Enhanced esterase activity and resistance to azinphosmethyl in target and nontarget organisms

Abstract

The organophosphorous compound azinphosmethyl (AzMe) is applied extensively in northern Patagonia (southern Argentina) to manage codling moths (Cydia pomonella). This area is irrigated by fast-flowing channels that provide a favorable habitat for many species, including amphipods (Hyalella curvispina) and a field-mixed population of black flies (Simulium bonaerense, Simulium wolffhuegeli, and Simulium nigristrigatum). In the present study, AzMe susceptibility and carboxylesterase (CarbE) activity from both insecticide-exposed and nonexposed field populations were studied. The median lethal dose determined in codling moths from an insecticide-treated orchard was significantly higher (3.48 microg/insect) than that observed in those from an untreated orchard (0.69 microg/insect). Similarly, the median lethal concentration (LC50) determined in black flies collected from the treated area (0.021 mg/L) was significantly higher than that recorded in those from the untreated site (0.011 mg/L). For amphipods, both a subpopulation susceptible to AzMe (LC50, 1.83 microg/L) and a resistant one (LC50, 390 microg/L) were found in the treated area. Both subpopulations were more resistant to AzMe than the population from the untreated site (LC50, 0.43 microg/L). Significant differences (p < 0.001) in CarbE activities were observed between populations from pesticide-treated and untreated areas. Mean activities +/- standard deviation from treated and untreated sites were 0.21 +/- 0.16 and 0.016 +/- 0.008 micromol/min/mg protein, respectively, for codling moths; 2.17 +/- 1.71 and 0.81 +/- 0.35 micromol/min/mg protein, respectively, for black flies; and 0.27 +/- 0.10 and 0.14 +/- 0.07 micromol/min/mg protein, respectively, for amphipods. The results suggest that enhanced CarbE activity is one of the mechanisms that provide AzMe resistance in H. curvispina, Simulium spp., and C. pomonella populations from the insecticide-treated areas.

Acute toxicity and biochemical effects of azinphos methyl in the amphipod Hyalella curvispina

“…). This was previously stated in the 48‐h bioassays (Anguiano et al, ). The calculated LC 50 values are listed in Table .…”

“…Survival was monitored daily, mortality was registered, and dead animals were removed. Animals were considered to be dead if no movement of the pleopods was visible during a 20‐s observation period using a stereoscopic microscope (Anguiano et al, ).…”

“…To compare the toxicity of AM determined in this study for H. curvispina inhabiting F. Oro irrigation channels, analysis of species sensitivity distributions was performed (ECOFRAM, 1999; Montagna et al, 2011) using acute toxicity data (LC 50 values) for aquatic freshwater organisms. Other amphipods (Nebeker and Gaufin, ; Sanders, ; Johnson and Finley, ; Mayer and Ellersieck, ; Ankley and Collard, 1995; Pantani et al, ; Anguiano et al, ) and local aquatic freshwater vertebrates evaluated in our previous studies (Ferrari et al, b) were included in the probabilistic analysis. The species were ranked by decreasing sensitivity and the rank was transformed to percentile values: [ i /( n + 1)], where i is the species rank, and n is the total number of species listed (ECOFRAM, 1999).…”

“…Both, GSH and antioxidant enzymes, have been extensively evaluated in ecotoxicological studies performed with diverse aquatic species such as fish species, amphibian embryos, aquatic gastropods, and oligochaetes (Oruç and Üner, ; Ferrari et al, ; Kristoff et al, ). Most aquatic invertebrate species exhibit higher sensitivity to OP and carbamates when compared to vertebrate species; however, in Argentina, few studies on the effects of OP have been carried out on aquatic invertebrates (Jergentz et al, ; Anguiano et al, ; Kristoff et al, ).…”

“…We have previously reported the occurrence of different populations of amphipods with differential susceptibility to OP, obtained from fruit‐producing and pristine areas, in a comparative study including other invertebrates as well (Anguiano et al, ). We could determine that an increased basal activity of the detoxifying enzyme CabE was in part responsible for the resistance to OP in these species.…”