Metabolomic and Transcriptomic Analyses of Soft-Body Coloration in Jinjiang Oyster (Crassostrea ariakensis)

The coloration of shellfish significantly influences both environmental adaptability and economic value. In the Jinjiang oyster (Crassostrea ariakensis), soft-body color varies between individuals, with an orange-yellow phenotype distinct from the milky white coloration of the wild type. To elucidate the compositional differences and molecular mechanisms underlying orange-yellow (designated as CaR) versus milky white (CaW) soft-body color in C. ariakensis, we conducted comparative ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) non-targeted and transcriptomic analyses. A total of 280 differential accumulation metabolites (DAMs) and 691 differentially expressed genes (DEGs) were detected between the CaR and CaW groups. The metabolite set enrichment analysis (MSEA) revealed that DAMs were significantly enriched in pigment metabolism pathways, including tyrosine metabolism, porphyrin metabolism, and lipid metabolism. Furthermore, genes associated with melanin synthesis and carotenoids conversions or transports were upregulated in the CaR vs. CaW group. These genes included Cyp4z1, Cyp4f22, Cyp17a1, Cyp1a5, Cyp2d28a, Lrp4, Aldh, and Tyr-3, potentially driving the accumulation of pheomelanin and carotenoids. This study demonstrates the vital roles of melanin and carotenoid metabolism in Jinjiang oyster body color formation, providing key insights into the molecular mechanisms of color determination in shellfish.