concentration of mercury in selected tissues of the caspian lamprey (caspiomyzon wagneri) migrants in spawning season

background: mercury (hg) is considered a global pollutant because hg0 which is the predominant form of atmospheric hg resides in the atmosphere for as long as 0.5 to 2 years. mercury has many negative effects on the reproductive, respiratory, and immune systems. methods: in this study, 24 caspian lampreys (caspiomyzon wagneri) were transported to the university laboratory and then stored in -20 oc until they were dissected. the liver, muscle, skin, ovaries, and testes were all dissected out. all samples were freeze-dried and ground by a mortar and pestle into powder. the specimens were analyzed by a leco ama254 mercury analyzer. results: the order of mercury concentration in the lamprey tissues was as follows: muscle > ovaries > liver > skin > testes. the mean values of mercury in muscle and testes were 192.25 ± 7.10 and 21.42 ± 1.48 hg ng/g dry weight, respectively. there were no significant differences (n = 24) between the sexes in the hg level of most tissues except for gonads. discussion: a comparison with some ammocoetes of jawless fishes shows a 10 times less concentration than other records. this difference probably is due to non-parasitic behavior and use of various sources of nutrition in other species. conclusion: in comparison of other kind of sea lamprey, due to detritivore habits of caspian lamprey on a very specific part of food web (non-live food only in the sea floor), the supposed species can introduce as a special indicator of mercury and heavy metal levels in the aquatic ecosystem.