Inducing hypoxia tolerance in blunt snout bream (Megalobrama amblycephala) through acute cold stress during early embryonic development

In aquaculture, ecological adaptability and stress resistance are two critical determinants of breeding and production values for the farmed fish. As an economically important species, cultivation of Megalobrama amblycephala is limited often by its lower hypoxia tolerance in practice. In this paper, a technique of acute cold stress is proposed to induce its hypoxia tolerance during early embryonic development, and a subpopulation of Megalobrama amblycephala with normal survival rates is successfully established. It is found that there exists highly expressed foxo3b in this subpopulation, and using the primary cells isolated from the larvae of Megalobrama amblycephala , a cell model is constructed to simulate the acute cold stress in vitro. On the basis of the proposed cell model, it is shown that the samples with high foxo3b expression can mitigate the effects of acute cold exposure, owing to the activated antioxidant genes, the reduced oxidative damage, and the alleviated cold stress-induced apoptosis. It is also demonstrated that the highly expressed foxo3b can positively regulate hif-3α transcription, which subsequently modulates the metabolic profiles under hypoxic conditions through the HIF-3α/PPAR-γ pathway. Consequently, hypoxia tolerance of Megalobrama amblycephala is enhanced. Clearly, these results are beneficial for cultivating new aquaculture strains with lower oxygen tolerance traits. • Identified a BSB subpopulation with tolerance to both acute cold and hypoxia stress. • Established an acute cold stress cell model of BSB. • Elucidated that BSB enhances hypoxia tolerance through the foxo3b/hif-3α/ppar-γ pathway.