Antioxidant enzyme activity in Daphnia magna under microscopic observation and shed carapace length as an alternative growth endpoint

• Published in: The Science of the total environment 2021-11, Vol.794, p.148771-148771, Article 148771
• Main Authors: Kim, Eun Hye, Jeong, Ju An, Choi, Eun Kyong, Jeong, Tae-Yong
• Format: Article
• Language: English
• Subjects: Alternative growth endpoint; Daphnia magna; Shed carapace length
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2021.148771

Daphnia magna is an important organism for exposure studies in ecotoxicology. Body length measurement of a daphnid is a useful endpoint that represents the adverse effects of exposed chemicals or conditions on growth. This study questioned whether stress on body length measurement conditions while maintaining Daphnia magna on a slide glass results in any impact to antioxidant enzyme activity or growth. At the same time, the shed carapace length was tested to see if it could predict body length and be used as an alternative endpoint. The measured catalase (CAT) activity decreased as the exposure time to the on-slide conditions increased from 30 s to 120 s, although glutathione-S-transferase (GST) activity was not affected. On the other hand, regression between body length and two parameters of shed carapace length showed R2 values, 0.869 and 0.924. Growth measured for each molting for three weeks was not affected by the exposure to the on-slide conditions. Finally, this study confirmed potential oxidative stress based on the exposure time dependent CAT activity in Daphnia magna under microscopic observation. More importantly, the shed carapace length was validated to reflect body length and it implies applicability of the new parameters to sublethal effect measurement using Daphnia magna. This study suggests potential interference is possible with the traditional growth measurement method on antioxidant enzyme activity in Daphnia magna and proposes better experimental practices to avoid the interference. [Display omitted] •Exposure to the on-slide conditions decreased catalase activity in Daphnia magna.•Body and shed carapace lengths showed significant linear correlation.•The results imply oxidative stress under the traditional measurement condition.•Shed carapace lengths were validated as alternative growth endpoints.