Multigenerational plasticity of Daphnia magna under thermal stress across ten generations

The effects of increasing temperature owing to thermal discharge and global warming on zooplanktons such as Daphnia magna are a growing concern. The purpose of this study was to evaluate the effects of elevated temperature (25 degrees C) on oxidative stress responses, growth, and reproduction of D. magna across 10 generations. The number of offspring per female at 21 d was significantly increased and the rate of adult somatic growth (5-21 d) was decreased in the F0 generation at 25 degrees C compared with those at the reference temperature 20 degrees C. However, the F3 generation showed the lowest number of offspring and the highest adult somatic growth rate and oxidative stress responses (5 d) at 25 degrees C. Moreover, all life-history traits seemed to recover to the levels of the control group from the F6 generation at 20 degrees C. These findings suggest that D. magna under continuous thermal stress exhibits non-adaptive responses in the early generations (F0-F3) and changes to adaptive responses in the later generations (F6-F9). However, the underlying epigenetic mechanism should be identified in the future.