Comparative toxicity of four insecticides, including imidacloprid and tebufenozide, to four aquatic arthropods

Abstract

The tolerance of four aquatic organisms to four chemicals (aldicarb, dimethoate, imidacloprid, and tebufenozide) was determined using 48‐h acute toxicity tests at 27°C. Species included two saline (Artemia sp. and Aedes taeniorhynchus (Wiedemann)) and two freshwater (Daphnia magna Straus and Aedes aegypti (L.)) organisms. Temperature was also evaluated as a toxicity modifying factor for the freshwater species. Two selective insecticides (imidacloprid and tebufenozide) were compared with two broad‐spectrum insecticides, aldicarb and dimethoate. In general, A. taeniorhynchus was the most susceptible, and Artemia sp. was the most tolerant to insecticides used under our experimental conditions. Both aldicarb and dimethoate caused neurotoxicity in all organisms tested. Mortality associated with molting suggested that tebufenozide affected the molting process of all organisms, causing the formation of an incompletely sclerotized head capsule and the failure of ecdysis in the mosquito species. These responses resulted in lethal larval molts. Imidacloprid, on the other hand, caused delayed symptoms of general nerve poisoning compared with the two acetylcholine esterase inhibitors. Our results suggest that both tebufenozide and imidacloprid would be selective insecticides that can be used with reasonable environmental safety toward nontarget aquatic crustaceans. There was a greater correlation of susceptibility to test chemicals within taxonomically close organisms than between organisms that share habitats.

Pressure-Induced Shifts in Trophic Linkages in a Simplified Aquatic Food Web

“…However, the observed strong interactions between different pesticide classes and nutrients for the different parts of the aquatic food web also present us with a puzzle: we have no clear explanations for the second and third-order effects that go beyond mere speculation. These effects observed in a quasi-natural setting differ markedly and qualitatively from laboratory incubations which show isolated effects on individual species (Salminen et al, 1996;Song et al, 1997;Stoughton et al, 2008), and indicate that effects on species can feed through to higher levels of organization in aquatic ecosystems, and likely inherent ecosystem processes, as described in Mills et al (1993) and Relyea and Hoverman (2006).…”

Traits and stress: keys to identify community effects of low levels of toxicants in test systems

“…For example, in test systems, abiotic stressors such as high temperature (Fisher and Wadleigh 1985; Song et al 1997; Lydy et al 1999) and a deficiency of food (Pieters et al 2005) were found to increase the sensitivity of macroinvertebrates to insecticides by a factor of from 2 to 10. UV radiation in conjunction with food deficiency increased sensitivity to copper by a factor of more than 30 (Liess et al 2001).…”

“…Hence, to determine the quantitative link between exposure and effect it is necessary to consider additional stress factors. Such factors include a wide range of stressors that increase the rate of mortality due to toxicants (factor of increase in brackets): exalted temperature (10) (Song et al 1997), food limitation (2) (Pieters et al 2005), exalted salinity (10) (Wildgust and Jones 1998), low oxygen (2) (Van der Geest et al 2002), UV radiation (30) (Liess et al 2001), competition (10) (Liess 2002), predation (8) (Beketov and Liess 2006), and the requirement of food acquisition (10) (Mommaerts et al 2010). …”

Tolerance of free‐living nematode species to imidacloprid and diuron

“…A study by Stoughton, Liber, Culp, and Cessna () demonstrated that the LC50 of target organisms such as Chironomus tentans was 5.75 µg/L after 96 hr. For nontarget organisms such as D. magna , the LC50 was greater than above that of chironomids (LC50 = 17 mg/L after 48 hr; Song et al, ) but was still 20 times lower than the highest tested concentration in nematodes (Table ), confirming the extreme resistance of nematodes and a predominantly insect‐selective mode of action for imidacloprid (Tomizawa & Casida, ).…”

“…A review by Tomizawa and Casida () highlighted that imidacloprid has a selective toxicity because of the different structures in nicotinic receptors between insects and mammals; this has been questioned by recent studies which proved its risk for nontarget species as well (Pisa et al, ). For the standard toxicity test organism Daphnia magna , imidacloprid was lethal to 50% of the animals exposed (LC50) at a concentration of 17 mg/L (Song, Stark, & Brown, ). However, some invertebrate groups (like nematodes) might have divergent capacities to deal with imidacloprid owing to structural differences in their nicotinic receptors (Tornøe, Bai, Holden‐Dye, Abramson, & Sattelle, ).…”