title: Valve closure response to uranium exposure for a freshwater bivalve (Corbicula fluminea): quantification of the influence of pH.
abstract: Laboratory experiments were carried out to analyze the first valve closure response of a freshwater bivalve (Corbicula fluminea) exposed to uranium during a 5-h period. Experiments were performed in a well-defined artificial water at two pH values, 5.5 and 6.5, with a noninvasive method of valve recording. Sensitivity thresholds, based on percentage of bivalve that close their valves in a given time, were determined. Response thresholds depended on the total uranium concentration, integration time of response (fast responses could only be observed for the highest concentrations), and pH. The bivalve is much more sensitive to total uranium concentration at pH 5.5 than pH 6.5. The minimal sensitivity threshold determined, expressed as the uranium concentration inducing the valve closure of 50% of the bivalves, was 0.05 micromol/L at pH 5.5 after 5 h of exposure. Moreover, higher concentrations of the free ion UO2(2-) are required at pH 5.5 than at pH 6.5 to illicit the same response. Two hypotheses can be proposed, that UO2(2-) is not the only detected species or that competition exists between H- and UO2(2-) for binding sites.
authors.affiliation: Laboratoire de Radioécologie et Ecotoxicologie, Institut de Radioprotection et de Sûreté Nucléaire Bât 186, BP 3, 13115 Saint-Paul-Lez-Durance, France. elodie.fournier@irsn.fr
authors.forename: Elodie
authors.initials: E
authors.lastname: Fournier
authors.forename: Damien
authors.initials: D
authors.lastname: Tran
authors.forename: Francis
authors.initials: F
authors.lastname: Denison
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Massabuau
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Garnier-Laplace
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004781:Environmental Exposure; D005618:Fresh Water / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008974:Mollusca / Q000187:drug effects* / Q000378:metabolism; D013997:Time Factors; D014501:Uranium / Q000737:chemistry / Q000633:toxicity*; D017974:Uranium Compounds / Q000633:toxicity; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D017974:Uranium Compounds; D014874:Water Pollutants, Chemical; D014501:Uranium; C047385:uranium oxide