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To determine the toxicity and bioaccumulation of copper, adult oribatid soil mites Oppia nitens were exposed for 28 days to LUFA 2.2 soil spiked at concentrations of 0–6400 mg Cu kg−1 dry soil. Effects on survival and reproduction were related to total and available (0.01 M CaCl2 extractable and pore water) concentrations in the soil and concentrations in the animals. The mites showed a concentration-dependent uptake of copper, which, however, decreased at toxic concentrations. Overall bioaccumulation factors were low, suggesting a low tendency for copper bioaccumulation. The estimated median lethal concentration (LC50) values were 3251 mg Cu kg−1 dry soil, 1130 mg Cu kg−1 dry soil, 1977 mg Cu L−1 pore water, and 592 mg Cu kg−1 dry body weight, and the estimated 50 % effective concentrations (EC50) for effects of copper on reproduction were 589 mg Cu kg−1 dry soil, 116 mg Cu kg−1 dry soil, 78.5 mg Cu L−1 pore water, and 413 mg Cu kg−1 dry body weight, based on measured soil total concentrations, 0.01 M CaCl2 extractable, porewater, and internal concentrations, respectively. The results show that the mite O. nitens is a suitable test organism for measuring metal bioavailability and toxicity in soil.

Avoidance behavior can be a useful parameter for assessing the ability of organisms to escape from pollutants in their environment. For soil evaluation, a variety of invertebrates is used including the oribatid mite Oppia nitens. Here, we tested the avoidance behavior of O. nitens using a two-chamber test and an escape test with exposures to different cadmium concentrations of up to 800 mg kg−1 dry LUFA 2.2 soil for 2, 4, and 6 days, and up to 7 weeks. With the two-chamber method, the oribatid mites had the choice between clean and polluted soils, whereas they were allowed to escape from a box with polluted soil to clean containers without soil with the escape method. Avoidance of cadmium was observed after 2 days in both tests and the net response of the mites in the two-chamber test increased with increasing cadmium exposure concentrations. Mite responses varied through time, especially with the escape method; with the avoidance behavior becoming more variable and overall non-significant with longer test durations. This is the first study investigating the escape test simultaneously with long-term avoidance of cadmium by O. nitens. This mite species is a promising species for avoidance testing in soil ecotoxicology, but more experiments are needed to evaluate the factors that influence its responses in laboratory tests and the consequences for its distribution in contaminated ecosystems.

The aim of this study was to assess the potential harmful effects of neonicotinoids inside honey bee colonies and especially on the honey bee pest, Varroa destructor. This paper shortly summarized previous studies which investigated the toxicity of neonicotinoids to honey bees. The possible exposure routes of these insecticides to Varroa mites inside and outside bee colonies were studied. And finally, the link between the adverse effects of neonicotinoids and Varroa mite life cycle in the brood cells and the influence of these chemicals on the mites inside bee colonies were investigated. It was concluded that the application of neonicotinoid insecticides on a variety of agricultural crops may result in the exposure of honey bees to these chemicals and as a consequence, Varroa mites (parasites living inside bee colonies) also got exposed to these insecticides indirectly. The present study re-emphasized on ecotoxicological attempts assessing the risk of these insecticides to honey bees as well as on ecological and behavioral aspects of their application inside bee colonies.

Micro-sized pyrogenic carbon (PyC) is expected to interact more efficiently with soil biota such as earthworms than coarse pyrogenic carbon. Little is known about whether the micro-sized PyC poses a threat to earthworms. We investigated the effects of hydrophilic micro-sized PyC on earthworm mortality in two contrasting soil substrates from young and old reclaimed soils of a successional chronosequence. These two soil substrates had different hydraulic properties, total organic carbon, pH, and nutrient status. Lower earthworm survival rates were observed in both soil substrates receiving dry micro-sized soil particles and the micro-sized PyC. Specifically, the addition of micro-sized PyC resulted in the lowest survival rate compared to the addition of micro-sized soil particles and the control from day 8 to 11. The decreased earthworm survival rate due to micro-sized PyC was more pronounced in the old soil substrate than in the young substrate. Fully moistened soil substrates containing micro-sized PyC or dry micro-sized soil substrate particles did not result in decreased earthworm survival. Micro-sized PyC turned from hydrophilic to hydrophobic when mixed with rhamnolipids, possibly hindering the uptake of dissolved oxygen by earthworm skins. Our results thus provide a new explanation for the negative effects of micro-sized PyC on earthworms and demonstrate the importance of assessing the hydraulic properties of both the micro-sized PyC and soil prior to PyC's application to soils.

