en Toxicology Toxicology پژوهشي Orginal research papers The present study investigated the effects of Cd, Cu and Zn on the sperm motility of <em>Caspiomyzon wagneri</em>. The sperm of the specimens were exposed to 0.01, 0.1, 1, 10, 100 and 1000 mg L^-1 of the heavy metals, and the duration of sperm motility and percentage of motile sperms were measured using a compound microscope and digital camera. Based on the results, sperm motility parameters decreased with increasing the concentrations of heavy metals. A concentration of 1000 mg L^-1 of heavy metals stopped completely the motile sperms. The present study indicated that heavy metals have detrimental effects on sperm motility and possibly decrease the fertilization and hatching rates of <em>C.&nbsp;wagneri</em> in the spawning ground, and thus a serious threat to the survival of this rare and native species. Pollution, Reproduction, Spawning, Mobility indices, Heavy metals. 2943 2953 http://jifro.ir/browse.php?a_code=A-10-537-3&slc_lang=en&sid=1 S. Eagderi soheil.eagderi@ut.ac.ir 100319475328460038322 100319475328460038322 Yes University of Tehran B. Mojazi Amiri bmamiri@ut.ac.ir 100319475328460038323 100319475328460038323 No University of Tehran H. Poorbagher poorbagher@ut.ac.ir 100319475328460038324 100319475328460038324 No University of Tehran M. Nasrollah Pourmoghadam soheil.eagderi@ut.ac.ir 100319475328460038325 100319475328460038325 No University of Tehran N. Nemati Mobin soheil.eagderi@yahoo.com 100319475328460038326 100319475328460038326 No University of Tehran N. Pourang n_pourang@yahoo.com 100319475328460038327 100319475328460038327 No Iranian Fisheries Science Research Institute (IFSRI), Agricultural Research Education and