Responses of different life stages of Physa acuta (Draparnaud, 1805) to the pesticides imidacloprid and tebuconazole: effects on growth, reproduction, and behavior

Abstract

Aquatic pollution caused by pesticides raises concerns about the effects on wildlife. While risk assessment protocols with invertebrates focus mainly on arthropods, the effects on gastropods are underexplored. In this way, the impact of exposure to imidacloprid, a neonicotinoid insecticide, and tebuconazole, an azole fungicide, on different life stages of the freshwater snail Physa acuta was investigated. Chronic tests with newly hatched (initial growth) and sexually mature adults (biomass and reproduction) were carried out, testing five environmentally relevant concentrations of imidacloprid (5 to 46 µg L⁻¹) and tebuconazole (18 to 272 µg L⁻¹). Besides, the displacement behavior was assessed in both stages. The exposure to insecticide did not alter the initial growth of the species; however, adults presented reduced reproduction marked by decreases in the number of egg clutches (20-40%) and eggs (25-50%). Besides, reductions in egg hatching reached 50%. The fungicide caused more pronounced responses, marked by declines in initial growth by 10 to 90% across all tested concentrations. To adults, the fungicide provoked reproductive losses of 45-60% regarding the number of clutches and 40-70% in egg counting. The egg hatchability was also reduced, and the effects were more pronounced when eggs were incubated in the contaminated medium, with inhibition reaching 100%. Both life stages exposed to tebuconazole presented reduced displacement capability, while only adults were affected by imidacloprid, despite its neurotoxic character. The output observed in hatchlings and adults of P. acuta demonstrates that relevant concentrations of both pesticides endanger freshwater gastropods with cascade effects on freshwater environments.