Parental hypoxic exposure confers offspring hypoxia resistance in zebrafish (Danio rerio)

SummaryMaternal influences are a potentially important component of transgenerational transfer of phenotype in vertebrates. This study on zebrafish (Danio rerio) examined how chronic hypoxic exposure on adults affected the phenotype of their offspring. Separate adult populations were exposed to hypoxia (13.1 kPa O2) or normoxia (21.1 kPa O2) for periods ranging from 1 to 12 weeks. Adults were then returned to normoxia and bred within experimental groups. Adult fecundity and egg characteristics (volume of egg, yolk and perivitelline fluid) were assessed. Subsequently, larval body length, time to loss of equilibrium in severe hypoxia (~4 kPa O2), and critical thermal minima (CTMin) and maxima (CTMax) were measured at 6, 9, 12, 15, 18, 21 and 60 days post fertilization (dpf). Adult fecundity was depressed by hypoxic exposure. Egg component volumes were also depressed in adults exposed to 1-2 weeks of hypoxia, but returned to control levels following longer hypoxic exposure. Adult hypoxic exposures of >1 week resulted in longer body lengths in their larval offspring. Time to loss of equilibrium in severe hypoxia (i.e. hypoxic resistance) in control larvae decreased from 6 to 12 dpf, remaining constant thereafter. Notably, hypoxic resistance from 6-18 dpf was ~15% lower in larvae whose parents were exposed to just 1 week of chronic hypoxia, but resistance was significantly increased by ~24-30% in 6-18 dpf in larvae from adults exposed to 2, 3 or 4 weeks of hypoxia. CTMin (~39.5°C) and CTMax (~10-12 °C) were unchanged by parental hypoxic exposure. This study demonstrates that parental hypoxic exposure in adult zebrafish has profound epigenetic effects on the morphological and physiological phenotype of their offspring.