Toxicokinetics and time-variable toxicity of cadmium in Oppia nitens Koch (Acari: Oribatida)

Abstract

The soil-living mite Oppia nitens Koch has recently been proposed as a promising test species for the ecotoxicological risk assessment of contaminated boreal soils. Adding oribatid mites to the assemblage of test species for soil is highly desirable given the enormous diversity and ecological significance of these microarthropods. The authors aimed at revealing how toxicity, lethal body concentration, and bioaccumulation of cadmium (Cd) changed over a period of 7 wk when mites were exposed to Cd-spiked natural soils. The estimated median lethal concentration (LC50) values showed a gradual decrease with time, but a steady state was not reached within 7 wk. Estimates for lethal body concentration varied from 44 mg Cd/g to 91 mg Cd/g dry body weight, with a tendency to increase with time. The estimated 50% effective concentration (EC50) for effects on reproduction after 7-wk exposure was 345 mg Cd/g dry soil. Accumulation of Cd in mites was extremely variable but overall showed a nonsaturating increase. A simple 1-compartment toxicokinetic model did not describe the data well. The analysis suggests that O. nitens has a storage-detoxification strategy that is not at equilibrium under chronic exposure. Considering the tiny body size of the animal, it is remarkable that long exposure times are necessary to reveal chronic toxicity. The use of oribatids provides a clear added value to soil risk assessment but trades off with exposure length. Environ Toxicol Chem 2017;36:408-413. #

Consequences of surface coatings and soil ageing on the toxicity of cadmium telluride quantum dots to the earthworm Eisenia fetida

“…3). For the unexposed controls, the background concentration of Cd in Lufa 2.2 soils was low (0.6 ± 0.2 mg Cd kg -1 dw, Figure 1) and consistent with previous reports for the same soil [e.g., 0.38 mg Cd kg -1 dw, (Keshavarz Jamshidian et al, 2017)]. In the control soil, less than 10 % of the total background Cd concentration was water and acid extractable, indicating that the background Cd in the control soil was not mobile.…”

“…Cadmium is a non-essential metal and known to bioaccumulate in earthworms (Hopkin, 1989). The background concentrations of Cd in soil are usually around 1 mg kg -1 dry weight (dw) or less (Keshavarz Jamshidian et al, 2017), but contaminated soils can have tens of mg of Cd (Spurgeon et al, 1994). Dissolved cadmium toxicity is well established in earthworms; with a 28-day lethal concentration (LC50) of 588 mg Cd kg -1 dw in artificial soil (Van Gestel et al, 1991), and 56-day EC50 for impairment of reproduction of 46.3 mg Cd kg -1 dw in artificial soil (Spurgeon et al, 1994).…”

Oppia nitens C.L. Koch, 1836 (Acari: Oribatida): Current Status of Its Bionomics and Relevance as a Model Invertebrate in Soil Ecotoxicology

“…Considering the metals’ effects on survival and reproduction, Cd was the most toxic metal to the mites, having the lowest median lethal concentration (LC50) value, 603 mg/kg, and the lowest reproduction median inhibitory concentration (EC50) value, 137 mg/kg. Keshavarz Jamshidian et al () reported a higher reproduction EC50 value of 345 mg/kg Cd in LUFA 2.2, a natural reference soil. Cadmium has been linked to deleterious effects on the community structure of mites in metal‐contaminated soils (Khalil et al ).…”

“…The toxicokinetics of Cd to O. nitens after a 7-wk exposure in LUFA 2.2 soil showed O. nitens to be a steady accumulator of Cd, with reduced elimination or depuration. Lethal body estimates ranged from 44 to 91 µg Cd/g dry body weight (Keshavarz Jamshidian et al 2017). Table 3 presents the response of O. nitens to contaminants in comparison with other soil invertebrate species used in soil ecotoxicity testing.…”

“…The toxicokinetics of Cd to O. nitens after a 7-wk exposure in LUFA 2.2 soil showed O. nitens to be a steady accumulator of Cd, with reduced elimination or depuration. Lethal body estimates ranged from 44 to 91 µg Cd/g dry body weight (Keshavarz Jamshidian et al 2017). 3).…”