Effects of Natural and Synthetic Astaxanthin on Growth, Body Color, and Transcriptome and Metabolome Profiles in the Leopard Coralgrouper (Plectropomus leopardus)

SIMPLE SUMMARY: The leopard coralgrouper (Plectropomus leopardus) is highly valuable in the ornamental fish market owing to its bright red color. Astaxanthin is commonly used as a red colorant in aquaculture. To investigate the genetic basis of red color formation in P. leopardus, we compared the effects of natural and synthetic astaxanthin on P. leopardus color and transcriptome and metabolome profiles. Natural astaxanthin had a superior effect on color compared to that of synthetic astaxanthin, as evidenced by increases in redness and yellowness. Carotenoid- and melanin-related genes were differentially expressed between groups treated with natural astaxanthin, synthetic astaxanthin, and no astaxanthin. These results provide a theoretical basis for color enhancement during the culture of P. leopardus. ABSTRACT: Natural and synthetic astaxanthin can promote pigmentation in fish. In this study, the effects of dietary astaxanthin on growth and pigmentation were evaluated in leopard coralgrouper (Plectropomus leopardus). Fish were assigned to three groups: 0% astaxanthin (C), 0.02% natural astaxanthin (HP), and 0.02% synthetic astaxanthin (AS). Brightness (L*) was not influenced by astaxanthin. However, redness (a*) and yellowness (b*) were significantly higher for fish fed astaxanthin-containing diets than fish fed control diets and were significantly higher in the HP group than in the AS group. In a transcriptome analysis, 466, 33, and 32 differentially expressed genes (DEGs) were identified between C and HP, C and AS, and AS and HP, including various pigmentation-related genes. DEGs were enriched for carotenoid deposition and other pathways related to skin color. A metabolome analysis revealed 377, 249, and 179 differential metabolites (DMs) between C and HP, C and AS, and AS and HP, respectively. In conclusion, natural astaxanthin has a better coloration effect on P. leopardus, which is more suitable as a red colorant in aquaculture. These results improve our understanding of the effects of natural and synthetic astaxanthin on red color formation in fish.