatechin gallate (EGCG). This research also involved structural characterization and the assessment of functional attributes of the composite films with varying EGCG concentrations. It was found that the inclusion of EGCG reduced the viscosity of the edible film solutions while enhancing their mechanical strength. Fourier transform infrared spectroscopy demonstrated adequate compatibility among the film-forming materials, with EGCG forming hydrogen bond interactions with KGM and SA. SEM analysis revealed that increasing EGCG concentration led to the formation of discontinuous blocks and rough surfaces, with smooth and fine-grained particles observed at 0.2% (w/v) EGCG concentration. Furthermore, results from the application of the KGM-SA-based films in chilled mandarin fish showed that they could exert antioxidant function when incorporated with EGCG. The values of TVB-N and TBARS of fish pieces were obviously decreased in the 12-day storage period, indicating their potential to increase the shelf life of freshwater fish food. Full article

Microorganisms play a key role in fish spoilage and quality deterioration, making the development of a rapid, accurate, and efficient technique for detecting surface microbes essential for enhancing freshness and ensuring the safety of mandarin fish consumption. This study focused on the total viable count (TVC) and Escherichia coli levels in the dorsal and ventral parts of fish, and we constructed a detection model using hyperspectral imaging and data fusion. The results showed that comprehensive and simplified models were successfully developed for quantitative detection across all wavelengths. The models performed best at predicting microbial growth on the dorsal side, with the RAW-CARS-PLSR model proving the most effective at predicting TVC and E. coli counts in that region. The RAW-PLSR model was identified as the optimal predictor of the E. coli concentration on the ventral side. A fusion model in the decision layer constructed using the Dempster–Shafer theory of evidence outperformed models relying solely on spectral or textural information, making it an optimal approach for detecting surface microbes in mandarin fish. The best prediction accuracy for dorsal TVC concentration achieved an Rp value of 0.9337, whereas that for ventral TVC concentration reached 0.8443. For the E. coli concentration, the optimal R_p values were 0.8180 for the dorsal section and 0.8512 for separate analysis. Full article

Two typical fish products—fermented mandarin fish and semi-dried yellow croaker—are associated with biogenic amines (BAs), which are harmful to human health. The objective of this study was to investigate the bacterial ecology of the two fish products and to determine their capacity for producing BAs. Putrescine and cadaverine were major BAs detected in the fish products. Concentrations of BAs were significantly corrected with microbial count (p < 0.05). BA-producing isolates (33) in the two fish products were all multiple BA producers. Several of them, including Lactobacillus sakei, Bacillus cereus and Hafnia alvei isolated from fermented mandarin fish, as well as Shewanella baltica, Aeromonas veronii, and Photobacterium phosphoreum isolated from semi-dried yellow croaker, showed remarkable BA-producing capacity. Hafnia alvei produced the greatest abundance of putrescine, cadaverine, tyramine and 2-phenylethylamine. Lactobacillus sakei mainly produced tryptamine and putrescine. Photobacterium phosphoreum showed the strongest histamine-producing capacity. Full article

Bacterial sepsis caused by Aeromonas hydrophila (A. hydrophila) and infectious spleen and kidney necrosis virus disease (ISKNVD) caused by infectious spleen and kidney necrosis virus (ISKNV) frequently result in significant mortality among Chinese perch (Siniperca chuatsi). Co-infection of mandarin fish with A. hydrophila and ISKNV occurs from time to time. In this study, a visual detection method for ISKNV and A. hydrophila was developed, using loop-mediated isothermal amplification (LAMP) and pre-addition of hydroxynaphthol blue. Primers for amplifying LAMP in the same system were designed based on the conserved regions of the MCP gene of infectious spleen and kidney necrosis virus, as well as the hlyA gene of A. hydrophila. The results showed that this method amplified bright trapezoidal bands in the presence of only A. hydrophila or ISKNV and both, with sky blue for positive amplification and violet for negative amplification. There was no cross-reactivity with other pathogens, and fragments of 182 bp, 171 bp and 163 bp appeared after digestion of the A. hydrophila LAMP product and 136 bp, 117 bp and 96 bp appeared after digestion of the ISKNV LAMP product. This holds true even when both positive products are present simultaneously. The minimum detection limit of this method was 100 fg for A. hydrophila and 100 fg for ISKNV, and the minimum detection limit for the mixed template was 1 pg. Overall, this method has high sensitivity and specificity to rapidly detect and distinguish between the two pathogens. Full article

A number of viral diseases have significantly impeded the growth of the aquaculture industry. Antiviral drugs represent an effective means of controlling infection. However, the efficacy of the entire therapeutic process is contingent upon the availability of an efficient delivery system. This study selected three common antiviral drugs and constructed corresponding drug delivery systems utilising single-walled carbon nanotubes (SWCNTs) as carriers. The reliability of carbon nanotubes as delivery carriers was evaluated by detecting the therapeutic effect on infectious splenic and renal necrosis virus (ISKNV). The findings demonstrated that SWCNTs can effectively enhance the absorption of the three drugs into the body, prolong their metabolic half-life, and improve the survival rate of fish infected with ISKNV. The Ribavirin-SWCNTs (RBV-SWCNTs) group exhibited the most pronounced protective effect, with a mortality rate of less than 25%. It was observed that SWCNTs facilitated the rapid transportation of ribavirin, with the drug content in the RBV-SWCNTs group being approximately double that of the free ribavirin group. Furthermore, this system markedly diminished the viral load, augmented enzyme activities, and elevated antiviral gene expression. This study indicated that carbon nanotubes are optimal carriers for antiviral drugs, which have considerable potential as a delivery vehicle for antiviral drugs to prevent viral infections in aquaculture. Full article

