Aquatic thresholds for ionisable substances, such as diclofenac, should consider pH-specific differences in uptake and toxicity

Diclofenac, a widely used nonsteroidal anti-inflammatory drug (NSAID), enters the aquatic environment worldwide. The effect values available for the derivation of an environmental quality standard (EQS) are markedly heterogeneous, even within the same species. This heterogeneity could partially be attributed to inter-laboratory variation, but is also observed in repeated tests within the same facility. Diclofenac is ionisable; its speciation and potential for uptake and thus toxicity is influenced by pH. A high correlation has previously been observed between effects in zebrafish embryos and the pH-specific partitioning coefficient logD for diclofenac. We hypothesized that the observed heterogeneity could also be attributed to differences in study pH. To test this hypothesis, we reviewed physicochemical data and selected ecotoxicity data that were considered to be reliable and relevant in the latest EU EQS Dossier for which a study pH was reported for further analysis and EQS derivation. We adjusted the reported effect concentrations for differences in uptake using the delta logD value for the worst case pH value of 6.5. pH adjustment of effect values resulted in decreased heterogeneity of the acute effect data and a better fit of the chronic species sensitivity distribution. Both, the MAC-EQS and the AA-EQS were derived using the deterministic approach as data requirements for deriving EQS based on the SSD were not fulfilled. Many studies had to be discarded because test pH was not reported or exposure concentrations had not been analytically verified. Physico-chemical data had to be discarded due to non-relevant experimental conditions or missing information. We strongly encourage scientists publishing ecotoxicity data for ionisable substances to report the test pH together with the effect values and encourage measurement of physico-chemical parameters at environmentally relevant conditions. We recommend to consider adjusting the effect data for ionisable substances according to a worst-case pH in future hazard assessments.

LogD-based modelling and ΔlogD as a proxy for pH-dependent action of ionizable chemicals reveal the relevance of both neutral and ionic species for fish embryotoxicity and possess great potential for practical application in the regulation of chemicals

Depending on the ambient pH, ionizable substances are present in varying proportions in their neutral or charged form. The extent to which these two chemical species contribute to the pH-dependant toxicity of ionizable chemicals and whether intracellular ion trapping has a decisive influence in this context is controversially discussed. Against this background, we determined the acute toxicity of 24 ionizable substances at up to 4 different pH values on the embryonic development of the zebrafish, Danio rerio, and supplemented this dataset with additional data from the literature. The LC₅₀ for some substances (diclofenac, propranolol, fluoxetine) differed by a factor of even >10³ between pH5 and pH9. To simulate the toxicity of 12 acids and 12 bases, six models to calculate a pH-dependant logD value as a proxy for the uptake of potentially toxic molecules were created based on different premises for the trans-membrane passage and toxic action of neutral and ionic species, and their abilities to explain the real LC₅₀ data set were assessed. Using this approach, we were able to show that both neutral and charged species are almost certainly taken up into cells according to their logD-based distribution, and that both species exert toxicity. Since two of the models that assume all intracellular molecules to be neutral overestimated the real toxicity, it must be concluded, that the toxic effect of a single charged intracellularly present molecule is, on the average, lower than that of a single neutral molecule. Furthermore, it was possible to attribute differences in toxicity at different pH values for these 24 ionizable substances to the respective deltas in logD at these pH levels with high accuracy, enabling particularly a full logD-based model on the basis of logP_ow as a membrane passage descriptor to be used for predicting potential toxicities in worst-case scenarios from existing experimental studies, as stipulated in the process of registration of chemicals and the definition of Environmental Quality Standards (EQS).

Thermobiological effects of temperature-induced color variations in Aglais urticae (Lepidoptera, Nymphalidae)

Coloration of animals is important for camouflage, for social behavior, or for physiological fitness. This study investigates the color variation in adults of Aglais urticae obtained on subjecting some pre‐imaginal stages to different temperature conditions and their thermobiological consequences. To investigate the evolutionary–ecological interactions of temperature and pigmentation in butterflies, caterpillars, and pupae of the small tortoiseshell, Aglais urticae (Lepidoptera, Nymphalidae), larvae from Central Europe and Scandinavia were reared at temperatures between 7 and 34°C in the laboratory or in the field. After emergence, the intensity of pigmentation of the imagines and their increase in body temperature under defined full‐spectrum light irradiation were quantified by image analysis and thermal imaging. At constant conditions, ambient rearing temperature and pigmentation intensity of imagines were negatively and linearly correlated in Central European butterflies, regardless of whether the pupal stage alone or, additionally, the last period of the larval stage was exposed to these conditions: low temperatures induced darker coloration and high temperatures led to lighter individuals. A thermal pulse of a few days alone at the beginning of pupal dormancy led to a similar, albeit weakened, effect. Caterpillars of the Scandinavian subspecies A. urticae polaris, whose pupal dormancy took place under Central European field conditions, developed into strongly pigmented imagines. The thermobiological relevance of more intense pigmentation was shown by significantly higher absorption of light, and thus stronger increased body temperature after 5 min of defined illumination, but this difference ceased after 15 min. Our results show that phenotypic plasticity in wing coloration is adaptive since temperature‐induced developmental changes provide thermobiological benefit in adult butterflies. We propose that, in subpolar latitudes, darker coloration likely has a selection advantage favoring individuals with reaction norms gradually shifted to stronger pigmented phenotypes, possibly leading to the establishment of a pigmentation cline.

Heart rate as an early warning parameter and proxy for subsequent mortality in Danio rerio embryos exposed to ionisable substances

Environmental risk assessments of organic chemicals usually do not consider pH as a key factor. Hence, most substances are tested at a single pH only, which may underestimate the toxicity of ionisable substances with a pK_a in the range of 4-10. Thus, the ability to consider the pH-dependent toxicity would be crucial for a more realistic assessment. Moreover, there is a tendency in acute toxicity tests to focus on mortality only, while little attention is paid to sublethal endpoints. We used Danio rerio embryos exposed to ten ionisable substances (the acids diclofenac, ibuprofen, naproxen and triclosan and the bases citalopram, fluoxetine, metoprolol, propranolol, tramadol and tetracaine) at four external pH levels, investigating the endpoints mortality (LC₅₀) and heart rate (EC₂₀). Dose-response curves were fitted with an ensemble-model to determine the true uncertainty and variation around the mean endpoints. The ensemble considers eight (heart rate) or twelve (mortality) individual models for binominal and Poisson distributed data, respectively, selected based on the Akaike Information Criterion (AIC). In case of equally good models, the mean endpoint of all models in the ensemble was calculated, resulting in more robust EC_x estimates with lower 'standard errors' as compared to randomly selected individual models. We detected a high correlation between mortality (LC₅₀) at 96 hpf and reduced heart rate (EC₂₀) at 48 hpf for all compounds and all external pH levels (r = 0.98). Moreover, the observed pH-dependent effects were strongly associated with log D and thus, likely driven by differences in uptake (toxicokinetic) rather than internal (toxicodynamic) processes. Prospectively, the a priori consideration of pH-dependent effects of ionisable substances might make testing at different pH levels redundant, while the endpoint of mortality might even be replaced by a reliable sublethal proxy that would reduce the exposure, accelerating the evaluation process.

Does Bti (Bacillus thuringiensis var. israelensis) affect Rana temporaria tadpoles?

Biocides based on toxins of Bacillus thuringiensis var. israelensis (Bti) are established as alternatives to conventional chemical insecticides for mosquito control all across the globe since they are regarded ecologically compatible and harmless to non-target species. Since recent studies on amphibian larvae have called this opinion into question, we exposed Rana temporaria tadpoles to single (1 mg/L), tenfold (10 mg/L) and hundredfold (100 mg/L) field concentrations of VectoBac^® WG (a water dispersible granule Bti formulation) in the laboratory for eleven days to investigate whether larvae were adversely affected by Bti and its endotoxin proteins. In addition to a negative (water) control, a positive control based on organic rice protein (50 mg/L) was run to check for the nutritional relevance of Bti proteins. There was no Bti-related mortality and a histopathological analysis of tadpole intestines revealed no adverse effects. Analyses of biomarkers for proteotoxicity (stress protein family, Hsp70) and neurotoxicity or metabolic action (b-esterases acetylcholine esterase (AChE) and carboxylesterases) revealed no significant differences between Bti treatments and the negative control. The responses of tadpoles in the protein-supplemented positive control differed from those of the negative control and the Bti treatments. Tadpoles in the positive control had reduced body mass and elevated AChE activity.

