Toxicological study of cyanobacteria (microcystisaeruginosa) on haematological and biochemical response in o. niloticus (l) of thomas reservoir, Kano, Nigeria

The study assessed the acute and sub chronic toxicity of Microcystisaeruginosa on Haematology and Biochemical responses in the Kidney, Liver and gills of Nile tilapia (Oreochromis niloticus) from Thomas reservoir, Kano, Nigeria between September and December, 2018. Field and laboratory investigations were performed using standard protocols. A total of 144 samples of Oreochromis niloticus with mean weight range of 26.5 ± 0.25 -37.5 ± 0.31g, mean length 15.0 ± 0.41 -17.3 ± 0.82cm were exposed to different concentrations of the cyanobacterial extract (0.0 mg/1-control, 50.0, 100.0 and 150.0mg/kg) for 28 days. The oral LC50 of the extract was 6.14µg/ml. The results obtained indicated significant reductions (P<0.05) with increased concentrations of the extract in; haemoglobin (Hb), Red blood Cell (RBC) and packed cell volume (PCV). The white blood cell (WBC) mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentrations (MCHC), Erythrocyte Sedimentation Rate (ESR) and mean corpuscular volume (MCV in fish were significantly (P<0.05) higher than that of the control. Antioxidant biomarkers activities revealed that Glutathione Reductase (GSH) and Glutathione S-transferase (GST) increase significantly (P<0.05) in the fish tissues. There was significant decrease (P<0.05) in Catalase (CAT) and Superoxide dismutase (SOD) activities. It can be deduced that alteration in the antioxidant enzymes reflects cyanobacterial effect in the fish tissues. Uncontrolled discharge from human activities should be controlled in order to curtail degradation of the reservoir in the long run.