Acute toxicity of a deltamethrin based pesticide (DBP) to the Neotropical electric fish Microsternarchus cf. bilineatus (Gymnotiformes)

Abstract

Deltamethrin is a pyrethroid insecticide widely used in pest control in Brazilian agriculture. The intensive and disordered use of this pesticide in the Amazon region can drive it into aquatic ecosystems in several ways, but mainly by runoff and leaching. The present study was conceived to determine the acute toxicity (LC50) of a deltamethrin based pesticide (DBP) and to characterize its effects on two biochemical biomarkers, glutathione-S-transferase (GST) and acetylcholinesterase (AChE), in tissues of the electric fish Microsternarchus cf. bilineatus. Fishes were exposed to concentrations of 1, 2, 3, 4 and 5 μg L-1 of DBP for up to 96 hours. For each treatment, the absolute activity of the enzymes GST (muscle and liver) and AChE (muscle and nervous tissue) were analyzed. The LC50-96 h for Microsternarchus cf. bilineatus was 2.15 μg L-1, the lowest concentration registered for an Amazonian fish species so far. None of the concentrations tested of this insecticide affected AChE activity for the exposure period tested. A significant increase in muscle GST activity was detected only for concentrations of 2 and 3 μg L-1.

Meio ambiente

“…Estudando a toxicidade aguda de um pesticida à base de deltametrina (PBD) no peixe elétrico neotropical Microsternarchus cf. bilineatus, foi observado que embora as alterações na AChE não tenham sido significativas, houve um aumento significativo na GST (glutationaS-transferase) nos peixes (músculo e fígado) indicando um mecanismo de eliminação desse xenobiótico nesse tecido, resultante do estresse oxidogenerado 26 . Em condições de campo, a resposta dos biomarcadores não está normalmente relacionada com um contaminante específico, mas sim com uma mistura de substâncias presentes no ambiente, pelo que é complexo interpretar os dados de biomonitorização ambiental, devido às múltiplas fontes de xenobióticos nos ecossistemas de água doce 27,21 .…”