Effects of guanylurea, the transformation product of the antidiabetic drug metformin, on the health of brown trout (Salmo trutta f. fario)

Background

Guanylurea is the main transformation product of the antidiabetic drug metformin, which is one of the most prescribed pharmaceuticals worldwide. Due to the high rate of microbial degradation of metformin in sewage treatment plants, guanylurea occurs in higher concentrations in surface waters than its parent compound and could therefore affect aquatic wildlife. In this context, data for fish are scarce up to now which made us investigate the health of brown trout (Salmo trutta f. fario) in response to guanylurea.

Methods

In two experiments, eggs plus developing larvae and juvenile brown trout were exposed to three different concentrations of guanylurea (10, 100 and 1,000 µg/L) and, as a negative control, filtered tap water without this compound. Low internal concentrations were determined. The investigated parameters were mortality, length, weight, condition factor, tissue integrity of the liver and kidney, levels of stress proteins and lipid peroxides, as well as behavioural and developmental endpoints. It was found that guanylurea did not significantly change any of these parameters in the tested concentration range.

Results

In conclusion, these results do not give rise to concern that guanylurea could negatively affect the health or the development of brown trout under field conditions. Nevertheless, more studies focusing on further parameters and other species are highly needed for a more profound environmental risk assessment of guanylurea.

Impact of the NSAID diclofenac on survival, development, behaviour and health of embryonic and juvenile stages of brown trout, Salmo trutta f. fario

The NSAID diclofenac is controversially discussed with respect to its environmental relevance. Since further information is need to assess whether diclofenac should be included as substance of priority in the EU water framework directive, we investigated the impact of this analgesic on the embryonic development of brown trout (Salmo trutta f. fario) from fertilized egg until the end of sac-fry stage and studied effects in juvenile fish six months post hatch. Embryos were exposed to five test concentrations (0.1, 0.5, 1, 10, 100μg/L) over 127days at 7°C. None of the treatments affected mortality, hatching, development or heart rate. Six months old juveniles exposed to five concentrations (0.1, 1, 10, 100, 200μg/L) over 25days at 7°C, however, showed increased mortality, reaching significance at 100μg/L. Furthermore, a significantly higher proportion of juvenile animals bore injuries at concentrations higher 10μg/L. Neither the levels of the stress protein Hsp70, nor the amount of lipid peroxides was affected by any of the treatments. Histological analyses of gill, liver and kidney revealed visible tissue reactions in fish from all experimental groups. Histological responses in livers of diclofenac-exposed fish outstripped the status of laboratory control fish, particularly when exposed to the two highest concentrations. Chemical analyses of fish muscle tissue revealed concentration-dependent uptake of DCF into the animal, but no relevant bioconcentration. Our study supports earlier findings indicating a lower sensitivity of trout early life stages compared to older individuals, suggesting that studies for risk assessment of diclofenac should predominantly focus on later life stages. Furthermore, fish mortality was found to increase with rising diclofenac concentrations, and the lowest observed effect concentration of 10μg/L on the organismic level emphasises the classification of diclofenac as a micropollutant that requires close attention.

Drifting Away of a FET Endpoint: The Heart Rate in Danio rerio Embryos is Extremely Sensitive to Variation in Ambient Temperature

Beyond the mere detection of presence or absence of heart beat in zebrafish (Danio rerio) embryos in a fish embryo test conducted referring to the OECD TG 236 at 48 hpf (hours post fertilization) onwards, embryo heart rate may serve as an additional and very sensitive endpoint in ecotoxicological studies. But by including heart rate as a sublethal endpoint, care has to be taken of separating effects exerted by a tested compound from those exerted by temperature. Therefore, profound knowledge on the natural variation of zebrafish heart rates at defined temperatures as a basis for the assessment of gained results is mandatorily needed. As such continuous information in D. rerio is lacking from the literature, we designed a study covering a span of 12°C (from 18 to 30°C in steps of 2°C) to quantify the relationship between heart rate and temperature in D. rerio embryos 48 hpf. Conducting a multiple regression analysis, we found a considerably strong relationship between treatment temperature and the log10 of the heart rate, ranging from 82.8 beats per minute at 18°C to 218.0 beats per minute at 30°C. Our results therefore may serve as a reference for heart rates measured under normal conditions to be able to detect potential effects of contaminants in other studies when working under certain temperatures.

Does wastewater treatment plant upgrading with activated carbon result in an improvement of fish health?

In the present study, the efficiency of a wastewater treatment plant (WWTP) upgraded with a powdered activated carbon unit for the reduction of micropollutants and the related advantages for fish health have been analyzed by means of different biomarkers, i.e. histopathological investigations, analyses of glycogen content and stress proteins, as well as by chemical analyses in different matrices. Comparative analyses were conducted prior and subsequent to the installation of the additional purification unit. Chemical analyses revealed a significant reduction of several pharmaceuticals, including diclofenac, carbamazepine and metoprolol, in samples of effluent and surface water downstream of the WWTP after its upgrade. In addition, diminished concentrations of diclofenac and PFOS were detected in tissues of analyzed fish. Histopathological investigations of fish liver, gills, and kidney revealed improved tissue integrity in fish after improved wastewater treatment. In parallel, biochemical measurements of glycogen revealed increased energy resources in fish liver and, furthermore, hsp70 levels in livers of exposed rainbow trout and in kidneys of exposed brown trout were lower after than before the WWTP upgrade. In summary, additional treatment with powdered activated carbon led to a reduction of potentially hazardous chemicals in the effluent and the adjacent river and, consequently, to an improvement of fish health in the receiving water course.

Nano-sized zeolites as modulators of thiacloprid toxicity on Chironomus riparius

This study investigated whether zeolites of different size (Y30 (nano-sized) and H-Beta(OH)-III (forming large aggregates/agglomerates composed of 50 nm small primary particles)) exerted acute toxicity on larvae of the non-biting midge, Chironomus riparius, and whether such zeolites are able to modulate the toxicity of a common insecticide, thiacloprid, by means of adsorption of a dissolved toxicant. We conducted acute toxicity tests with fourth instar larvae of C. riparius. In these tests, larvae were exposed to zeolites or thiacloprid solely, or to mixtures of both compounds. The mixtures comprised 1.0 µg/L thiacloprid in addition to low (5.2 mg/L), medium (18.2 mg/L), and high (391.7 mg/L) zeolite concentrations, resulting in different adsorption rates of thiacloprid. As biological endpoints, changes in mortality rates and in behavior were monitored every 24 h over a total investigation period of 96 h. Furthermore, we conducted chemical analyses of thiacloprid in the medium and the larvae and located the zeolite particles within the larvae by LA-ICP-MS imaging techniques. Our results demonstrate that both types of zeolites did not exert acute toxicity when applied as single-substances, but led to reduced acute toxicity of thiacloprid when applied together with thiacloprid. These results are in line with the sorption properties of zeolites indicating reduced bioavailability of thiacloprid, although our data indicate that thiacloprid can desorb from zeolites to some extent. While freely dissolved (i.e., non-sorbed) fraction of thiacloprid was a good parameter to roughly estimate toxic effects, it did not correlate with measured internal thiacloprid concentrations. Moreover, it was shown that both zeolite types were ingested by the larvae, but no indication for cellular uptake of them was found.

