Comparative acute toxicity of two phytosanitary molecules, lambda-cyhalothrin and acetamiprid, on Nile Tilapia (Oreochromis Niloticus) juveniles

Abstract

This study aimed to compare the toxicity for fish of two active ingredients (lambda-cyhalothrin-20 g L⁻¹, a pyrethroid, and acetamiprid-15 g L⁻¹, a neonicotinoid) which are components of a commercial insecticide (Acer 35 EC) used in cotton crop in many West African countries. The juveniles of Oreochromis niloticus (4.01 ± 0.34 g, mean body weight) were exposed for 96 h to increasing concentrations of active ingredients (lambda-cyhalothrin and acetamiprid) or a mixture similar to Acer 35 EC (composed by 20 g of chemical compound lambda-cyhalothrin and 15 g of acetamiprid dissolved in 1 L of acetone). The experiments were carried out under controlled conditions in aquaria according to OECD Guidelines. During the experiments, the behavioral responses (loss of balance, color change, hyperactivity, etc.) that usually precede death were observed in exposed fish. Mortalities were recorded in each aquarium and the LC₅₀-96h of each chemical was determined. The LC₅₀-96h obtained were respectively 0.1268, 0.0029, 182.9 and 0.5685 ppm for Acer 35 EC, lambda-cyhalothrin, acetamiprid and mixture. All insecticides used in this study had profound impact on Nile tilapia behavior which may confirm the neurotoxicity of each single active compound as well as of their mixture.

Keywords:

• Pyrethroids
• neonicotinoids
• acute toxicity
• Nile tilapia
• LC50-96h
• behavioral responses

Acknowledgments

This research was conducted in the Research Laboratory in Aquaculture and Aquatic Ecotoxicology (LaRAEAq) at University of Parakou (Benin). The authors express sincere gratitude to François Brose (ULiège), for his technical assistance and to the following Master degree students (Dorcas AKOUETE, Edith YACOUTO, Thibaut MARTINS) from the Departement of Science and Technique of Animal Production of the University of Parakou and Master degree MoRAP (Monitoring des ressources Aquatiques et Aménagement des Pêches continentales) of University of Abomey-Calavi (Benin) for their contribution to this work. Many thanks to AJINOMOTO-OMNICHEM S.A. (Belgium) for providing technical grade of lambda-cyhalothrin and acetamiprid.