title: Metamorphosis Affects Metal Concentrations and Isotopic Signatures in a Mayfly (Baetis tricaudatus): Implications for the Aquatic-Terrestrial Transfer of Metals.
abstract: Insect metamorphosis often results in substantial chemical changes that can alter contaminant concentrations and fractionate isotopes. We exposed larval mayflies (Baetis tricaudatus) and their food (periphyton) to an aqueous zinc gradient (3-340 μg Zn/l) and measured zinc concentrations at different stages of metamorphosis: larval, subimago, and imago. We also measured changes in stable isotopes (δ15N and δ13C) in unexposed mayflies. Larval zinc concentrations were positively related to aqueous zinc, increasing 9-fold across the exposure gradient. Adult zinc concentrations were also positively related to aqueous zinc, but were 7-fold lower than larvae. This relationship varied according to adult substage and sex. Tissue concentrations in female imagoes were not related to exposure concentrations, but the converse was true for all other stage-by-sex combinations. Metamorphosis also increased δ15N by ∼0.8‰, but not δ13C. Thus, the main effects of metamorphosis on insect chemistry were large declines in zinc concentrations coupled with increased δ15N signatures. For zinc, this change was largely consistent across the aqueous exposure gradient. However, differences among sexes and stages suggest that caution is warranted when using nitrogen isotopes or metal concentrations measured in one insect stage (e.g., larvae) to assess risk to wildlife that feed on subsequent life stages (e.g., adults).
authors.affiliation: Department of Biology, University of South Dakota , Vermillion, South Dakota 57069, United States.
authors.forename: Jeff S
authors.identifier: 0000-0001-6058-7972
authors.initials: JS
authors.lastname: Wesner
authors.affiliation: U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado 80526, United States.
authors.forename: David M
authors.identifier: 0000-0002-4237-2158
authors.initials: DM
authors.lastname: Walters
authors.affiliation: U.S. Geological Survey, Colorado Water Science Center, Denver, Colorado 80225, United States.
authors.forename: Travis S
authors.identifier: 0000-0003-1400-0637
authors.initials: TS
authors.lastname: Schmidt
authors.affiliation: U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado 80526, United States.
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Kraus
authors.affiliation: U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado 80526, United States.
authors.forename: Craig A
authors.initials: CA
authors.lastname: Stricker
authors.affiliation: Department of Fish, Wildlife & Conservation Biology and Graduate Degree Program in Ecology, Colorado State University , Fort Collins, Colorado 80523, United States.
authors.forename: William H
authors.initials: WH
authors.lastname: Clements
authors.affiliation: PerkinElmer, Inc. San Jose, California 95134, United States.
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Wolf
mesh_terms: D000818:Animals; D065133:Ephemeroptera; D007814:Larva / Q000187:drug effects; D008670:Metals / Q000494:pharmacology; D008675:Metamorphosis, Biological / Q000187:drug effects*; D015032:Zinc / Q000494:pharmacology
chemical_list: D008670:Metals; D015032:Zinc