title: Clutch morphology and the timing of exposure impact the susceptibility of aquatic insect eggs to esfenvalerate.
abstract: We investigated Baetis spp. (mayfly), Hesperoperla pacifica (stonefly), and Brachycentrus americanus (caddisfly) susceptibility at the egg stage to esfenvalerate, a synthetic pyrethroid insecticide. Eggs were obtained from the field or from field-collected gravid females at sites near Corvallis (OR, USA) and the Metolius River at Camp Sherman (OR, USA) for static exposures under controlled conditions for temperature and light. Eggs were exposed to esfenvalerate for 48 h at concentrations ranging from 0.025 to 4.0 microg/L. No effect on mortality or posthatch growth was detected in H. pacifica eggs exposed to esfenvalerate concentrations up to 1.0 microg/L. Exposure to 0.07 microg/L of esfenvalerate, however, caused a significant increase in Baetis spp. egg mortality, and exposure of near-eclosion eggs to lower concentrations (0.025 and 0.05 microg/L) resulted in behavioral effects and reduced survivorship in newly hatched Baetis nymphs. Early stage B. americanus eggs were 10-fold more sensitive to esfenvalerate when removed from the gelatinous clutch before exposure, an indication that the gelatin affords protection from toxicant exposure. Exposures of near-hatch B. americanus clutches to esfenvalerate concentrations ranging between 0.035 and 0.2 microg/L, however, resulted in significant clutch death within clutches resulting from behavioral aberrations of first-instar larvae. The results of the present study suggest that aquatic insect egg clutch morphology can be a strong influence on susceptibility of embryos to esfenvalerate exposure.
authors.affiliation: Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: Katherine R
authors.initials: KR
authors.lastname: Palmquist
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Jenkins
authors.forename: Paul C
authors.initials: PC
authors.lastname: Jepson
mesh_terms: D000818:Animals; D001681:Biological Assay; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure; D004784:Environmental Monitoring; D007313:Insecta; D007306:Insecticides / Q000633:toxicity; D007814:Larva / Q000187:drug effects*; D008027:Light; D009570:Nitriles / Q000633:toxicity*; D011722:Pyrethrins / Q000633:toxicity*; D013696:Temperature; D013997:Time Factors
chemical_list: D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C017690:fenvalerate