Impact of Heavy Metals on Freshwater Fish Cirrhinus Mrigala in Relation to Oxygen Consumption *
B.R.Chavan* and M. P. Bhilave ** AARM, Asian Institute of Technology, Pathumthani-12120, Thailand ** Dept. of Zoology, Shivaji University, Kolhapur - 416 004, India
[email protected] ABSTRACT
Industrialization affects the environmental pollution of air, soil and water with both organic and inorganic. Metal affects the metabolism of aquatic organisms. The latter can accumulate both essential (Fe, Zn, Cu, Mn) and non essential (Hg, Pb, Cd) metal present in water (Kumar, 2001). However these non-degradable persistent trace metals are the most pressing problems of the present day. Some important physiochemical factors which influence toxicity and uptake of metals by organisms include temperature, Oxygen content, water hardness, and concentration of organic compound, pH and salinity. The effects of cadmium and lead in relation to oxygen consumption in freshwater fish Cirrhinus mrigala (C. mrigala) have been investigate. The fish were exposed to predetermined LCo (0.098 and 19.352 ppm) and LC50 (0.132 and 21.849 ppm) concentrations of cadmium chloride and lead acetate respectively for 96 h. Both the heavy metals showed increased rate of oxygen consumption when compared to control. The fluctuated response in respiration may be attributed to inhibition in mitochondrial oxidation and energy metabolism due to the heavy metal stress. Keywords: Heavy metals, cirrhinus mrigala, respiration 1. INTRODUCTION Rapid industrialization coupled with geochemical alterations posed a major threat to environmental pollution of air, soil and water with both organics and inorganic is a matter of great concern; however the non-degradable persistent trace metals are the most pressing problems of the present day. They are the most Insidious pollutants because of their nonbiodegradable nature and property to affect all forms of ecological systems. Naturally occurring metals move through aquatic environments independently of human activities, usually without any detrimental effects. Artificial sources include effluents of industries which cause non-repairable damage to environment and on individual. Oxygen consumption is a useful measure to assess the sub lethal effects of xenobiotics as energy processes serve as indicators of overall physiological state (Sigmon, 1979). Respiration represents an important physiological index of any aerobic organism (Rajalekshmi and Mohandas, 1998). Perusal of literature shows that, following workers have worked on the rate of respiration on various aquatic animals exposed to different toxicants. (Muley and Mane, 1989; Muley 1990; Kamble, 1999 and Deshpande, 2000). Considering the impact of heavy metals on metabolic rates of aquatic animals and since the fishes have been the most popular test organisms and their importance in food web of aquatic ecosystem, the present study is undertaken to evaluate the impact of heavy metal on freshwater fish Cirrhinus mrigala in relation to the oxygen consumption.
2. MATERIALS AND METHODS The fingerlings of C. mrigala brought from local rearing centre, and they were acclimated for 7 days in laboratory. Acute toxicity experiments were conducted for 96 h using a static bioassay technique and LCo and LC5o values were recorded. Control group of fish were also run simultaneously. During experimentation no food was provided to the fish. Water in the aquaria was renewed after every 24 h. Temperature, pH, dissolved oxygen and hardness of the water used to hold the fish were determined by using standard methods (APHA, 1989). Oxygen consumption experiments were performed in a specially designed respiratory glass jar of one liter capacity fitted with rubber cork having inlet and outlet connected with rubber tubes. The marked fishes were kept one in each jar and immediately filled with water through siphon and then pinch corked at both the ends. The fishes were kept aside in an airtight jar for one hour. After one hour water was siphoned out from the respiratory jar in a Stoppard bottle and oxygen was estimated. For the determination of oxygen consumption, the fishes from control, LCo and LC5o groups were individually marked. These marked individuals were separately used throughout experiment period for determination of oxygen consumption. The rate of oxygen consumption of fishes from control, LCo and LC5o groups belonging to both the heavy metal toxicity experiments was determined at 24 h interval starting from zero to 96 h. The fishes were weighed prior to the determination of oxygen consumption. The rate of oxygen consumption was determined by Winkler's titratlor) method using Aquamerk R 11107 oxygen Test Kit (E Merck, 64271; Darmstadt, Germany). All the values were subjected to statistical analysis for confirmation. The difference in oxygen content of the water prior to the experiment and one hour was taken as mg of oxygen consumed /liter/hr/gm body weight of fish. Comparing the results with control, the changes in rate of oxygen consumption from LCo and LC5o groups were statistically calculated (Dowdeswell, 1959) for each metal. The experiment was repeated for five times for each heavy metal. 3. RESULTS Physico-chemical parameters of water used for holding the fish during experiment, temperature was 26.1 - 28.5°C, pH 7.8 - 8.4, dissolved oxygen 4.2 - 5.4 mg/l and hardness 60-83 mg/l. The observed LCo ar1d LC5o values for cadmium chloride were 0.09 and 0.13 ppm, and those for lead acetate were 19.35 and 21.84 ppm respectively. 3.1 Oxygen Consumption The changes in the rate of oxygen consumption in fishes during 96 h acute exposure to heavy metals along with control are given in Table -1. In control group of fishes the rate of oxygen consumption fluctuated between 0.151 to 0.194 mg/l/h/g weight of body during 0 to 96 h. There was steady increase in the rate of oxygen consumption in fishes exposed to cadmium and lead in LCo and LC5o groups from 0 to 96 h. In fishes exposed to cadmium, the rate of oxygen consumption in LCo group fluctuated between 0.17 to 0.30 mg/l/h/g of body weight. The increase in rate of oxygen uptake was more at 24 h followed by subsequent increase upto 96 h. In LC5o group, the rate of oxygen
consumption fluctuated between 0.18 to 0.32 mg/i/h/g weight of body. The increase in rate of oxygen consumption was less in LCo than LC5o group, but follows a similar trend (table 1). Table 1. Rate of Oxygen Consumption in Cirrhinus mrigala during acute exposure (mg/l/h/g weight of body) Exposure period Control Cadmium chloride Lead acetate (h) LCo LC5o LCo LC5o 24 0.174 0.202 0.208 0.188 0.195 ±0.006 ±0.003 ±0.003 ±0.005 ±0.004 48
0.154 ±0.003
0.193 ±0.004
0.295 ±0.005
0.171 ±0.004
0.184 ±0.004
72
0.194 ±0.004
0.272 ±0.001
0.314 ±0.003
0.225 ±0.002
0.239 ±0.001
0.167 0.303 ±0.003 ±0.004 Values in parenthesis are percentages. ± S.D. of five animals.
