Hypoxia Causes Transgenerational Impairment of Ovarian Development and Hatching Success in Fish

Hypoxia is a pressing environmental problem in both marine and freshwater ecosystems globally, and this problem will be further exacerbated by global warming in the coming decades. Recently, we reported that hypoxia can cause transgenerational impairment of sperm quality and quantity in fish (in F0, F1, and F2 generations) through DNA methylome modifications. Here, we provide evidence that female fish (Oryzias melastigma) exposed to hypoxia exhibit reproductive impairments (follicle atresia and retarded oocyte development), leading to a drastic reduction in hatching success in the F2 generation of the transgenerational group, although they have never been exposed to hypoxia. Further analyses show that the observed transgenerational impairments in ovarian functions are related to changes in the DNA methylation and expression pattern of two gene clusters that are closely associated with stress-induced cell cycle arrest and cell apoptosis. The observed epigenetic and transgenerational alterations suggest that hypoxia may pose a significant threat to the sustainability of natural fish populations.