Do Low Doses of Imidacloprid Cause Oxidative Stress in Adult Marsh Frogs?

Studying the effects of neonicotinoids on non-target organisms is still an urgent task in today's world, where they are used in substantial quantities. Initially, it is interesting to find out the change in easy-to-detect parameters under insecticide exposure conditions that may indicate some exposure. Therefore, we investigated the parameters of oxidative changes (SOD, CAT, MDA, and total protein) in sexually mature marsh frogs caused by exposure to imidacloprid. Thirty frogs were selected for the experiment and divided into five groups of six individuals each. The exposure concentrations of imidacloprid were 10 µg/L and 100 µg/L. The duration of insecticide exposure was 7 and 21 days. After the finish of the experiment, the liver, kidney, and blood were taken from the animals under anesthesia. It was found that after 7 days of exposure, the group exposed to 100 µg/L imidacloprid solution had lower serum total protein than the control and 10 µg/L exposure groups (p<0.05). Also, after 21 days of imidacloprid exposure at a concentration of 100 µg/L, there was an increase in the SOD value in the frog liver compared to the control group (p<0.05). No significant differences were found in other parameters (p>0.05). The findings cast doubt on the unconditional use of common oxidative stress indices in adult marsh frogs as biomarkers of low-dose imidacloprid exposure. The obtained results for the adult marsh frog may support the possibility of using the liver SOD level only as a biomarker of imidacloprid exposure at environmentally significant concentrations.