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 fieldcollected 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 g/L. No effect on mortality or posthatch growth was detected in H. pacifica eggs exposed to esfenvalerate concentrations up to 1.0 g/L. Exposure to 0.07 g/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 g/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 nearhatch B. americanus clutches to esfenvalerate concentrations ranging between 0.035 and 0.2 g/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.

Assessing Impacts of Insecticides on Different Embryonic Stages of the Nontarget Aquatic Insect Cheumatopsyche brevilineata (Trichoptera: Hydropsychidae)

“…The impacts of pesticides on the egg stage of aquatic insects have attracted the interest of several researchers (Friesen 1979;Palmquist et al 2008;Suman et al 2013…”

“…The impacts of pesticides on the egg stage of aquatic insects have attracted the interest of several researchers (Friesen 1979;Palmquist et al 2008;Suman et al 2013). However, the wileyonlinelibrary.com/ETC © 2019 SETAC effects of exposure duration and timing on the toxicity of a pesticide to aquatic insect eggs have not been sufficiently clarified.…”

“…Friesen (1979) found that, in H. rigida, mid-stage eggs, the embryonic form of which had just become discernible, were more sensitive to methoxychlor than were early-stage eggs that had just been oviposited. Palmquist et al (2008) studied the impacts of esfenvalerate on the egg stage of several aquatic insects. They reported that this pyrethroid exerted more harmful effects on B. americanus egg clutches containing late-stage embryos with eye spots than on those containing early-stage embryos.…”

“…Differences in sensitivity to the organochloride insecticide methoxychlor among developmental stages have been observed in eggs of the burrowing mayfly, Hexagenia rigida (Friesen 1979). Palmquist et al (2008) showed the importance of embryonic stage at the time of exposure in determining vulnerability of the egg mass of the caddisfly Brachycentrus americanus to the synthetic insecticide esfenvalerate. Freshly laid eggs of mosquitoes were more sensitive to 3 insect growth regulators than embryonated eggs (Suman et al 2013).…”

Caddisfly egg mass morphology mediates egg predation: potential costs to individuals and populations

“…The spumaline swells with water and provides a physical barrier, which may protect against some predators, parasites and fungi (Hinton, ), and even some toxins (e.g. esfenvalerate insecticide, Palmquist, Jenkins & Jepson, ). The shape and thickness of this spumaline layer varies between species, and it is possible that egg masses with thick spumaline (i.e.…”