Haematological and Histological Responses of Clarias gariepinus Fingerlings Exposed to Premium Motor Spirit (PMS)

Abstract

Fish is sensitive to the devastating consequences of oil contamination or deliberate discharge of chemicals to water ways. This study investigated haematological and histological changes in C. gariepinus juveniles before death under controlled laboratory exposure to different concentrations of Premium Motor Spirit (PMS). Eighty (80) Clarias gariepinus juveniles of average weight 50g were exposed to different concentrations of PMS at 0ml/70L of water (control), 45, 55 and 65 ml/70L of water respectively on ten (10) fish per replicate in two replicates. The median lethal concentration (LC₅₀) value of PMS on C. gariepinus juveniles was 50ml/70L of water. Each treatment was subjected to 96 hours bioassay test to determine its acute toxicity in a completely randomized design experiment. Changes in water quality and fish mortality in all treatments were monitored daily in addition to behavioural and histological responses. Haematological analysis; Haematocrit (PCV), Red Blood Cell (RBC), White Blood Cell (WBC) and haemoglobin (Hb) were also investigated.  Except the control, there were significant differences (p˂0.05) in values of pH (7.50±0.02 - 4.70±0.03) and Dissolved Oxygen (5.50±0.03 - 2.04±0.03) mg/L among all the treatments before and after the experiment. Mortality was highest (100%) in fish exposed to 65ml of PMS/70L of water at 72hrs exposure. As concentration and time of exposure increased, fish showed restlessness, rapid opercula movement, erratic swimming, discoloration and loss of reflex before death. Major histological effects were hypertrophy, necrosis of hepatocyte and secondary lamella of the liver, gills and kidney. Haematological changes reflected a highly significant reduction in Red Blood Cell counts from T₁ (3.78+ 0.46/μl) to T₄ (2.68 + 0.18/μl). Also a significant decrease was recorded in haemoglobin (Hb) from 12.25±0.5g/L in control (0ml/70L of water) to 7.83±0.99g/L in T₄ (65ml/70L). It is obvious from this study that higher concentration of PMS negatively affects internal metabolism, respiration, produce nervous signs and could lead to mortality in the test fish.