Relevance of body size and shell colouration for thermal absorption and heat loss in white garden snails, Theba pisana (Helicidae), from Northern France

The internal temperature of land snails depends on environmental factors, such as exposure to electromagnetic radiation and airflow as well as biotic factors including shell size, shell colouration and thickness or the resting position of the snail. In controlled field experiments, we quantified heating by thermal absorption of light and airflow-induced heat loss in the white garden snail, Theba pisana, from Normandy, France. Heating experiments revealed a significant positive relation of the internal body temperature with illumination period, shell temperature and air temperature at different times of day. The size of the snails was negatively related with both of the given illumination times: smaller animals heated up stronger than larger ones. The temperature at the surface of the shell significantly depended on the illumination period and the time of day. An AIC-based quality assessment of multiple linear modelling showed that, for explaining both shell surface and internal temperature of the soft body, several factors, i.e., exposure time, daytime, shell size and colouration contributed to the best models, respectively. Similarly, heat loss of the soft body after and during exposure of the snails to sunlight by a constant airflow depended on the initial body temperature, shell size, colouration and ambient air temperature. Our study revealed also the importance of both shell size and colouration for the loss of body temperature under natural conditions: small and banded animals that had heated up to temperatures above 30°C cooled down faster than large and un-banded ones.

Two novel real time cell-based assays quantify beta-blocker and NSAID specific effects in effluents of municipal wastewater treatment plants

Pharmaceuticals, such as beta-blockers, nonsteroidal anti-inflammatory drugs (NSAIDs) as well as their metabolites are introduced into the water cycle via municipal wastewater treatment plant (WWTP) effluents in all industrialized countries. As the amino acid sequences of the biological target molecules of these pharmaceuticals - the beta-1 adrenergic receptor for beta-blockers and the cyclooxygenase for NSAIDs - are phylogenetically conserved among vertebrates it is reasonable that wildlife vertebrates including fish physiologically respond in a similar way to them as documented in humans. Consequently, beta-blockers and NSAIDs both exhibit their effects according to their mode of action on one hand, but on the other hand that may lead to unwanted side effects in non-target species. To determine whether residuals of beta-1 adrenergic receptor antagonists and cyclooxygenase inhibitors may pose a risk to aquatic organisms, one has to know the extent to which such organisms respond to the total of active compounds, their metabolites and transformation products with the same modes of action. To cope with this demand, two cell-based assays were developed, by which the total beta-blocker and cyclooxygenase inhibitory activity can be assessed in a given wastewater or surface water extract in real time. The measured activity is quantified as metoprolol equivalents (MetEQ) of the lead substance metoprolol in the beta-blocker assay, and diclofenac equivalents (DicEQ) in the NSAID assay. Even though MetEQs and DicEQs were found to surpass the concentration of the respective lead substances (metoprolol, diclofenac), as determined by chemical analysis by a factor of two to three, this difference was shown to be reasonably explained by the presence and action of additional active compounds with the same mode of action in the test samples. Thus, both in vitro assays were proven to integrate effectively over beta-blocker and NSAID activities in WWTP effluents in a very sensitive and extremely rapid manner.

Reduction of dioxin-like toxicity in effluents by additional wastewater treatment and related effects in fish

Efficiency of advanced wastewater treatment technologies to reduce micropollutants which mediate dioxin-like toxicity was investigated. Technologies compared included ozonation, powdered activated carbon and granular activated carbon. In addition to chemical analyses in samples of effluents, surface waters, sediments, and fish, (1) dioxin-like potentials were measured in paired samples of effluents, surface waters, and sediments by use of an in vitro biotest (reporter gene assay) and (2) dioxin-like effects were investigated in exposed fish by use of in vivo activity of the mixed-function, monooxygenase enzyme, ethoxyresorufin O-deethylase (EROD) in liver. All advanced technologies studied, based on degradation or adsorption, significantly reduced dioxin-like potentials in samples and resulted in lesser EROD activity in livers of fish. Results of in vitro and in vivo biological responses were not clearly related to quantification of targeted analytes by use of instrumental analyses.

A sublethal imidacloprid concentration alters foraging and competition behaviour of ants

Neonicotinoid pesticides, such as the widely used compound imidacloprid, are suspected to impair cognitive capacity, behaviour, and fitness of a number of non-target species. We tested whether sublethal imidacloprid concentrations alter the foraging and aggression behaviour of two European ant species. Even though the nestmate-recruitment of Lasius niger was not affected by pesticide exposure, these ants required more time to become active and the number of foraging workers was lower than in sub-colonies not exposed to imidacloprid. In interspecific confrontations, imidacloprid increased the aggressiveness of a usually subordinate species (Lasius flavus) enormously (3.7-fold increase in average number of aggressive encounters), whereas they did not affect a subdominant species (L. niger) that severely (1.2-fold increase in average number of aggressive encounters). The high frequency of aggressive encounters of L. flavus vs. non-exposed L. niger workers, reduced their survival probability significantly down to 60 %. The observed behavioural alterations of the two ant species have the potential to impair their viability and co-occurrence with behaviourally dominate species due to a decreased exploitative competition and a reduced chance to locate and use resources before competitors. As competition is considered key in structuring ant communities, changes in aggressiveness are likely to alter established dominance hierarchies and thereby the dynamic and structure of ant communities.

Metallothionein and Hsp70 trade-off against one another in Daphnia magna cross-tolerance to cadmium and heat stress

The association between the insensitivity of adapted ecotypes of invertebrates to environmental stress, such as heavy metal pollution, and overall low Hsp levels characterizing these organisms has been attracting attention in various studies. The present study seeks to induce and examine this phenomenon in Daphnia magna by multigenerational acclimation to cadmium in a controlled laboratory setting. In this experiment, interclonal variation was examined: two clones of D. magna that have previously been characterized to diverge regarding their cadmium resistance and levels of the stress protein Hsp70, were continuously exposed to a sublethal concentration of Cd over four generations to study the effects of acclimation on Hsp70, metallothionein (MT), reproduction and cross-tolerance to heat stress. The two clones differed in all the measured parameters in a characteristic way, clone T displaying Cd and heat resistance, lower Hsp70 levels and offspring numbers on the one hand and higher MT expression on the other hand, clone S the opposite for all these parameters. We observed only slight acclimation-induced changes in constitutive Hsp70 levels and reproductive output. The differences in MT expression between clones as well as between acclimated organisms and controls give evidence for MT accounting for the higher Cd tolerance of clone T. Overall high Hsp70 levels of clone S did not confer cross tolerance to heat stress, contrary to common expectations. Our results suggest a trade-off between the efforts to limit the proteotoxic symptoms of Cd toxicity by Hsp70 induction and those to sequester and detoxify Cd by means of MT.

PIXE-electrophoresis shows starving collembolan reallocates protein-bound metals

One of multiple functions of metalloproteins is to provide detoxification to excess metal levels in organisms. Here we address the induction and persistence of a range of low to high molecular weight copper- and zinc binding proteins in the collembolan species Tetrodontophora bielanensis exposed to copper- and zinc-enriched food, followed by a period of recovery from metal exposure, in absence and presence of food. After 10 days of feeding copper and zinc contaminated yeast, specimens were either moved to ample of leaf litter material from their woodland stand of origin or starved (no food offered). The molecular weight distribution of metal binding proteins was determined by native polyacryl gel electrophoresis. One gel was stained with Comassie brilliant blue and a duplicate gel dried and scanned for the amount of copper and zinc by particle-induced X-ray emission. Specimens exposed to copper and recovered from it with ample of food had copper bound to two groups of rather low molecular weight proteins (40-50 kDa) and two of intermediate size (70-80 kDa). Most zinc in specimens from the woodland stand was bound to two large proteins of about 104 and 106 kDa. The same proteins were holding some zinc in metal-exposed specimens, but most zinc was found in proteins <40 kDa in size. Specimens recovered from metal exposure in presence of ample of food had the same distribution pattern of zinc binding proteins, whereas starved specimens had zinc as well as copper mainly bound to two proteins of 8 and 10 kDa in size. Thus, the induction and distribution of copper- and zinc-binding proteins depend on exposure conditions, and the presence of low molecular weight binding proteins, characteristic of metallothioneins, was mainly limited to starving conditions.

