Toxicological & Environmental Chemistry, Apr.–June 2006; 88(2): 355–365 Oxidative stress and changes in locomotor behavior and gill morphology of Gambusia affinis exposed to chromium GHOUSIA BEGUM, J. VENKATESWARA RAO, & K. SRIKANTH Toxicology Unit, Biology Division, Indian Institute of Chemical Technology, Hyderabad 500-007, India (Received 27 April 2005; revised 22 July 2005; in final form 7 February 2006) Abstract Sublethal effects of chromium trioxide on mosquito fish, Gambusia affinis, were carried out for 28 days on day 4, 8, 12, 16, 20, 24, and 28. The sublethal effects of chromium (LC 10 , 77.62 mg L 1 ) on antioxidant enzymes, thiobarbituric acid reactive substance (TBARS), locomotor behavior, and gill morphology were studied. The antioxidant enzymes like superoxide dismutase (SOD) and catalase were induced throughout the exposure span of 28 days. Percent induction was also increase with the days of exposure. Lipid peroxidation product, malondialdehyde was enhanced in the viscera tissue of chromium-exposed fish. Perturbation of locomotor behavior like decrease in distance travelled (m min 1 ) and in swimming speed (cm s 1 ) was observed in exposed fish. Chromium toxicity caused alterations in gill morphology like hypertrophy and hyperplasia in secondary lamellae followed by detached epithelium with severe necrosis. It can be concluded from the results that Cr intoxication in Gambusia fish, caused induction in antioxidant enzymes and lipid peroxidation, plus changes in gill morphology and locomotor behavior. Keywords: Sublethal, toxicity, chromium, viscera, antioxidant enzymes and TBARS, behavior, gills, morphology Introduction Heavy metals and their salts constitute a very important group of environmental pollutants since they are potent metabolic inhibitors. The inherent toxicity of a metal depends upon its capacity to disturb the dynamic life processes in biological system by combining with cell organelles, macromolecules, and metabolites. The indiscriminate introduction of chromium from various industries into the aquatic ecosystem poses a major threat for survival and Correspondence: Ghousia Begum, Toxicology Unit, Biology Division, Indian Institute of Chemical Technology, Hyderabad 500-007, India. Tel.: þ91-40-27193191. Fax: þ91-40-27173387. E-mail: ghousia@ins.iictnet.com ISSN 0277-2248 print/ISSN 1029-0486 online ß 2006 Taylor & Francis DOI: 10.1080/02772240600635985