Methanogens represent the final decomposition guild in anaerobic degradation of organic matter, occurring in digestive tract of various invertebrates. However, factors determining their community structure and activity in distinct gut sections is still debated. In this study, we focused on the tropical millipede species Archispirostreptus gigas (Diplopoda, Spirostreptidae) and Epibolus pulchripes (Diplopoda, Pachybolidae), which release considerable amounts of methane. We aimed to characterize relationships between physicochemical parameters, methane production rates, and methanogen community structure in the two major gut sections, midgut and hindgut. Microsensor measurements revealed that both sections were strictly anoxic, with reducing conditions prevailing in both millipedes. Hydrogen concentration culminated in anterior hindgut of E. pulchripes In both species, the intestinal pH was significantly higher in the hindgut than in the midgut. An accumulation of acetate and formate in the gut indicated bacterial fermentation activities in the digestive tract of both species. Phylogenetic analysis of 16S rRNA genes showed a prevalence of Methanobrevibacter spp. (Methanobacteriales), accompanied by a small fraction of so far unclassified "Methanomethylophilaceae" (Methanomassiliicoccales), in both species, which suggests that methanogenesis is mostly hydrogenotrophic. We conclude that anoxic conditions, negative redox potential, and bacterial production of hydrogen and formate promotes the gut colonization by methanogens. The higher activities of methanogens in the hindgut are explained by the higher pH of this compartment and their association with ciliates, which are restricted to this compartment and present an additional source of methanogenic substrates.ImportanceMethane (CH4) is the second most important atmospheric greenhouse gas after CO2 and is believed to account for 17% of global warming. Methanogens are a diverse group of archaea and can be found in various anoxic habitats including digestive tract of plant-feeding animals. Termites, cockroaches, the larvae of scarab beetles, and millipedes are the only arthropods known to host methanogens and emit large amounts of methane. Millipedes are ranked third most important detritivores after termites and earthworms, and they are considered keystone species in many terrestrial ecosystems. Both methane producing and non-emitting species have been observed in millipedes, but what limits their methanogenic potential is not known. In the present study, we show that physico-chemical gut conditions and the distribution of symbiotic ciliates are important factors determining CH4 emission in millipedes. We also find great similarities to other methane-emitting arthropods, which might be associated with their similar plant-feeding habits.

Millipedes are among the largest and most important invertebrates, with over 12,000 identified and 80,000 expected species worldwide. Millipedes are detritivores living on leaf litter, deadwood, or soil. Because of the poor nature of their diets, millipedes compensate through high food consumption. Thanks to this, they are keystone species in many terrestrial ecosystems. In fact, in tropical and temperate zones, they rank the third most essential macrodetritivores after termites and earthworms and consume 10-36% of the annual litter. Thus, they contribute to soil formation and are essential forest ecosystem engineers. Despite their ecological importance, it remains unclear what role does their microbiome play in their diet.We studied the gut microbiota of 11 millipede species and measured key physicochemical conditions (redox, pH and O2 levels). We found that the bacterial and archaeal communities were phylogenetically conserved while the fungi matched the diet. Methanogenic millipedes had a distinct community dominated by fermenting and syntrophic microorganisms. Follow-up experiments on the methanogenic and non-methanogenic species Epibolus pulchripes and Glomeris connexa, respectively, showed that both could survive prolonged antibiotic treatment, although with some disruption of their digestion. Antibiotics treatment significantly reduced the faecal bacterial colony counts after seven days in both species. Additionally, methane production dropped by 74% in the group treated with antibiotics and 52%, in the group that received sterile feed without antibiotics.Microbiome analysis of these groups showed major shifts of the community composition in response to antibiotics, but less so with sterile feed. Apart from the presence of methanogens, high methane production correlated with a high relative abundance of Bacteroidia, while Gammaproteobacteria dominated the guts of millipedes with low, or no, methane production.By supplementing the millipedes' diet with BES, methane production could be suppressed entirely within 21 days. Microscopic analysis of the faeces (using CARD-FISH) revealed methanogens from the orders Methanobacteriales and Methanomassiliicoccales associated with ciliates. These methanogens persisted even in the absence of methane production.Our results indicate a significant gut microbiome activity in cellulolytic, fermentative and methanogenic litter decomposition processes, however, unlike in ruminants and termites with a limited nutritional contribution to the host.

