International Journal of Scientific and Research Publications, Volume 4, Issue 3, March 2014 1 ISSN 2250-3153 www.ijsrp.org Sublethal effects of phenolic compounds on biochemical, histological and ionoregulatory parameters in a tropical teleost fish Oreochromis mossambicus (Peters) Remya Varadarajan, Hari Sankar H .S, Jisha Jose and Babu Philip Department of Marine Biology, Microbiology & Biochemistry, Cochin University of Science & Technology, Fine Arts Avenue, Cochin – 16, Kerala, India Abstract- Sub lethal toxicity of phenolic compounds in a tropical teleost fish Oreochromis. mossambicus was investigated. Experimental animals were exposed to sub lethal (1/10th of 96 hr LC 50 ) concentration of phenol (3.12 mg l-1) and m-cresol (2.2 mg l-1) for a period of 21 days using a semi-static test bioassay system. Significant (P<0.05) lack of cortisol response was observed on exposure to both the phenolics. Furthermore total carbohydrate significantly (P<0.05) decreased in liver and muscle and blood glucose level was also significantly (P<0.05) decreased. The LDH (lactate dehydrogenase) showed significantly (P<0.05) elevated activity in the liver and kidney of fishes treated with phenol suggesting anaerobic glycolysis. Elevation in the activity (P<0.05) of ALT (alanine amino transferase) can be considered as a response to meet the excess energy demand. Increased serum ACP (acid phosphatase) activity suggests an increase in lysosomal mobilization. Also a significant (P<0.05) inhibition of branchial ATPases (Na + K + - ATPase, Mg 2+ -ATPase and Ca 2+ -ATPase) was observed. Moreover gill histopathological analysis on phenol exposure revealed severe lesions such as architectural loss, necrosis, desquamation of epithelial layer, hyperplasia and telangiectesis. Significant changes observed on m-cresol exposure were lamellar necrosis, lamellar shortening, telangiectesis and lamellar clubbing. Phenolic compounds even at very low concentrations (1/10th of 96 hr LC 50 ) for a short duration of 21 days induce metabolic stress, impair branchial functioning and are likely to induce tissue damage in O. mossambicus. Index Terms- biomarker, branchial ATPases, m-cresol, fish, phenol I. INTRODUCTION henolic compounds are a group of wide spread xenobiotics. They are common constituents of aqueous effluents from the industrial processes such as resin production, oil refining and coking plants [1]. Aquatic biota uptake these pollutants directly from water, sediments, suspended and particulate matter. Phenols are listed among the potent chemical toxicants adversely affecting the aquatic habitats [2]. Among the different phenolic compounds, we were interested to study about phenols and cresols which are widely used as organic solvents. These compounds have also been identified in water- soluble fractions of crude oil since they are potential degradation products of aromatic hydrocarbon metabolism [3]. Also phenol is a toxic metabolite of benzene, a ubiquitous industrial and environmental pollutant [4]. Phenol is among the first compound described as toxic by the Environmental Protection Agency - United States and due to its relevance as an ecotoxin it has been maintained in the priority list. Creosote is classified as a hazardous substance for occupational exposure [5]. Crude cresol (commercial grade) contains appromximately 20% o-cresol, 40% m-cresol, and 30% p-cresol. Fish can be used as bioindicators to evaluate the environmental contamination levels of hydrocarbons, because these pollutants tend to accumulate more in organisms than in the environment [6]. The aim of this study was to investigate the impact of sub-lethal concentrations (1/10th of LC 50 /96 h) of phenol and m-cresol in a tropical teleost fish, Oreochromis mossambicus. For this biochemical, physiological and histological biomarkers were experimented by the end of the exposure period (21days). II. RESEARCH ELABORATIONS Animals and Experimental Exposure Investigations were carried out in a fresh water fish Oreochromis mossambicus (15±3g) procured from the culture ponds of Kerala Agricultural University (Puduvypu), India. The water in the aquarium was renewed daily and was aerated mechanically. The average values of water quality parameters were as following: dissolved oxygen content of 7.8 ± 0.03 mg l -1 , hardness below detectable amounts, pH 7.0 ± 0.37, temperature 26 ± 30ºC and salinity 0 ppt (parts per thousand) [7]. They were fed on a commercial diet ad libitum and were maintained in tanks for a month before the experiment in order to acclimate to the experimental system. Sub-lethal toxicity studies The acute LC 50 value of phenol and m-cresol was determined in the laboratory using semi-static method. The LC 50 levels and 95% confidence limits were calculated using Probit analysis [8]. The acclimated fishes (15±3 g) were divided into three groups (10 fishes each) in control and sub lethal concentrations of phenol and m-cresol. Triplicates were kept for both the treated groups and respective controls. Sub lethal concentration of phenol (3.12 mg l -1 ) and m-cresol (2.2 mg l -1 ), corresponding to 10% of the LC 50 -96h of the respective compound was used. The system water was renewed every 24h (semi-static) with the same P