India is known as an agricultural country where the Indian lifestyle is mostly dependent on agricultural crops production. Agriculture is an important part of Indian economy. India could contribute to feeding not just itself but the world. For the secure food or crops production various types of insecticides and pesticides are use in all over India. Pesticides are a very important group of environmental pollutants used in intensive agriculture for protection against diseases and pests. Pesticides have contributed considerably to the human welfare, but their residues often reach ecosystems causing undesirable impact. The use of pesticides had a very positive impact in the overall increase in food production; the risks associated with this include deterioration of human health, water contamination, livestock animal poisoning and death of beneficial insects, wildlife endangerment and pesticide tolerance (Gupta, 2004 and Zhang et. al., 2004). The estimated annual application is more than 4 million tons, but only 1% of this reaches the target pests (Gavrilescu, 2005). These pesticides leave residues in the soil and water for several days after their application, and pose a constant threat to the non-target organisms especially fishes (Magare and Patil, 2000). The agricultural runoff from treated areas enters the rivers and aquaculture ponds that are supplied by rivers are posed a threat on survival of fish and other aquatic organism. Such rivers and the adjacent aquaculture ponds are likely to be contaminated by pesticides (Begum, 2004). Misuse of highly toxic pesticides, coupled with a weak or a totally absent legislative framework in the use of pesticides is one of the major reasons for the high incidence of pesticide poisoning in developing countries (Konradsen et al., 2003; Remor et al., 2009). This kinds of pesticides applied to the crops are volatile in nature. The illiteracy of the rural population, lack of information and training on pesticide safety, poor spraying technology and inadequate personal protection during pesticide use have been reported to play a major role in the intoxication scenario (Hurtig et al., 2003; Atreya, 2008). Hence, pesticides have become an increasingly serious source of chemical pollution to the environment. Human population growth and industrial development have been the major causes of coastal contamination around the world during recent years (Caussy et al., 2003).
Pesticide is defined by United Nations Environment Programme (UNEP, 2005) as any substance or mixture of substances intended for preventing, destroying, repelling or mitigating any pest. Pesticides are “Biocides”, i.e. they are designed to kill life (Singh, 1999). The role played by the magic chemicals, called “pesticides” are quite significant but have given rise to serious other health problems (Gupta, 1989). Majority of the pesticides used for agriculture and domestic pest control purpose, disperse rapidly in the environment with longer persistence in soil, aquatic bodies, air, food material and the bodies of living beings (Mencher 1991). Widespread use of pesticide is now a worldwide phenomenon (Omitoyin et al., 2006). The indiscriminate use of the pesticides worldwide for agricultural and other activities poses great threat to the environment (Pandey et. al., 2009). Pesticides play an important role in sustaining the agricultural production by protecting all kinds of crops from pest attack and vector-borne diseases (Adhikari et al. 2004; Abhilash and Singh 2009).
Use of pesticides in India began in 1948 when DDT (dichloro diphenyl tri chloroethane) was imported for malaria control and BHC (benzene hexachloride) for locust control. India started pesticide production with manufacturing plant for DDT and BHC, HCH (hexachloro cyclohexane) in the year 1952. In India, 51% of foods commodities are contaminated with pesticide residues and out of these, 20% have pesticides residues above the maximum residue level values on a worldwide basis (Gupta, 2004; Agnihotri, 1999). Among all pesticides, the organophosphates are widely used to control pests because of their rapid effectiveness and easy biodegradation (Mahboob and Siddiqui, 2002). Pesticides have contributed considerably to the human welfare but their residues often reach ecosystems causing undesirable impact (Vani et. al., 2012).
Organophosphate (OP) compounds are one of the most commonly used insecticides in agriculture and public health, accounting for 50% of the global insecticidal use (J.E. Casida, G.B. Quistad 2004). Organophosphorus are the most common pesticides used in most countries around the world to protect agricultural crops against pests (Kazemi et. al., 2012). Organophosphorus insecticides represent one of the most widely used classes of pesticide with high potential for human exposure in both rural and residential environments (Ngoula et al., 2007). They have become increasingly popular for both agricultural and home use because of their unstable chemical structure leads to rapid hydrolysis and little long-term accumulation in the environment (Kumar et. al., 2010). The first organophosphorus insecticide, tetraethyl pyrophosphate, was developed and used in 1937 (Dragun et al., 1984). At the same time, two chemical warfare agents (also called nerve agents); Tabun and Sarin were developed and produced. Later, several other organophosphorus pesticides were developed and commercialized. These pesticides are widely used worldwide to control agricultural and household pests. Overall, organophosphorus compounds account for 36% of total pesticides used globally (Pradnya et al., 2004). Organophosphorus (OP) is the general name for organic derivatives of phosphorus. OP compounds are usually esters, amides, or thiol derivatives of phosphoric, phosphonic, phosphinic, or thiophosphoric acids with two organic and additional side chains such as cyanide, thiocyanate, and phenoxy group (Carlton et al., 1998; Balali-Mood and Saber 2012). Their widespread use and accessibility have resulted in increased numbers of human poisonings especially in developing countries of Asia (Maiti et. al., 2011).