Background: Iron overload is caused early progression of atherosclerosis in beta thalassemia patients due to regular repeated blood transfusion. MRI T2* is a gold standard non-invasive method for detecting hepatic and cardiac iron overload. The aim of this study was the comparison of carotid intima media thickness (CIMT) in the patients and healthy control groups with Doppler ultrasound for early diagnosis of atherogenesis. Another purpose was to assess the relationship between CIMT and iron overload among patients. Materials and methods: This cross-sectional study was performed on twenty patients referred to the Sarvar clinic and twenty age- and sex-matched control group. The CIMT was measured with Color Doppler ultrasound in both groups. Then, MRI T2* results, demographic, and therapeutic information were extracted from their documents. Results: CIMT was insignificantly higher in the patients compared to the control group. For example, it was 0.49 ± 0.05 vs. 0.45 ± 0.03 (p = 0.009) for the right common carotid artery (RCCA) and 0.48 ± 0.06 vs. 0.46 ± 0.04 (p = 0.17) for the left common carotid artery (LCCA). There was no strong relationship between CIMT and age (p = 0.09 for RCCA, p = 0.00 for LCCA), sex, chelation type (for example, p = 0.51 for RCCA with Desferal and p = 0.91 for LCCA with Desferal), age at diagnosis, age at the beginning on transfusion (p = 0.49 for RCCA, p = 0.20 for LCCA), age at the start of chelator (p = 0.74 for RCCA, p = 0.78 for LCCA), and hepatic and cardiac iron overload. Conclusion: Preventive and curative methods should be planned to cease its progression. Furthermore, early initiation of chelator drugs with better efficacy and compliance may reverse the hepatotoxic and adverse myocardial effects of excessive iron.

The main aim of this short review was to assess the effect of test medium on the bioavailability of metals to the soil invertebrate Folsomia candida and the barley plant Hordeum vulgare. Solution-only exposures and sand-solution media were suitable media with control survival of > 80%. Comparing toxicity and accumulation data, LC50 and/or EC50 values as well as internal concentrations of cadmium (Cd) and copper (Cu) were similar in the tests with different porewater composition for springtails and barley plants. Similar results for toxicity and bioaccumulation of Cd and Cu using different test substrates, suggest the importance of physiological handling of the effects by the organisms rather than the influence of test medium composition.

The bioavailability of metals can be influenced not only by soil properties but also by other species living at polluted sites. However, in laboratory experiments, usually only one test species is used to estimate bioavailability. In this study, a two-species approach was applied to assess the impact of the earthworm Lumbricus rubellus on the bioavailability of cadmium and lead to the springtail Folsomia candida using natural soils from a gradient of metal pollution. Earthworms were kept in half of the soil replicates for 4 weeks. Subsequently, the uptake and elimination kinetics of cadmium and lead in F. candida exposed for 21 days to the soils was determined. Earthworm activity affected soil properties but did not significantly affect metal uptake rate constants in springtails. The slightly higher uptake due to the presence of earthworms, which was consistent in all tested soils and for both metals, suggests that further research is needed on the role of species interactions in affecting metal bioavailability in soil.

The aim of this study was to assess the effect of major cations (Ca2+, Mg2+, Na+, K+, and H+) on cadmium toxicity to the springtail Folsomia candida. Survival of the animals was determined after seven days exposure to different cadmium concentrations in an inert sand-solution medium, in different experimental setups with modification of the cation concentrations. Among the cations tested, Ca2+ and Mg2+ had protective effects on the toxicity of cadmium to the springtails while Na+, K+, and H+ showed less competition with free cadmium ions for binding to the uptake sites of the collembolans. Toxicity predicted with a biotic ligand model agreed well with the observed values. Calculated conditional binding constants and the fraction of biotic ligands occupied by cadmium to show 50% effects were similar to values reported in the literature. The results emphasize the important role of solution chemistry in determining metal toxicity to soil invertebrates.

