Time-Dependent Responses of Oxidative Stress, Growth, and Reproduction of Daphnia magna Under Thermal Stress

Abstract

The present study evaluated the effects of temperature (20 and 25 degrees C) on the oxidative stress responses and life-history traits of Daphnia magna depending on exposure time. Daphnid exposed to an elevated temperature for 21days had notably higher activities of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase while the enzyme activities did not differ significantly between the two temperature groups for daphnid exposed for 5days. However, the results of body length were opposite where only the 5days exposure daphnid had significantly longer bodies at 25 degrees C compared to those at 20 degrees C (p<0.05). Despite the earlier reproduction for daphnids at 25 degrees C, the cumulative number of offspring per female for 21days was not significantly different from those at 20 degrees C (p<0.05). These findings suggest that D. magna undergo strategic changes in oxidative stress response, growth, and reproduction throughout the exposure period of 21days.