Heavy metals in epigeic fauna: trophic-level and physiological hypotheses

Arthropods in landfills and their accumulation potential for toxic elements: A review

Landfills, as a source of potentially toxic elements (PTEs), pose a threat to the environment and human health. A literature review was conducted to explore the diversity of arthropods inhabiting solid waste landfills, as well as on the bioaccumulation of PTEs by arthropods. This review presents scientific papers over the last 20 years. Their importance in landfill ecosystems has been the subject of research; however, the issue of the accumulation of compounds such as toxic elements is emphasized only in a few studies. The bioaccumulation of PTEs was studied for 10 arthropod species that founded in landfills: Orthomorpha coarctata and Trigoniulus corallinus (class Diplopoda), Armadillidium vulgare and Trachelipus rathkii (class Malacostraca), the 6 species of the class Insecta - Zonocerus variegatus, Anacanthotermes ochraceus, Macrotermes bellicosus, Austroaeschna inermis, Calathus fuscipes and Harpalus rubripes.

The transfer of trace metals in the soil-plant-arthropod system

Essential and non-essential trace metals are capable of causing toxicity to organisms above a threshold concentration. Extensive research has assessed the behaviour of trace metals in biological and ecological systems, but has typically focused on single organisms within a trophic level and not on multi-trophic transfer through terrestrial food chains. This reinforces the notion of metal toxicity as a closed system, failing to consider one trophic level as a pollution source to another; therefore, obscuring the full extent of ecosystem effects. Given the relatively few studies on trophic transfer of metals, this review has taken a compartment-based approach, where transfer of metals through trophic pathways is considered as a series of linked compartments (soil-plant-arthropod herbivore-arthropod predator). In particular, we consider the mechanisms by which trace metals are taken up by organisms, the forms and transformations that can occur within the organism and the consequences for trace metal availability to the next trophic level. The review focuses on four of the most prevalent metal cations in soil which are labile in terrestrial food chains: Cd, Cu, Zn and Ni. Current knowledge of the processes and mechanisms by which these metals are transformed and moved within and between trophic levels in the soil-plant-arthropod system are evaluated. We demonstrate that the key factors controlling the transfer of trace metals through the soil-plant-arthropod system are the form and location in which the metal occurs in the lower trophic level and the physiological mechanisms of each organism in regulating uptake, transformation, detoxification and transfer. The magnitude of transfer varies considerably depending on the trace metal concerned, as does its toxicity, and we conclude that biomagnification is not a general property of plant-arthropod and arthropod-arthropod systems. To deliver a more holistic assessment of ecosystem toxicity, integrated studies across ecosystem compartments are needed to identify critical pathways that can result in secondary toxicity across terrestrial food-chains.

Trace Element Concentrations in Tree Leaves and Lichen Collected Along a Metal Pollution Gradient Near Olkusz (Southern Poland)

The aim of the study was to assess the metal pollution in the vicinity of the Bukowno smelter near Olkusz in southern Poland. Birch and oak leaves, pine needles and a lichen Hypogymnia physodes, overgrowing pine bark were collected at stands at different distances from the smelter and analysed for cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) content. Concentrations of metals in the lichen were usually higher than in the tree leaves/needles and decreased with distance from the smelter, apart from the Cu content. The strongest correlation was noticed between Cd and Pb concentrations, which indicates a common pollution source (the smelter). Our results show that birch leaves can be potentially useful as a bioindicator of Zn air pollution since this species was shown to accumulate high amounts of zinc, related to environmental pollution with that metal, in their leaves.

Assessment of biotransfer and bioaccumulation of cadmium, lead and zinc from fly ash amended soil in mustard-aphid-beetle food chain

