Exploratory Integrated Transcriptomic and Metabolomic Analysis of Body-Weight Divergence in Naozhou Large Yellow Croaker (Larimichthys crocea)

Large yellow croaker (Larimichthys crocea) is an economically important mariculture species in China, but marked individual variation in body weight reduces production uniformity. To explore molecular features underlying this phenotypic divergence, liver tissues from high-weight and low-weight fish from the Naozhou population were subjected to integrated transcriptomic and untargeted metabolomic analyses. A total of 3390 DEGs were identified in the high-weight group (HWG) compared with the low-weight group (LWG), including 1576 upregulated and 1814 downregulated genes. Functional annotation indicated that the DEGs were predominantly associated with pathways governing cell-cycle progression, DNA synthesis and replication, lipid turnover, and amino acid-related metabolic processes. Untargeted metabolomic profiling identified 2263 annotated metabolites, of which 241 were differentially accumulated between the two groups. Pathway enrichment indicated that these altered metabolites were primarily associated with lipid-related processes, amino acid turnover, and cellular energy metabolism. Integrated analysis further revealed significant correlations between DEGs and differential metabolites and highlighted several co-enriched pathways, including linoleic acid metabolism, biosynthesis of amino acids, carbon metabolism, and fatty acid biosynthesis. These findings provide preliminary evidence that body-weight differences in large yellow croaker may reflect coordinated changes at both the transcriptomic and metabolomic levels, with lipid metabolism, amino acid metabolism, and energy-related pathways being particularly involved. As an exploratory study, these results should be regarded as candidate molecular associations that require further validation in larger populations before being applied to breeding or nutritional regulation.