Global Veterinaria 12 (3): 393-398, 2014 ISSN 1992-6197 © IDOSI Publications, 2014 DOI: 10.5829/idosi.gv.2014.12.03.82429 Corresponding Author: Nageshwar Wast, Department of Zoology, Govt Holkar Science College, Indore, India. 393 Acute Toxicity of Chlorpyriphos 50% + Cypermethrin 5% EC to the Guppy, Poecilia reticulata (Peters, 1859) Nageshwar Wast, A.K. Gupta, 1 2 M.M. Prakash and S. Gaherwal 1 1 Department of Zoology, Govt Holkar Science College, Indore, India 1 College of Fisheries, Maharana Pratap University of Agriculture and Technology, Udaipur, India 2 Abstract: The present study was aimed to investigate the acute toxicity of Chlorpyriphos 50% +Cypermethrin 5% EC to the juveniles, males, females and mixed population of a freshwater fish, Poecilia reticulata (Peters). The experimental water of hardness 560±5 mg/l and pH 7.4±0.3 were used in bioassay tests. The LC values 50 and the 95 percent confidence limits were calculated statistically at different concentrations and time intervals (24, 48, 72 and 96 hrs) to juveniles, males, females and mixed population of Poecilia reticulata by Probit analysis method. Behavioural changes in the studied fish were also observed carefully after subjected to the various concentrations of this pesticide. The order of sensitivity of selected pesticide to different specimens of Poecilia reticulata was recorded as: females < mixed population <males< juveniles. The presumable safe or harmless concentration and safe dischargeable concentrations of Chlorpyriphos 50% + Cypermethrin 5% EC were ranged in between 4.381to 32.216 and 1.044 to1.069 ppb respectively. Key words: Toxicity Chlorpyriphos Cypermethrin LC Values Poecilia reticulata 50 INTRODUCTION fish [11]. Therefore, an attempt has been made to Chlorpyriphos is a broad-spectrum Cypermethrin 5% EC to juveniles, males, females and organophosphorus compound, used as a contact and mixed population of a freshwater fish, Poecilia reticulata stomach poison for the control of pest such as (Peters, 1859) to estimate the LC values, the 95 percent cockroaches, mosquitoes, flies, bedbugs and ants on a confidence limits, presumable safe and safe dischargeable wide variety of crops [1]. It is extremely toxic to aquatic concentrations for better management of aquaculture. invertebrates, freshwater fish and marine organisms [2]. Chlorpyriphos inhibit the cholinesterase enzyme causes MATERIALS AND METHODS accumulation of acetylcholine in the synaptic cleft which leads to neurotoxicity and eventually death [3, 4]. The experimental fish, Poecilia reticulata were Cholinesterase inhibition was observed at very low collected from local ditches of Udaipur and separated as concentrations of this insecticide during acute toxicity juveniles, males and females for further rearing and tests in fish [5]. Acute toxicity of Chlorpyriphos is due to acclimatization. The juveniles, males and females were production its active metabolite Chlorpyriphosoxon [6]. acclimatized separately in plastic tank of 250 litres Cypermethrin is a synthetic, broad-spectrum capacity for ten days prior starting the experiment and pyrethroid based insecticide, extensively used in were fed rice bran and oil cake (1:1). During the bioassay households, industrial and agriculture fields [7] for tests, the fishes were not provided any food supplement controlling many insect pests [8]. Cypermethrin enters to avoid excretory waste products and change in into aquatic system through agriculture run-off water and metabolic rate, which may influence the toxicity of the test affects the non-target organisms like fishes and thus alter solution. Healthy, juveniles (1.0±0.2cm), males (2.8±0.2cm) the metabolism [9], haematology [10] and population of and females (3.9±0.3 cm) were selected for the bioassay screen the short-term toxicity of Chlorpyriphos 50% + 50