Determination of genotoxic effects of aluminum on Cirrhinus mrigala and Ctenopharyngodon idella using comet assay and micronucleus test

Metals are the major pollutants in aquatic environment. A lot of research literature is available globally about accumulation of heavy metals in aquatic ecosystems as well as in different body organs of aquatic animals, especially fish. Heavy metals mainly generate reactive oxygen species (ROS) in aquatic animals that lead to oxidative stress production. ROS cause oxidative damage to different animal tissues and cellular components, like protein and DNA. Aluminum exists in aquatic environments of Pakistan in concentration higher than permissible limits. So, the present study is conducted to determine toxic effects of aluminum on DNA in peripheral blood erythrocytes of fish viz., Cirrhinus mrigala and Ctenopharyngodon idella. For this purpose, fingerlings of each species were exposed to four sublethal concentrations of 17, 25, 33 and 50%. The effects of aluminum on 96-h LC50 concentrations were evaluated for a period of 30 days under controlled laboratory conditions. Results revealed significant toxic effect of this metal on genetic material of fish. Among the four treatments, 50% sublethal concentration 96-h LC50 of aluminum caused significantly higher percentage of DNA damage, genetic damage index and cumulative tail length of comets. Highest frequency of micronuclei was observed in 50% treatments of 96-hr LC50 exposure of aluminum which was not statistically (p<0.05) similar to micronuclei frequency caused by 33% of 96-hr LC50 of aluminum in fish. The findings of this experiment showed that aluminum exposure caused genetic damage in fish. Moreover, comet assay and micronucleus test appeared to be reliable indicators of metallic ion toxicity in aquatic animals.