title: Multi-generation studies with Chironomus riparius--effects of low tributyltin concentrations on life history parameters and genetic diversity.
abstract: While toxicological data are available for numerous chemicals from standard tests, little is known on effects of pollutants over several generations or regarding chronic effects of chemicals on genetic diversity. Within the experiments, effects of the model pollutant tributyltin (TBT) were investigated over eleven generations at a sublethal TBT concentration of 4.46 microg as Sn kg-1 sediment dw on life-cycle parameters and genetic variability of Chironomus riparius. Moreover, the adaptation potential towards TBT was determined. This experimental design enables the identification of TBT effects on life-cycle parameters and the determination of a potential extinction risk caused by chronic exposure. Furthermore, effects on the genetic structure can be determined, which are not predictable based solely on knowledge of the toxic mode of action of the chemical. Genetic variety was determined via microsatellite analysis, measuring individual length differences of highly variable satellite DNA fragments. For the identification of changes in tolerances towards the stressor, acute and chronic toxicity experiments were conducted. During the multi-generation study, significant effects on development and reproduction were determined. For some generations, the emergence was significantly (p<0.05) delayed under TBT exposure. Reproduction seems to be a sensitive parameter as well, whereby females laid significantly larger egg masses (p<0.05) in the latter generations. TBT did not affect the population growth rate nor the genetic variability, while clear deviations from the Hardy-Weinberg equilibrium appeared. The study also provides strong evidence for the acquirement of a higher tolerance towards the stressor in the TBT-exposed group.
authors.affiliation: J.W. Goethe University, Institute of Ecology, Evolution and Diversity, Department Aquatic Ecotoxicology, Siesmayerstrasse 70, D-60323 Frankfurt am Main, Germany. vogt@bio.uni-frankfurt.de
authors.forename: Christian
authors.initials: C
authors.lastname: Vogt
authors.forename: Carsten
authors.initials: C
authors.lastname: Nowak
authors.forename: Joao Barateiro
authors.initials: JB
authors.lastname: Diogo
authors.forename: Matthias
authors.initials: M
authors.lastname: Oetken
authors.forename: Klaus
authors.initials: K
authors.lastname: Schwenk
authors.forename: Jörg
authors.initials: J
authors.lastname: Oehlmann
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002683:Chironomidae / Q000187:drug effects* / Q000235:genetics* / Q000254:growth & development; D004351:Drug Resistance; D014644:Genetic Variation / Q000187:drug effects; D007814:Larva / Q000187:drug effects; D018895:Microsatellite Repeats; D017711:Nonlinear Dynamics; D012098:Reproduction / Q000187:drug effects; D012744:Sex Ratio; D014220:Trialkyltin Compounds / Q000032:analysis / Q000633:toxicity*
chemical_list: D014220:Trialkyltin Compounds; C011559:tributyltin