Effects of dietary esfenvalerate exposures on three aquatic insect species representing different functional feeding groups

Abstract

Given the chemical properties of synthetic pyrethroids, it is probable that compounds, including esfenvalerate, that enter surface waters may become incorporated into aquatic insect food sources. We examined the effect of dietary esfenvalerate uptake in aquatic insects representing different functional feeding groups. We used three field-collected aquatic insect species: A grazing scraper, Cinygmula reticulata McDunnough (Ephemeroptera: Heptageniidae); an omnivorous filter feeder, Brachycentrus americanus Banks (Trichoptera: Brachycentridae); and a predator, Hesperoperla pacifica Banks (Plecoptera: Perlidae). Laboratory-cultured algae were preexposed for 24 h to esfenvalerate concentrations of 0, 0.025, 0.05, and 0.1 microg/L and provided to two C. reticulata age classes (small and final-instar nymphs). Reduction in small nymph growth was observed following three weeks of feeding on algae exposed to 0.05 and 0.1 microg/L of esfenvalerate, and the highest dietary exposure reduced egg production in final-instar nymphs. The diet for B. americanus and H. pacifica consisted of dead third-instar Chironomus tentans larvae preexposed for 24 h to esfenvalerate concentrations ranging between 0.1 and 1.0 microg/L. Consumption of larvae exposed to 0.5 to 1.0 microg/L of esfenvalerate caused case abandonment and mortality in B. americanus caddisfly larvae. Although H. pacifica nymphs readily consumed esfenvalerate-exposed larvae, no adverse effects were observed during the present study. Furthermore, no evidence of esfenvalerate-induced feeding deterrence was found in any of the species tested, suggesting that aquatic insects may not be able to distinguish between pyrethroid-contaminated and uncontaminated food sources. These findings indicate that feeding deterrence is not a factor in regulating aquatic insect dietary exposures to synthetic pyrethroids.

Pyrethroid Insecticides: Use, Environmental Fate, and Ecotoxicology

“…Preexposure of dietary items to 0.75 and 1.0 µg/L esfenvalerate for 24 hours resulted in increased rates of case-abandonment and mortality following consumption (Palmquist et al, 2008a). Although the dietary pyrethroids concentrations necessary to affect aquatic invertebrates appear to be significantly higher than aqueous concentrations, these results suggest that pyrethroids may still be toxicologically active when adsorbed to organic material.…”

“…After three weeks, mayfly nymphs (Cinygmula reticulata) fed on algae pre-exposed for 24-hours to 0.5 to 1.0 µg/L esfenvalerate were smaller than control organisms. Further, consumption of diet exposed to 1.0 µg/L esfenvalerate for 10 days by final instar C. reticulata nymphs reduced the number and length of eggs in emerged females (Palmquist et al, 2008a).…”

“…Undoubtedly, some fraction of toxicity observed in invertebrate sediment exposure studies does result from consumption of pyrethroid-contaminated material, but separation of dietary uptake from cuticular uptake under these scenarios is difficult. Palmquist et al (2008a) examined the impact of consumption of esfenvalerate-exposed dietary items on 3 species of aquatic insects. No evidence of feeding deterrence was observed, as none of the species tested rejected the esfenvalerate contaminated food.…”

Metabolism, bioaccumulation, and toxicity of pesticides in aquatic insect larvae

“…141) Brachycentrus americanus (caddisfly) and Cinygmula reticulata (mayfly) fed on esfenvalerate-treated algal cultures showed increasing mortality with case abandonment and growth inhibition with lower egg production, respectively, clearly indicating the dietary uptake of the insecticide. In contrast, when esfenvalerate-treated C. tentans larvae were fed to Hesperoperla pacifica (stonefly), no significant toxic effects were observed without a prey rejection, most likely due to the rapid metabolism of the insecticide.…”

Esfenvalerate toxicity to the cladoceran Ceriodaphnia dubia in the presence of green algae, Pseudokirchneriella subcapitata

“…Though adsorption of pyrethroids to POM may reduce cutaneous exposure to aquatic invertebrates, results suggest that dietary exposure may still be an issue. In a study of dietary exposure of esfenvalerate to three aquatic invertebrates from different phylogenetic groups, Cinygmula reticulata (grazing scraper, Mayfly), Brachycentrus americanus (omnivorous filter feeder, Caddis fly), and Hesperoperla pacifica (predator, Stonefly); Palmquist et al (2008) found that not only did lethal and sub-lethal effects from dietary exposure occur, but also that there was no indication that animals avoided contaminated food. It has been estimated that daphnids consume an average of 84,000 cells of algae daily, depending on the species (Infante and Litt 1985).…”