Background and aim Arbuscular mycorrhizal fungi (AMF) have an important role in plant-microbe interactions. But, there are few studies in which the combined effect of AMF with a stress factor, such as the presence of a metal, on plant species were assessed. This study investigated the effect of arbuscular mycorrhizal (AM) fungus Rhizophagus intraradices and other soil microbial groups in the presence of copper on three plant species in a microcosm experiment. Methods Two grass species Poa compressa and Festuca rubra and one herb species Centaurea jacea were selected as model plants in a pot-design test in which soils were artificially contaminated with copper. Treatments were bacteria (control), saprophytic fungi, protists, and a combined treatment of saprophytic fungi and protists, all in the presence or absence of the AM fungal species. After sixty days, plants were harvested and the biomass of grass and herb species and microbial respiration were measured. Results The results showed almost equal above- and belowground plant biomass and microbial respiration in the treatments in the presence or absence of R. intraradices. The herb species C. jecea responded significantly to the soil inoculation with AM fungus, while grass species showed inconsistent patterns. Significant effect of AMF and copper and their interactions was observed on plant biomass when comparing contaminated vs. non-contaminated soils. Conclusion Strong effect of AMF on the biomass of herb species and slight changes in plant growth with the presence of this fungal species in copper-spiked test soils indicates the importance of mycorrhizal fungi compared to other soil microorganisms in our experimental microcosms.

This study investigated the effect of different plant litter types and developmental stages of the cockroach species Blaptica dubia on food consumption, animal growth, and excrement production. Three leaf litter species Alnus glutinosa, Acer platanoides, and Quercus robur were selected as model plants in a microcosm test in which plant litter was consumed by three different cockroach instar groups during five consecutive one-week intervals. At each interval, litter consumption, animal weight, and produced excrements were measured. The results showed slightly higher consumption of A. glutinosa compared to other leaf litter species in all three age/size groups of animals. Animals gained weight with time, especially Group B (medium-sized class animals) feeding on Alnus. The production of excrements was higher in Group C (big class animals) and increased in Alnus among litter species. Foliar litter consumption and excrement production rates were highest in B and C animal groups and in Alnus treatments; however, animal growth rates did not show a clear pattern, except for A. glutinosa. Measured energy contents showed highest values for animals, but slightly higher for leaves compared to excrements. Our results show that using energy budget parameters can help explain the relationship between litter type, cockroach sizes, and their consumption in this microcosm experiment.

The biotic ligand model (BLM) approach is used to assess metal toxicity, taking into account the competition of other cations with the free metal ions for binding to the biotic ligand sites of aquatic and soil organisms. The bioavailable fraction of metals, represented by the free metal ion, is a better measure than the total concentration for assessing their potential risk to the environment. Because BLMs are relating toxicity to the fraction of biotic ligands occupied by the metal, they can be useful for investigating factors affecting metal bioaccumulation and toxicity. In the present review, the effects of major cations on the toxicity of metals to soil and aquatic organisms were comprehensively studied by performing a meta-analysis of BLM literature data. Interactions at the binding sites were shown to be species- and metal-specific. The main factors affecting the relationships between toxicity and conditional binding constants for metal binding at the biotic ligand appeared to be Ca2+, Mg2+, and protons. Other important characteristics of the exposure medium, such as levels of dissolved organic carbon and concentrations of other cations, should also be considered to obtain a proper assessment of metal toxicity to soil and aquatic organisms. Environ Toxicol Chem 2015;34:2194–2204. © 2015 SETAC

The aim of this study was to assess infestation levels of Varroa destructor in some honey bee colonies from the National breeding program in the central part of Iran, and the relationship between mite infestation levels and postcapping period (PCP) of worker brood cells. Shortening the PCP is an important parameter limiting the success of varroa mite reproduction in honey bee colonies. In the present study, four pure-bred line colonies from isolated areas were selected to investigate the brood capping durations and mite infestation levels. Cages were used to synchronize egg laying of the queens and the time of capping and emerging of the brood cells was recorded at two-hour intervals. The results did not show any significant differences on the average of PCP of brood cells and mite infestation levels among test colonies. In addition, non-significant correlations were found between mite infestation and the capping period during the experiment. A relatively shorter capping period of brood cells was observed...

