Yuhong Yang

Global freshwater salinization endangers aquatic species, yet its impacts on crustaceans remain poorly understood. This study investigated the hepatopancreatic response of Eriocheir sinensis to carbonate alkalinity stress (0, 4.375, 8.75, 17.5, and 35 mmol/L) over 24, 48, and 96 h, integrating histology, ultrastructure, gene expression (RT-qPCR), and non-specific immune enzyme assays. Histopathological and ultrastructural analyses revealed concentration- and time-dependent damage, including vacuolization, hepatic tubule disintegration, nuclear condensation, mitochondrial reduction, and loss of cellular integrity. Molecular analysis demonstrated upregulation of genes associated with the TLR2-MyD88-NF-κB pathway and inflammatory genes (LITAF, IL-16), alongside increased HSP70 expression, confirming severe inflammation and cellular stress. Furthermore, apoptosis was induced via upregulated Bax and Caspase-3, downregulated Bcl-2, and DNA fragmentation. Non-specific immune responses in the hepatopancreas exhibited dynamic changes: acid phosphatase (ACP) was initially activated at low alkalinity but inhibited at high concentrations, while alkaline phosphatase (AKP) activity increased at 96 h. Notably, the hepatopancreas proved more sensitive to this stress than the hemolymph. Collectively, carbonate alkalinity causes multidimensional hepatopancreatic injury in E. sinensis through structural disruption, inflammation mediated by TLR2-MyD88-NF-κB signaling pathway-related genes, apoptosis induction, and immune enzyme dysregulation, posing a significant threat to crab health in salinized waters.

Rice–crab coculture, as China’s third-largest integrated farming model, is pivotal for sustainable Chinese mitten crab aquaculture. This study conducted untargeted metabolomics and 16S rRNA gene sequencing on gut contents of crabs from rice fields and ponds, integrating metabolic and microbial profiles. We aimed to reveal the chemical traits of rice-field Chinese mitten crab linked to gut microbiota, providing scientific guidance for optimizing culture practices and developing microbial additives. Both groups were dominated by the phyla Firmicutes, Proteobacteria, and Bacteroidota, but the phylum Bdellovibrionota was not detected in group R. A total of 1271 distinct amplicon sequence variants (ASVs) were identified, which were annotated to 649 genera. At the ASV level, the Chao1 index for the R group (197.12 ± 17.88) was notably lower compared to the P group (288.75 ± 30.59) (p < 0.01). In contrast, the Shannon index for the R group (3.90 ± 0.06) was significantly greater than that of the P group (3.70 ± 0.06) (p < 0.01). The PCA plot demonstrated a distinct discrimination between the groups. The P group had more microbial species but was dominated by Candidatus_Bacilloplasma, resulting in uneven distribution. In contrast, the R group had fewer species but a more balanced distribution. Among 3531 metabolites identified in both groups, 865 differed significantly. Compared to P, 736 metabolites were significantly upregulated and 129 were significantly downregulated in R. Key metabolic pathways included amino acid, carbohydrate, cofactor and vitamin metabolism, signaling, and xenobiotics biodegradation. Group R had higher levels of L-leucine, L-phenylalanine, L-tyrosine, 2-amino-1-phenylethanol, choline, and pyrophaeophorbide a, which correlated with genera like Candidatus_Hepatoplasma and Aeromonas (p < 0.05), suggesting better nutritional value, flavor, and metabolic health in rice-field crabs.

This study aimed to assess the impact of incorporating rapeseed meal (RM) as a partial substitute for fish meal (FM) in the diet of cultured hybrid sturgeon ( Acipenser schrenckii ♀ × Acipenser baerii ♂). A total of 450 juvenile hybrid sturgeon with similar weights were randomly assigned to five dietary groups, each with triplicates of 30 fish per tank. For 12 weeks, FM was replaced with varying percentages of RM (0%, 25%, 50%, 75%, and 100%). Results indicated a decreasing trend in final body weight (FBW), weight gain, and survival rates (SRs) as the ratio of RM increased. Growth performance was less affected when the substitution ratio of FM was below 50%. The replacement of FM with RM showed a decreasing trend in crude protein and ash content of sturgeon body composition and no significant effect on moisture and crude lipid content ( p > 0.05). Essential amino acids (EAAs) in whole fish, such as methionine (Met), threonine (Thr), and lysine (Lys), increased with higher substitution rates ( p > 0.05). The lysozyme (LZM) activities in the pyloric cecum, duodenum, and valve intestine of the sturgeon showed a decreasing trend ( p > 0.05). Nevertheless, at a 50% substitution level, sturgeon liver superoxide dismutase (SOD) and malondialdehyde (MDA) activities reached their peak. At 100% substitution, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were significantly higher than in other groups ( p < 0.05). At 50% substitution, sturgeon valve intestinal protease activity reached its maximum, and the duodenal villus height (VH) was not significantly different from that of the control group (morphological and structural indices were lower in the treatment groups). Gene expression of pro‐inflammatory factors IL‐1 β , IL‐6, IL‐8, and TNF‐ α increased with the substitution ratio, while anti‐inflammatory factor IL‐10 showed the opposite trend. NF‐ κ B and myeloid differentiation factor 88 (MyD88) expression increased with substitution ratio, and Toll‐like receptor 1 (TLR1) and Toll‐like receptor 2 (TLR2) showed the opposite trend in the intestine. The results of this study suggest that replacing less than 50% of fishmeal with RM in hybrid sturgeon diets can reduce the amount of fishmeal used without compromising fish health.