Effects of a commercial formulation of a neonicotinoid insecticide (Assail® 70) and its active ingredient (acetamiprid) on Biomphalaria straminea (ollusca: Planorbidae)

Abstract

The use of neonicotinoids in agriculture has rapidly expanded at a large scale in recent years. They emerged as a new generation of environmentally safe insecticides in order to replace more toxic and persistent compounds such as organophosphates. Neonicotinoids act as agonists of the nicotinic acetylcholine receptors in the target pest but they may also cause lethal and sublethal effects on non-target organisms. We aimed to study the effects of the commercial formulation Assail® 70 and its active ingredient (a.i. acetamiprid (ACP)) on biochemical biomarkers in a non-target native freshwater gastropod from Argentina, Biomphalaria straminea. The assay included five treatments: dechlorinated tap water (control), a.i. ACP at 150 and 1500 μg L-1 (ACP 1 and ACP 2), and the equivalent to those concentrations of the formulation Assail® 70 (ACP F1 and ACP F2). Seven glass vessels per treatment were used with six snails each. After 14 days of exposure, homogenates were made with the organisms? soft tissues. The following parameters were measured: cholinesterases (ChEs), carboxylesterases (CEs) with two substrates (p-NPA and p-NPB), glutathione S-transferase (GST), superoxide dismutase (SOD), glutathione (GSH), catalase (CAT), total antioxidant capacity (TAC) and reactive oxygen species (ROS). ChE and CE (p-NPA) activities were not altered by the a.i. nor the formulation of ACP. Conversely, the lowest concentration of the formulation and the highest concentration of both a.i. and formulation (ACP F1, ACP 2 and ACP F2) significantly increased CE (p-NPB) activity (by 18, 32 and 37 %, respectively). Both concentrations of the formulation (ACP F1 and ACP F2) caused a significant increase in GST activity (by 17 and 15 %, respectively). The lowest concentration of both a.i. and formulation (ACP 1 and ACP F1) significantly decreased SOD activity (by 23 and 25 %, respectively) and only the highest concentration (ACP F2) significantly decreased CAT activity (by 25 %). Both concentrations of the a.i. and formulation (ACP 1, ACP 2, ACP F1 and ACP F2) significantly increased GSH content (by 15, 38, 36 and 52 %, respectively). The highest concentration of both a.i. and formulation caused a significant decrease in ROS production (both by 18%) but ACP did not affect TAC.A subchronic exposure to Assail® 70 and its a.i. ACP did not affect ChE activity, which is consistent with neonicotinoids mode of action. Nevertheless, they triggered a toxic response on B. straminea where detoxifying (CE and GST) and antioxidant parameters (GSH, SOD and CAT) are involved. The formulation showed to be more toxic than the a.i. since it caused a greater response in the measured parameters.Acknowledgments: To UBA and AGENCIA for the grants awarded.