title: Exposure to sediments from polluted rivers has limited phenotypic effects on larvae and adults of Chironomus riparius.
abstract: Laboratory studies have sometimes failed to detect a relationship between toxic stress and morphological defects in invertebrates. Several hypotheses have been proposed to account for this lack of effect. (1) It was suggested that only a combination of stressful conditions - rather than a single one - would affect the phenotype. (2) Phenotypic defects should be detected on adult individuals, rather than on juveniles. (3) Phenotypic abnormalities might mostly affect the progeny of the exposed individuals, some contaminants exhibiting trans-generational effects. In the present study, we test those three hypotheses. We first examined the effects of a multiple exposure by using laboratory Chironomus riparius larvae cultured on two sediments sampled in contaminated rivers and those containing a mixture of mineral and organic compounds. On the larvae, we investigated mentum phenotypes: the frequency of phenodeviants, the shape fluctuating asymmetry and the mean shape. To test whether adult's morphology was more sensitive than the larval's, we also measured asymmetry and mean shape of the adult wings. Finally, to test for a trans-generational phenotypic effect, we measured mentum shape variations in the offspring derived from the measured adults. Overall, our results point out a very limited phenotypic response to contaminated sediments, suggesting that a multiple exposure is not necessarily sufficient to generate phenotypic defects. Adult traits were no more affected than larval traits, discarding the hypothesis that adult phenotypes would be more sensitive biomarkers. Finally, no effect was detected on the offspring generation, suggesting that no trans-generational effect occurs. This general lack of effect suggests that the use of phenotypic defects in C. riparius as an indicator of sediment contamination should be considered cautiously.
authors.affiliation: Département Ville Durable, CETE Ile de France, IFFSTTAR-ERA n°35, 12 rue Teisserenc de Bort, 78190 Trappes, France. Electronic address: helene.arambourou@bio.kuleuven.be.
authors.forename: Hélène
authors.initials: H
authors.lastname: Arambourou
authors.affiliation: Ecole Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES), 1 Quai Koch BP 61039, 67070 Strasbourg, France; Laboratoire Image, Ville, Environnement (LIVE) UMR 7362 CNRS, Université de Strasbourg, 3 rue de l'Argonne, 67083 Strasbourg, France.
authors.forename: Jean-Nicolas
authors.initials: JN
authors.lastname: Beisel
authors.affiliation: Département Ville Durable, CETE Ile de France, IFFSTTAR-ERA n°35, 12 rue Teisserenc de Bort, 78190 Trappes, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Branchu
authors.affiliation: UMR 7205 ISySEB Département Systématique et Evolution, Museum National d'Histoire Naturelle, 45 rue Buffon, 75005 Paris, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Debat
mesh_terms: D000818:Animals; D002683:Chironomidae / Q000033:anatomy & histology / Q000502:physiology*; D004784:Environmental Monitoring / Q000379:methods; D019015:Geologic Sediments / Q000737:chemistry*; D007814:Larva / Q000033:anatomy & histology / Q000502:physiology*; D010641:Phenotype; D045483:Rivers / Q000737:chemistry; D018675:Toxicity Tests / Q000379:methods; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical
keywords: Chironomus riparius; Fluctuating asymmetry; Phenodeviation; Polluted sediment; Shape changes