Drug and Chemical Toxicology, 29:255–267, 2006 Copyright © Taylor & Francis Group, LLC ISSN: 0148-0545 print DOI: 10.1080/01480540600651543 LDCT 0148-0545 1525-6014 Drug and Chemical Toxicology, Vol. 29, No. 03, March 2006: pp. 0–0 Drug and Chemical Toxicology Sublethal Effects of Profenofos on Locomotor Behavior and Gill Architecture of the Mosquito Fish,Gambusia affinis Effect of Profenofos on Behavior and Gill of Fish Venkateswara Rao et al. J. Venkateswara Rao, 1 Ghousia Begum, 1 N. M. Jakka, 1 K. Srikanth, 1 and R. Nageswara Rao 2 1 Toxicology Unit, Biology Division, Indian Institute of Chemical Technology, Hyderabad, India 2 Analytical Division, Indian Institute of Chemical Technology, Hyderabad, India Subacute studies of profenofos on mosquito fish, Gambusia affinis, were carried out for 20 days to assess the locomotor behavior and structural integrity of gill in relation to bioaccumulation and targeted enzyme acetylcholinesterase (AChE; EC 3.1.1.7). The sublethal concentration of 0.13 mg/L (1/5 of LC 50 ) altered locomotor behavior such as distance traveled and swimming speed in exposed fish. This could be due to inhibition in the activity of acetylcholinesterase and deformities in the primary and secondary lamella of gill. The bioaccumulation values indicated that the accumulation of profeno- fos was highest in viscera followed by head and body. The average bioconcentration fac- tor values are 254.83, 6.18, and 2.52 μg/g for viscera, head, and body. The findings revealed that profenofos is highly toxic even at sublethal concentrations to the mos- quito fish, Gambusia affinis. Keywords AChE, Behavior, Bioaccumulation, Fish, Gill, Profenofos. INTRODUCTION Synthetic pesticides are fairly well recognized as a cost-effective method of con- trolling pests, but these chemicals are toxic to aquatic species, particularly fish. There is a growing concern worldwide over the indiscriminate use of such chemicals, resulting in environmental pollution and toxicity risk to nontar- geted organisms (Coppage and Bradeich, 1976; Venkateswara Rao, 2004a). Responses of aquatic organisms are broad-ranged depending on the toxic com- pound, exposure time, water quality, and the species (Eisler, 1970; Fisher, Address correspondence to J. Venkateswara Rao, Scientist, Toxicology Unit, Biology Division, Indian Institute of Chemical Technology, Hyderabad 500 007, India; Fax: +91 (40) 2719 3227; E-mail: jv@india.com; jv@iict.res.in