Fish embryo tests with Danio rerio as a tool to evaluate surface water and sediment quality in rivers influenced by wastewater treatment plants using different treatment technologies

In order to evaluate surface water and the sediment quality of rivers connected to wastewater treatment plants (WWTPs) with different treatment technologies, fish embryo tests (FET) with Danio rerio were conducted using native water and sediment samples collected upstream and downstream of four WWTPs in Southern Germany. Two of these WWTPs are connected to the Schussen River, a tributary of Lake Constance, and use a sand filter with final water purification by flocculation. The two others are located on the rivers Schmiecha and Eyach in the area of the Swabian Alb and were equipped with a powdered activated carbon stage 20 years ago, which was originally aimed at reducing the release of stains from the textile industry. Several endpoints of embryo toxicity including mortality, malformations, reduced hatching rate, and heart rate were investigated at defined time points of embryonic development. Higher embryotoxic potentials were found in water and sediments collected downstream of the WWTPs equipped with sand filtration than in the sample obtained downstream of both WWTPs upgraded with a powdered activated carbon stage.

Biological plausibility as a tool to associate analytical data for micropollutants and effect potentials in wastewater, surface water, and sediments with effects in fishes

Discharge of substances like pesticides, pharmaceuticals, flame retardants, and chelating agents in surface waters has increased over the last decades due to the rising numbers of chemicals used by humans and because many WWTPs do not eliminate these substances entirely. The study, results of which are presented here, focused on associations of (1) concentrations of micropollutants in wastewater treatment plant (WWTP) effluents, surface waters, sediments, and tissues of fishes; (2) results of laboratory biotests indicating potentials for effects in these samples and (3) effects either in feral chub (Leuciscus cephalus) from two German rivers (Schussen, Argen) or in brown trout (Salmo trutta f. fario) and rainbow trout (Oncorhynchus mykiss) exposed in bypass systems to streamwater of these rivers or in cages directly in the rivers. The Schussen and Argen Rivers flow into Lake Constance. The Schussen River is polluted by a great number of chemicals, while the Argen River is less influenced by micropollutants. Pesticides, chelating agents, flame retardants, pharmaceuticals, heavy metals, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were detected in effluents of a WWTP discharging to the Schussen as well as in surface water, and/or fishes from downstream of the WWTP. Results obtained by biotests conducted in the laboratory (genotoxicity, dioxin-like toxicity, and embryotoxicity) were linked to effects in feral fish collected in the vicinity of the WWTP or in fishes exposed in cages or at the bypass systems downstream of the WWTP. Dioxin-like effect potentials detected by reporter gene assays were associated with activation of CYP1A1 enzymes in fishes which are inducible by dioxin-like chemicals. Abundances of several PCBs in tissues of fishes from cages and bypass systems were not associated with these effects but other factors can influence EROD activity. Genotoxic potentials obtained by in vitro tests were associated with the presence of micronuclei in erythrocytes of chub from the river. Chemicals potentially responsible for effects on DNA were identified. Embryotoxic effects on zebrafish (Danio rerio), investigated in the laboratory, were associated with embryotoxic effects in trout exposed in streamwater bypass systems at the two rivers. In general, responses at all levels of organization were more pronounced in samples from the Schussen than in those from the Argen. These results are consistent with the magnitudes of chemical pollution in these two streams. Plausibility chains to establish causality between exposures and effects and to predict effects in biota in the river from studies in the laboratory are discussed.

Antioxidant defence and stress protein induction following heat stress in the Mediterranean snail Xeropicta derbentina

The Mediterranean snail Xeropicta derbentina (Pulmonata, Hygromiidae), being highly abundant in Southern France, has the need for efficient physiological adaptations to desiccation and over-heating posed by dry and hot environmental conditions. As a consequence of heat, oxidative stress manifests in these organisms, which, in turn, leads to the formation of reactive oxygen species (ROS). In this study, we focused on adaptations at the biochemical level by investigation of antioxidant defences and heat shock protein 70 (Hsp70) induction, both essential mechanisms of the heat stress response. We exposed snails to elevated temperature (25, 38, 40, 43 and 45°C) in the laboratory and measured the activity of the antioxidant enzymes catalase (CAT) and glutathione peroxidase (GPx), determined the Hsp70 level and quantified lipid peroxidation. In general, we found a high constitutive level of CAT activity in all treatments, which may be interpreted as a permanent protection against ROS, i.e. hydrogen peroxide. CAT and GPx showed temperature-dependent activity: CAT activity was significantly increased in response to high temperatures (43 and 45°C), whereas GPx exhibited a significantly increased activity at 40°C, probably in response to high levels of lipid peroxides that occurred in the 38°C treatment. Hsp70 showed a maximum induction at 40°C, followed by a decrease at higher temperatures. Our results reveal that X. derbentina possesses a set of efficient mechanisms to cope with the damaging effects of heat. Furthermore, we demonstrated that, besides the well-documented Hsp70 stress response, antioxidant defence plays a crucial role in the snails' competence to survive extreme temperatures.

An intron-containing, heat-inducible stress-70 gene in the millipede Tachypodoiulus niger (Julidae, Diplopoda)

The highly conserved part of the nucleotide-binding domain of the hsp70 gene family was amplified from the soil diplopod Tachypodoiulus niger (Julidae, Diplopoda). Genomic DNA yielded 701, 549 and 540 bp sequences, whereas cDNA from heat shocked animals produced only one distinct fragment of 543 bp. The sequences could be classified as a 70 kDa heat shock protein (hsp70), the corresponding 70 kDa heat shock cognate (hsc70) and a glucose-related hsp70 homologue (grp78). Comparisons of genomic and cDNA sequences of hsc70 identified two introns within the consensus sequence. Generally, stress-70 expression levels were low, which hampered successful RT-PCR and subsequent subcloning. Following experimental heat shock, however, the spliced hsc70 was amplified predominantly, instead of its inducible homologue hsp70. This finding suggests that microevolution in this soil-dwelling arthropod is directed towards low constitutive stress-70 levels and that the capacity for stress-70 induction presumably is limited. hsc70, albeit having introns, apparently is inducible and contributes to the stress-70 response.

Invertebrates as indicators for chemical stress in sewage-influenced stream systems: toxic and endocrine effects in gammarids and reactions at the community level in two tributaries of Lake Constance, Schussen and Argen

The present study investigates the impact of releases from waste water treatment plants and storm water overflow basins on gammarids and other macrozoobenthos. The study relates to a recent upgrading of a waste water treatment plant (Langwiese) at the Schussen river, an important tributary to Lake Constance. Samples were taken at different sites at the Schussen river upstream and downstream of a storm water overflow basin and the waste water treatment plant Langwiese and, in parallel, at the Argen river, a less polluted reference stream. We assessed the influence of water quality on the distribution of macrozoobenthos and on the health of gammarid populations by a variety of ecotoxicological methods including biomarkers prior to the expansion of the waste water treatment plant. Through histopathological studies, the impact of parasites on host tissue health was evaluated. Analyses of heat shock protein (hsp70) levels allowed us to draw conclusions about the proteotoxicity-related stress status of the organisms. Furthermore, gammarid populations from all sites were investigated in respect to sex ratio, parasitism rate, and fecundity. Macrozoobenthos community integrity was determined by means of the saprobic index and the abundance as well as by the number of taxa. In gammarids, the sex ratio was significantly shifted towards females, fecundity was significantly decreased, and the hsp70 level was significantly increased downstream of the waste water treatment plant Langwiese, compared to the upstream sampling site. Similarly, these effects could be detected downstream of three small storm water overflow basins. In the macrozoobenthos communities, the abundance of taxa, the number of taxa, the number of ephemeroptera, plecoptera, and trichoptera taxa (EPT-taxa), and the number of sensitive taxa decreased downstream of the storm water overflow basin Mariatal as well as downstream of the waste water treatment plant Langwiese. Our study showed, that waste water treatment plants and storm water overflow basins affected macroinvertebrate communities and the health of gammarids.

Wildlife ecotoxicology of pesticides: can we track effects to the population level and beyond?

During the past 50 years, the human population has more than doubled and global agricultural production has similarly risen. However, the productive arable area has increased by just 10%; thus the increased use of pesticides has been a consequence of the demands of human population growth, and its impact has reached global significance. Although we often know a pesticide's mode of action in the target species, we still largely do not understand the full impact of unintended side effects on wildlife, particularly at higher levels of biological organization: populations, communities, and ecosystems. In these times of regional and global species declines, we are challenged with the task of causally linking knowledge about the molecular actions of pesticides to their possible interference with biological processes, in order to develop reliable predictions about the consequences of pesticide use, and misuse, in a rapidly changing world.

