Abstract

Fenthion is an organophosphate pesticide commonly used in agriculture and public health for the control of insect pests. The present study investigated the toxic effect of fenthion and the histopathological alterations in the gill tissue of African catfish Clarias gariepinus. The 96 h LC₅₀ value of fenthion in C. gariepinus determined by probit analysis was found to be 39.97 mg/L. Fish exposed to different fenthion concentrations showed clinical signs such as erratic swimming, attempt to jump out of water, increased opercula frequencies, air gasping, mucus secretion followed by exhaustion and death. To evaluate the histopathological changes in the gill tissue, fish were exposed to 2.0, 4.0 and 8.0 mg/L corresponding to 1/20, 1/10 and 1/5^th, respectively of 96 h LC₅₀ of fenthion for 21 days and 7 days recovery. Gill disorder and fusion of the secondary lamellar were pronounced in all treatments. Alterations in gill structure exposed to the highest concentration were oedema, lifting of lamellar epithelia, destruction of gill architecture and lamellar fusion. From the findings, it can be deduced that fenthion-induced alterations are irreversible and therefore should be applied with caution in the environment so as to reduce its damage to aquatic organisms.

Key words: Clarias gariepinus, fenthion, lethal concentration, histopathology.

Abbreviation

OP, Organophosphate; AChE, acetylcholinesterase; ACh, acetylcholine; EPA, Environmental Protection Agency; RUP, restricted use pesticide; MDA, melondialdehyde; KMnO₄, potassium permanganate.