The present study investigates the extent of biotransfer and bioaccumulation of cadmium (Cd), lead (Pb) and zinc (Zn) from fly ash amended soil in mustard (Brassica juncea)-aphid (Lipaphis erysimi)-beetle (Coccinella septempunctata) food chain and its subsequent implications for the beetle. The soil was amended with fly ash at the rates of 0, 5, 10, 20 and 40% (w/w). Our results showed that the uptake of Cd, Pb and Zn from soil to mustard root increased with the increase in fly ash application rates, but their root to shoot translocation was relatively restricted. Increase in chlorophyll content and dry mass of mustard plant on treatments ≥20% even at elevated accumulation of Cd (1.67mgkg^-1), Pb (18.25mgkg^-1) and Zn (74.45mgkg^-1 dry weight) in its shoot showed relatively higher tolerance of selected mustard cultivar to heavy metal stress. The transfer coefficient (TC¹) of Cd from mustard shoot to aphid was always >1, indicating that Cd biomagnified in aphids at second trophic level. But, there was no biomagnification of Cd in adult beetles at third trophic level. Zinc accumulation was 2.06 to 2.40 times more in aphids than their corresponding host shoots and 1.26-1.35 times more in adult beetles than their prey (aphids) on which they fed. Lead was only metal whose TC was <1 at both second and third trophic levels. The elimination of Cd via honeydew of aphids was most efficient as the ratio of metal in honeydew to aphid (ranging from 0.21 to 0.26) was higher than the Pb (0.16 to 0.20) and Zn (0.07 to 0.09). The statistically consistent (p>0.05) biomass and predation rate of predatory beetles indicated that all levels of soil amendments with fly ash did not have any lethal or sub-lethal effects on beetles.

Energy reserves and accumulation of metals in the ground beetle Pterostichus oblongopunctatus from two metal-polluted gradients

Living in an area chronically polluted with metals is usually associated with changes in the energy distribution in organisms due to increased energy expenses associated with detoxification and excretion processes. These expenses may be reflected in the available energy resources, such as lipids, carbohydrates, and proteins. In this context, the energy status of Pterostichus oblongopunctatus (Coleoptera: Carabidae) was studied in two metal pollution gradients near Olkusz and Miateczko Śląskie in southern Poland. Both regions are rich in metal ores, and the two largest Polish zinc smelters have been operating there since the 1970s. Beetles were collected from five sites at each gradient. Zinc and cadmium concentrations were measured in both the soil and the beetles. The possible reduction in energy reserves as a cost of detoxifying assimilated metals was evaluated biochemically by determining the total lipid, carbohydrates, and protein contents. At the most polluted sites, the Zn concentration in the soil organic layer reached 2,906 mg/kg, and the Cd concentration reached 55 mg/kg. Body Zn and Cd concentrations increased with increasing soil Zn and Cd concentrations (p = 0.003 and p = 0.0001, respectively). However, no relationship between pollution level and energetic reserves was found. The results suggest that populations of P. oblongopunctatus inhabiting highly metal-polluted sites are able to survive without any serious impact on their energy reserves, though they obviously have to cope with elevated body metal concentrations.

Effect of long-term zinc pollution on soil microbial community resistance to repeated contamination

The aim of the study was to compare the effects of stress (contamination trials) on the microorganisms in zinc-polluted soil (5,018 mg Zn kg(-1) soil dry weight) and unpolluted soil (141 mg Zn kg(-1) soil dw), measured as soil respiration rate. In the laboratory, soils were subjected to copper contamination (0, 500, 1,500 and 4,500 mg kg(-1) soil dw), and then a bactericide (oxytetracycline) combined with a fungicide (captan) along with glucose (10 mg g(-1) soil dw each) were added. There was a highly significant effect of soil type, copper treatment and oxytetracycline/captan treatment. The initial respiration rate of chronically zinc-polluted soil was higher than that of unpolluted soil, but in the copper treatment it showed a greater decline. Microorganisms in copper-treated soil were more susceptible to oxytetracycline/captan contamination. After the successive soil contamination trials the decline of soil respiration was greater in zinc-polluted soil than in unpolluted soil.

Uptake and elimination of cadmium and zinc by Eisenia andrei during exposure to low concentrations in artificial soil

Bioaccumulation factors (BAFs) are often used in the risk assessment process to estimate trophic transfer of contaminants such as metals from soil. BAFs can be derived from laboratory studies through the determination of steady-state concentrations or kinetic estimation methods. In this study, bioaccumulation tests were performed with artificial soil spiked at low levels with cadmium or zinc to determine uptake and elimination kinetics of both metals by the compost worm Eisenia andrei. The metal-amended soils were acclimated for 21 days prior to the test, after which worms were individually incubated in the soils. The uptake phase comprised 0-21 days, after which the test organisms were transferred into clean soil and the elimination phase continued for an additional 21 days. Subsamples of soil and earthworms (whole body) were collected from independent replicates throughout the uptake phase and elimination phase and analyzed for total metal concentrations. Uptake of Cd in E. andrei increased linearly with time and did not reach steady state within the testing period. Cd uptake and excretion were described by a one-compartment first-order kinetics model. Zn concentrations rapidly increased in E. andrei after 1 day of exposure but subsequently decreased to background levels throughout the remainder of the uptake phase; internal Zn concentrations did not change from background levels during the elimination phase. Kinetic BAFs were calculated for Cd and Zn. Cd is a nonessential metal that is bioaccumulated at a relatively rapid rate, while Zn is an essential metal, and as such, it is regulated by E. andrei. Metal essentiality and concentration significantly impact bioaccumulation of metals by terrestrial invertebrates.