0.327 ±0.003
0.231 ±0.004
0.257 ±0.004
96
In fishes exposed to lead, the rate of oxygen consumption in LCo group fluctuated between 0.15 to 0.23 mg/l/h/g weight of body. The increase in rate of oxygen uptake was more at 24 h followed by subsequent increase up to 96 h. In LC5o group, the rate of oxygen consumption fluctuated between 0.161 to 0.25 mg/l/h/g weight of body. The increase in the rate of oxygen consumption was less in LC0 than LC5o group, but follows a similar trend (Figure1).
Concentration of toxicant (mg/l/h/g)
0.35 0.3 0.25 24 0.2
48 72
0.15
96 0.1 0.05 0 Lco Control
LC5o
Cadmium chloride
LCo
LC5o
Lead acetata
Figure 1. Rate of Oxygen consumption in Cirrhinus mrigala during acute exposure
4. DISCUSSION Toxic effects of pollutants are due to disturbance of the normal physiological functions of the affected organisms. Respiration represents an important physiological index of any aerobic organism because, respiratory rates reflect the metabolism of animal, and it can be affected by a variety of physico-chemical parameters and other substances. Ferguson et al (1966) reported increased rate of oxygen consumption in mosquito fish exposed to endrin. Mane et al (1983) reported increased rate of oxygen uptake in LC5o groups than the control and LCo groups of estuarine clam Katelysia opima (Grnelin) exposed to endosulfan. Mane et al (1983) observed that when the bivalve Indonaia caeruleus was exposed to LC0 and LC5o values of Cythion malathion, the rate of oxygen consumption increased as compared to the control one. Increased oxygen consumption is required to support enhanced physiological activities in metabolizing and eliminating the pollutants by the exposed organisms. Kamble (1999) reported significant increase in the rate of oxygen consumption in LC0 and LC5o groups when compared to control at 96 h in fish Sarotherodon mossambicus exposed to endosulfan and chlorpyriphos Deshpande (2000) also reported increased oxygen uptake in LCo and LC5o groups when compared to control at 96 h in fish Labeo rohita exposed to cypermethrin and Fenvalerate. In the present study, the behavior manifestations like hyper activity, surfacing and darting movements on exposure to heavy metals may be related to the higher oxygen consumption. In both the LCo and LC5o concentrations of cadmium and lead, fishes showed increased rate of oxygen consumption when compared to control. The fluctuated response in respiration may be attributed to reduction in gill permeability causing a drop in oxygen consumption for which the fish compensates by increasing the ventilation volume. There might be inhibition in mitochondrial oxidation and energy metabolism due to the heavy metal stress. The increase in the rate of oxygen consumption might be due to natural defense to compensate the inhibited mitochondrial oxidation and energy metabolism. The high metabolic rate may be because of the metabolic activity of the brain, which is a predominating factor governing the rate of oxygen consumption in fish (Freeman, 1950), Probably excitement may be effective via central nervous system causing increase muscle tone and consequently increased rate of oxygen consumption (Reddy et al, 1987 and Chanchal et al, 1990).
Acknowledgements The authors are thankful to the Head, Department of Zoology, Shivaji University, Kolhapur for providing necessary facilities to carry out present work. 5. REFERENCES Chanchal, A.K; S. Kumar; S.S. Prasad and K. Prasad.1990. Effect of two pesticides on oxygen consumption of freshwater fish Puntis so,ohore. Proc. 7th Ind. Sc. Congo Part III (Ad.Ab) 145. Deshpande, V. Y.2000. Effects of synthetic pyrethroids on freshwater fish Labeo rohita. Thesis submitted to Shivaji University, Kolhapur (MS), India. Dowdeswell, W.H. 1959. Practical animal ecology. Methun and Co. Ltd., London. Ferguson, D.E; J.L. Ludke and G.G. Murphy. 1966. Dynamic of endrin uptake and release by
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