External and internal shell formation in the ramshorn snail Marisa cornuarietis are extremes in a continuum of gradual variation in development

BACKGROUND

Toxic substances like heavy metals can inhibit and disrupt the normal embryonic development of organisms. Exposure to platinum during embryogenesis has been shown to lead to a "one fell swoop" internalization of the shell in the ramshorn snail Marisa cornuarietis, an event which has been discussed to be possibly indicative of processes in evolution which may result in dramatic changes in body plans.

RESULTS

Whereas at usual cultivation temperature, 26°C, platinum inhibits the growth of both shell gland and mantle edge during embryogenesis leading to an internalization of the mantle and, thus, also of the shell, higher temperatures induce a re-start of the differential growth of the mantle edge and the shell gland after a period of inactivity. Here, developing embryos exhibit a broad spectrum of shell forms: in some individuals only the ventral part of the visceral sac is covered while others develop almost "normal" shells. Histological studies and scanning electron microscopy images revealed platinum to inhibit the differential growth of the shell gland and the mantle edge, and elevated temperature (28 - 30°C) to mitigate this platinum effect with varying efficiency.

CONCLUSION

We could show that the formation of internal, external, and intermediate shells is realized within the continuum of a developmental gradient defined by the degree of differential growth of the embryonic mantle edge and shell gland. The artificially induced internal and intermediate shells are first external and then partly internalized, similar to internal shells found in other molluscan groups.

Effects of inbreeding on mouthpart deformities of Chironomus riparius under sublethal pesticide exposure

Mouthpart deformities in chironomids have been reported to indicate adverse effects of environmental pollutants. The authors assessed rates of mouthpart deformities in tributyltin-exposed, inbred, and outcrossed Chironomus riparius larvae over multiple generations. The authors found that the occurrence of mouthpart deformities was significantly correlated with inbreeding, whereas no correlation was found with the tributyltin exposure. The present study confirms the strong effect of high inbreeding rates on developmental deformities in chironomids.

Solar radiation stress in climbing snails: behavioural and intrinsic features define the Hsp70 level in natural populations of Xeropicta derbentina (Pulmonata)

Ectotherms from sunny and hot environments need to cope with solar radiation. Mediterranean land snails of the superfamily Helicoidea feature a behavioural strategy to escape from solar radiation-induced excessive soil heating by climbing up vertical objects. The height of climbing, and also other parameters like shell colouration pattern, shell orientation, shell size, body mass, actual internal and shell surface temperature, and the interactions between those factors may be expected to modulate proteotoxic effects in snails exposed to solar radiation and, thus, their stress response. Focussing on natural populations of Xeropicta derbentina, we conducted a 'snapshot' field study using the individual Hsp70 level as a proxy for proteotoxic stress. In addition to correlation analyses, an IT-model selection approach based on Akaike's Information Criterion was applied to evaluate a set of models with respect to their explanatory power and to assess the relevance of each of the above-mentioned parameters for individual stress, by model averaging and parameter estimation. The analysis revealed particular importance of the individuals' shell size, height above ground, the shell colouration pattern and the interaction height × orientation. Our study showed that a distinct set of behavioural traits and intrinsic characters define the Hsp70 level and that environmental factors and individual features strongly interact.

Arresting mantle formation and redirecting embryonic shell gland tissue by platinum2+ leads to body plan modifications in Marisa cornuarietis (Gastropoda, Ampullariidae)

To evaluate the threat that anthropogenic substances pose to animals when they are emitted into the environment, tests like the invertebrate embryo toxicity test with the ramshorn snail Marisa cornuarietis have been developed. These tests are used to investigate substances like the heavy metal platinum (Pt) that is used in catalytic converters and is gradually released in car exhausts. In 2010, our group reported that high Pt concentrations cause body plan alterations in snails and prevent the formation of an external shell during M. cornuarietis embryogenesis. Now, this study presents scanning-electron micrographs and histological sections of platinum(2+) (Pt(2+))-treated and untreated M. cornuarietis embryos and compares "normally" developing and "shell-less" embryos during embryogenesis, to reveal the exact course of events that lead to this body plan shift. Both groups showed similar development until the onset of torsion 70- to 82-h postfertilization. In the Pt(2+)-exposed embryos, the rudimentary shell gland (=anlage of both shell gland and mantle, which usually evaginates, grows, and eventually covers the visceral sac) does not spread across the visceral sac but remains on its ventral side. Without the excessive growth of the shell gland, a horizontal rotation of the visceral sac relative to head and foot does not occur, as being normal during the process of torsion.

Histopathological effects of copper and lithium in the ramshorn snail, Marisa cornuarietis (Gastropoda, Prosobranchia)

The aim of this study was to determine and quantify effects of copper and lithium in tissues of early juveniles of the ramshorn snail, Marisa cornuarietis. For this purpose, hatchlings of M. cornuarietis were exposed for 7d ays to a range of five different sublethal concentrations of copper (5, 10, 25, 50, and 75 μg Cu²⁺L⁻¹) and lithium (50, 100, 200, 1000, and 5000 μg Li⁺ L⁻¹). Both metals changed the tissue structure of epidermis, hepatopancreas, and gills, varying between slight and strong reactions, depending on the copper and lithium concentration. The histopathological changes included alterations in epithelial and mucous cells of the epidermis, swelling of hepatopancreatic digestive cells, alterations in the number of basophilic cells, abnormal apices of digestive cells, irregularly shaped cilia and changes in the amount of mucus in the gills. The most sensible organ in M. cornuarietis indicating Cu or Li pollution is the hepatopancreas (LOECs were 10 μg Cu²⁺ L⁻¹, or 200 μg Li⁺ L⁻¹). In epidermis, mantle and gills relevant effects occurred with higher LOECs (50 μg Cu²⁺ L⁻¹, or 1000 μg Li⁺ L⁻¹). Base on LOECs, our results indicated that histopathological endpoints are high sensitivity to copper and lithium compared to endpoints for embryonic developmental toxicity.

Genotoxicity of platinum in embryos of zebrafish (Danio rerio) and ramshorn snail (Marisa cornuarietis)

The metal platinum is inter alia used for industrial and medical purposes. Due to its application in automobile catalytic converters and as an anti-cancer drug, Pt enters the aquatic environment via road runoff and hospital sewage and raises concerns about its environmental impact and toxicity to organisms. Therefore, the genotoxicity of Pt at 0, 0.1, 1, 10, 50, 100 and 200μg/l PtCl(2) was tested on two freshwater organisms, zebrafish (Danio rerio) and ramshorn snail (Marisa cornuarietis) using the single cell gel electrophoresis, also called comet assay. PtCl(2) did not show any genotoxicity for D. rerio at the tested concentrations, whereas significantly elevated DNA damage was observed in M. cornuarietis at 1μg/l PtCl(2) and beyond. The results of the study suggest a high sensitivity of M. cornuarietis concerning the genotoxic impact of PtCl(2).

Turning snails into slugs: induced body plan changes and formation of an internal shell

The archetypal body plan of conchiferan molluscs is characterized by an external calcareous shell, though internalization of shells has evolved independently in a number of molluscan clades, including gastropod families. In gastropods, the developmental process of torsion is regarded as a hallmark that is associated with a new anatomical configuration. This configuration is present in extant prosobranch gastropod species, which predominantly bear external shells. Here, we show that short-term exposure to platinum during development uncouples at least two of the processes associated with torsion of the freshwater snail Marisa cornuarietis. That is, the anus of the treated snails is located anteriorly, but the gill and the designated mantle tissue remains in a posterior location, thus preventing the formation of an external shell. In contrast to the prosobranchian archetype, platinum treatment results in the formation of a posterior gill and a cone-shaped internal shell, which persists across the lifetime. This first finding of artificially induced snail-slug conversion was also seen in the pulmonate snail Planorbarius corneus and demonstrates that selective alteration of embryonic key processes can result in fundamental changes of an existing body plan and-if altered regulation is inherited-may give rise to a new one.

