Effect of Malathion on Survival, Growth, and Food Consumption of Indian Cricket Frog (Limnonectus limnocharis) Tadpoles H. P. Gurushankara, 1 S. V. Krishnamurthy, 2 V. Vasudev 1 1 Department of P.G. Studies and Research in Applied Zoology, Kuvempu University, Shankaraghatta-577451, Shimoga, Karnataka, India 2 Department of P.G. Studies and Research in Environmental Science, Kuvempu University, Shankaraghatta-577451, Shimoga, Karnataka, India Received: 27 January 2006 /Accepted: 26 July 2006 Abstract. The effects of short-term exposure (28 days) of free- feeding Limnonectus limnocharis (Indian cricket frog) tadpoles to field concentrations of malathion were investigated. This frog species is a major biotic component of the agroecosystems of the Western Ghats (13°18¢, 75°25¢ and 13°22¢, 75°28¢), where malathion (diethyl [(dimethoxy phosphino thioyl] bu- tanediote), an organophosphate pesticide, is being used exten- sively. Although malathion is known to cause nonreversible acetylcholine inhibition and diminishes activity, growth and development in amphibian tadpoles, such data on Indian amphibian species are lacking. In the present study, increments in the following were used to assess such an impact: tadpole growth; increase in total length, body length, tail length, and body weight; and food consumption. The different concentra- tions of malathion employed were 500, 1000, 1500, 2000, and 3000 lgL –1 . Malathion exposure produced significant effects on all measured parameters. Tadpole survival decreased from 20 to 6 tadpoles, with an increase in concentration followed by a decrease in growth. Food consumption of surviving tadpoles also decreased (0.067 mg.g –1 .d –1 to 0.0075 mg.g –1 .d –1 ) with increased malathion. Decreased food consumption, growth, and development of L. limnocharis tadpoles with an increase of malathion concentration (within field concentration range) over temporal scale reveal the possible threat to this species in the agroecosystems of the Western Ghats. More than a decade ago, the widespread decrease in amphibian populations prompted alarm among biologists throughout the world. A number of possible reasons for the apparent decrease—including habitat loss, overharvesting, ultraviolet-B radiation, global warming, diseases, and chemical pollution of the environment—have since been proposed and analyzed (Dalton 2002; Krishnamurthy & Hussain 2004). Different arguments still exist about how the various factors affect amphibian populations and whether subtle environmental influences, such as pesticide residues, have a greater impact on amphibians than the direct loss of habitat (Daniels 1991; Beik et al. 2002; Glennemeier & Begnoche 2002). Pesticides are important in controlling domestic, agriculture, and industrial pests, including vector organisms. Pesticides adversely affect nontarget organisms and are widely used in agricultural ecosystems, wherein amphibians, the nontarget species, are major components of the wetland biota. Thus, frogs living in agricultural ecosystems and wetlands are exposed to these pesticides (Kaur & Chemma 1986; Lambert 1997). Malathion (diethyl [(dimethoxy phosphino thioyl] butanediotae) is an organophosphate pesticide and is one of the five most commonly used pesticides in India, accounting for 65% of all organophosphate pesticides applied in the field (Indian Chemical Statistics 2002). The environmental concentration of this pesticide in agroecosystem sediment and water have been reported to vary from 2.62 to 129 lg kg –1 and from 0.699 to 298 lgL –1 , respectively (Rao & Pillala 2001). Malathion residue was frequently detected in soil, water, and human, animal, and plant tissue (Harris et al. 1998; Karanth 2002; Rajendran 2003). Malathion, at a concentration of 0.3 mg L –1 , had direct effects on tadpoles and is known to kill larval anuran at higher concentrations (Relyea et al. 2005). As a result of this pesticideÕs intensive use, the amphibian population may be severely threatened. Several studies have indicated that organophosphate pollution may occur at higher concentrations in small and shallow ponds (Berrill et al. 1994, 1995). In the central Western Ghats, such small pools and puddles are preferred breeding habitats for many amphibians, including L. limnocharis tadpoles. Mohanty-Hejmadi and Dutta (1981) found an increase in the time required for completion of tadpole metamorphosis with exposure to malathion (1.5 to 3.5 mg L –1 ). However, the impact of malathion on other semiaquatic anuran gen- eralists has not been studied in detail. Therefore, the purpose of this experiment was to determine the impact of malathion on survival, growth, development, and food con- sumption of L. limnocharis (Indian cricket frog) tadpoles. The tadpoles of this species were selected as the test species because the tadpoles are handy and maintainable in the laboratory. Correspondence to: S. V. Krishnamurthy; email: svkrishnamurthy@ yahoo.co.in Arch. Environ. Contam. Toxicol. 52, 251–256 (2007) DOI: 10.1007/s00244-006-0015-5