Effect of Aqueous Extract of Ichthyotoxic Plant Bridelia micrantha (Hochst) (Baill) on Haematology, Histopathology and Carcass Characteristics of African Catfish (Clarias gariepinus) (BURCHELL, 1822) Juvenile

Abstract

Ayotunde Ezekiel Olatunji and Igbang Kenneth Sunday

The Bridelia micrantha (Hochst.) (Phyllanthaceae) is an ichthyotoxic plant used in catching fish in Nigeria. The toxicity of aqueous extract of B. micrantha on Clarias gariepinus was investigated under statics bioassay conditions. The concentrations of the leaves extract used were 0.00, 0.10, 0.20, 0.30, 0.40, 0.50 and 0.0.60ml/l. The 24hrs, 36hrs, 48hrs, 72hrs, and 96hrs LC50 were 0.40mg/l, 0.30mg/l, 0.26mg/l, 0.22mg/l and 0.21mg/l respectively, with the range of maximum admissible concentration (MATC) were 0.004 – 0.04, 0.003 – 0.03, 0.0026 – 0.026, 0.0022 – 0.022, and 0.0021 – 0.021 respectively. The opercula ventilation and loss of reflex increased with an increase in the concentrations of the leaves extract at the end of 96-hour exposure period. Respiratory distress, loss of balance, settling at the bottom motionless and erratic swimming was observed before death during the exposure period. There was no significant difference in physicochemical parameters of test media (P<0.05) before, during and after the experimental period. Total Dissolved Solids and Conductivity increased significantly (p<0.05) with increase in extract concentration. Temperature had nonsignificant (p<0.05) reduction at all extract concentrations. Blood analysis revealed significant (P<0.05) reduction in the blood parameters (Haemoglobin, Packed Cell Volume, Red Blood Cells, White Blood Cells, Platelet, Mean Corpuscular Volume and Mean Corpuscular Haemoglobin) of exposed fish.

There was severe reduction in Carcass/Proximate (Moisture, Crude Protein, Crude Lipid, Ash, NFE, and Energy) composition of Clarias gariepinus juvenile exposed to B. micrantha. Histopathological examinations of the test fish showed some pathological disruptions, such as skin layer with severe superficial spreading of melanoma, The liver cells revealed hepatic tissue with severe ground glass (GG) appearance of the cytoplasm and intra hepatic hemorrhage (IHH), The gill showed severe effect on the gill architecture with hypertrophy of the gill arch, gill filament and aggregate of inflammation (AI), while the kidney revealed severe degeneration of the renal tissue with severe intra renal necrosis (TN). The result of this study calls for the need to discourage the use of toxic plants for catching fish in Cross River and Nigeria water bodies.

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