Toxicity of heavy metal copper and its effect on the behaviour of fresh water Indian cat fish, Clarias batrachus (Linn.) *Akhter Ali Siddiqui and Noori Arifa Post Graduate Department of Zoology, Poona College of Arts, Science and Commerce, Camp, Pune - 411 001.Maharastra. India *E- mail: akhter_1956@yahoo.co.in ABSTRACT The behavioural impairment of fresh water Indian cat fish, Clarias batrachus was studied on exposure to heavy metal copper after finding the Lc 50. The experimental animal was exposed to four different doses of copper (0.25, 0.50, 0.75, 1ppm) for a period of 15 days and observed that there was no mortality in any group of experimental animal during the study period. No behavioural changes was noted at 0.25 ppm, however, at 0.50 ppm the animal began restlessness. Erratic swimming, jerky body movements, rolling the body, convulsions, mucous secretion over the body was observed at 0.75 ppm and loss of equilibrium, rapid opercular movements, difficulty in respiration, and lethargy was noted at 1ppm. In short the effects and the dosage were found to be directly proportional to the behaviour of the experimental animal. KEY WORDS: Behaviour, Clarias batrachus, equilibrium, toxicity INTRODUCTION Essential heavy metals like copper and zinc play an important role in various biological processes including oxidative phosphorylation, gene regulation, free radical, homeostasis, oxygen transport and as essential cofactors. However, when their concentration exceed than metabolic requirement they become harmful and show a high degree of impact on various metabolism. The harmful effects increase with both the concentration and length of exposure. The problem of appearance of heavy metals in aquatic ecosystem is presently closely connected with increased concentration of different types of pollutants, which enter water bodies with industrial waste waters. Metals are redistributed naturally in the environment by both geologic and biologic cycles. Many metals, whether organically complex or not are known to accumulate in plants and animals tissues to very high level, posing a potential toxic hazards to organism themselves, or organisms higher in the food chain including humans which may consume them (Abel,1998). Evidence of toxic effect of heavy metals has been reported on fishes and population eating contaminated food (Cheng, 1996). Aquatic pollution undoubtedly has direct effects on fish health and survival. a heavy metal is 405
widely used in various industrial plants. Effluents from such plants are sources of copper into aquatic environments. Most aquatic organisms have the capability of concentrating metals by feeding and metabolic processes, which can lead to accumulation of high concentration of metals in their tissues. When their concentration exceeds, they become harmful (Bennet et al., 1995). Metals interact with legends in proteins particularly, enzymes and inhibit their biochemical and physiological activities (Passow et al., 1961). Behavioral changes in animals are indicative of such internal disturbances of the body functions. The elimination of aquatic animals by small insidious physiological or behavioural changes has been reported to be more serious than a massive fish kill, since it is less likely to be observed and corrected (Larsson et al., 1976). The present study was conducted to investigate the behavioural abnormalities in fresh water fish Clarias batrachus on exposure to copper treatments and the observed changes are discussed. MATERIALS AND METHODS The fresh water Indian cat fish, C. batrachus was procured from the local market Ganesh Peth, Pune, Maharashtra and were transferred to large plastic troughs. The fishes were daily fed on rice bran and mustard oil cake with an interval of 12 hours morning and evening. Fish were acclimatized in dechlorinated tap water in laboratory for 10 days prior to exposure. The acclimated fish of equal size were divided into five experimental groups each and treated with different concentration of copper sulphate (1.0, 1.5, 2.0, 2.5 and 3.0 ppm) respectively. The mortality rate was noted, the test medium and dead fishes were removed immediately. The LC 50 was calculated by using Probit analysis method (Finney,1971). Water temperature varied according to the ambient laboratory conditions but averaged 21 0 C, and a photoperiod of 15L:13D was maintained with fluorescent tubes. In order to investigate the behavioural changes in the experimental animal four different concentration of heavy metal copper ( 0.25, 0.50, 0.75, 1ppm ) were selected. Before treatment, the fish (average standard length 10.5±1.5 