title: Selenium:mercury molar ratios in bullfrog and leopard frog tadpoles from the northeastern United States.
abstract: Vertebrates experience adverse effects from methylmercury, largely obtained through their food. Selenium has the potential to reduce the toxic effects of methylmercury (and vice versa). In this paper, we examine the selenium:mercury molar ratios in tadpoles (Lithobates sphenocephalus, Lithobates catesbeianus (formerly Rana), and a newly documented leopard frog species currently referred to as R. sp. nov.) and fully formed leopard frog metamorphs. There were no significant differences in metal levels between the two leopard frog species, and data were therefore combined. Selenium:mercury molar ratios varied from 19 to 38 for bullfrog tadpoles, from 16 to 330 for leopard frog tadpoles, and from 7 to 17 for leopard frog metamorphs. Leopard frog tadpoles with less than 45 days exposure to field conditions had significantly higher molar ratios than other tadpoles and leopard frog metamorphs. There were significant locational differences for the molar ratios of bullfrogs, and leopard frog tadpoles with more than 45 days of field exposure. At the sites where we were able to sample both leopard frog tadpoles and leopard frog metamorphs, there were significant differences between the two distinct life stages. Most of the variation in the ratio was accounted for by selenium levels, field sites, and exposure period.
authors.affiliation: Division of Life Sciences, Rutgers University, 604 Allison Road, Piscataway, NJ, 08854, USA, burger@biology.rutgers.edu.
authors.forename: Joanna
authors.initials: J
authors.lastname: Burger
authors.forename: Jeremy
authors.initials: J
authors.lastname: Feinberg
authors.forename: Christian
authors.initials: C
authors.lastname: Jeitner
authors.forename: Michael
authors.initials: M
authors.lastname: Gochfeld
authors.forename: Mark
authors.initials: M
authors.lastname: Donio
authors.forename: Taryn
authors.initials: T
authors.lastname: Pittfield
mesh_terms: D000818:Animals; D004347:Drug Interactions; D007814:Larva / Q000187:drug effects*; D008767:Methylmercury Compounds / Q000009:adverse effects / Q000032:analysis*; D008954:Models, Biological; D009511:New England; D065840:Protective Factors; D011892:Rana catesbeiana; D011894:Rana pipiens; D012044:Regression Analysis; D012643:Selenium / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000009:adverse effects / Q000032:analysis*
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D012643:Selenium