Vol. 1, Issue 7, Part F (2015)

Abstract
The toxicity of cobalt chloride (30, 60, 90, 120 and 150 ppm) on freshwater fish Oreochromis mossambicus were investigated (96 hrs). LC50 was observed at 340 ppm. Micronucleus (MN) was observed in fish erythrocytes for cytogenetic abnormalities. MN frequencies were significantly increased in different dose levels. Haemoglobin and RBC’s count were found higher in control than exposed groups and WBC’s count found higher in 150 ppm group. Tissues such as gill, liver (histology) and muscle (biochemical) were analyzed. Carbohydrate, Cholesterol and Protein levels were gradually reduced in treated concentrations (30 > 60 > 90 > 120 > 150 ppm) than control. Gill and liver tissues of treated groups showed several histopathologies than control. These alterations could affect vital physiological functions of gill and liver such as respiration, osmotic and ionic regulations, nitrogenous waste excretion and absorption, storage and secretion of various enzymes could ultimately affect the survival and growth of O. mossambicus. These observations strongly suggested that an even low concentration (ppm) of Cobalt Chloride was toxic; and seriously alters the major haematological, biochemical and histoarchitecture of fishes. Thus, all possible remedial measures should be adopted to prevent the occurrence of Cobalt Chloride exceeding permissible limit in the aquatic environment.