The aim of the present study was to improve our understanding of cadmium bioavailability by linking toxicokinetics and toxicodynamics. The springtail Folsomia candida was exposed to different cadmium concentrations in solutions embedded in inert quartz sand. Survival and cadmium uptake in the animals were followed for 21 d. After 10 d, some animals were transferred to clean medium to assess cadmium elimination. Using a first-order one-compartment model, an overall uptake rate constant (k1) of 0.18 L kganimal–1 d−1 and an elimination rate constant (k2-TK) of 0.02 d−1 were calculated. Survival decreased with time, resulting in an estimated final median lethal concentration (LC50) of 0.51 mM. A lethal body concentration (LBC) of 4.6 µmol Cd g−1 dry body weight was estimated by multiplying the final LC50 by the bioconcentration factor (k1/k2-TK). The LC50animal values based on internal cadmium concentrations were between 3.56 µmol Cd g−1 and 9.91 µmol Cd g−1 dry body weight, with an overall value of 7.9 µmol Cd g−1 dry body weight (95% confidence interval [CI]: 3.8–12.0 µmol Cd g−1 dry body wt). Because the 95% CI of the LC50animal included the LBC, there was good agreement of cadmium toxicokinetics and toxicodynamics. Environ Toxicol Chem 2014;33:1570–1577. © 2014 SETAC

Nitrogen supplement by adding N-fertilizer and/or growing of N-fixing trees are considered as important stimulus for the development of early vegetation. We performed pot experiments to determine the responses of legumes (N-fixing) and grasses (non-N fixing) in respect to their biomass to N fertilization, legacy of N, and combination of these two in various ages of post mining soils. N legacy was achieved either by long-term mineral N fertilization (legacy of inorganic N) (experiment 1) or growing of N2 fixing plant (legacy of N-fixing) (experiment 2). The first pot experiment was conducted to test N fertilization and legacy of inorganic N and these two on growth of Festuca rubra and Lotus corniculatus when grown separately. Following this, plant-soil feedback was defined as positive or negative by comparing the second generation of plant biomass in soils with and without plants in the previous generation. In the second pot experiment, we compared the performance of P. compressa and L. corniculatus in the presence of legacy of N-fixing and N fertiliaztion when grown together, and at the same time, plant-soil feedback was determined. N fertilization increased the growth of grasses, but only increased biomass of legumes in young soils. N-legacy induced variable plant growth, in particular often decreased the biomass of legumes. Legacy of inorganic N was only beneficial for grasses rather than legumes in medium soils. When growing in the same pot, legacy of N-fixing showed positive effects on grasses, depending on soil age and N fertilization. Repeated growing of plants in the same soil mostly resulted in negative plant-soil feedback. Negative plant-soil feedback was not alleviated by N fertilization and legacy of inorganic N for both grasses and legumes when grown separately. However, growing grasses and legumes together can induce positive plant-soil feedback with no legacy of N-fixing. In conclusion, N addition often stimulates plant growth more than long-term N effect. Legacy of N tends to be only beneficial for non-N fixing plants in medium aged soils. While negative plant-soil feedback occurs for grasses and legumes both grown separately or together, legumes can induce positive plant-soil feedback when grown with grasses in no legacy of N-fixing soils.

To improve our understanding of metal bioavailability to soil-living invertebrates, the effect of porewater composition on the toxicodynamics of copper and cadmium in Folsomia candida (Collembola) was investigated. Assuming that porewater is the main exposure route, F. candida was exposed to simulated soil solutions of different composition. Toxicity of copper was slightly lower in a calcium-only solution than in a multication solution. With increasing copper concentrations from 0.005 mM to 1.37 mM, internal copper concentrations similarly increased in both exposure solutions, suggesting that a single cation nutrient solution is suitable for testing F. candida. In the second experiment, animals were exposed for 7 d to copper and cadmium in simplified soil solutions with different calcium (0.2 mM, 0.8 mM, 3.2 mM, 12.8 mM) and pH (5.0, 6.0, 7.0) levels. The median lethal concentration (LC50) values decreased with time in both the calcium and pH series. A hormetic-type effect was observed for copper in the second test, as well as in the calcium-only solution in the first experiment. Because of stronger hormesis, LC50s for copper were higher at lower calcium concentrations. For cadmium, LC50 values were higher at higher calcium concentrations, suggesting competition of calcium with the free cadmium ion. Toxicity of cadmium increased with decreasing pH, while copper was more toxic at intermediate pH. The results show that a toxicodynamics approach can help to improve the interpretation of metal toxicity to soil invertebrates, taking into account soil solution properties. Environ Toxicol Chem 2013;32:2746–2754. © 2013 SETAC

