Qianrong Liang

Mandarin fish (Siniperca chuatsi) is a highly valued freshwater species in China, owing to its high-quality meat and economic importance. This study comparatively evaluated the effects of an industrialized recirculating aquaculture system (RAS) and traditional pond aquaculture system (TPAS) on the muscle quality and further explored the role of gut microbiota in muscle quality regulation. Our results showed that the RAS resulted in superior textural properties, with meat that was significantly more tender and elastic. The RAS also promoted higher muscle protein and reduced lipid levels. Notably, the RAS elevated sweet-tasting amino acids (Gly and Pro) while suppressing bitter amino acids (His). Electronic nose and GC-iMS analyses revealed distinct flavor compound profiles between the two systems, and the RAS enriched desirable volatiles (esters and alcohols) while suppressing aldehydes (e.g., nonanal and heptanal) associated with off-flavors. Gut microbiota profiling indicated higher diversity and enriched beneficial genera (e.g., Cetobacterium, Lactobacillus) in RAS-treated fish. We found that the Cetobacterium in the RAS group showed a significant positive correlation with sweet amino acids and pleasant flavor substances (such as esters, alcohols), while exhibiting a negative correlation with undesirable flavor precursors (such as certain aldehydes). This finding contributes to the sustainable and high-efficiency advancement of intensive Siniperca chuatsi aquaculture.

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.

In order to understand the immune response of largemouth bass against Micropterus salmoides Rhabdovirus (MSRV), assisting disease resistance breeding, three largemouth bass breeding varieties Micropterus salmoides “Youlu No 3” (U3), “Youlu No 1” (U1) and “Zhelu No 1” (P1) were challenged intraperitoneally with MSRV. Serum and tissues were sampled to study the changes in non-specific immune parameters, viral loads, and transcript levels of immune-related genes, and the cumulative mortality rate was recorded daily for 14 days. The results showed that the cumulative mortality rates in the U1, P1, and U3 groups were 6.66% ± 2.89%, 3.33% ± 2.89%, and 0, respectively. The higher mortality may attribute to the increased viral loads after infection in the liver (2.79 × 10⁵ and 2.38 × 10⁵ vs. 1.3 × 10⁴ copies/mg), spleen (2.14 × 10⁵ and 9.40 × 10⁴ vs. 4.21 × 10³ copies/mg), and kidney (3.59 × 10⁴ and 8.40 × 10³ vs. 2.42 × 10³ copies/mg) in the U1 and P1 groups compared to the U3 group. The serum non-specific immune parameters (lysozyme, catalase, and acid phosphatase) were found to be increased significantly in the U3 group. In addition, the transcripts of interferon-related genes (IFN-γ, IRF3, and IRF7) and pro-inflammatory-related genes (TNF-α and IL-1β) exhibited up-regulation and peaked at 6 h post infection in the U3 group, which also exhibited up-regulation but peaked at 12–24 h post infection in the U1 and P1 groups. In conclusion, these findings indicate that earlier activation of interferon and pro-inflammatory response is beneficial to largemouth bass against MSRV infection. This experiment may provide an insight into understanding the immune mechanism of largemouth bass against MSRV infection and contributes to molecular-assisted selection.

The Chinese soft-shelled turtle (Pelodiscus sinensis) is an important aquatic species in southern China that is threatened by many serious diseases. Edwardsiella tarda is one of the highly pathogenic bacteria that cause the white abdominal shell disease. Yet, little is known about the immune and metabolic responses of the Chinese soft-shelled turtle against E. tarda infection. In the paper, gene expression profiles in the turtle liver were obtained to study the immune responses and metabolic regulations induced by E. tarda infection using RNA sequencing. A total of 3908 differentially expressed unigenes between the experimental group and the control group were obtained by transcriptome analysis, among them, were the significantly upregulated unigenes and downregulated unigenes 2065 and 1922, respectively. Further annotation and analysis revealed that the DEGs were mainly enriched in complement and coagulation cascades, phagosome, and steroid hormone biosynthesis pathways, indicating that they were mainly associated with defense mechanisms in the turtle liver against E. tarda four days post infection. For the first time, we reported on the gene profile of anti-E. tarda response in the soft-shelled turtle, and our research might provide valuable data to support further study on anti-E. tarda defense mechanisms in turtles.