Acetylcholinesterase activity in the terrestrial snail Xeropicta derbentina transplanted in apple orchards with different pesticide management strategies

Apple orchards are highly manipulated crops in which large amounts of pesticides are used. Some of these pesticides lack target specificity and can cause adverse effects in non-target organisms. In order to evaluate the environmental risk of these products, the use of transplanted sentinel organisms avoids side-effects from past events and facilitate comparison of multiple sites in a short time. We released specimens of the terrestrial snail Xeropicta derbentina in each 5 of two kinds of apple orchards with either conventional or organic management strategies plus in a single abandoned orchard. After one month, individuals were retrieved in order to measure acetylcholinesterase (AChE) activity. Mean values of AChE activity were significantly reduced in all conventional apple orchards compared to the others. Results show that the measurement of biomarkers such as AChE inhibition in transplated X. derbentina could be useful in the environmental risk assessment of post-authorized pesticides.

Metal sensitivity of the embryonic development of the ramshorn snail Marisa cornuarietis (Prosobranchia)

We investigated the effects of metal ions on the embryonic development of the ramshorn snail, Marisa cornuarietis, by exposing embryos to varying concentrations of copper (0, 50, 100, and 250 μg Cu(2+)/L), lead (0, 5, 10, and 15 mg Pb(2+)/L), lithium (0, 1, 2.5, and 3 mg Li(+)/L), or palladium (0, 50, 100, and 500 μg Pd(2+)/L). Effects of these metals were examined by recording mortality, the rate of tentacles and eyes formation, heart rate, hatching success, and weight after hatching. Compared to the control, we found a significant delay in the formation of tentacles and eyes after treatment with 100 μg Cu(2+)/L, 15 mg Pb(2+)/L, 2.5 mg Li(+)/L or 500 μg Pd(2+)/L. The heart rate decreased significantly at 500 μg Pd(2+)/L. At 10 mg Pb(2+)/L, 2.5 mg Li(+)/L, or 500 μg Pd(2+)/L, hatching was delayed significantly; 50 μg Cu(2+)/L induced a significantly earlier hatching, and reduced body weight. The LC(50) values were calculated to be about 50 μg Cu(2+)/L, 500 μg Pd(2+)/L, 2500 μg Li(+)/L, and 10000 μg Pb(2+)/L. These results show that the embryonic development of M. cornuarietis is about as sensitive to copper and lithium, compared to the most sensitive fishes used in embryo toxicity testing. Even though the MariETT is a laboratory-based assay focusing on toxicological endpoints of a selected model species, future application is envisaged to include testing of "natural" samples such as stream water or sediment interstitial water.

Impairment of trophic interactions between zebrafish (Danio rerio) and midge larvae (Chironomus riparius) by chlorpyrifos

The effects of chemicals on biotic interactions, such as competition and predation, have rarely been investigated in aquatic ecotoxicology. This study presents a new approach for the investigation of predator-prey interactions between zebrafish (Danio rerio) and midge larvae (Chironomus riparius) impaired by chlorpyrifos (CHP), a neurotoxic insecticide. With a simple experimental design including four different treatments: (1) control, (2) predator exposed, (3) prey exposed and (4) both, predator and prey, exposed, we were able to detect by visual observation an increase in the feeding rate of zebrafish preying on exposed chironomids after acute (2 h) exposure to 6 μg/l CHP. Previously, a decrease in the burrowing behaviour of exposed chironomid larvae was observed. However, when pre-exposing simultaneously both predators and prey, no significant differences in the feeding rate of zebrafish were observed. This suggests an impairment in prey recognition of the exposed zebrafish. At a lower CHP concentration (1 μg/l), no differences in feeding rate of zebrafish were observed. We therefore propose the use of trophic interactions as parameters in higher tier studies for chemical testing and evaluation of ecotoxicological risk assessment.

Interactions between effects of environmental chemicals and natural stressors: a review

Ecotoxicological effect studies often expose test organisms under optimal environmental conditions. However, organisms in their natural settings rarely experience optimal conditions. On the contrary, during most of their lifetime they are forced to cope with sub-optimal conditions and occasionally with severe environmental stress. Interactions between the effects of a natural stressor and a toxicant can sometimes result in greater effects than expected from either of the stress types alone. The aim of the present review is to provide a synthesis of existing knowledge on the interactions between effects of "natural" and chemical (anthropogenic) stressors. More than 150 studies were evaluated covering stressors including heat, cold, desiccation, oxygen depletion, pathogens and immunomodulatory factors combined with a variety of environmental pollutants. This evaluation revealed that synergistic interactions between the effects of various natural stressors and toxicants are not uncommon phenomena. Thus, synergistic interactions were reported in more than 50% of the available studies on these interactions. Antagonistic interactions were also detected, but in fewer cases. Interestingly, about 70% of the tested chemicals were found to compromise the immune system of humans as judged from studies on human cell lines. The challenge for future studies will therefore be to include aspects of combined stressors in effect and risk assessment of chemicals in the environment.

Histopathological alterations and induction of hsp70 in ramshorn snail (Marisa cornuarietis) and zebrafish (Danio rerio) embryos after exposure to PtCl(2)

The platinum group metals (PGMs) platinum (Pt), palladium (Pd), and rhodium (Rh) are used in automobile catalytic converters, from which they have been emitted into the environment to an increasing degree during the last 20 years. Despite the bioavailability of these metals to plants and animals, studies determining the effects of PGMs on organisms are extremely rare. In the present study, effects of various concentrations of PtCl(2) (0.1, 1, 10, 50 and 100 microg/L) were investigated with respect to the induction of hsp70 and histopathological alterations in the zebrafish, Danio rerio and the ramshorn snail, Marisa cornuarietis. Histopathological investigations revealed effects of Pt on both species, which varied between slight and strong cellular reactions, depending on the PtCl(2) concentration. The hsp70 level in M. cornuarietis did not show an increase following Pt exposure whereas it was significantly elevated at 100 micorg/L PtCl(2) in D. rerio.

Assessing toxicity of the insecticide thiacloprid on Chironomus riparius (Insecta: Diptera) using multiple end points

Since data documentation on neonicotinic toxicity to nontarget organisms should be enhanced, we investigate the effects of thiacloprid, a novel neonicotinoid insecticide, on the sediment-dwelling nontarget insect Chironomus riparius. Further, we wanted to validate the sensitivity of end points on different biological levels and obtain the greatest amount of information regarding the effects of this compound by using a battery of several end points such as larval mortality, behavior, body weight gain, emergence rate, time of development, gender ratio, Hsp70 stress protein level, and larval mouthpart deformities after exposure at a concentration range of 0.1 to 1000 microg/L thiacloprid. C. riparius was impacted starting at concentrations of 0.5 microg/L, a concentration that can be considered environmentally relevant. Larval mortality, behavior, emergence, and Hsp70 protein level were sensitive indicators for the toxic effect of thiacloprid, whereas gender ratio and mouthpart morphology were not affected. In our case life-cycle end points like survival rate (LC(50): 1.57 microg/L) and emergence rate (EC(50): 0.54 microg/L) proved to be more sensitive than tested physiological end points for the neurotoxic insecticide.

Embryo development, stress protein (Hsp70) responses, and histopathology in zebrafish (Danio rerio) following exposure to nickel chloride, chlorpyrifos, and binary mixtures of them

Two different classes of chemicals were tested in a multilevel approach in this study: NiCl(2) as a representative for heavy metals and chlorpyrifos, a pesticide. Both, the single substances and mixtures of them were investigated for their effects on embryonic development, histological alterations, and the stress protein (Hsp70) response in the zebrafish Danio rerio. Fishes were exposed from fertilization of eggs up to a maximum of 168 h post fertilization, depending on the investigated endpoint. NiCl(2) led to effects in all tests which, however, were less severe at the histopathological level than in developmental (hatching success) and stress protein studies. Chlorpyrifos did not lead to developmental alterations but it was found to induce the Hsp70 response as well as histopathological damages. Mixtures of both substances resulted in similar results as the single substances; the results suggest an independent mode of action of these two substances and additivity of their effects.

