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

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 microg/L; 48-h exposures to 0.2 and 0.4 microg/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 microg/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 microg/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.

Pyrethroid Insecticides: Use, Environmental Fate, and Ecotoxicology

“…Pyrethroid exposure has also been demonstrated to interfere with the complex building behaviors exhibited by case-building caddisflies (Brachycentrus americanus); these cases provide protection from predation, improve respiration and act as a refuge during pupation. Following 48-hour esfenvalerate exposures of 0.05 µg/L and greater, caddisfly larvae were observed to exit their cases, an abnormal behavior not observed in non-exposed larvae (Johnson et al, 2008). More significantly, case-rebuilding behaviors were also negatively affected by esfenvalerate exposure.…”

Potential Influence of Suspended Sediments on the Population Dynamics and Behavior of Filter-Feeding Brachycentrus occidentalis (Trichoptera: Brachycentridae) Larvae in a Southeastern Minnesota, USA, Trout Stream

“…However, other effects of suspended sediments on Brachycentrus behavior, specifically their filter-feeding, are not known. Brachycentrus larvae have been reported to respond to various stressors (e.g., changing water temperatures or food supplies, and toxic substances) by ceasing filter-feeding, withdrawing into their cases, altering their case building, burrowing into the bottom substrates, sealing off their cases, or even abandoning their cases [21,29,60,61]. Our laboratory observations, while admittedly limited in duration and very cautiously extrapolated to longer-term field conditions, suggest that Brachycentrus larvae may cease filter-feeding, withdraw into their cases, and stop adjusting their positions toward more optimal filtering sites when exposed to high suspended-sediment concentrations (e.g., turbidities of 500 NTU).…”

“…Some taxa can be very sensitive to environmental pollution [18,19], while at the same time becoming very abundant when conditions are favorable for them [20]. Filter-feeding caddisfly larvae in the genus Brachycentrus are one such taxon, highly sensitive to organic pollution, synthetic pyrethroids, and fine sediment [18,21,22], while being tolerant of other stressors [23][24][25]. They often comprise a dominant component of benthic communities in many streams [20,26].…”

Adverse outcome pathways and ecological risk assessment: Bridging to population‐level effects

“…Even for a given population, some combined datasets may cover a broad temporal range (e.g., several decades). Costs and time are the limiting factors in resolving 72 Environ. Toxicol.…”

“…Expanding the test species used for identifying and confirming AOPs to those needed for population modeling would help reduce the cross-species and cross-taxa extrapolation that can be necessary. For example, rather than extrapolating from studies in the standard Chironomus species, conducting toxicity studies on field-collected Trichoptera caddisfly species could help define AOPs in the context of the lifehistory attributes of the population of interest [72].…”