Abstract

A four day acute toxicity test was conducted to determine the LC₅₀ of Tetrapleura tetraptera leaf powder on Clarias gariepinus juveniles (46.68±0.62 g) following static bioassay procedures. The range finding test was carried out to ascertain the lethal concentration of the botanical on C. gariepinus juveniles and was found to induce varying behavioral responses to the fish. The 96 h median lethal concentration was 1.60 g L^-1 was ascertained graphically. Percentage mortality of the test fish followed a regular pattern, increasing with increasing concentration. Prior to death, fish exhibited marked behavioural changes such as hyperventilation, erratic swimming (vertical/spiral uncoordinated swimming movement), abnormal operculum and tail frequencies, forfeiture of reflex and settling at the bottom. Histological examination revealed proliferation of the mucosal cells, degeneration in the epithelium of gill filaments and severe sub-mucosal congestion particularly at the secondary lamellae at higher concentrations of Tetrapleura tetraptera leaf powder. The liver showed vacuolation of the hepatocyte, inflammation in the hepatocellular parenchyma and extensive portal and central venous congestion. There was also fibrosis of the port area. Lastly, the heart showed slight lesion and variation in the heart cell arrangement disintegration of heart muscles, vacuolation and degeneration of the cardiac muscle fiber at higher concentrations of T. tetraptera leaf powder. Dissolved oxygen (DO₂), pH and temperature values of the water were within tolerable limits for fish culture.

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