The aim of the present study was to investigate the influence of Ca and pH on the uptake and effects of Cu in Folsomia candida (Collembola). Assuming that soil pore water is the main route of exposure, F. candida were exposed for seven days to Cu in simplified soil solutions at different Ca concentrations and different pH levels. A hormetic-type effect was seen for the effect of Cu on F. candida survival. Toxicity of Cu was slightly decreased and Cu uptake increased at the highest Ca concentrations. Cu toxicity and uptake were not significantly affected by pH. Conditional binding constants for Cu2+, Ca2+ and H+, calculated with a Langmuir isotherm, were used to relate Cu toxicity to the fraction of occupied binding sites (BL). The estimated 50% effect level (fCu-BL50) was 0.14 when all data were combined. To verify the Langmuir parameters, binding constants calculated based on internal Cu concentrations were used to estimate predicted effects and compared with the measured values. A good correlation between predicted and measured survival indicated that the principles of a biotic ligand model may be applicable to explain Cu toxicity to F. candida in simplified soil solutions.

The aim of this study was to improve our understanding of metal bioavailability in soil by linking the biotic ligand approach with toxicokinetics modelling. We determined cadmium bioaccumulation kinetics in Folsomia candida (Collembola) as a function of soil pH. Animals were exposed for 21 days to LUFA 2.2 soil at 5 or 20 μg Cd g −1 dry soil followed by 21 days elimination in clean soil. Internal cadmium concentrations were modelled using a first-order one-compartment model, relating uptake rate constants ( k 1 ) to total soil, water or 0.01 M CaCl 2 extractable and porewater concentrations. Based on total soil concentrations, k 1 was independent of soil pH while it strongly increased with increasing pH based on porewater concentrations explaining the reduced competition of H + ions making cadmium more bioavailable in pore water at high pH. This shows that the principles of biotic ligand modelling are applicable to predict cadmium accumulation kinetics in soil-living invertebrates.

The present study sought to quantify the components of a biotic ligand model (BLM) for the effects of Cd on Folsomia candida (Collembola). Assuming that soil porewater is the main route of exposure and to exclude the effects of soil particles on metal availability, animals were exposed for 7 d to different Cd concentrations between 0.1 mM and 100 mM in simplified soil solutions at different Ca concentrations (0.2 mM, 0.8 mM, 3.2 mM, and 12.8 mM) or at different pH (5.0, 6.0, and 7.0). Higher Ca concentrations decreased the toxicity of Cd (adult survival) in test solutions, whereas toxicity was slightly lower at pH 7 and 6 than at pH 5, suggesting a mitigating effect of Ca and to a lesser extent pH on Cd toxicity to F. candida. Internal Cd concentrations in the animals increased with increasing exposure level but were significantly reduced by increasing Ca concentrations and were not significantly affected by pH. By using Langmuir isotherms, binding constants for Cd, Ca, and protons and the fraction of binding sites occupied by Cd were calculated and used to predict effects of Cd on survival. Predicted toxicity showed a good agreement with measured responses when Ca and pH were used as separate factors or combined together. The present study shows indications of protective effects of Ca but less of protons on the toxicity and uptake of Cd in F. candida on exposure to simplified soil solutions, which can be described using the principles of a biotic ligand model. Environ Toxicol Chem 2013;32:1759–1767. © 2013 SETAC

The frequency of damaged Varroa destructor Anderson and Trueman (Mesostigmata: Varroidae) found on the bottom board of hives of the honey bee, Apis mellifera L. (Hymenoptera: Apidae) has been used as an indicator of the degree of tolerance or resistance of honey bee colonies against mites. However, it is not clear that this measure is adequate. These injuries should be separated from regular dorsal dimples that have a developmental origin. To investigate damage to Varroa mites and regular dorsal dimples, 32 honey bee (A. mellifera) colonies were selected from four Iranian provinces: Isfahan, Markazi, Qazvin, and Tehran. These colonies were part of the National Honey bee Breeding Program that resulted in province-specific races. In April, Varroa mites were collected from heavily infested colonies and used to infest the 32 experimental colonies. In August, 20 of these colonies were selected (five colonies from each province). Adult bees from these colonies were placed in cages and after introducing mites, damaged mites were collected from each cage every day. The average percentage of injured mites ranged from 0.6 to 3.0% in four provinces. The results did not show any statistical differences between the colonies within provinces for injuries to mites, but there were some differences among province-specific lines. Two kinds of injuries to the mites were observed: injuries to legs and pedipalps, and injuries to other parts of the body. There were also some regular dorsal dimples on dorsal idiosoma of the mites that were placed in categories separate from mites damaged by bees. This type of classification helps identifying damage to mites and comparing them with developmental origin symptoms, and may provide criteria for selecting bees tolerant or resistant to this mite.

