The importance of the exposure route when testing the toxicity of pesticides to saprotrophic isopods

Abstract

When effects of pesticides are tested on nontarget invertebrates, substrate exposure is mostly used. Routes of uptake of pesticides by saprotrophic invertebrates may, however, also occur through the food, since the litter layer will be their main food source. These organisms live in close contact with the soil surface and litter layer. The ecotoxicity of the pesticides benomyl, carbofuran, and diazinon was investigated in a series of experiments. The toxicity was tested in lethal concentrations (leading to LC50 estimations), and sublethal concentrations leading to no‐observed‐effect concentration (NOEC) estimations on growth. Both substrate and dietary exposure were used to evaluate the most critical exposure route for each case. For food exposure, the chemicals were offered in ground leaves, while for substrate exposure the test organisms were kept on treated sand. Experiments were done with the tropical isopod Porcellionides pruinosus. For all three pesticides, substrate exposure was more critical than dietary exposure. The LC50 values (active ingredient per dry mass of food or soil) for benomyl, carbofuran, and diazinon, when mixed with food, were >31,000, 485, and 74.15 μg/g, respectively, and when mixed with sand 1,221, 21.41, and 3.03 μg/g, respectively. Sublethal effects on body growth were found for benomyl (NOEC = 1,000 μg/g) and diazinon (NOEC = <8.71 μg/g) after dietary exposure, but no effects were found in the course of the experiment for substrate exposure. Based on the results, it is concluded that the exposure route is of great importance for determining lethal effects as well as sublethal effects of pesticides on nontarget invertebrates in soil. The most critical exposure route depends both on the mode of action of the chemical and on the toxicological end point considered.

Metabolic responses of the isopod Porcellionides pruinosus to nickel exposure assessed by 1H NMR metabolomics

“…Exposure to xenobiotics may affect edaphic organisms, consequently changing the overall soil function, and decreasing soil quality and soil services [14]. The species Porcellionides pruinosus has been described as a good test-organism to evaluate soil contamination or changes in its habitat and several endpoints, from the individual to lower organizational levels, have been used to evaluate the effects caused by different stressors [15][16][17][18][19].…”

Toxicokinetics of Ag in the terrestrial isopod Porcellionides pruinosus exposed to Ag NPs and AgNO3 via soil and food

“…Organic matter content is an important factor that determines the bioavailability of metals when comparing soil and dietary exposures. Due to strong sorption of metals to organic matter, the high organic matter content in leaf material leads to greater sorption of metals when compared to soil (Sousa et al, 2000;Vink et al, 1995), especially of the loosely bound or free fractions of metal (Vijver et al, 2006). It may result in lower bioavailability of metals when exposed via food.…”

“…The aim of the present study was to evaluate the uptake and elimination kinetics of Ag in the terrestrial isopod Porcellionides pruinosus, considering two forms of Ag: ionic (with AgNO3) and nanoparticulate (Ag NPs). As different routes of exposure are essential to fully evaluate the bioavailability of contaminants in the environment (Ardestani et al, 2014;Loureiro et al, 2002;Sousa et al, 2000;Vijver et al, 2004;Vink et al, 1995), kinetic studies were conducted using soil and dietary exposures for comparison. In addition, and to understand and confirm results from uptake and elimination kinetics, µX-ray fluorescence mapping was carried out in isopods exposed to Ag NPs in soil.…”

Effect of Endosulfan and Parathion on Energy Reserves and Physiological Parameters of the Terrestrial Isopod Porcellio dilatatus

“…For these reasons, terrestrial isopods are suitable candidates to be used as test organisms in both ecological studies and soil ecotoxicological research (Hopkin, 1991;Donker, 1992;Drobne, 1997). In fact, the number of tests with isopods has been increasing in the past few years (Van Straalen and Verweij, 1991;Donker et al, 1993;LeH on and Van Gestel, 1994;Drobne and Hopkin, 1994;Crommentuijn et al, 1995;Vink et al, 1995;Van Brummelen et al, 1996a, b;Caseiro, 1997;Ribeiro et al, 1999).…”