Toxic effects of Trebon, a synthetic pyrethroid based insecticide formulation, on Oreochromis mossambicus (Family: Cichlidae)

Abstract

Trebon ® (active ingredient: Etofenprox) is a recently developed potential pyrethroid insecticide formulation and reported to bring about adverse effects to non-targeted organisms in agricultural fields and associated habitats. The toxic effects of Trebon ® on fingerlings of tilapia (Oreochromis mossambicus) were studied in the present investigation following standard laboratory experimentation procedures. Results revealed that the 24-hr and 96-hr LC50 s of Trebon ® were 0.0657 mg L -1 and 0.0087 mg L -1 respectively which are nearly 23 times and 172 times below its recommended field dose which is 1.5 mg L -1 . It therefore appears that Trebon ® brings about mortality to tilapia fingerlings at concentrations that are milder than the field dose within a short period of exposure. Gill hyperplasia, deformation and telangiectasis of secondary gill lamella, mucosal cell proliferation, lamella disorganization and fusion were observed in the insecticide exposed test fishes. The liver tissues were also damaged with intracellular vacuolation, aggregation of melanomacrophages, blood congestion and focal necrosis. The severity of these damages increased with the level of dosage and the exposure period. The fingerlings suffered respiratory distress while the body coloration gradually changed into a pale hue upon exposure to Trebon ® .