Abstract: The present study investigated the effects of salinity (20 and 25) and temperature (20℃ and 25℃) stress on activities of SOD（Superoxide Dlismutase）, CAT(Catalase) and MDA(Maldondialdehyde) content in juvenile and adult of Daphniopsis tibetana Sars, by method for experimental ecology, respectively. The result showed that high concentration of salt stress treatment increased the activities of SOD and CAT and reduced MDA content in juvenile. There were no significant differences in adult SOD activity induced by high salinity stress. And the activity of CAT and MDA content were higher in experimental group (salinity 20 and 25) compared with the control group (salinity 16). High temperature stress (20℃ and 25℃) obviously increased the activities of SOD and CAT, MDA content in juvenile. While the adult under high temperature treatment showed the increase SOD and CAT activities, yet the decrease of MDA content. The results indicated that the juveniles were more tolerant to high salinity stress, less tolerant to high temperature stress than the adults. The results were opposite in adults compared with juveniles under high salinity or temperature stress. These results provide some basic data for the research on antioxidative enzyme system in other cladocerans species under environmental stress, and scientific base for the domestication and large-scale culture of Daphniopsis tibetana Sars.

Key words: environmental stress, Daphniopsis tibetana Sars, SOD, CAT, MDA