The bioavailability of metals in soil is a dynamic process. For a proper extrapolation to the field of laboratory studies on fate and effects, it is important to understand the dynamics of metal bioavailability and the way it is influenced by soil properties. The aim of this study was to assess the parallel (concurrent) effect of pH and aging time on the partitioning of cadmium in natural LUFA 2.2 soil. Cadmium nitrate-spiked pH-amended LUFA 2.2 soils were incubated under laboratory conditions for up to 30 weeks. Measured pHpw was lower after 3 weeks and decreased only slightly toward the end of the test. Cadmium concentrations in the pore water increased with time for all soil pH levels, while they decreased with increasing pH. Freundlich kf values ranged between 4.26 and 934 L kg(-1) (n = 0.79 to 1.36) and were highest at the highest pH tested (pH = 6.5). Multiple linear regression analysis, based on a soil ligand modeling approach, resulted in affinity constants of 2.61 for Ca(2+) (log KCa-SL) and 5.05 for H(+) (log KH-SL) for their binding to the active sites on the soil surface. The results showed that pH and aging time are two important factors which together affect cadmium partitioning and mobility in spiked natural soils.

The effect of pH and calcium on copper bioavailability to the springtail Folsomia candida was determined by assessing uptake kinetics upon copper exposure for 15 days in simplified soil solutions. A slight bioaccumulation of copper was observed in all treatments and controls. The effect of exposure concentration and calcium level on copper accumulation was not significant. Although pH and time slightly but significantly affected copper concentrations in the body, copper uptake rates were not significantly different from zero. This suggests that copper uptake in F. candida exposed to sub-lethal copper concentrations in soil pore water is not affected by pH and calcium. © 2013 Elsevier GmbH.

Uptake and elimination kinetics of metals in soil invertebrates are a function of both soil and organism properties. This study critically reviewed metal toxicokinetics in soil invertebrates and its potential use for assessing bioavailability. Uptake and elimination rate constants of different metals are summarized. Invertebrates have different strategies for essential and non-essential metals. As a consequence, different types of models must be applied to describe metal uptake and elimination kinetics. We discuss model parameters for each metal separately and show how they are influenced by exposure concentrations and by physiological properties of the organisms. Soil pH, cation exchange capacity, clay and organic matter content significantly affect uptake rates of non-essential metals in soil invertebrates. For essential metals, kinetics is hardly influenced by soil properties, but rather prone to physiological regulation mechanisms of the organisms. Our analysis illustrates that toxicokinetics can be a valuable measurement to assess bioavailability of soil-bound metals. © 2014 Elsevier Ltd. All rights reserved.

The aim of the present study was to improve our understanding of cadmium bioavailability by linking toxicokinetics and toxicodynamics. The springtail Folsomia candida was exposed to different cadmium concentrations in solutions embedded in inert quartz sand. Survival and cadmium uptake in the animals were followed for 21 d. After 10 d, some animals were transferred to clean medium to assess cadmium elimination. Using a first-order one-compartment model, an overall uptake rate constant (k1) of 0.18 L kg(animal)(-1) d(-1) and an elimination rate constant (k(2-TK)) of 0.02 d(-1) were calculated. Survival decreased with time, resulting in an estimated final median lethal concentration (LC50) of 0.51 mM. A lethal body concentration (LBC) of 4.6 µmol Cd g(-1) dry body weight was estimated by multiplying the final LC50 by the bioconcentration factor (k1/k(2-TK)). The LC50(animal) values based on internal cadmium concentrations were between 3.56 µmol Cd g(-1) and 9.91 µmol Cd g(-1) dry body weight, with an overall value of 7.9 µmol Cd g(-1) dry body weight (95% confidence interval [CI]: 3.8-12.0 µmol Cd g(-1) dry body wt). Because the 95% CI of the LC50(animal) included the LBC, there was good agreement of cadmium toxicokinetics and toxicodynamics.

The biotic ligand model (BLM) is a theoretical, potentially mechanistic approach to assess metal bioavailability in soil and aquatic systems. In a BLM, toxicity is linked to the fraction of biotic ligand occupied, which in turn, depends on the various components of the solution, including activity of the metal. Bioavailability is a key factor in determining toxicity and uptake of metals in organisms. In this study, the present status of BLM development for soil and aquatic organisms is summarized. For all species and all metals, toxicity was correlated with the conditional biotic ligand binding constants. For almost all organisms, values for Ag, Cu, and Cd were higher than those for Zn and Ni. The constants derived for aquatic systems seem to be equally valid for soil organisms, but in the case of soils, bioavailability from the soil solution is greatly influenced by the presence of the soil solid phase.

