Paulina Kramarz

Time to death response in carabid beetles exposed to multiple stressors along a gradient of heavy metal pollution.

We investigated the responses of invertebrates inhabiting polluted environments to multiple stressors. Carabid beetles (Pterostichus oblongopunctatus F.) were subjected to food deprivation and insecticide treatment (dimethoate) to resolve trends associated with a gradient of heavy metal pollution. Metal concentrations along the gradient of five sites ranged from approximately 150 to 10,500 mg/kg Zn, 136 to 2600 mg/kg Pb, and 0.84 to 81.9 mg/kg Cd. There was no difference in body mass along the pollution gradient. However, the beetles originating from the most contaminated sites were significantly less tolerant to food deprivation than beetles from the reference site. Median survival time was 120 h for the two most polluted sites, compared with 168 h at the reference site. Beetles from the two most polluted sites were also significantly more susceptible to dimethoate at 0.1 microgram active ingredient/beetle. Median survival times were 12 and 123 h for beetles from the two most polluted sites and 359 h for the reference site. Carabid beetles exposed to chronic pollution, therefore, exhibit elevated susceptibility to additional stressors.

Interactions between toxic chemicals and natural environmental factors — A meta-analysis and case studies

The paper addresses problems arising from effects of natural environmental factors on toxicity of pollutants to organisms. Most studies on interactions between toxicants and natural factors, including those completed in the EU project NoMiracle (Novel Methods for Integrated Risk Assessment of Cumulative Stressors in Europe) described herein, showed that effects of toxic chemicals on organisms can differ vastly depending purely on external conditions. We compiled data from 61 studies on effects of temperature, moisture and dissolved oxygen on toxicity of a range of chemicals representing pesticides, polycyclic aromatic hydrocarbons, plant protection products of bacterial origin and trace metals. In 62.3% cases significant interactions (p< or =0.05 or less) between natural factors and chemicals were found, reaching 100% for the effect of dissolved oxygen on toxicity of waterborne chemicals. The meta-analysis of the 61 studies showed that the null hypothesis assuming no interactions between toxic chemicals and natural environmental factors should be rejected at p=2.7 x 10(-82) (truncated product method probability). In a few cases of more complex experimental designs, also second-order interactions were found, indicating that natural factors can modify interactions among chemicals. Such data emphasize the necessity of including information on natural factors and their variation in time and across geographic regions in ecological risk assessment. This can be done only if appropriate ecotoxicological test designs are used, in which test organisms are exposed to toxicants at a range of environmental conditions. We advocate designing such tests for the second-tier ecological risk assessment procedures.

Decreased Energetic Reserves, Morphological Changes and Accumulation of Metals in Carabid Beetles (Poecilus cupreus L.) Exposed to Zinc- or Cadmium-contaminated Food

The prime objective of the study was to find out whether contamination of food with metals affects body size, energetic reserves and developmental instability in ground beetles (Poecilus cupreus L.: Carabidae). The transfer of Cadmium (Cd) and Zinc (Zn) from medium (nominal concentrations in the medium: 0, 40, 160, 640 or 800 mg kg−1 for Cd and 0, 400, 1600 or 6400 mg kg−1 for Zn) to housefly larvae to beetles was also studied. Feeding the beetles throughout their entire lifetime with Cd-contaminated housefly pupae resulted in a significant decrease in body caloric value and the size of the elytrae, tibiae and rear femora. Although body mass also decreased with increasing Cd concentration, this effect was non-significant due to large variance in all treatments. Similar trends were also found in beetles fed pupae contaminated with Zn, but the effect on body mass and caloric value was non-significant. Zn exerted significant effects only on the size of the elytrae, middle and rear tibiae, and front and rear femora. No effect on fluctuating asymmetry (FA) was found in Cd- or Zn-treated beetles. The results indicate that ground beetles exposed to metal-contaminated food have lower amounts of energy available, which may be reflected in lower energetic reserves and changed body growth. However, the metals do not cause developmental instability in the carabids studied, at least not in the first generation. The concentrations of Zn were efficiently regulated in carabids, resulting in only minor differences between the beetles exposed to different Zn treatments. In contrast, Cd accumulated both in the housefly and the beetles, and the concentrations increased significantly with increasing medium contamination level.

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.

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 animals life-stage and sex.

