Abstract
During present study, the copper (Cu) mediated oxidative stress was measured that induced DNA damage by concentrating in the tissues of fish, Catla catla (14.45±1.24g; 84.68±1.45mm) (Hamilton,1822). Fish fingerlings were retained in 5 groups for 14, 28, 42, 56, 70 and 84 days of the exposure period. They were treated with 2/3, 1/3, 1/4 and 1/5 (T1-T4) of 96h lethal concentration of copper. Controls were run along with all the treatments for the same durations. A significant (p < 0.05) dose and time dependent concentration of Cu was observed in the gills, liver, kidney, muscles, and brain of C. catla. Among organs, the liver showed a significantly higher concentration of Cu followed by gills, kidney, brain, and muscles. Copper accumulation in these organs caused a significant variation in the activities of enzymes viz. superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). The SOD activity varied significantly in response to the exposure time of Cu as 56 > 70 > 42 > 84 > 28 > 14 days while CAT activity exhibited an inverse relationship with the increase in Cu concentration. POD activity showed a significant rise with an increase in Cu exposure duration. Comet assay exhibited significant DNA damage in the peripheral erythrocytes of Cu exposed C. catla. Among four exposure concentrations, 2/3rd of LC50 (T1) caused significantly higher damage to the nuclei compared to control. Increased POD and SOD activity, as well as a decrease in CAT activity in response to Cu, demonstrates the involvement of a protective mechanism against reactive oxygen species (ROS), whereas increased ROS resulted in higher DNA damage. These above-mentioned molecular markers can be efficiently used for the biomonitoring of aquatic environments and conservation of edible fish fauna.
Highlights
Copper is found throughout the world as one of the potential environmental toxicants due to its easier bioavailability and high oxidizing potential (Kováčik, 2017)
Increased POD and superoxide dismutase (SOD) activity, as well as a decrease in CAT activity in response to Cu, demonstrates the involvement of a protective mechanism against reactive oxygen species (ROS), whereas increased ROS resulted in higher DNA damage
The present study investigates the molecular biomarkers which cause changes in multiple routes and mechanisms related to oxidative stress, DNA damage in the Cu treated fish, C. catla
Summary
Copper is found throughout the world as one of the potential environmental toxicants due to its easier bioavailability and high oxidizing potential (Kováčik, 2017). Its widespread presence in aquatic ecosystems as a result of excessive use in various industrial activities, as well as the subsequent disposal of untreated effluents directly into running freshwaters, has alarmed eco-toxicologists. The natural aquatic ecosystems in Pakistan have been heavily polluted with toxicants that are generated through various natural and anthropogenic activities. Prominant anthropogenic sources of aquatic contamination include mining operations, untreated industrial effluents, domestic sewage, waste dump leachates and combustion emissions (Al‐Ghanim et al, 2016; Shahid et al, 2021). Its bioavailability in water and toxicity to fish vary with physico-chemical properties of water like pH, suspended solids, organic compound content, alkalinity, and hardness (Di Giulio and Meyer, 2008)
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