Responses of terrestrial arthropods to air pollution: a meta-analysis

BACKGROUND, AIM, AND SCOPE

Arthropods, with over a million species described, are ubiquitous throughout different environments. Knowledge of their responses to human impact is crucial for understanding and predicting changes in ecosystem structure and functions. Our aim was to investigate the general patterns and to identify sources of variation in changes of the diversity, abundance and fitness of terrestrial arthropods (including Arachnida, Collembola and Insecta) in habitats affected by point polluters.

MAIN FEATURES

We found 134 suitable studies which were published between 1965 and 2007. These data came from impact zones of 74 polluters in 20 countries with the largest representation from Russia (28 polluters), Poland (12 polluters) and the USA (six polluters). The database allowed calculation of 448 effect sizes (i.e. relative differences between measurements taken from polluted and control sites) on the effects of various point polluters like non-ferrous industries, aluminium plants, cement, magnezite, fertilising and chemical plants, power plants, iron- and steel-producing factories. We used meta-analysis to search for general effects and to compare between polluter types and arthropod groups, and linear regression to describe the latitudinal gradient and to quantify relationships between pollution and arthropod responses.

RESULTS

The overall effect of pollution on arthropod diversity did not differ from zero. However, species richness of soil arthropods (both living on the soil surface and within the soil) tended to decrease, and species richness of herbivores to increase, near point polluters. Abundance of terrestrial arthropods near point polluters decreased in general. This decrease resulted from strong adverse effects on soil arthropods, especially on decomposers and predators. Densities of herbivores increased, but a number of research biases that we discovered in published data may have led to overestimation of the latter effect. The dome-shaped density pattern along pollution gradients was discovered only in 5% of data sets. Among herbivores, only free-living defoliators and sap-feeders demonstrated higher densities in polluted sites; the effects of pollution on other guilds were not significant. Near the polluters, conifers suffered higher increase in damage from herbivores than deciduous woody plants and herbs. Overall effect of pollution on arthropod performance was negative; in particular, individuals from polluted sites were generally smaller than individuals from control sites. This negative effect weakened with increase in duration of the pollution impact, hinting evolution of pollution resistance in populations inhabiting polluted sites. Stepwise regression analysis demonstrated that pollution-induced changes in both the density and performance of arthropods depended on climate of the locality. Negative effects on soil fauna increased with increase in annual precipitation; positive effects on herbivore population density increased with increases in both mean July temperature and annual precipitation.

DISCUSSION

We detected effects of research methodology on the outcome of published studies. Many of them suffer from research bias-the tendency to collect data on organisms or under conditions in which one has an expectation of detecting significant effects. Pseudoreplicated studies (one polluted site contrasted to one control site) frequently reported larger effects than replicated studies (several polluted sites contrasted with several control sites). These methodological flaws especially influenced herbivory studies; we conclude that increase in herbivory in both heavily and moderately polluted habitats is not as frequent as it was earlier suggested. In contrast, the decrease in abundance of predators is likely to be a widespread phenomenon. Thus, our analysis supports the hypothesis that pollution may favour herbivore populations by creating an enemy-free space. Consistent declines in abundance of soil arthropods in impact zones of different polluters suggest that this group can potentially be used in bioindication of pollution-induced changes in terrestrial ecosystems.

CONCLUSIONS

Main effects of pollution on arthropod communities (decreased abundance of decomposers and predators and increased herbivory) may have negative consequences for structure and services of entire ecosystems. Responses of arthropods to pollution depend on both temperature and precipitation in such a way that ecosystem-wide adverse effects are likely to increase under predicted climate change.

RECOMMENDATIONS AND PERSPECTIVES

Our analysis confirmed that local severe impacts of industrial enterprises on biota are well-suited to reveal the direction and magnitude of the biotic effects of aerial pollution, as well as to explore the sources of variation in responses of organisms and communities. Although we analysed the effects of point polluters, our conclusions can be applied to predict consequences of pollution impacts on regional and even global scales. We argue that possible interactions between pollution and climate should be accounted for in the analyses of global change impacts on biota.