Uptake of platinum by zebrafish (Danio rerio) and ramshorn snail (Marisa cornuarietis) and resulting effects on early embryogenesis

Platinum group elements (PGEs), platinum, palladium and rhodium are widely used in automobile catalytic converters. PGEs are emitted into the environment and enter the aquatic ecosystem via runoff rainwater. The present study investigated the bioavailability of platinum chloride for the zebrafish (Danio rerio) and the ramshorn snail (Marisa cornuarietis) and determined the bioaccumulation rate of platinum. Applying the fish early life stage assay for D. rerio (DarT) and the Marisa embryo toxicity test ("Mariett") for M. cornuarietis, effects of platinum chloride on the embryonic development were investigated. Platinum concentrations tested in this study ranged from environmentally relevant concentrations of 38 ng L(-1) up to a concentration of 74.2 microg L(-1) for D. rerio and of 200 ngL(-1) up to 98.7 microg L(-1) for M. cornuarietis. Platinum was found to be accumulated in both organisms. Bioaccumulation factors (BAFs) were in the range of 5-55 for D. rerio and of 218.4-723.9 for M. cornuarietis, depending on the tested Pt concentrations. During the embryonic development, platinum was shown to alter the heart rate of both organisms already at the lowest tested concentration. At higher concentrations, platinum decelerated the hatching rate of the embryos of both species. Additionally, a retardation of the general development and a loss of weight due to platinum exposure was observed in M. cornuarietis. Results of this study contribute important data on the ecotoxicity of a rarely studied element.

Behavioural and developmental toxicity of chlorpyrifos and nickel chloride to zebrafish (Danio rerio) embryos and larvae

In order to assess the combined toxicity of environmental chemicals with different modes of action in acute (2 h) and subchronic (11 d) exposures, embryos and larvae of Danio rerio were exposed to a heavy metal salt, nickel chloride (NiCl2), the insecticide chlorpyrifos (CHP) and their binary mixtures. Chlorpyrifos is an acetylcholine esterase inhibitor, which is likely to affect behaviour of the organism. NiCl2 targets the active sites of enzymes and is regarded as an unspecific toxicant for aquatic organisms. Several endpoints, such as locomotor activity, morphological abnormalities, and mortality of D. rerio embryos and larvae were studied. During acute exposures to > or =0.25 mg/L of chlorpyrifos, locomotor activity tended to increase. However, this activity decreased significantly at > or =7.5 mg Ni/L. Subchronic exposures to CHP resulted in behavioural changes at much lower concentrations (> or =0.01 mg/L) and considerably earlier than the observed increase in morphological abnormalities and mortality (LC(50) (10 d): 0.43 mg/L). Combined CHP and NiCl2 mixtures led to an antagonistic deviation from the concept of independent action, in the case of locomotor activity. Compared to developmental or survival parameters, behaviour was the most sensitive endpoint for CHP exposure in this study; therefore we recommend this parameter to complement already established endpoints.

Cadmium tolerance in seven Daphnia magna clones is associated with reduced hsp70 baseline levels and induction

The stress protein hsp70 is part of the intracellular alarm and repair system which enables organisms to counteract negative effects of toxicants on protein integrity. Under long-term selection pressure exerted by environmental pollution, in particular heavy metals, this system may be expected to play a major role in the course of local, microevolutionary events leading to the acquisition of toxicant resistance. Seven clones of Daphnia magna from different geographical regions were characterized regarding their sensitivity to Cd, their hsp70 expression, and Cd accumulation. In an acute immobilisation assay, the tested clones showed remarkable differences in their sensitivity to Cd. The highest EC(50) values by far were obtained for the clone displaying lowest hsp70 expression. In general, hsp70 levels reflected the order of sensitivity to Cd among the seven clones reciprocally. Clonal variations in sensitivity and hsp70 expression could not be related to differential accumulation of Cd, though. In summary, the association of stress insensitivity with low hsp70 induction which has been exemplarily reported for populations of different invertebrates under strong selection pressure could be affirmed for a largely parthenogenetic species for the first time. Furthermore, our observation has serious consequences for the interpretation of toxicological assays using a single D. magna clone solely.

Embryo toxicity of pesticides and heavy metals to the ramshorn snail, Marisa cornuarietis (Prosobranchia)

An invertebrate embryo toxicity test with the ampullariid snail, Marisacornuarietis, to assess the toxicity of pesticides and heavy metals recently was established. Snail embryos were treated with atrazine (100, 1000, 10000, and 30000 microg/L), imidacloprid (10000, 25000, and 50000 microg/L), Ni(2+) (0.1, 1, 10, and 100 microg/L) or Zn(2+) (100, 200, 500, 1000, 2000, and 5000 microg/L). The effect of these substances was examined by monitoring the following endpoints: mortality, formation of tentacles and eyes, heart rate, hatching, and weight after hatching. Effects in term of a significant delay on the formation of both tentacles and eyes were found after treatment with 100 microg/L Ni(2+) or 200 microg/L Zn(2+). The heart rate was shown to significantly decrease at 25000 microg/L imidacloprid or 1000 microg/L Zn(2+). At 100 microg/L atrazine, 10 microg/L Ni(2+), or 1000 microg/L Zn(2+) a significant delay in hatching became visible. No significant mortality was observed for the tested concentrations of atrazine, imidacloprid, or Ni(2+), while 5000 microg/L Zn(2+) resulted in 100% mortality after 10d. The weight of freshly hatched individuals remained unaffected in all treatments. On the basis of the lowest observed effect concentrations (LOECs) recorded, we could show the M.cornuarietis embryo toxicity test (MariETT) to react up to three orders of magnitude more sensitive (for metals) and at least one order of magnitude more sensitive (for the tested organics) than the established Danio rerio embryo test.

Snail phenotypic variation and stress proteins: do different heat response strategies contribute to Waddington's widget in field populations?

On the basis of studies with laboratory strains of Drosophila and Arabidopsis, it has been hypothesized that potential buffers to the expression of phenotypic morphological variation, such as Hsp90 and possibly Hsp70, represent important components of Waddington's widget, which may confer capacitive evolution. As studies on field populations of living organisms to test this hypothesis are lacking, we tested whether a heat response strategy involving high stress protein levels is associated with low morphological variation and vice versa, using four natural populations of Mediterranean pulmonate snails. In response to 8 hr of elevated temperatures, a population of Xeropicta derbentina with uniform shell pigmentation pattern showed remarkably high Hsp70 but low Hsp90 levels. In contrast, a highly variable population of Cernuella virgata kept both Hsp90 and Hsp70 levels low when held at diverse though environmentally relevant temperatures. Two other populations (Theba pisana and another X. derbentina population) with intermediate variation in shell pigmentation pattern were also intermediate in inducing Hsp70, though Hsp90 was maintained at a low level. The observed correlation of stress protein levels and coloration pattern variation provide the first indirect evidence for an association of stress proteins with Waddington's widget under natural conditions.

Effects of 3,4-dichloroaniline and diazinon on different biological organisation levels of zebrafish (Danio rerio) embryos and larvae

In this study the effects of 3,4-dichloroaniline (3,4-DCA), a decomposition product of the herbicides propanil and diuron (and other pesticides), and diazinon, a neurotoxic insecticide, on early life stages of zebrafish Danio rerio were assessed. The toxicity of these substances with different modes of action (acetylcholine esterase inhibitor vs. polar narcosis) was tested for single substances as well as in binary mixtures. To study effects on different biological organisation levels (from the molecular up to the whole organism level) the molecular stress response regarding Hsp70, the embryonic and larval development and the locomotor activity were investigated as integrative biomarkers. In single substance tests 3,4-dichloroaniline elicited deformations at > or = 0.25 mg/l during the 11 days subchronic test, whereas locomotor activity and mortality were impaired at > or = 0.5 mg/l. Diazinon effects on those parameters were obvious at > or = 2 mg/l, except for the deformation rate (11 days:1 mg/l). In equitoxic mixtures of both substances concentration additivity was observed for deformation rate and mortality (11 days). An increase in the Hsp70 content occurred in zebrafish exposed to 0.25 mg 3,4-DCA/l as well as to 0.05 mg diazinon/l; in mixtures concentration additivity could be shown. The investigated endpoints varied in respect to their sensitivity, with deformations and Hsp70 levels as most sensitive parameters concerning 3,4-DCA and Hsp70 as most sensitive parameter concerning diazinon. Accordingly, for an integrated understanding of the effects of chemicals and their mixtures on fish, a battery of different test methods should be applied.