Quinalphos is an organophosphate compound, which is widely used in Indian agriculture for control of pests of various crops such as sugarcane, cotton, groundnut, rice etc. Quinalphos is classified as number 2 group in toxicity by the WHO. The various trade names of Quinalphos are Bayrusil, Ekalux etc. This chemical produces it’s effects when comes into contact or ingested by a wide range of chewing, sucking and mining pests belonging to the genus Lepidoptera, Diptera, Coleoptery, Hemiptera etc. It is a contact, non-persistent insecticide & acaricide, which is effective against caterpillars, mosquitoes & mites. The major use of Quinalphos in farming is to protect corn, cotton and fruit trees against insects. It is rapidly degraded in the environment. The half life of quinalphos in the field can vary greatly depending on the application rate, soil type, and environmental variables such as temperature and moisture. The half life range is between 10 to 16 days in soil, less than 24 hours in water (Racke, 1993). It is a hard insecticide, which has become a matter of concern because of its potential and hazardous effect. It is highly toxic to non-target organisms, including humans; Quinalphos (O, O-diethyl O-quinoxalin-2-yl phosphorothiate) is a synthetic organophosphate, non-systemic, broad spectrum insecticide and acaricide, acting as a cholinesterase inhibitor with contact, stomach and respiratory action. The acute and chronic health effects are similar to other correct OPs, and cancer risks have been reported (Gandhi and Snedeker, 1999).
Fig. I. Structure of Quinalphos

PRODUCT IDENTITY AND USES
Pesticide type : Insecticide, Acaricide
Substance group : Organophosphate
Physical and Chemical properties of Quinalphos
Common names : Quinalphos 25% EC
Molecular formula : C12H15N2O3PS
IUPAC name : O,O-diethyl O-2-quinoxalinyl phosphorothioate
CAS name : O,O-diethyl O-2-quinoxalinyl phosphorothioate
CAS registry number : 13593-03-8
Relative molecular mass (g mol-1) : 298.297
Melting point (oC) : 31 (88 oF; 304 K)
Vapour pressure 25 oC (mPa) : 0.346
Water solubility (25 oC) : 22 mg/l
Physical state : Colorless crystals
Fish play a major role for the flow of energy in aquatic ecosystems and are constitute one of the major food resources for human. Fishes have greater sensitivity to changes in the aquatic environment (Vinodhini and Narayanan, 2008). Capacity to accumulate large quantity of pollutants and important link in the food chain, fishes are often used as indicator organisms to monitor quality of aquatic systems the world over (Rajkowska and Protasowicki, 2011). Fish sensitivity to different pesticides could be explained by their relatively slow metabolism and elimination of these compounds (David, 2003). They are exposed continuously to contaminants in the natural habitat and constitute an important part of human diet (Jha, 2004). Fishes have been the most popular test organisms because they are presumed to be the best understood organisms in the aquatic environment (Palanikumar et al., 2012). Fishes are widely used to evaluate the health of aquatic systems and physiological changes in fishes serve as biomarkers of environmental pollution (Winger et al., 1990).
For the present investigation, the freshwater teleost, Channa gachua is a most common fish present in freshwater ecosystem has been selected as the test fish due to its easy availability throughout the year, hardy nature, ease to maintain in the laboratory conditions with minimum care and moderate nutritional value. C. gachua is commonly occurring in the water bodies located in the Kaygaon (19.6327° N, 75.0286° E) region in Aurangabad. Channa belongs to the category of air breathing fishes and can live without water for about 14 hrs provided the body is kept moist i.e., In addition to aquatic oxygen they are privileged to respire atmospheric oxygen as a result of which they can be easily handled and kept in living conditions for longer duration without much precautions. On account of the shape of the head which resembles that of a snake, the fish has acquired a common name “Dwarf Snake Headed Fish”. It belongs to the family “Ophiocephalidae” which includes 9 species out of which Channa gachua is the smallest. It is locally available throughout the year and is commonly known as “Dhok” in Hindi. Its common name in the Aurangabad region is the Dok and Dhokarya. It is the best food fish (protinaceous), available and fetches a good price.