Hypoxia to the skeletal systems of teleost: Impacts, mechanisms, and health implications

Eutrophication, organic pollution, and climate change have fueled the frequency and extent of hypoxia in global aquatic ecosystems. Severe hypoxia in water bodies often results in mass mortality of aquatic organisms, a decline in fish populations, elimination of sensitive species. Hypoxia poses a significant threat to Darwinian fitness traits especially growth and reproductive capacities. While most studies focused on impacts of hypoxia on behaviors, development, and reproduction of fish, relatively few studies investigated the effects of hypoxia on skeletal systems. Notably, moderate hypoxia can induce skeletal deformities during embryonic and larval stages of fish, thereby affecting their locomotion, predator avoidance, inter- and intra-specific competition, and mating, which ultimately may affect population sustainability. The adverse impacts of hypoxia on fish skeletal system may be long-term and persist for multiple generations, warranting an updated systematic evaluation. This review summarizes the current knowledge of the impacts of hypoxia on the fish skeletal system, ranging from genetic and epigenetic mechanisms to multigenerational effects and potential health implications. Knowledge gaps are identified, and multigenerational research is proposed to assess bone integrity and fish health at epigenetic, molecular, proteomic, cellular, tissue, organismal, and population levels using model transgenic fish and wild fish. The critical dissolved oxygen level required for the induction of bone deformities and the underlying genetic and epigenetic mechanisms can serve as a guideline for assessing the health risks of hypoxia to fish for conservation and management purposes.