Soil and plant diet exposure routes and toxicokinetics of lindane in a terrestrial isopod

Abstract

In most studies dealing with effects of toxic substances in saprotrophic isopods, animals are exposed to the test substance through contaminated food. Because these animals can be in a close contact with the soil surface, the substrate, as an exposure pathway, should not be neglected. Here the authors analyze the toxicokinetic behavior of lindane (␥-hexachlorocyclohexane [␥-HCH]) in the isopod species Porcellionides pruinosus, comparing two exposure routes: food and two soil types (artificial Organisation for Economic Cooperation and Development [OECD] soil and a natural agricultural soil). In the feeding experiment, a strong decrease of ␥-HCH concentration over time was observed on the food material, with the animals showing a broader range in chemical assimilation efficiency values (averaging 17.7% and ranging from 10 to 40%). The ␥-HCH bioaccumulation results indicate that when animals incubated under both soil types reached a steady state, they displayed much higher body burdens (1,359.60 pg/ animal on OECD soil and 1,085.30 pg/animal on natural soil) than those exposed to contaminated food (43.75 pg/animal). Kinetic models also revealed much lower assimilation and elimination rates in the food experiment (20.66 pg/d and 0.10 pg/d) than in both soil experiments (238.60 pg/d and 350.54 pg/d for the assimilation rate and 0.19 pg/d and 0.32 pg/d for the elimination rate). Differences in results between exposure routes are discussed according to equilibrium-partitioning theory and the enhanced relevance of the substrate exposure route is analyzed under future prospects on chemical toxicity testing using isopods.

Toxicity of abamectin to the terrestrial isopod Porcellio scaber (Isopoda, Crustacea)

“…This is in agreement with the studies on earthworms by Sun et al (2005) and on sturgeon by Shen et al (2005). Sousa et al (2000) demonstrated that exposure route is important in the kinetics of lipophilic chemicals in isopods. In the case of lindane, the assimilation rate was much greater when exposed to contaminated soil compared to contaminated food exposure (Sousa et al 2000).…”

“…Sousa et al (2000) demonstrated that exposure route is important in the kinetics of lipophilic chemicals in isopods. In the case of lindane, the assimilation rate was much greater when exposed to contaminated soil compared to contaminated food exposure (Sousa et al 2000). As the food was not contaminated by abamectin, we might expect that most of the chemical was assimilated via the body surface.…”

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.…”

“…Kinetic studies with isopods are considered a better indicator of bioavailability than body burden measurements, since the flux of the contaminants into the organisms is more important in determining toxicity than total body concentration (van Straalen et al, 2005). Even though there are no standard protocols or guidelines to test bioaccumulation in isopods, the species Porcellionides pruinosus has been previously used successfully to evaluate the uptake kinetics of the pesticide lindane (Sousa et al, 2000;Loureiro et al 2002). This species is able to dig into the soil and therefore stay in more direct contact with soil particles when compared to other isopod species that mainly live on the top soil (litter) layer Moreover, the isopod Porcellionides pruinosus can easily be collected and cultured under lab conditions.…”

“…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.…”