Imidacloprid is one of the most commonly used pesticides in the world. Wide application of the imidacloprid-based insecticides has led to major ecological problems. Several studies detected this substance in the aquatic environment, posing a threat to the hydrobionts. Aquatic organisms, including the invertebrates, are used for ecological biomonitoring all over the world. A preliminary assessment of the effects of the novel insecticide Zhukoed, comprising three active agents of different structural classes namely alpha-cypermethrin (125 g/L), imidacloprid (100 g/L), and clothianidin (50 g/L), on small model groups of newborn (younger than 24 hours) and mature Daphnia magna was performed. Populational characteristics and tests for acute and chronic toxicity were used to examine the effects of the test substance. The linear size of the body and age at first reproduction of the crustaceans were lower at all examined concentrations of the insecticide (3.0 × 10-1, 3.0 × 10-2 and 3.0 × 10-7 mg/L of the imidacloprid equivalent), as compared to the control group. A statistically significant decrease was observed in the population dynamics and relative growth rate (r) of the juvenile population due to inhibited oocyte development, caused by the insecticide (3.0 × 10-1 mg/L), under the conditions imitating rapid water exchange. In case of slow water turnover, 1-day exposure to the insecticide leads to irreversible consequences.
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