Fish meal (FM) replacement is essential for sustainable aquaculture development. This study investigated the effects of FM replacement with poultry by-product meal (PBM) on growth performance, hepatic and intestinal health and ammonia nitrogen stress resistance in mandarin fish (Siniperca chuatsi). A 52-day feeding trial was conducted using PBM to replace fish meal at levels of 0%, 17.5%, 35.0%, 52.5% and 70.0%. The results showed that FM replacement with PBM did not influence growth performance in mandarin fish. Moderate PBM replacement (≤35.0%) did not harm liver health and enhanced the intestinal structure. However, excessive replacement (≥52.5%) caused hepatocyte damage, reduced antioxidant capacity and decreased survival under ammonia nitrogen stress. Notably, 70% PBM replacement led to severe hepatic lipid accumulation, inhibiting fatty acid β-oxidation and triglyceride hydrolysis pathways. Furthermore, high PBM levels (≥52.5%) also reduced intestinal muscularis thickness, downregulated tight junction proteins and induced inflammation. In conclusion, while PBM replacement does not hinder growth, maintaining levels below 35.0% (PBM ≤ 28.5%) is essential for preserving hepatic lipid metabolism, intestinal health and antioxidant defense in mandarin fish. Full article

This study evaluated the habitat coloration preferences of Siniperca chuatsi and Cirrhinus molitorella in both solitary (n = 1) and group (n = 3) settings across six colors. The results indicated that both individual and group S. chuatsi spent the majority of their time in and made frequent visits to the black area, followed by the blue area. While individual C. molitorella spent the majority of their time and visits in the blue region, groups showed a preference for the blue and white regions. These findings highlight the distinct habitat coloration preferences of S. chuatsi and C. molitorella in different group states, suggesting that habitat coloration has an important effect on fish behavior and environmental adaptation. From a behavioral ecology perspective, these preferences may be closely related to the survival strategies of fish. Notably, C. molitorella’s strong preference for blue and white backgrounds may reflect anti-predator behavior, helping C. molitorella avoid predators, such as S. chuatsi, in natural environments, thereby improving its chances of survival. This study provides a scientific basis for optimizing aquaculture environments, emphasizing the importance of considering habitat coloration and substrate type in designing environments to enhance fish welfare. Full article

The ORA (olfactory receptor class A) gene family in teleosts is related to the V1R (vomeronasal 1 receptors) family in mammals and plays a key role in odor detection. Although ORA genes have been identified in several teleosts, their characteristics in mandarin fish (Siniperca chuatsi) have not been explored. In this study, we conducted a comprehensive genomic analysis of the mandarin fish and discovered a complete ORA gene family consisting of five members located on chromosome 2 (ORA1, ORA2, ORA3, ORA4) and chromosome 16 (ORA6). Phylogenetic, synteny, and gene structure analyses revealed typical exon–intron conservation with strong evidence of purifying selection. Tissue expression analysis showed distinct expression profiles for each ORA gene, with some showing sexual dimorphism in specific tissues. The expression of ORA1 and ORA2 in the olfactory epithelium exhibits sexual dimorphism, while ORA3 shows sexual dimorphism in the brain. In situ hybridization confirmed that ORA1, ORA2, ORA3, and ORA6 are expressed in the microvillar sensory neurons of the olfactory epithelium, while ORA4 is expressed in crypt cells. Additionally, molecular docking simulations indicated that the five ORA proteins have a high binding affinity with seven bile acids (LAC, GLAC, CA, TLCA, 3-KLCA, 7-KLCA, and 12-KLCA), with ORAs showing stronger binding affinity with LCA and CA. This study comprehensively characterizes the ORA gene family in mandarin fish, examining its phylogeny, synteny, gene structure, and selection pressure. Furthermore, we found that each ORA displays a distinct expression pattern across multiple tissues, with notable sexual dimorphism, and shows potential binding interactions with specific bile acids and pheromones. Our findings provide valuable insights that enhance the overall understanding of fish ORAs and their potential functions. Full article

Microorganisms, including bacteria, fungi, and protists, are key drivers in aquatic ecosystems, maintaining ecological balance and normal material circulation, playing vital roles in ecosystem functions and biogeochemical processes. To evaluate the environmental impact of different river crab polyculture practices, we set up two different river crab (Eriocheir sinensis) polyculture practices: one where river crabs were cultured with mandarin fish (Siniperca chuatsi), silver carp (Hypophthalmichthys molitrix), and freshwater fish stone moroko (Pseudorasbora parva), and another where river crabs were cultured just with mandarin fish and silver carp. These two polyculture practices were referred to as PC and MC, respectively. We analyzed the water bacterial, fungal, and protist communities in the PC and MC groups using 16S, ITS, and 18S ribosomal RNA high-throughput sequencing. We found that the PC group obviously increased the diversity of microbial communities and altered their composition. The bacterial community held the narrowest habitat niche and exhibited the weakest environmental adaption compared to fungal and protist communities. The PC group altered the co-occurrence networks of bacteria, fungi, and protist, leading to more complex and stable communities of fungi and protist. Furthermore, the PC group shifted the assembly mechanism of the bacterial community from being predominantly deterministic to predominantly stochastic processes, with relatively minor impacts on the fungal and protist communities. Environmental factors, especially dissolved oxygen (DO), were significantly associated with the communities of bacteria, fungi, and protists, with DO being the major contributor to changes in the microbial communities. Our results suggest that the polyculture of river crab with mandarin fish, silver carp, and stone moroko was an effective and viable attempt, and it was superior in terms of microbial community diversity and stability. Full article