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Esfenvalerate-induced case-abandonment in the larvae of the caddisfly (Brachycentrus americanus)

Authors

  • Katherine R. Johnson,

    Corresponding author
    1. Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331, USA
    Current affiliation:
    1. Exponent Consulting, 15375 SE 30th Place, Bellevue, WA 98005, USA
    • Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331, USA; Published on the Web 10/02/2007
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  • Paul C. Jepson,

    1. Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331, USA
    2. Integrated Plant Protection Center, Oregon State University, Corvallis, Oregon 97331, USA
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  • Jeffrey J. Jenkins

    1. Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331, USA
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Abstract

Field-collected Brachycentrus americanus Banks (Trichoptera: Brachycentridae) larvae were used to investigate the relationship between esfenvalerate exposure and case-abandonment response, determine larval ability to construct a new case, and measure the change in predation risk to insects in rebuilt cases. We evaluated case-abandonment following four environmentally relevant esfenvalerate exposures, 0.05, 0.1, 0.2, and 0.4 μg/L; 48-h exposures to 0.2 and 0.4 μg/L (nominal) esfenvalerate both resulted in over 60% of larvae abandoning cases and were statistically indistinguishable. Propensity to engage in building behaviors was significantly diminished in 0.2 and 0.4 μg/L esfenvalerate-exposed insects that had abandoned cases, with less than 20% of exposed insects producing cases. Cases built by intoxicated larvae were characterized by a disorganized composition, and required half the pressure to crush versus cases built by nonexposed larvae. Pre-exposing case-building material to 1 μg/L esfenvalerate also reduced the physical strength of rebuilt cases. Larvae inhabiting weaker rebuilt cases and larvae without cases were significantly more susceptible to predation by second year Hesperoperla pacifica Banks (Plecoptera: Perlidae) stonefly nymphs than those in original cases. Overall, we concluded that small behavioral responses can have profound consequences for survival of species and reveal susceptible stages in life-cycles that can be overlooked by conventional approaches to ecological risk assessment.

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