RESUMO
Malathion was used in vivo on fresh water fish Labeo rohita to study its toxicity. The acute toxicity tests were conducted during certain intervals in various concentrations [5, 10, 15, 20, 25 and 30 mg/L] of malathion. The physical and chemical analyses of water were carried out by following APHA methods. While treating with malathion, the percentage of fish mortality was assessed during 24, 48, 72 and 96 hours. The lethal and sub-lethal concentration of malathion were found to be LC[100] [25 mg/L] and LC[0] [5 mg/L], respectively. The antioxidant enzyme activity [Catalase 43.1 +/- 2.3, 16.5 +/- 0.57, 23.9 +/- 0.17 micro moles of phenol liberated/min/100mg protein and Glutathion-S-transferase [GST] 270.5 +/- 0.16, 143.2 +/- 1.03, 215.5 +/- 0.72 micro moles of phenol liberated/min/100mg protein], in the liver, muscle and gill, respectively increased during the accumulation of malathion, whereas it decreased [Catalase 17 +/- 1.44, 7.9 +/- 0.23, 10.7 +/- 0.69 micro moles of phenol liberated/min/100mg protein and GST 219.5 +/- 1.12, 108.1 +/- 0.34, 160.2 +/- 0.46 micro moles of phenol liberated/min/100mg protein] during depuration period. The effects of malathion resulted in the gradual decrease of nucleic acids, protein, free amino acids [FAA] and glycogen. During recovery period, the levels of biochemical components progressively increased indicating a probable recovery from the disruption of internal organ. Hence, the pesticide intoxication has made a disturbance in normal functioning of cells with significant alterations in the fundamental biochemical mechanisms of fish. It suggests that the continuous exposure of pesticide leads to abnormal changes causing fish to death