Influence of the antidiabetic drug metformin on the aquatic crustacean Daphnia magna

BACKGROUND: The antidiabetic drug metformin has been repeatedly detected in surface waters worldwide. This study investigates the effects of the environmentally relevant concentration of metformin on a non-target aquatic organism - a freshwater crustacean, Daphnia magna, with an emphasis on the stress response of daphnids and the long-term effects on their consecutive generations. METHODS: The chronic toxicity test and the consecutive generations test were inspired by the OECD method. The total antioxidant capacity (Trolox equivalent - TEAC), superoxide dismutase (SOD) activity, and catalase (CAT) activity were related to the protein content in the tested daphnids. RESULTS: Elevated antioxidant activities were revealed in daphnids exposed to metformin in comparison to the control group (1.9 × for TEAC, 1.7 × for SOD; 1.3 × for CAT). Furthermore, diminished body sizes and malformations in the digestive system, spine and carapace were detected in newborn juveniles in the second and third generations exposed to metformin. CONCLUSION: Long-term exposure to metformin in environmentally relevant concentrations led to a significant detrimental reaction in aquatic crustaceans.