The effects of ethylene glycol and ethanol on the body mass and elemental composition of insects collected with pitfall traps

Insects often used as accumulation indicators of hazardous elements. Pitfall traps with ethylene glycol as trapping fluid are frequently used to collect insects. We studied the effect of glycol and preservation with ethanol on the elemental composition of hand collected firebugs. Control samples were stored in a freezer and the following treatments were used: insect kept in trapping fluid for 2 weeks, and for 1 month, trapping fluid for 2 weeks plus 2 weeks in ethanol, and trapping fluid for 1 month plus ethanol for 1 month. Insects kept in trapping fluid gained mass with respect to control: 26% for the short trapping and 37% for the long trapping. Preservation in ethanol reversed this effect in each case. Trapping fluid did not alter the dry mass. A significant loss in dry mass only occurred in the long trapping plus long preservation treatment. We analysed the concentration of eight elements: Ca, Cu, K, Mg, Mn, Na, Sr and Zn. We found significant difference in the concentrations of elements among the four treatments in the case of all elements, except magnesium and zinc. Our results indicate the potential of both certain trapping fluids as well as preservation in ethanol influencing the concentration of certain elements in insects. Live trapping for collection and storage in under freezing conditions for preservation could be a more reliable method if quantitative analytical studies are to be performed, when invertebrates are used as indicators of the presence and concentrations of hazardous substances in the environment.

Phycoerythrobilin synthase (PebS) of a marine virus. Crystal structures of the biliverdin complex and the substrate-free form

The reddish purple open chain tetrapyrrole pigment phycoerythrobilin (PEB; A(lambdamax) approximately 550 nm) is an essential chromophore of the light-harvesting phycobiliproteins of most cyanobacteria, red algae, and cryptomonads. The enzyme phycoerythrobilin synthase (PebS), recently discovered in a marine virus infecting oceanic cyanobacteria of the genus Prochlorococcus (cyanophage PSSM-2), is a new member of the ferredoxin-dependent bilin reductase (FDBR) family. In a formal four-electron reduction, the substrate biliverdin IXalpha is reduced to yield 3Z-PEB, a reaction that commonly requires the action of two individual FDBRs. The first reaction catalyzed by PebS is the reduction of the 15,16-methine bridge of the biliverdin IXalpha tetrapyrrole system. This reaction is exclusive to PEB biosynthetic enzymes. The second reduction site is the A-ring 2,3,3(1),3(2)-diene system, the most common target of FDBRs. Here, we present the first crystal structures of a PEB biosynthetic enzyme. Structures of the substrate complex were solved at 1.8- and 2.1-A resolution and of the substrate-free form at 1.55-A resolution. The overall folding revealed an alpha/beta/alpha-sandwich with similarity to the structure of phycocyanobilin:ferredoxin oxidoreductase (PcyA). The substrate-binding site is located between the central beta-sheet and C-terminal alpha-helices. Eight refined molecules with bound substrate, from two different crystal forms, revealed a high flexibility of the substrate-binding pocket. The substrate was found to be either in a planar porphyrin-like conformation or in a helical conformation and is coordinated by a conserved aspartate/asparagine pair from the beta-sheet side. From the alpha-helix side, a conserved highly flexible aspartate/proline pair is involved in substrate binding and presumably catalysis.

Effects of nickel and temperature on the ground beetle Pterostichus oblongopunctatus (Coleoptera: Carabidae)

In natural ecosystems it is not unusual for an organism to be exposed both to chemical and physical stressful factors at the same time. Herein we present results of the study on nickel toxicity to the carabid beetle, Pterostichus oblongopunctatus, and effect of Ni and temperature on the beetles respiration rates. In the first part of the study (Experiment I) we measured the survival, respiration rates and internal Ni concentrations in animals exposed for 245 d at constant temperature (20 degrees C) to food contaminated with Ni at nominal concentrations 0; 600; 1,200; 2,400; 4,800; and 9,600 mg kg(-1) dry weigh (dw). The LC(50) was estimated at 8,351 mg Ni kg(-1), with no effect on fertility. We found a significant positive correlation between Ni concentration in food and internal body concentration of Ni, and a negative correlation between Ni exposure and the respiration rate. Based on these results, the concentration of 2,400 mg kg(-1) (LOEC for the respiration rate) was selected for the second part of the study (Experiment II) in which field-collected males of P. oblongopunctatus were exposed to Ni-contaminated food for 64 d and then to uncontaminated food for the next 64 d at three temperatures: 10, 15 and 20 degrees C. In this part of the study we found that the temperature under which the beetles were kept affected their respiration rates, and that effect of Ni on the respiration was significant only in animals originating from 20 degrees C. The results from both experiments indicate that negative effects of nickel appear only after relatively long exposure.

