Impact of β-Carotene Enrichment on Carotenoid Composition and Gene Expression in Metanauplii.

Background: Carotenoids play essential nutritional and physiological roles in aquatic animals. Since aquatic species cannot synthesize carotenoids de novo, they must obtain these compounds from their diet to meet the physiological and adaptive requirements needed in specific aquaculture stages and conditions. Carotenoid supplementation in represents a promising strategy to enhance pigmentation, health, and growth in aquaculture species, particularly in larvae and other early developmental stages.

Methods: In this study, a β-carotene enrichment process was applied to metanauplii to investigate the biological fate and potential effects of β-carotene.

Results: The results indicated significant β-carotene uptake by , with peak levels observed at 12 h. Alongside β-carotene, two xanthophylls-canthaxanthin and echinenone-were detected in , each exhibiting distinct patterns during the enrichment and subsequent depletion phases. The transcriptome analysis identified 2705 differentially expressed genes (DEGs), offering valuable insights into gene functions associated with carotenoid absorption, metabolism, and antioxidant mechanisms. The findings suggest that β-carotene enrichment enhances metabolic activity and energy pathways, supporting the physiological functions of . Notably, unlike other crustaceans, lack certain enzymes necessary for converting β-carotene into astaxanthin, restricting them to producing keto-carotenoids like canthaxanthin. Furthermore, the study highlights the upregulation of genes encoding lipid transport proteins, such as CD36 and ABC transporters, which may contribute to carotenoid absorption in . Additional functional insights are provided by the gene BCO2, which regulates pigmentation by preventing excessive carotenoid accumulation, along with ketolase and hydroxylase enzymes in carotenoid metabolic pathways.

Conclusions: This research advances our understanding of carotenoid metabolism in crustaceans, with potential implications for aquaculture nutrition and feed formulation.