Toxicity of crude extract of Terminalia superba sawdust to Clarias gariepinus (Burchell 1822)

Abstract

The study examined the toxicity of Afara tree (Terminalia superba) sawdust extract to African catfish, Clarias gariepinus. The fish were exposed to four concentrations 55 ml/L, 60 ml/L, 65 ml/L, 70 ml/L and the control for 96 hours. C. gariepinus juveniles exposed to sublethal concentrations of T. superba extract were examined in a static bioassay with reference to behavioural, haematological and histopathological changes. Early observations of fish exposed to T. superba extract showed erratic swimming, loss of equilibrium and respiratory distress. The behavioural response was dose-dependent and decreased with a decrease in concentration. At 24-96 hours of exposure, there were no significant differences in the temperature and pH (p>0.05) while there was a significant difference (p<0.05) in dissolved oxygen at 48-96 hours. The haematological results showed varying degrees of effects of the extracts on blood parameters. The histopathological changes of the gills of fish exposed to T. superba at 65-70 ml/L showed gills distortion, epithelial hyperplasia and disruption of primary lamellar epithelium and that of gills of fish in the control revealed a normal gill filament. Also, the liver of C. gariepinus of the control fish revealed normal structures. Histology of the liver of C. gariepinus in 65 ml/L and 70 ml/L showed varying degrees of space formation, vacuoles in the tissue and increased haemorrhage. The LC₅₀ value of 53.35 ml/L was gotten. It was therefore concluded that sawmill wood waste did not only impact the water quality but also negatively affected the proper functioning of the gills and liver of C. gariepinus.