Metabolomic Signatures Uncover Domestication-Driven Hypoxia Tolerance in Common Carp (Cyprinus carpio)

Hypoxia represents a pervasive selective pressure in aquaculture systems, prompting aquatic organisms to develop distinct tolerance strategies through diverse physiological and biochemical responses. The common carp (Cyprinus carpio), a species characterized by extensive geographical distribution and a long history of artificial selection, exhibits considerable inter-varietal and inter-population variation in hypoxia tolerance. Nevertheless, the mechanistic basis underlying hypoxia tolerance in the context of domestication remains poorly understood. The present study employed mirror carp (C. carpio var. specularis), a highly domesticated strain with proven hypoxia tolerance, and Hebao red carp (C. carpio var. wuyuanesis), a locally distributed, minimally domesticated variety that is relatively sensitive to hypoxia, to investigate the metabolic responses and underlying mechanisms associated with hypoxia tolerance. Focusing on muscle and liver tissues, we performed separate statistical and bioinformatics analyses of the metabolic profiles derived from the two strains. The results revealed that hypoxia exposure induced only minor perturbations in energy metabolism in mirror carp, whereas Hebao red carp exhibited a profound metabolic depression in muscle, accompanied by signs of insufficient energy production in the liver. Notably, an enhanced nitric oxide (NO) pathway, implicated in vascular tone regulation and oxygen delivery, was observed in the liver of mirror carp but not in that of Hebao red carp. Collectively, these findings delineate distinct metabolic patterns between common carp strains subjected to differing degrees of domestication, which may account for their differential hypoxia tolerance. Moreover, this study offers a theoretical foundation for the selective breeding of hypoxia-resilient fish strains in aquaculture practices.