Uranium contents and (235)U/(238)U atom ratios in soil and earthworms in western Kosovo after the 1999 war

The uranium content and (235)U/(238)U atom ratio were determined in soils and earthworms of an area of Kosovo (Djakovica garrison), heavily shelled with depleted uranium (DU) ammunition during the 1999 war. The aim of the study was to reconstruct the small-scale distribution of uranium and assess the influence of the DU added to the surface environment. The total uranium concentration and the (235)U/(238)U ratio of topsoils showed great variability and were inversely correlated. The highest uranium levels (up to 31.47 mg kg(-1)) and lowest (235)U/(238)U ratios (minimum 0.002147) were measured in topsoils collected inside, or very close to, the clusters of DU penetrator holes. Regarding the fractionation of uranium in the surface soils, the uranium concentrations in the soluble and exchangeable fractions increased as the total uranium concentration of the topsoils increased. High and rather uniform percentage contents of uranium (24-36%) were associated with the poorly crystalline iron oxide phases of soils. In the U-enriched soils the elevated levels of the element were probably due to the presence of very small, unevenly distributed oxidized DU particles. The total uranium concentration in earthworms was in the range 0.142-0.656 mg kg(-1), with the highest concentrations in Lumbricus terrestris. The juveniles of all three studied species seemed to accumulate uranium more than adults, probably due to age-related differences in metabolism. The (235)U/(238)U ratio in the earthworms was variable (0.005241-0.007266) and independent of both the total uranium contents in soils and the absolute uranium levels in the animals. Bioconcentration was greater at lower U concentrations in soil, probably due to an increasing rate of elimination of uranium by the earthworms as the soil contents of the element increase. The results of this study clearly indicate that DU was added to the soil of the study area. Nevertheless, the phenomenon was very limited spatially and the total uranium concentrations fell within the natural range of the element in soils. Moreover, the absolute uranium concentrations indicate that there was no contamination of the earthworm species studied.

Oribatid mite communities and metal bioaccumulation in oribatid species (Acari, Oribatida) along the heavy metal gradient in forest ecosystems

The responses of oribatid communities to heavy metal contamination were studied. Concentration of cadmium, copper and zinc in nine oribatid species along a gradient of heavy metal pollution was measured. Oribatid mites were sampled seasonally during two years in five forests located at different distances from the zinc smelter in the Olkusz District, southern Poland. The most numerous and diverse oribatid communities were found in the forest with moderate concentrations of heavy metals. Analysis by atomic absorption spectrophotometry revealed large differences in metal body burdens among species. All studied oribatid species appeared to be accumulators of copper with Oppiella nova, Nothrus silvestris and Adoristes ovatus characterized by the highest bioaccumulation factors. Most species poorly accumulate cadmium and zinc. The accumulation of heavy metals in the body of oribatids was not strictly determined by their body size or the trophic level at which they operate.

Absence of cadmium excretion and high assimilation result in cadmium biomagnification in a wolf spider

Cd biomagnification in the terrestrial food chain appears to be dependent on the physiological properties of the organisms rather than on their trophic level. Although high Cd body burdens in spiders from the field have been reported many times, experimental verification of the key factors that determine the rate of cadmium accumulation is lacking. We investigated the cadmium assimilation rate in the common wolf spider Pirata piraticus fed with contaminated fruit flies. Spiders were fed for 42 days with contaminated flies, followed by a detoxicification period of 28 days. Every 14 days, a subsample of spiders and flies was taken for Cd determination. It was demonstrated that a high cadmium assimilation (69.5%) and an excretion rate approaching zero resulted in high Cd concentration factors. The results indicate the importance of spiders in cadmium biomagnification along critical pathways.

