Dietary Curcumin Improves Muscle Nutritional Quality and Hepatopancreatic Homeostasis in the Green–Pacific Abalone Hybrid (Haliotis discus hannai ♀ × H. fulgens ♂): Physiological and Transcriptomic Evidence

Curcumin is a plant-derived polyphenol with antioxidant, immunomodulatory, and metabolic regulatory activities, but its integrated effects on edible-tissue quality and hepatopancreatic homeostasis in abalone remain unclear. We evaluated five dietary curcumin levels (0, 0.02%, 0.04%, 0.06%, and 0.08%) in 240 green–Pacific abalone hybrids (Haliotis discus hannai ♀ × H. fulgens ♂) for 8 weeks. The 0.04% treatment increased muscle crude protein, while 0.04–0.06% increased total amino acids; all supplemented diets reduced crude lipid and free fatty acids. Curcumin improved hepatopancreatic histology, reduced Oil Red O-positive lipid deposition, increased superoxide dismutase, glutathione peroxidase, and total antioxidant capacity, and decreased malondialdehyde. Acid phosphatase, alkaline phosphatase, and lysozyme increased in all supplemented groups, whereas polyphenol oxidase peaked at 0.04%. Transcriptomic comparison of the control and 0.04% groups identified 622 differentially expressed genes (336 upregulated and 286 downregulated), with enrichment involving lysosome, phagosome, Toll/Imd, MAPK, and FoxO-associated processes. RT-qPCR confirmed increased SOD2, CAT, and HSP70 expression. Overall, 0.04% dietary curcumin produced the most consistent benefits, improving muscle nutritional quality, redox status, and hepatopancreatic health in hybrid abalone.