A wide variety of chemicals especially metals contaminate the aquatic ecosystem and stimulate a variety of toxicity mechanisms, such as oxidative damage to proteins, DNA and lipids. Very limited efforts have been made to investigate the genotoxic effects of metals in fish. Therefore, the present study was conducted to determine copper induced genotoxic damage in peripheral blood erythrocytes of 150-day old four freshwater fish species viz. Labeo rohita, Cirrhina mrigala, Catla catla and Ctenopharyngodon idella by using micronucleus test. For this purpose, 96-hr LC50 and lethal concentration of copper for all the four fish species were determined. Each fish species was exposed to four different sub-lethal concentrations (17, 25, 33, 50% of 96-hr LC50) of copper, separately, for a period of 30 days. Results showed exposure concentration dependent increases in the frequencies of micronuclei and other nuclear abnormalities. Findings of the experiment also confirmed that the micronucleus test acts as a useful tool in determining the potential genotoxicity of metals in erythrocytes of various fish species. Among four fish species, Cirrhina mrigala showed significantly higher frequency of micronuclei with the mean value of 16.98±11.70%, followed by that of Ctenopharyngodon idella, Catla catla and Labeo rohita. However, frequency of other nuclear abnormalities followed the order: Labeo rohita > Cirrhina mrigala > Ctenopharyngodon idella > Catla catla.
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.
The acute toxicity, in terms of 96-hr LC50 and lethal concentration, of aluminum (Al) regarding four fish species viz. Labeo rohita, Cirrhina mrigala, Catla catla and Ctenopharyngodon idella of 90-, 120-and 150-day age groups was determined under the wet laboratory under static bioassay. All the tests were performed, separately, at constant water temperature (30°C), pH (7.5) and hardness (300mgL-1). All fish species showed significantly (p<0.05) variable sensitivity to different concentrations of aluminum. However, Labeo rohita of all the three age groups showed significantly least sensitivity, in-terms of 96-hr LC50 and lethal concentration, against aluminum. For the age groups, 90-day fish showed significantly higher sensitivity, followed by that of 120-and 150-day old fish groups. Among fish species, Ctenopharyngodon idella exhibited significantly (P<0.05) higher sensitivity to aluminum with the mean 96-hr LC50 and lethal concentrations of 56.91±22.17 and 85.66±23.33mgL‾ 1 , respectively while Labeo rohita were significantly least sensitive with the mean 96-hr LC50 and lethal concentrations of 75.50±21.09 and 118.71±23.00mgL‾ 1 , respectively. Physico-chemical variables viz., dissolved oxygen showed highly significant and inverse relationship with aluminum concentration while ammonia had highly significant but positive impact on aluminum concentration of the test media.
Present research work was conducted to measure the effects of tertiary metals mixture (Fe+Zn+Mn) on superoxide dismutase (SOD) activity in various tissues of two major carps, Cirrhina mrigala and Labeo rohita at controlled laboratory conditions. 90-day-old fingerlings of both fish species were exposed to 1/4th and 1/5th of their respective 96-hr LC50 value of Fe+Zn+Mn mixture, for 24 days. After 6, 12, 18, and 24-day exposure, fish from each treatment will be sampled, dissected and their tissues viz. brain, gills, kidney, and heart isolated for the SOD enzyme assay. The physical and chemical parameters of test media viz. pH, temperature, dissolved oxygen, total hardness, carbon dioxide, total ammonia, magnesium, and calcium were determined on a 12-hourly basis. It was observed that with an increase in metal concentration, the activity of enzymes increased significantly in both fish species which was maximum at 1/4th of LC50 with the mean value of 49.35±10.04 UmL-1 in C. mrigala. In Labeo rohita, SOD activity decreased with an increase in exposure duration. SOD activity was maximum on day 6 at 52.22±12.91 UmL-1, and on day 24, it was minimum at 35.01±6.91 UmL-1. Among the organs, the SOD activity followed the trend: gills > heart > kidney > brain. The various tissues of metals mixture treated fish Cirrhina mrigala showed significantly increased activity of SOD in comparison to Labeo rohita. All the physicochemical parameters varied significantly at p<0.05 during this study period.
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