cm and average body weight 15.2± 2.2 gram) were divided into five groups (four experimental and one control) comprising 12 animals each, placed in individual treated aquaria of 30 litre capacity and used for experiment. The water in the tank was changed daily with dechlorinated water containing the same test concentration of the metal. The experiments lasted for 15 days. The experimental and control fish were with out food during the period of observation. The present study is carried out in the post graduate department of zoology, Poona College of Arst, Science and Commerce, Camp, Pune in the year 2010. RESULTS AND DISCUSSION The given table indicates that there was no change in the behaviour of the animal at the lowest treatment of copper 0.25 ppm. The avoidance behaviour of animals to pollutant in the surrounding water was observed at 0.50 ppm. The erratic swimming, jerky body movements, rolling the body, convulsion, and mucous secretion over the body observed in the experimental fish at 0.75 ppm. In the highest treatment of copper, 1 ppm fish exhibit loss of 406
equilibrium, rapid opercular movements, difficulty in breathing and lethargic. It is evident from the observed behavioural changes in C. batrachus that the lowest treatment of copper did not cause any significant changes. However, in the next treatment the restlessness while in subsequent treatment the drastic changes in the behaviour of exposed fish noted. The entire observation concluded as the effect and the dose was found to be directly proportional to the behaviour of the experimental fish. Behavioral abnormalities in various fish species on exposure to heavy metal have been reported by several researchers. According to Ghatak and Konar (1990) Tilapia mossambica when exposed to cadmium showed frequent surfacing with irregular opercular movements and loss of equilibrium. Similarly Holcombe et al., (1970) reported hyperactivity, erratic swimming and loss of equilibrium in Brook trout, Salvalinus fontinallis, in response to lead treatment. The loss of equilibrium, frequent surfacing, sinking, burst of erratic swimming, and gradual onset of inactivity in Rainbow trout, Salmo gairdneri, on mercury exposure, have also been determined (MacLeod and Pessah, 1973). According to Lewis and Lewis, (1971) Notiemigonus crysoleucus, when exposed to 5 ppm copper piped at the surface, became restless and finally lost equilibrium. Similar results obtained when Lepomis macrochiurs treated with different concentration of copper (Ellgaard and Guillot, 1988). Lethargic response and frequent surfacing along with gulping of air in exposure to 0.25 ppm copper were observed in Heteropneusta fossilis (Singh and Reddy, 1990). Eutroplus maculatus on exposure to copper, mercury and selenium showed irregular erratic swimming, frequent surfacing, gulping of air, revolving, convulsions and accelerated ventilation with rapid arrhythmic opercular and mouth movements (Veena et al., 1907). Behavioural abnormalities have been attributed to nervous impairment due to blockage of nervous transmission between the nervous system and various effectors sites (Nriagu, 1970). According to Cearley (1971) the dysfunctions of enzyme may cause paralysis of respiratory muscles and depression of respiratory centre in the medulla oblongata. Disturbances in energy pathways which results in depletion of energy may a cause of lethargy in fish due to toxicity (Ellgaard and Guillot, 1988). In the present study no change in fish behaviour at 0.25 ppm indicates, the avoidance behaviour of the animal to metal. It is further suggested that the least concentration of copper do not reach the stage of exhaustion, rather they accommodated and adapted to the stressor. The toxicants interfere with the functions of the nervous system resulting in loss of coordination and locomotion, instability followed by hyper excitability, tremors and convulsions (Wouters and Van den Brecken, (1978). The hyper excitability of fish exposed to copper at 0.75 ppm may probably be due to disturbances in acetylcholine esterase activity (Ach E) in the nervous system as suggested earlier (Reddy, et al., 1991 and David, 2004) which leads to accumulation of acetylcholine causing prolonged postsynaptic excitability. 407
