en عمومى General پژوهشي Research <p><strong>Background:</strong> Chlorpyrifos is an organophosphate pesticide that elicits broad-spectrum insecticidal activity against a number of important arthropod pests. Determining the insecticides&rsquo; toxicity to amphibians can give us a better understanding regarding the role of toxicants in amphibian declines. This information would be beneficial to assess their ecological relevance at environmental concentrations. The present study assessed toxicity of chlorpyrifos to an anuran <em>Rana cyanophlyctis</em>.</p> <p><strong>Methods:</strong> For the determination of LC₅₀ values for chlorpyrifos, four-day static renewal acute toxicity test was used. Five replicates each containing ten frogs were subjected to each concentration of chlorpyrifos (2, 4, 6, 8, 10, 12, 14 and 16 mg/L) for the test. Mortality of the frog at different exposure periods (24, 48, 72 and 96 h) was subjected to Probit analysis with the POLO-PC software (LeOra Software) to calculate the LC₅₀ and 95% confidence level.</p> <p><strong>Results:</strong> The LC₅₀ values of chlorpyrifos for the frog<em> R. cyanophlyctis</em> at 24, 48, 72, and 96 h were 8.252, 7.254, 6.247 and 4.993mg/L, respectively.</p> <p><strong>Conclusion:</strong> Mortality has been noticed in chlorpyrifos treated frogs related to the decline in amphibian population. Therefore, chlorpyrifos should not be used near water reservoirs.</p> LC50, Toxicity, Chlorpyrifos, Anuran, Amphibian, Organophosphate Amphibian, Anuran, Chlorpyrifos, LC50, Organophosphate, Toxicity 45 49 http://ijt.arakmu.ac.ir/browse.php?a_code=A-10-74-5&slc_lang=en&sid=1 Ajai Kumar Srivastav ajaiksrivastav@hotmail.com 10031947532846006106 10031947532846006106 Yes Department of Zoology, DDU Gorakhpur University, Gorakhpur, India. Shilpi Srivastava ajaisrivastav@hotmail.com 10031947532846006107 10031947532846006107 No Department of Zoology, DDU Gorakhpur University, Gorakhpur, India. Sunil Kumar Srivastav 10031947532846006108 10031947532846006108 No Department of Zoology, DDU Gorakhpur University, Gorakhpur, India. Nobuo Suzuki 10031947532846006109 10031947532846006109 No Professor, Noto Marine Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Ogi, Noto-cho, Ishikawa, Japan.