Among xenobiotics, metals gained attention because of their toxicity and harmful effects on aquatic ecosystems, fish and the human health. Present experiment was conducted to determine the genotoxic effects of individual metals viz. arsenic (As), copper (Cu), and zinc (Zn) in peripheral blood erythrocytes of four freshwater fish species viz. Labeo rohita (rohu), Cirrhina mrigala (mori), Catla catla (thaila) and Ctenopharyngodon idella (grass carp) by using Comet assay. For this purpose fish were exposed to four different sub-lethal concentrations (17, 25, 33 and 50% of LC₅₀) of As, Cu, and Zn for a period of 30-day. All the four fish species showed significantly different extant of DNA damage in-terms of percent damaged cells, genetic damage index (GDI) and cumulative tail length of comets due to metals exposure. Among four fish species, Cirrhina mrigala showed significantly (P<0.05) higher percentage of damaged cells, GDI and cumulative tail length of comets with the mean values of 52±6%, 1.6±0.3 and 152±35 µm, respectively. However, Catla catla showed significantly lower percentage of damaged cells and GDI with the mean values of 29±4% and 1.1±0.1, respectively. This study indicated that individual metals and metals mixture, existing in aquatic habitats of Pakistan can induce DNA damage in indigenous fish fauna.

Key words: Comet assay, DNA damage, Fish, Heavy metals, Peripheral blood erythrocytes