STRUCTURAL DEFORMATION IN THE KIDNEY AND LIVER OF Clarias gariepinus JUVENILES EXPOSED TO GRADED CONCENTRATION OF ZINC  

The structural deformation of the kidney and the liver of African catfish, Clarias gareipinus exposed to graded concentration of zinc was determine for a period of 96 hours. The stock solution was prepared with zinc and the fish juveniles were exposed to the following concentration in mg/L : 0.5, 0.75. 1.00, 1.25 and 1.50 with a control of 0.0mg/L where the zinc was not introduced. The regression plot of the probit value transformed mortality against the concentration of zinc showed a strong relationship with the death of the fish exposed to the concentration of the metal with R² value of 0.8725. All the same no death was observed in the control throughout the 96 hours period of the study while the lowest death of 15% was recorded in the 0.5mg/L and the highest of 60% in the 1.50mg/L concentration of zinc. The LC₅₀ was determined to be 1.25mg/L during the study time. The ultrastructural characteristics showed pathological lesion in the kidney and vacuolation of the hepatocytes of liver of the fish. The DO of the water was below the recommended level for the survival of the fish in the waters that the concentration of zinc was introduced and may cause distress to the fish.  The fish showed erratic movement and distressful behavoiur where they were exposed to zinc and eventually the ones that could not tolerate the toxicity metal died.   The study conclude that the fish should not be exposed to the elevated concentration of zinc as it is toxic and recommend that anthropogenic activities that release zinc into the environment should be controlled.