Toxicity Study on Nucleic Acid Dynamics of Synthetic Pyrethroid on Fresh Water Cat Fish Clarias Batrachus

Abstract

The credits of pesticides include enhanced economic potential in terms of increased production of food and fiber, and amelioration of vector-borne diseases; their debits have resulted in serious health implications to man and his environment. Fishes major contributors in the field of aquaculture, an important concern today since pesticides hamper the normal physiological processes of the organisms. The growth and the development of the fishes depend on the nucleic acid content (DNA and RNA), which serve as biochemical indices. Cellular enlargement and active protein synthesis are dependent on DNA and RNA content. DNA and RNA dynamics during conditions of stress corresponds to degenerative changes in the tissues leading decreased protein synthesis and cellular proliferation activity since energy is diverted for maintenance of metabolism during stress as evidenced by breakdown and utilization of stored carbohydrates, depletion of protein and lipid. The damage inflicted on the DNA templates, unless repaired, may interfere with replication and transcription resulting in lethal mutations. There has been a dramatic increase in the recent years in the use of pyrethroid pesticides to control insect pests. Owing to the excessive use of synthetic pyrethroids today, the environment and water resources are being rapidly polluted thus endangering aquatic life directly and human life indirectly. Lambda-cyhalothrin is highly toxic to fishes and aquatic invertebrates. However, little is known about the toxicity of sediment associated pyrethroid residues to aquatic organisms despite the agricultural use of these compounds for more than decades. Cat fishes which are extensively grown in rice paddy slurries provide additional source of income to the farmers. In the present study an attempt was made to assess the effect of toxicity in nucleic acid content at two different sub-lethal concentrations of lambda-cyhalothrin on freshwater catfish, Clarias batrachus. The technical grade synthetic pyrethroid, lambda-cyhalothrin with 95% purity used for the study. Healthy Clarias batrachus were chosen and sorted out into three groups Group I, Group II and Groupd III were exposed to the two different sub-lethal concentrations of lambda-cyhalothrin for a period of 45 days. At the end of every of 15, 30 and 45 days blood was collected from five fishes each of the control and test groups. Extraction of total nucleic acids was done; DNA and RNA were estimated. Assay of free radical induced DNA damage was studied and the values were expressed as nanomoles of malondialdehyde formed/hour/mg DNA.