Increased response to cadmium and Bacillus thuringiensis maize toxicity in the snail Helix aspersa infected by the nematode Phasmarhabditis hermaphrodita

To determine the effect of nematode infection on the response of snails to selected toxins, we infected Helix aspersa with 0-, 0.25-, 1-, or 4-fold the recommended field dose of a commercial nematode application for agricultural use. In the first experiment, the snails also were exposed to cadmium via food and soil at concentrations of 0, 30, 60, 120, or 240 mg/kg in a full-factorial design. In the second experiment, snails were infected with nematodes and also fed either Bt (expressing Bacillus thuringiensis toxin) maize or non-Bt maize. The snails were weighed at the beginning and end (after four weeks) of the experiments, and mortality was checked daily. Neither exposure of snails to nematodes nor exposure of snails to cadmium or Bt toxin affected the survival rates of snails. The number of dead snails was highest for combinations of nematode treatments with cadmium concentrations of 120 and 240 mg/kg. In both experiments (Bt and cadmium), the growth rate decreased with increasing nematode dose. The Bt maize was not harmful to the snails in the absence of nematodes, but infected snails grew faster when fed non-Bt maize. The growth rate of snails exposed to cadmium decreased with exposure to increasing Cd concentrations and differed significantly between the no-nematode treatment and the treatments with nematode doses of one- and fourfold the recommended field dose. Snails treated with the highest dose of nematodes accumulated the highest cadmium concentrations.

The respiration rate of the beet armyworm pupae (Spodoptera exigua) after multi-generation intoxication with cadmium and zinc.

The beet armyworm (Spodoptera exigua) were fed on artificial food contaminated with zinc (200 mg kg(-1) dry mass) or cadmium (66 mg kg(-1) dry mass) for 15 generations. In 15th generation, O2 output and CO2 production of pupae were measured. Exposure to cadmium did not cause any effects whilst exposure to zinc led to a significant increase in the respiration rate of pupae. The average respiratory quotient (RQ) did not differ between treatments (ca. 0.7).

Combined effect of environmental pollutants (nickel, chlorpyrifos) and temperature on the ground beetle, Pterostichus oblongopunctatus (Coleoptera: Carabidae)

Terrestrial organisms in the field often are exposed to a combination of stress factors of various origins, but little is known about interactions between different types of stressors. In the present study, we demonstrate the results of a study on interactions between Ni, chlorpyrifos (CPF), and temperature in the ground beetle, Pterostichus oblongopunctatus. The results revealed that all factors, and their interactions, influenced life-cycle parameters of the beetles (survival and reproduction). Significant three-factor interactions were found for effects on beetle survival, indicating that the combined negative effect of Ni and CPF was temperature dependent. In addition, significant effects of body mass were found: The survival of beetles treated with CPF and the reproduction of beetles exposed to Ni were positively correlated with body mass. All studied endpoints were affected by temperature. The results indicate that understanding interactions between temperature and toxicants, as well as among chemicals themselves, is essential for proper ecological risk assessment.

Effect of interaction between density dependence and toxicant exposure on population growth rate of the potworm Enchytraeus doerjesi

Laboratory cultures of the potworm Enchytreaus doerjesi were exposed to zinc-contaminated soil at nominal concentrations 0, 75, 150, 300, or 600 mg Zn/kg dry weight for four weeks (one generation) at five different initial densities (5, 10, 20, 40, or 80 individuals per 20 g soil). The final culture numbers and the instantaneous population growth rate, r(i) were used as measures of culture response to both factors. In all treatments, the number of individuals increased during the experiment; thus, all the cultures exhibited positive r(i) values. The population growth rates decreased significantly with increasing Zn concentration and were also affected by the initial density. However, the latter effect was nonlinear and the initial density of 20 individuals resulted in the highest r(i) values throughout the whole range of Zn concentrations tested, while the lowest population growth rates were recorded for the highest initial density. Significant interaction between zinc toxicity and population size was found for the two lowest initial densities, where synergistic effects were noted. No effect of density on zinc toxicity was found at initial densities of 20 to 80 individuals, most probably because the animals were fed ad libitum and thus were not food limited.

Toxicity and possible food-chain effects of copper, dimethoate and a detergent (LAS) on a centipede (Lithobius mutabilis) and its prey (Musca domestica)

Toxicity of copper (Cu) and two biodegradable chemicals—an insecticide (dimethoate) and a detergent (LAS), was tested on a common forest litter invertebrate carnivore Lithobius mutabilis and its prey, Musca domestica. The chemicals were mixed into artificial food medium for housefly larvae, and the centipedes were kept on contaminated OECD soil and fed contaminated larvae. The concentrations of chemicals were selected to cover the whole range of survival of a prey animal: from no increased mortality (control) up to100% mortality during development from egg to adult. The housefly larvae were significantly more affected than their predators by all three chemicals. The LC50 values for housefly from egg to emergence were (in mg kg ˇ1 dry mass food): Cu, 708; dimethoate, 0.330; LAS, 110. In contrast, LC50 values for L. mutabilis for all three chemicals were above the range of concentrations tested: Cu > 1500; dimethoate > 0.8; LAS > 10 000 (nominal concentrations in soil and housefly medium). No significant sublethal effects on body weight or respiration rates were found in centipedes. This may suggest that in contaminated areas, except for direct toxicity, a lack of food may be an important factor in reducing centipede populations. The centipede prey, being mostly detritivores feeding directly on and living in a contaminated medium, are more exposed to a toxicant than epigeic species such as centipedes. # 1999 Elsevier Science B.V. All rights reserved.