title: Exposure to a widespread non-pathogenic bacterium magnifies sublethal pesticide effects in the damselfly Enallagma cyathigerum: from the suborganismal level to fitness-related traits.
abstract: While there is increasing concern that pesticide stress can interact with stress imposed by antagonistic species including pathogens, it is unknown whether this also holds for non-pathogenic bacteria. We exposed Enallagma cyathigerum damselfly larvae to the pesticide chlorpyrifos and a non-pathogenic Escherichia coli strain. Both exposure to chlorpyrifos and E. coli reduced growth rate and fat storage, probably due to the observed energetically costly increases in physiological defence (glutathione-S-transferase and Hsp70) and, for E. coli, immune defence (phenoloxidase). Moreover, these stressors interacted for both fitness-related traits. Most importantly, another fitness-related trait, bacterial load, increased drastically with chlorpyrifos concentration. A possible explanation is that the upregulation of phenoloxidase in the presence of E. coli changed into a downregulation when combined with chlorpyrifos. We argue that the observed interactive, partly synergistic effects between pesticides and widespread non-pathogenic bacteria may be common and deserves further attention to improve ecological risk assessment of pesticides.
authors.affiliation: Laboratory of Aquatic Ecology, Evolution and Conservation, University of Leuven, Charles Deberiotstraat 32, B-3000 Leuven, Belgium. lizanne.janssens@bio.kuleuven.be
authors.forename: Lizanne
authors.initials: L
authors.lastname: Janssens
authors.forename: Robby
authors.initials: R
authors.lastname: Stoks
mesh_terms: D000818:Animals; D004390:Chlorpyrifos / Q000378:metabolism / Q000633:toxicity*; D004785:Environmental Pollutants / Q000378:metabolism / Q000633:toxicity*; D004926:Escherichia coli / Q000254:growth & development; D005260:Female; D007306:Insecticides / Q000378:metabolism / Q000633:toxicity*; D063191:Odonata / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology*; D013312:Stress, Physiological
chemical_list: D004785:Environmental Pollutants; D007306:Insecticides; D004390:Chlorpyrifos