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Neurotoxic insecticides are ubiquitous in aquatic ecosystems, frequently as part of complex mixtures. Freshwater gastropods are generally underrepresented in neurotoxicity evaluations and cumulative toxicity testing. This study investigates the behavioural and biochemical effects of acute exposures to the carbamate carbaryl, the organophosphate chlorpyrifos, and the neonicotinoid acetamiprid on the freshwater gastropod Chilina gibbosa. First, we evaluated behavioural neurotoxicity and cholinesterase (ChE), carboxylesterase (CE), and glutathione S-transferase (GST) activities in acute (48h) single-chemical exposures to increasing concentrations of carbaryl (0.5-500 μg L -1 ), chlorpyrifos (10-7500 μg L -1 ), and acetamiprid (1-10000 μg L -1 ). We then studied the effects of acute (48h) exposures to binary mixtures of carbaryl and chlorpyrifos equivalent to 0.5, 1, and 1.5 ChE 48h-IC 50 . None of the insecticides caused severe behavioural neurotoxicity, except for a significant lack of adherence by 5000 μg L -1 chlorpyrifos. Carbaryl caused concentration-dependent inhibition of ChEs (NOEC 5 μg L -1 ; 48h-IC 50 45 μg L -1 ) and CEs with p-nitrophenyl butyrate as substrate (NOEC 5 μg L -1 ; 48h-IC 50 37 μg L -1 ). Chlorpyrifos caused concentration-dependent inhibition of ChEs (NOEC 50 μg L -1 ; 48h-IC 50 946 μg L -1 ) but did not affect CEs (NOEC ≥7500 μg L -1 ). Carbaryl-chlorpyrifos mixtures inhibited ChEs additively, inhibited CEs with p-nitrophenyl butyrate, and did not affect behaviour. GST activity was not affected by single or mixture exposures. Acute exposure to acetamiprid did not affect any of the endpoints evaluated. This study provides new information on carbaryl, chlorpyrifos, and acetamiprid toxicity on C. gibbosa, relevant to improve gastropod representation in ecotoxicological risk assessment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Neonicotinoids emerged as an environmentally safe alternative to previous generations of insecticides becoming one of the most widely applied in modern agriculture. Nevertheless, they have been reported to affect several non-target organisms. Most toxicity studies focus on the effects on pollinators or terrestrial invertebrates and evaluate either the active ingredient or the commercial formulation. In the present study, we aimed to assess the long-term effects of the active ingredient acetamiprid and a broadly used commercial formulation (Assail® 70) on the non-target freshwater gastropod Biomphalaria straminea using a battery of biomarkers. A 14 day-exposure of adult organisms to both active ingredient and commercial formulation increased carboxylesterase activity and glutathione content, inhibited superoxide dismutase activity and decreased reactive oxygen species levels. The commercial formulation additionally increased glutathione S-transferase activity and inhibited catalase activity. The results indicate a greater toxicity of the commercial formulation than that of the active ingredient alone. Cholinesterase activity, development and offspring survival of B. straminea were not impaired. We conclude that the toxicity of acetamiprid on this gastropod species is mainly related to effects on detoxification and oxidative metabolism responses. This study provides novel information about the adverse effects of the active ingredient and a commercial formulation of a widely used neonicotinoid on a non-target aquatic species., (Copyright © 2020. Published by Elsevier Inc.)

This work aimed to study in the freshwater gastropod Planorbarius corneus the effects of acute (2 days) and subchronic (14 days) exposures to an environmental concentration of the organophosphate azinphos-methyl on different reproductive parameters, offspring survival and B-esterase activities in gonads and in the whole organism soft tissue. The acute exposure inhibited only carboxylesterase activity in both tissues while the subchronic exposure also inhibited cholinesterase activity, decreased the number of hatched-eggs and increased offspring lethality (92%). On the other hand, B-esterases in gonads were more effective biomarkers than B-esterases in the whole organism due their inhibition appeared earlier in time (cholinesterase activity) and their activity remained inhibited for a longer time (carboxylesterase activity) when recovery studies were performed. We concluded that B-esterases and reproductive parameters can be used as effect biomarkers of aquatic contamination with azinphos-methyl. Our studies showed that a 14 days exposure to an environmental concentration of azinphos-methyl produced severe signs of toxicity in adult organisms, egg masses and juveniles that could cause negative effects at the population level in contaminated environments., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Organophosphate insecticides (OPs) are commonly used in Argentina and around the world for pest control in food crops. They exert their toxicity through the inhibition of the enzyme acetylcholinesterase. In the present study, we aimed to evaluate biochemical and reproductive effects in Biomphalaria straminea, a freshwater gastropod naturally distributed in Argentina, of subchronic exposures to environmental azinphos-methyl concentrations (20 and 200 µg L -1 ). For biochemical parameters, adult organisms were exposed for 14 days and the activity of cholinesterases (ChEs), carboxylesterases (CEs), glutathione S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), the production of reactive oxygen species (ROS), the total antioxidant capacity (TAC), glycogen and proteins were determined. For reproductive parameters, the egg masses of B. straminea were exposed to azinphos-methyl for one month, and the hatching time and success as well as the offspring survival were registered. We found different toxic effects elicited by the insecticide on the studied biomarkers. CEs activity was significantly inhibited while CAT and GST activities, ROS production and TAC were significantly increased, with respect to the solvent control group. ChE and SOD activities and protein and glycogen contents were not altered by azinphos-methyl. The hatching time and success were not statistically different from control. Nevertheless, the offspring survival was severely affected by the insecticide. Our results show that the primary target of the insecticide (ChE) was not inhibited but CEs, GST, CAT, ROS, TAC and offspring survival were sensitive biomarkers and valuable endpoints for subchronic toxicity assessments in this species., (Copyright © 2018 Elsevier Inc. All rights reserved.)