After feeding carnivorous mandarin fish (Siniperca chuatsi) with formulated feed, obvious phenotypic differences in body weight and other traits were obser

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.

Artificial selection enables the targeted alteration of allele frequencies within a population, leading to the consolidation and enhancement of beneficial variations and the stable genetic development of new varieties. Mandarin fish (Siniperca chuatsi) is a commercially important freshwater fish species in China. Through four generations of artificial selection targeting growth rate and survival rate as key traits, our team developed the new variety “Guangqing No. 1”. To identify the genomic loci subjected to selection during the artificial selection process, we conducted whole-genome resequencing on 150 individuals, comprising two wild populations of S. chuatsi (HN and AH) as the base populations and the selectively bred population “Guangqing No. 1”. A total of 3.90 million high-quality SNPs were identified across the three groups. Analysis of population structure and genetic diversity revealed that the individuals were divided into three groups, consistent with their geographical origins. Moreover, the selectively bred population was subjected to more intensive selection and exhibited reduced genetic diversity. Using Fst, Pi ratio, and XP-EHH, this study identified 71 significantly selected regions in S. chuatsi populations, along with 424 candidate genes potentially under selection. Among the candidate genes identified through selection loci analysis, some are closely associated with key economic traits such as growth, immunity, reproduction, and feeding (e.g., pfkp, igf1, Ig, il4i1, npy2r, omp, lrat, c2orf71, sept12). In this study, we identified valuable candidate genes and selection markers for the artificial selection of S. chuatsi, offering valuable insights and guidance for future aquatic breeding efforts.

Largemouth bass (Micropterus salmoides) represents an important freshwater aquaculture species. Dietary protein strategies significantly influence growth performance, immune markers, and intestinal microbiota homeostasis. This study evaluated the physiological effects of five phased protein regimens on juvenile largemouth bass (9.77 ± 0.03 g) over 60 days. A constant 46% protein diet (CON) served as the control, compared with four dynamic regimens (LLH, LMH, LHH, HML) comprising low (L, 43%), medium (M, 46%), or high (H, 50%) protein levels across three 20-day phases. Seven hundred fish were randomly allocated into five groups (four replicates each). Daily feed intake was recorded, body weight was measured at the start and end, and survival rates were monitored. Post-trial assessments included body composition, serum biomarkers, intestinal morphology, and intestinal microbiota. Results showed that the LHH regimen significantly increased immunoglobulin M, complement C3 and C4, lysozyme activity, catalase, glutathione peroxidase, and total antioxidant capacity compared to the CON group. The LHH group also exhibited a reduced relative abundance of Stenotrophomonas_A. Functional predictions indicated downregulation of limonene/pinene degradation and the renin–angiotensin system. The LHH feeding regimen synergistically enhances immune-antioxidant function and optimizes intestinal microbiota in juvenile largemouth bass.