Exposure of freshwater gastropods to chlorpyrifos and cadmium: Predictable and unpredictable responses

Abstract

Aquatic environments near agricultural areas are increasingly contaminated by mixtures of pesticides and heavymetals, posing a threat to non-target aquatic invertebrates. Because mixtures may induce unexpected biologicalresponses, their study is essential for realistic environmental risk assessment. This study investigated the acuteand chronic effects of the pesticide chlorpyrifos (CPF), cadmium (Cd), and their mixture on the freshwatergastropods Biomphalaria glabrata and Planorbarius corneus under controlled laboratory conditions. A panel ofbiochemical and cellular biomarkers was used to evaluate neurotoxicity, oxidative stress, metabolic alterationsand immunotoxicity.Acute CPF exposure, alone or combined with Cd, inhibited B-esterase activity and increased TBARS, indicatingneurotoxic and pro-oxidant effects. Glutathione-S-transferase (GST) and catalase (CAT) remained unaltered.Hemolymph glucose levels increased with all treatments, with a synergistic hyperglycemic response to CPF + Cdobserved only in B. glabrata. Cd exposure induced hypercholesterolemia in B. glabrata and hypertriglyceridemiain both species. Hemocyte revealed enhanced reactivity in response to contaminants alone, an effect absent in themixture. Notably, under chronic CPF + Cd exposure, a pronounced hemocyte clumping occurred, an immunotoxicresponse, not previously reported.These findings highlight B-esterase inhibition and lipid peroxidation as sensitive biomarkers of acute CPFexposure; while hemolymph metabolic parameters may serve as complementary indicators of acute Cd exposure.GST and TBARS levels emerged as informative indicators of chronic Cd toxicity. Notably, the contaminantmixture unpredictably suppressed or amplified only certain biological responses, particularly on immune cells.This study underscore the value of integrative biomarker approaches to better predict ecological risks associatedwith contaminant mixtures.