Effects of the neurotoxic insecticides carbaryl, chlorpyrifos, and acetamiprid on the immune system of a freshwater gastropod

Abstract

Growing concern about the immunotoxicity of insecticides on wildlife led us to study the effects of a short-term 48-hour exposure to molar equivalent and environmentally relevant concentrations of the carbamate carbaryl (CAR, 13 μg L-1), the organophosphate chlorpyrifos (CPF, 22 μg L-1), and the neonicotinoid acetamiprid (ACP, 14 μg L-1), on the immune system of the freshwater gastropod Chilina gibbosa. All of the tested neurotoxic chemicals affected this species' innate immune system in a similar manner: although the total number of hemocytes in all cases remained similar, hemocyte viability was reduced 24% by CAR and ACP and 26% by CPF, while phagocytic activity was reduced 41% by CAR, 51% by CPF, and 36% by ACP. We also characterized for the first time the different cell types involved in the immune response of C. gibbosa; we identified hyalinocytes, granulocytes, and blast-like cells through their tinctorial properties. Furthermore, all three pesticides also affected the distribution of cell types by increasing the proportion of granulocytes 9% by CAR, 10% by CPF, and 9% by ACP and reducing the proportion of hyalinocytes 16% by CAR, 13% by CPF, and 19% by ACP. This study broadens the knowledge of freshwater gastropod immunity and how neurotoxic insecticides can affect wildlife's immune systems. It shows that C. gibbosa immunologic endpoints could be considered sensitive biomarkers for aquatic toxicology.