title: Mercury speciation and selenium in toothed-whale muscles.
abstract: Mercury accumulates at high levels in marine mammal tissues. However, its speciation is poorly understood. The main goal of this investigation was to establish the relationships among mercury species and selenium (Se) concentrations in toothed-whale muscles at different mercury levels. The concentrations of total mercury (T-Hg), methylmercury (MeHg), inorganic mercury (I-Hg) and Se were determined in the muscles of four toothed-whale species: bottlenose dolphins (n=31), Risso's dolphins (n=30), striped dolphins (n=29), and short-finned pilot whales (n=30). In each species, the MeHg concentration increased with increasing T-Hg concentration, tending to reach a plateau. In contrast, the proportion of MeHg in T-Hg decreased from 90-100% to 20-40%. The levels of T-Hg and Se showed strong positive correlations. Se/I-Hg molar ratios rapidly decreased with the increase of I-Hg and reached almost 1 in all species. These results suggested that the demethylated MeHg immediately formed Se/I-Hg equimolar complex of mercury selenide (HgSe) in their muscles. In addition, an X-ray absorption fine structure analysis (XAFS) of a bottlenose dolphin muscle confirmed that the dominant chemical form of the Se/I-Hg equimolar complex was HgSe. HgSe was mainly localized in cells near the endomysium using electron probe microanalysis (EPMA). These results suggested that the demethylated MeHg finally deposits within muscle cells of bottlenose dolphin as an inert HgSe.
authors.affiliation: National Institute for Minamata Disease, Hama 4058-18, Minamata, Kumamoto 867-0008, Japan. Electronic address: sakamoto@nimd.go.jp.
authors.forename: Mineshi
authors.initials: M
authors.lastname: Sakamoto
authors.affiliation: Ehime University, Bunkyo 2-5, Matsuyama 790-8755, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Itai
authors.affiliation: National Institute for Minamata Disease, Hama 4058-18, Minamata, Kumamoto 867-0008, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Yasutake
authors.affiliation: Tohoku National Fisheries Research Institute, 25-259 Shimomekurakubo, Aomori 031-0841, Japan.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Iwasaki
authors.affiliation: Institute of Cetacean Research, 4-5 Toyomi, Tokyo 104-0055, Japan.
authors.forename: Genta
authors.initials: G
authors.lastname: Yasunaga
authors.affiliation: Institute of Cetacean Research, 4-5 Toyomi, Tokyo 104-0055, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Fujise
authors.affiliation: National Institute for Minamata Disease, Hama 4058-18, Minamata, Kumamoto 867-0008, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Akita University School of Medicine, Hondo 1-1-1, Akita 010-8543, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Murata
authors.affiliation: University of Ottawa, Marie-Curie, Ottawa, ON, Canada KIN 6N5.
authors.forename: Hing Man
authors.initials: HM
authors.lastname: Chan
authors.affiliation: School of Medicine, IISPV, Universitat "Rovira i Virgili", Reus, Spain.
authors.forename: José L
authors.initials: JL
authors.lastname: Domingo
authors.affiliation: National Institute for Minamata Disease, Hama 4058-18, Minamata, Kumamoto 867-0008, Japan.
authors.forename: Masumi
authors.initials: M
authors.lastname: Marumoto
mesh_terms: D000818:Animals; D004289:Dolphins / Q000378:metabolism*; D004577:Electron Probe Microanalysis; D004784:Environmental Monitoring; D005260:Female; D008297:Male; D008628:Mercury / Q000493:pharmacokinetics*; D017669:Mercury Compounds / Q000493:pharmacokinetics; D008767:Methylmercury Compounds / Q000493:pharmacokinetics; D009132:Muscles / Q000378:metabolism*; D012643:Selenium / Q000493:pharmacokinetics*; D018036:Selenium Compounds / Q000493:pharmacokinetics; D013045:Species Specificity; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics; D056928:X-Ray Absorption Spectroscopy
chemical_list: D017669:Mercury Compounds; D008767:Methylmercury Compounds; D018036:Selenium Compounds; D014874:Water Pollutants, Chemical; C032901:mercury-selenium complex; D008628:Mercury; D012643:Selenium
keywords: Mercury selenide; Methylmercury; Muscle; Selenium; Toothed-whale