effect of sub-lethal concentrations of manganese on sperm motility of the caspian lamprey (cspimyzon wagneri)

the pollution of aquatic ecosystems may affect natural reproduction of fish populations by decreasing the fertilization efficiency. among the various sources of pollution, heavy metals are important group, being found in both freshwater and marine environment. the present study investigated changes of sperm characteristics of caspimyzon wagneri when exposed to manganese (mn). spermatozoids were exposed to 0 (control), 0.01, 0.1, 1, 10, 100 and 1000 mg l‑1 of mn, duration of sperm motility and percent of motile sperms were measured using a light microscope and digital camera as a semi-quantitative method. total duration of spermatozoids motility decreased with increase of mn concentration in all treatments. this study indicated that mn could seriously affect the reproductive success of the caspian lamprey in a polluted environment through decreasing the duration of spermatozoid motility and possibly fertilization and hatching rates. hence, contact to this metal could decrease the survival rate of this endangered species, especially during the reproduction.