Water quality parameters and histopathological changes in gills and liver of Clarias gariepinus juveniles exposed to ethanol leaf extract of Senna occidentalis

The leaf of coffee senna or septic weed, Senna occidentalis, is among the medicinal and toxic plants whose toxicity on fish has not thoroughly been assessed. The study used 120 Clarias gariepinus juveniles with an average body weight of 16 ± 2 g and length of 8.5 ± 0.5 cm, randomly distributed in 12 plastic tanks of 35 L capacity filled up to 10 L volumes of water, acclimatised for 14-day, and fed twice daily with 1.8 mm skretting feed. Various ethanol leaf extracts of Senna occidentalis (0, 3000, 5000 and 7000 mg L-1) were added with a 5 mL syringe across the 12 plastic tanks, adopting a renewal bioassay, following the range-finding test of 500, 1000, and 1500 mg L-1, which had no visible impacts on the tested fish samples over 96-h. Five in-situ parameters (Dissolved Oxygen, Temperature, Conductivity, and Total Dissolved Solids) were monitored daily for water quality over 96 hours. Analysis of Variance analysed the data with the Duncan Multiple Range Test separating the mean. There were no significant (p > 0.05) differences across the monitored water parameters. The control fish had normal histopathology (gills and liver), while the gill of the exposed fish had severe lamellar hyperplasia with complete occlusion and congestion of pillar capillaries. Moderate hepatic necrosis, mild sinusoidal congestion and atrophy of hepatocytes were observed on the liver of the test C. gariepinus. The study concluded that levels of the Senna occidentalis used in the main experiment exhibited phytotoxicity, thereby necessitating adherence to the levels used in the range-finding test.