Influence of nickel chloride, chlorpyrifos, and imidacloprid in combination with different temperatures on the embryogenesis of the zebrafish Danio rerio

Two independent types of stressors, chemicals and high temperatures, which frequently act together in the environment, are addressed in this study. Pesticides (imidacloprid and chlorpyrifos) as well as a metal salt (nickel chloride) were investigated for their toxic effect at different temperatures. Tests focused on the early development of zebrafish (Danio rerio) embryos and larvae (from fertilization up to 168 h postfertilization) when exposed to the three respective chemicals at an optimum temperature (26 degrees C) and three higher temperatures (up to 33.5 degrees C). At all temperatures tested, the two pesticides did not have a significant impact on the early development of the zebrafish at the highest test concentrations (imidacloprid, 50 mg/l; chlorpyrifos, 1 mg/l). Nickel led to a significant decrease of hatching success at all temperatures; the combination of elevated temperature and nickel exposure revealed a synergistic effect of both stressors.

Effects of neurotoxic insecticides on heat-shock proteins and cytokine transcription in Chinook salmon (Oncorhynchus tshawytscha)

This study investigated sublethal, molecular effects of two current-use insecticides, chlorpyrifos (CP) and esfenvalerate (EV) in juvenile Chinook salmon. Heat-shock protein (hsp60, hsp70, hsp90) expression was quantified by Western blotting in muscle, liver and gill, and transcription of four cytokines (TGF-beta, IL-1beta, IGF-1, Mx-protein) was measured by real-time TaqMan PCR in anterior kidney and spleen. Expression of hsp was increased in muscle and liver at 1.2 and 7.2 microg/L CP, and at 0.01 and 0.1 microg/L EV, respectively. Transcription of IL-1beta and TGF-beta was elevated in kidney at 1.2 microg/L CP, while EV had no effect. No changes in cytokine transcription were observed in the spleen. Our results show that these insecticides cause cellular effects at environmental concentrations, and that hsps are sensitive indicators of sublethal exposure to CP and EV. In addition, CP may exert immunotoxic effects by altering the transcription of important mediators of the fish immune system.

The impact of environmental chemicals on wildlife vertebrates

A plethora of papers have been published that address the affects of chemicals on wildlife vertebrates. Collectively, they support a connection between environmental pollution and effects on wildlife vertebrate populations; however, causal relationships between exposure, and reproduction or population structure effects have been established for only a few species. In a vast number of fish species, particularly in teleosts, it is accepted that EDCs affect the endocrine system of individuals and may alter sexual development and fertility. However, only few studies have demonstrated population-level consequences as a result of exposure to EDCs. The same applies to fish populations exposed to contaminants or contaminant mixtures with non-endocrine modes of action; few studies link EDCs directly to population affects. Amphibian populations are declining in many parts of the world. Although environmental chemicals have been shown to affect reproduction and development in single organism tests, the degree to which chemicals contribute to the decline of amphibians, either alone, or in concert with other factors (habitat loss, climate change, introduction of neozoa, UV-B irradiation, and direct exploitation) is still uncertain. Because reptilian endocrinology is so variable among species, EDC effects reported for individual species cannot easily be extrapolated to others. Nevertheless, for some species and locations (e.g., the Lake Popka alligators), there is considerable evidence that population declines are caused or triggered by chemical pollution. In birds, there is ample evidence for EDC effects on the reproductive system. In some bird species, effects can be linked to population declines (e.g., based on egg-shell thinning induced by DDT/DDE). In contrast, other bird species were shown to be rather insensitive to endocrine disruption. Oil spills, which also may exert endocrine effects, are usually regarded to cause only transient bird population effects, although long-term data are largely missing. Mammal population declines have been correlated with organochlorine pollution. Moreover, numerous studies have attributed reproductive and non-reproductive dysfunctions in mammals to EDC exposure. However, in the majority of cases, it is uncertain if effects at the population level can be attributed to chemical-induced reproductive effects. Evidence shows that selected species from all vertebrate classes were negatively affected by certain anthropogenic chemicals. Affects on some species are well characterized at the organismal level. However, the proof of a direct link between chemical exposure and population decline was not given for the vast majority of studied species. This review clearly shows the gaps in knowledge that must be filled for the topic area addressed. We, herewith, make a plea for long-term studies to monitor effects of various environmental chemicals on wildlife vertebrate populations. Such studies may be augmented or combined with mechanistically-oriented histological, cytological and biochemical parallel investigations, to fill knowledge gaps.

Expression of immune-regulatory genes in juvenile Chinook salmon following exposure to pesticides and infectious hematopoietic necrosis virus (IHNV)

Impairment of fish immune function as a consequence of polluted aquatic environments can result in changes in susceptibility to disease. In this study, we investigated the effects of two widely used insecticides, chlorpyrifos (CP) and esfenvalerate (EV), and a pathogen, infectious hematopoietic necrosis virus (IHNV), singly and in combination, on survival and cytokine (Mx protein, IL-1beta, TGF-beta and IGF-1) expression in juvenile Chinook salmon. Fish were exposed for 96 h to sublethal concentrations of CP (3.7 microg L(-1)) or EV (0.08 microg L(-1)), allowed to recover in clean water for seven days, then exposed to IHNV (6.4x10(5)TCID(50)mL(-1)) for 1.5h. Mortality was recorded daily, and spleen and anterior kidney samples were collected on day 4 (after CP or EV treatment), day 20 and day 60 (after CP or EV treatment and subsequent IHNV exposure) of the experiment. Significant mortality after 60 days was observed following exposure to EV (17%) or IHNV (20%), and prior insecticide exposure did not synergize the acute effects of pathogen treatment. By day 4, exposure to CP as well as EV led to a significant decrease of Mx protein and IL-1beta expression; by day 20, EV-exposed fish significantly overexpressed IL-1beta. Mx protein transcription was up-regulated in spleen and kidney of all IHNV-exposed fish groups by day 20. All but one treatment (EV) led to significantly decreased IGF-1 transcription in spleen on days 20 and 60, whereas a short-term increase was seen after CP exposure (day 4). In kidney, decreases of IGF-1 transcription were less pronounced. TGF-beta transcription was up-regulated in CP/IHNV and EV/IHNV exposure groups. Our results indicate that CP and EV alter the expression of cytokines, but this did not negatively affect the ability of fish to survive a subsequent exposure to IHNV. Induced TGF-beta transcription indicated that the combined stressors affected fish in a synergistic manner, but the consequences are unknown. Increased transcription of Mx protein was a reliable indicator of virus exposure.

Acute effects of diclofenac and DMSO to Daphnia magna: immobilisation and hsp70-induction

To determine the toxicity of the anti-rheumatic drug diclofenac to Daphnia magna, acute toxicity tests according to the OECD guideline 202 were combined with biochemical investigations of the hsp70 level as a biomarker for proteotoxicity. Particular attention was paid to the impact of the solvent DMSO as a confounding factor to diclofenac toxicity by means of testing different variations of producing stock solutions. In the acute immobilisation tests, diclofenac was most toxic as a singular test substance, with indication of a slight antagonistic interaction between the two substances. The highest EC50 values were obtained in those approaches using diclofenac pre-dissolved in DMSO. Thus, the observed antagonism seems to be intensified by pre-dissolution. Hsp70 levels of 12- to 19-days-old D. magna were determined after 48h exposure using a highly reproducible immunological protocol. Hsp70 induction occurred at a LOEC of 30mgl(-1) diclofenac plus 0.6mll(-1) DMSO, and at a LOEC of 40mgl(-1) for diclofenac alone. In summary, DMSO showed only slight confounding effects on diclofenac action in the applied range of concentrations.