The increased opercular movements and corresponding increase in frequency of surfacing of experimental fish, C. batrachus in the present study clearly indicate that fish must adaptively be shifting towards aerial respiration from aquatic one and trying to avoid contact with the toxicant through gill chamber. The accumulation and increased secretion of mucous on the body surface of Clarias batrachus exposed to copper toxicity may be an adaptive response perhaps providing additional protection against corrosive nature of the toxicant and to avoid the absorption of toxicant by the general body surface. This is in agreement with the earlier findings of Das and Mukherjee, (2003), Yilmaz, (2004), and Prashanth et al., (2005). Behavioural changes produced by many toxicants result in a progressive series of poisoning symptoms such as hyperactivity, tremors, ataxia, convulsions, eventually paralysis and death observed by several workers (Muniyan and Veeraraghavan, 1999, Mushigeri and David, 2004). Increase in swimming activity with increased breathing rate, lethargic condition and loss of equilibrium as observed in C. batrachus exposed to 0.75 and 1 ppm copper are attributed probably to the disturbances in the metabolic reactions resulting in the depletion of energy. It is possible that animals which have higher metabolic activity could require higher levels of oxygen and thus would have a higher respiration or breathing rate (Canl and Karg, 1995). Lethargy and loss of equilibrium may be due to depletion of energy in the body of the experimental animal exposed to different copper dose. A drop in the metabolic production of cellular energy in the form of high-energy bond in Bluegill sunfish Lepomis macrochiurs, on exposure to copper has been reported (Ellgaard and Guillot, 1988). Decreased and increased glucose levels on cadmium exposure have been reported in Heteropneustes fossilis and Labeo rohita respectively (Das and Banerjee, 1980). The varying levels of blood glucose are indicative of abnormal carbohydrate metabolism and possibly the result of impaired hormonal control (Andersson, et al., 1988). The release of corticosteroid hormones in Sockey Salmon, Oncorhyncus nerka when treated with copper has been reported (Donaldson and Dye, 1975). Heavy metal exposure alter carbohydrate metabolism in Cyprinion watsoni and resulted in the depletion of energy, (Shah, et al., 1995). This depletion of energy might be the cause of behavioural impairments observed in our experimental fish, C. batrachus. Undoubtedly the over all results of the present study are in agreement with the findings of the above researchers. CONCLUSION The role of copper in various biological processes such as oxidative phosphorylation, gene regulation, free radical, essential cofactor, homeostasis and oxygen transport is very significant. However, when its concentration exceed than the metabolic requirement it proves to be harmful. In the present study the toxicity of copper and its harmful effect revealed various prominent abnormal behaviour such as erratic swimming, convulsion, loss of balance and difficulty in breathing in the exposed animal. 408
It is suggested that the behavioral impairment of the experimental animal may be due to interference of copper with the function of nervous system and disturbance in acetylcholine esterase activity resulting in loss of coordination and locomotion followed by hyper excitability. Difficulty in breathing, lethargic condition and loss of equilibrium in the animal at a higher concentration of copper is attributed probably to the disturbance in the pathway of metabolic reactions and alter in carbohydrate metabolism resulting in depletion of energy. Table 1: Behavioural changes in C. batrachus exposed to different concentration of heavy metal copper Parameters/ events 0.25 ppm 0.5 ppm 0.75 ppm 1 ppm Behavioural change --- + ++ +++ Restlessness --- ++ +++ +++ Erratic swimming --- + ++ +++ Jerky body movement --- --- ++ +++ Rolling the body --- --- + +++ Convulsion --- --- + +++ Mucous secretion --- + ++ +++ Loss of equilibrium --- --- --- +++ Rapid opercular movement --- --- ++ +++ Difficulty in breathing --- --- ++ +++ Lethargic --- --- ++ +++ +++ Intensely, ++ Moderately, + Lightly, --- No REFERENCES Albel, P. D. 1998. Water Pollution Biology. Taylor and Francis Ltd. London. Andersson, T., Forlin, L., Hardig, L., and Larsson, A. 1988. Physiological Disturbances in fish living in coastal water polluted with bleached kraft pulp mill effluents. Can. J. Fish. Aquat. Sci. 45: 1525-1536. Bennet, W. A., Sosa, A., and Britinger, T.L., 1995. Oxygen tolerance of fathead minnow previously exposed to copper. Bull. Environ. Contam.Toxicol. 55 (4): 517-524. Canl, M., and Kargin. F. 1995. A comparative study on heavy metal (Cd, Cr, Pb and Ni) accumulation in the tissue of Carp, Cyprinus carpio and Nile fish, Tilapia nilotica. Tr. J. of Zoology. 19: 165-171. 409
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