Hao Chen

Grass carp (Ctenopharyngodon idella) is an important freshwater aquaculture species in China. However, high-density farming often leads to significant growth differentiation among individuals, seriously affecting yield and product quality. Here, we conducted an integrated transcriptomic and data-independent acquisition (DIA) proteomic analysis across the brain, liver, and muscle tissues of fast-growing (FG) and slow-growing (SG) grass carp after 9 months of high-density culture. Our analysis revealed that the core mechanism driving growth differentiation is a deep decoupling of transcription and translation, where enhanced muscle translational efficiency dictates the fast-growth phenotype, while slow growth is constrained by central stress and hepatic energy depletion. In the slow growth group, the brain exhibited translational arrest and neuroinflammation, and the liver entered a state of hypermetabolism mediated by AMPK, evidenced by the post-transcriptional up-regulation of key sensors such as CAB39 (PRM ratio = 1.634) and CAMKK2 (PRM ratio = 1.295). Conversely, in the fast-growing group, the mTOR–ribosome signaling axis was strongly activated at the post-transcriptional level in the muscle (GSEA NES = −1.852), triggering myofibrillar protein deposition despite transcriptional silence in classical growth pathways. These findings elucidate the systemic molecular mechanisms of growth divergence and provide high-confidence molecular targets for developing fast-growing, stress-resilient grass carp strains for precision aquaculture breeding.

Grass carp (Ctenopharyngodon idella) is a major freshwater aquaculture species in China, but its growth is limited under intensive high-density farming. This study aimed to investigate the characteristics of plasma exosomes associated with distinct growth performance by isolating and characterizing exosomes from fast- and slow-growing grass carp after nine months of culture. Exosomes showed typical morphology and expressed characteristic markers (CD63, CD81, TSG101). Small RNA sequencing identified 3325 miRNAs, with 177 highly abundant miRNAs differentially expressed: immune-related miRNAs were upregulated, while development-inhibitory miRNAs were downregulated in fast-growing fish. Target gene enrichment highlighted pathways in neural and skeletal development and amino acid metabolism. Integrative analysis across tissues revealed 26 miRNAs with coordinated expression patterns between plasma exosomes and brain, liver, or muscle, validated by qPCR. DIA proteomics quantified 4203 proteins, identifying 843 differentially enriched proteins linked to immune response, energy metabolism, and endoplasmic reticulum stress. Notably, TYMP was upregulated in muscle and exosomes, while several proteins (e.g., GYG2, BHMT) showed coordinated downregulation across tissues and exosomes in large fish. These results provide comprehensive evidence of exosome-mediated cross-tissue communication in teleosts and suggest a potential role for plasma exosomal miRNAs and proteins as non-invasive biomarkers correlated with growth status in aquaculture.

Nanoplastics (NPs) are emerging aquatic pollutants that may threaten farmed fish health. This study evaluated whether dietary nanocurcumin (NCUR) modulates NP-associated biological disturbances in largemouth bass (Micropterus salmoides). A total of 480 fish (initial weight 11.52 ± 0.02 g) were assigned to four treatments for 21 days: control, 0.2% NCUR, 100 μg/L NPs, and 0.2% NCUR + 100 μg/L NPs. NP exposure significantly reduced growth and feed intake (p < 0.05) and was accompanied by gill, hepatic and intestinal tissue alterations, disturbed serum lipid parameters, changes in hepatic antioxidant enzyme activities, and altered mRNA expression of antioxidant- and metabolism-related genes. Dietary NCUR was associated with partial modulation of several NP-associated responses, including hepatic and intestinal structural alterations, serum lipid changes, adaptive antioxidant enzyme responses, and transcriptional changes in Nrf2/Keap1- and SIRT1/FoxO1-associated genes. However, NCUR did not alleviate NPs-induced gill damage, and NCUR alone also caused branchial histopathological alterations. Therefore, 0.2% NCUR may partially mitigate selected NPs-induced disturbances in M. salmoides, but its independent effects, branchial safety, and pathway-level mechanisms require further investigation.