title: Acute contamination with esfenvalerate and food limitation: chronic effects on the mayfly, Cloeon dipterum.
abstract: Results of environmental risk assessments based merely on toxic effects of contaminants at the individual level, without consideration of population-level effects, may be questionable. The aim of the present study was to investigate how limited food resources, resulting in intraspecific competition, could interact with the chronic effect of short-term contamination with the insecticide esfenvalerate. Larvae of the mayfly, Cloeon dipterum, were exposed to esfenvalerate (0.001-100 microg/L) for 1 h and then transferred to indoor microcosms containing insecticide-free water, where they were maintained at various food levels until emergence. The results showed that short-term exposure to 10 or 100 microg/L resulted in acute mortality. Chronic effects on survival occurred at concentrations up to three orders of magnitude lower than that causing the acute effect (0.01 microg/L). Food limitation increased effects on organisms during medium-term observation (8-15 d), but assessment of long-term survival rates suggested that the chronic effects of low insecticide concentrations could be compensated for, at least regarding some endpoints. The authors assume that in limited-food conditions, lethal and sublethal effects reduced competition between individuals, resulting in significantly increased final survival.
authors.affiliation: Western Siberian Center for Environmental Monitoring, P.O. Box 156, 630048 Novosibirsk, Russia. mbeketov@mail.ru
authors.forename: Mikhail A
authors.initials: MA
authors.lastname: Beketov
authors.forename: Matthias
authors.initials: M
authors.lastname: Liess
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D020387:Food Chain; D007313:Insecta / Q000187:drug effects* / Q000378:metabolism; D007306:Insecticides / Q000633:toxicity*; D007814:Larva / Q000187:drug effects* / Q000378:metabolism; D009570:Nitriles / Q000633:toxicity*; D011157:Population Dynamics; D011722:Pyrethrins / Q000633:toxicity*; D015996:Survival Rate; D013997:Time Factors; D023382:Toxicity Tests, Acute; D036401:Toxicity Tests, Chronic; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; D014874:Water Pollutants, Chemical; C017690:fenvalerate