To improve our understanding of metal bioavailability to soil-living invertebrates, the effect of porewater composition on the toxicodynamics of copper and cadmium in Folsomia candida (Collembola) was investigated. Assuming that porewater is the main exposure route, F. candida was exposed to simulated soil solutions of different composition. Toxicity of copper was slightly lower in a calcium-only solution than in a multication solution. With increasing copper concentrations from 0.005 mM to 1.37 mM, internal copper concentrations similarly increased in both exposure solutions, suggesting that a single cation nutrient solution is suitable for testing F. candida. In the second experiment, animals were exposed for 7 d to copper and cadmium in simplified soil solutions with different calcium (0.2 mM, 0.8 mM, 3.2 mM, 12.8 mM) and pH (5.0, 6.0, 7.0) levels. The median lethal concentration (LC50) values decreased with time in both the calcium and pH series. A hormetic-type effect was observed for copper in the second test, as well as in the calcium-only solution in the first experiment. Because of stronger hormesis, LC50s for copper were higher at lower calcium concentrations. For cadmium, LC50 values were higher at higher calcium concentrations, suggesting competition of calcium with the free cadmium ion. Toxicity of cadmium increased with decreasing pH, while copper was more toxic at intermediate pH. The results show that a toxicodynamics approach can help to improve the interpretation of metal toxicity to soil invertebrates, taking into account soil solution properties.

This study aimed to assess the bioavailability of copper in soil, by measuring its uptake kinetics into a representative soil invertebrate, the collembolan Folsomia candida. The animals were exposed to 25 or 100 μg Cu g−1 dry LUFA 2.2 soil at nominal \( {\text{pH}}_{{{\text{CaCl}}_{ 2} }} \) 4.5, 5.5, or 6.5 during 14 days after which they were transferred to clean soil for 14 days elimination. Uptake and elimination rate constants were calculated based on total and extractable soil concentrations and porewater concentrations using one-compartment first-order kinetics modelling. Copper was present in the animals at a basal physiological level of 40–90 μg g−1dry weight, on top of this uptake and elimination kinetics were observed. Uptake rates constants varied between 0.02 and 0.17 gsoil ganimal−1 day−1, being higher at lower exposure level, but did not differ significantly between different soil pH levels. Elimination rate constants ranged between 0.04 and 0.20 day−1 and were negligible (k2 < 0.001 day−1) at pH 4.5 and 6.5. Multiple linear regressions showed that the pH effect on copper uptake was only significant when taking into account cation exchange capacity, or calcium and dissolved organic carbon levels in the pore water. Copper concentrations in the animals however, never were higher than 185 μg g−1 dry weight, independent of exposure level and pH, suggesting homeostatic regulation. These results show that the chemical composition of the pore water does affect bioavailability of copper in soil, but that copper uptake in collembolans is dominated by homeostatic regulation rather than by soil properties like pH.

The present study sought to quantify the components of a biotic ligand model (BLM) for the effects of Cd on Folsomia candida (Collembola). Assuming that soil porewater is the main route of exposure and to exclude the effects of soil particles on metal availability, animals were exposed for 7 d to different Cd concentrations between 0.1 mM and 100 mM in simplified soil solutions at different Ca concentrations (0.2 mM, 0.8 mM, 3.2 mM, and 12.8 mM) or at different pH (5.0, 6.0, and 7.0). Higher Ca concentrations decreased the toxicity of Cd (adult survival) in test solutions, whereas toxicity was slightly lower at pH 7 and 6 than at pH 5, suggesting a mitigating effect of Ca and to a lesser extent pH on Cd toxicity to F. candida. Internal Cd concentrations in the animals increased with increasing exposure level but were significantly reduced by increasing Ca concentrations and were not significantly affected by pH. By using Langmuir isotherms, binding constants for Cd, Ca, and protons and the fraction of binding sites occupied by Cd were calculated and used to predict effects of Cd on survival. Predicted toxicity showed a good agreement with measured responses when Ca and pH were used as separate factors or combined together. The present study shows indications of protective effects of Ca but less of protons on the toxicity and uptake of Cd in F. candida on exposure to simplified soil solutions, which can be described using the principles of a biotic ligand model.