Activity of carboxylesterase and glutathione S-transferase in different life-stages of carabid beetle (Poecilus cupreus) exposed to toxic metal concentrations

Among the cytoplasmatic enzymes responsible for neutralization of organic xenobiotics, carboxylesterases (CarE) and glutathione S-transferases (GST) play important roles. Our study tested to what extent dietary Zn or Cd could modify the activity of CarE and GST at different life-stages of the carabid beetle Poecilus cupreus. Treatment and stage effects generally were statistically significant. For CarE activity in the beetles exposed to cadmium, only treatment was a significant factor. In all cases, the interaction between studied factors was statistically significant, implying that the physiological condition of the animals may enhance or reduce enzyme activity. We also observed differences between animals treated with cadmium and zinc in the pattern of enzyme activity, and a difference in GST activity measured with two different substrates. Our results confirmed that in studying enzyme activity under metal stress one should consider the animal's life-stage and sex.

Effects of cadmium and zinc on larval growth and survival in the ground beetle, Pterostichus oblongopunctatus

Carabid beetles, like Pterostichus oblongopunctatus, living in metal contaminated areas may be exposed to elevated levels of metals within their diets. However, when compared to other second order consumers, they have one of the lowest observed levels of metals, indicating methods of detoxification to deal with such toxicants. In this study, we investigated if chronic, multigenerational exposure to metals leads to resistance to toxic metal concentrations, and if so, what are the costs associated with them. Adult organisms were collected from two sites, a polluted and a reference site near Olkusz, in southern Poland. These adults were immediately mated, and eggs were collected twice weekly to assess the effects in the larvae of the F(1) generation. Larvae were randomly exposed to one of four artificial mediums: control, 50 mg kg(-1) Cd, 500 mg kg(-1) Zn, and a combined treatment of 50 mg kg(-1) Cd and 500 mg kg(-1) Zn to investigate possible interactions. Individuals were sacrificed at 10, 30, and 40 days. Although metals were not accumulated in larvae (p>0.05), larvae fed the Cd or the Zn treatment grew significantly slower, and had the lowest survival rate (p<0.05) in respect to control. Out of metal treated animals, those on the combined treatment of CdZn grew the quickest and had the highest observed survival (p<0.05). Although previous studies have demonstrated changes in adult population parameters under chronic, multigeneration exposure to toxic metal concentrations, our study did not reveal any changes in the larval stage.

Storage mediums affect metal concentration in woodlice (Isopoda)

Terrestrial invertebrates are becoming widely established as tools to assess heavy metal pollution at contaminated sites. A practical and time saving method to sample terrestrial invertebrates consist of pitfall traps, often filled with a 4% formaldehyde solution and some detergent. The reliability of metal concentrations based on organisms captured and stored in this solution might however be questioned and we therefore tested the effect of formaldehyde on Zn, Cu, Cd and Pb concentration experimentally in three isopod species. Our results showed that in many cases, significant decreases in Cu concentrations compared to animals stored in a freezer were observed that could be as high as 40%, while Zn, Cd and Pb concentrations increased. A regression analysis of individual dry weight on individual size revealed that formaldehyde decreases the dry weight substantially and in that way causes increased measurements of Zn, Cd and Pb concentrations. We conclude that pitfall traps with formaldehyde should better not be used to collect animals in which concentrations of heavy metals or other toxic substances will be determined.

Transfer and effects of cadmium in an experimental food chain involving the snail Helix aspersa and the predatory carabid beetle Chrysocarabus splendens

The transfer and the toxic effects of Cd were studied in an experimental food chain involving the snail Helix aspersa as prey organism and one of its natural predators, the carabid beetle Chrysocarabus splendens. Juvenile snails were fed plant-based food enriched with 0, 10, 50 and 100 microg g(-1) of Cd, then were offered as prey to beetle larvae from egg hatching to pupation stage. Cd concentrations in snail tissues increased with increasing Cd concentration in food and with duration of exposure. Bioaccumulation factors ranged from 1.87 to 3.39, showing that H. aspersa snails, even in their early life stages, belong to macroconcentrator species for Cd. No significant reduction of snail consumption by beetles was found in exposed groups. Cd concentrations in beetle larvae remained very low (lower than 1 microg g(-1) for all groups), demonstrating a very effective regulation capacity in beetle larvae. However, Cd concentrations in highest exposed groups were higher than those found in control groups. Cd contents in adult beetles were lower than in larvae, showing a loss of Cd during metamorphosis. Despite the low Cd concentrations found in beetles, their exposure to Cd contaminated snails led to 31% of mortality, which occurred only during pupation and for the highest exposure level. No clear sublethal effects were found. These results showed that snails inhabiting heavily polluted areas may represent a risk of secondary poisoning for predatory invertebrates and provided quantitative data on the transfer of Cd between two compartments of a terrestrial food chain.