Some Pathological Effects of Sub-lethal concentrations of the Methanolic Extracts of Raphia hookeri on Clarias gariepinus
Raphia hookeri is a piscicidal plant introduced into inland waterways by artisanal fishermen in Nigeria to stupefy fish for easy catch. This study was aimed at evaluating the sub-lethal toxicity of methanol extracts of Raphia hookeri (MERH) based on histopathological alterations in the gills, liver, kidney, brain and heart of the African catfish (Clarias gariepinus) over a 56-day exposure and 56-day post-exposure period respectively. Prolonged exposure resulted in pathological changes like erosion of gill filament, thinning of gill lamellae, swollen and oedematous gill filament in the gills and centrilobular vacuolar degeneration, kupffer cell hyperplasia and focal necrosis in the liver. Severe widespread tubular degeneration, sub-capsular congestion and haemorrhage were also observed in the kidney. Pathological changes like meningeal congestion; neuronal degeneration and satellitosis were observed in the brain while hyaline degeneration, epicardial congestion and haemorrhage were some of the changes observed in the heart. In view of these findings, the use of R. hookeri extracts in harvesting fish by local fishermen in Nigeria should be discouraged until information that aid its application in a sustainable manner is made available by further studies.
Keywords: methanolic extract, Raphia hookeri, sub-lethal toxicity, fish pathology, Clarias gariepinus