Lowest Observed Effect Concentration Research Articles

Effects of nitrate on early life stages of Astacus astacus (Linnaeus, 1758) and Procambarus virginalis (Lyko, 2017)

We examined the effects of nitrate on the embryonic development of two freshwater crayfish species, the indigenous noble crayfish (Astacus astacus) and the invasive marbled crayfish (Procambarus virginalis). Nitrate measurements show concentrations of 50 mg/L in surface waters of Germany, while concentrations in groundwater measure up to 100 mg/L. Performing a chronic exposure experiment, we exposed embryos of both species to nitrate concentrations of between 0.0 mg/L and 500 mg/L to estimate the influences of nitrate concentrations on survival, hatching development time, malformations and growth. We observed the first effects on survival at 14 mg/L LOEC (lowest observed effective concentration) nitrate for marbled crayfish. For noble crayfish, we estimated an EC50 value of 55.7 mg/L on hatching rate. Our results show that eutrophication of surface waters can negatively affect the embryonic development of freshwater crayfish with serious consequences on recruitment.

One uncertainty factor does not fit all: Identifying mode of action and species specific acute to chronic ratios for aquatic life

In ecological risk assessment, acute to chronic ratio (ACR) uncertainty factors are routinely applied to acute mortality benchmarks to estimate chronic toxicity thresholds. To investigate variability of aquatic ACRs, we first compiled and compared 56 and 150 pairs of acute and subchronic/chronic growth/reproductive toxicity data for fishes (Pimephales promelas (53), Danio rerio (2), and Oryzias latipes (1)) and the crustacean Daphnia magna, respectively, for 172 chemicals with different modes of action (MOA). We found that there were only significant relationships between P. promelas acute median lethal concentrations and growth lowest-observed effect concentrations for class 1 (nonpolar narcosis) chemicals, though significant relationships were demonstrated for D. magna to all Verhaar et al. MOA classes (Class 1: nonpolar narcosis, Class 2: polar narcosis, Class 3: reactive chemicals, and Class 4: AChE inhibitors and estrogenics). Probabilistic ecological hazard assessment using chemical toxicity distributions was subsequently employed for each MOA class to estimate acute and chronic thresholds, respectively, to identify MOA and species specific ecological thresholds of toxicological concern. Finally, novel MOA and species specific ACRs using both chemical toxicity distribution comparison and individual ACR probability distribution approaches were identified using representative MOA and chemical categories. Our data-driven approaches and newly identified ACR values represent robust alternatives to application of default ACR values, and can also support future research and risk assessment and management activities for other chemical classes when toxicity information is limited for chemicals with specific MOAs within invertebrates and fish.

Better define beta\u2013optimizing MDD (minimum detectable difference) when interpreting treatment-related effects of pesticides in semi-field and field studies

The minimum detectable difference (MDD) is a measure of the difference between the means of a treatment and the control that must exist to detect a statistically significant effect. It is a measure at a defined level of probability and a given variability of the data. It provides an indication for the robustness of statistically derived effect thresholds such as the lowest observed effect concentration (LOEC) and the no observed effect concentration (NOEC) when interpreting treatment-related effects on a population exposed to chemicals in semi-field studies (e.g., micro-/mesocosm studies) or field studies. MDD has been proposed in the guidance on tiered risk assessment for plant protection products in edge of field surface waters (EFSA Journal 11(7):3290, 2013), in order to better estimate the robustness of endpoints from such studies for taking regulatory decisions. However, the MDD calculation method as suggested in this framework does not clearly specify the power which is represented by the beta-value (i.e., the level of probability of type II error). This has implications for the interpretation of experimental results, i.e., the derivation of robust effect values and their use in risk assessment of PPPs. In this paper, different methods of MDD calculations are investigated, with an emphasis on their pre-defined levels of type II error-probability. Furthermore, a modification is suggested for an optimal use of the MDD, which ensures a high degree of certainty for decision-makers.

Acute toxicity of the lampricides TFM and niclosamide: Effects on a vascular plant and a chironomid species

The lampricides 3-trifluoromethyl-4-nitrophenol (TFM) and niclosamide have been used for about 60 years to control sea lamprey (Petromyzon marinus) in the Great Lakes Basin and Lake Champlain. To register these chemicals as pesticides in North America, their environmental effects must be reviewed on a periodic basis. As a part of this effort, toxicity of TFM and niclosamide to duckweed (Lemna gibba), and of niclosamide to aquatic midge (Chironomus dilutus), was assessed. Results of these studies indicate that for both lampricides, the no observed and lowest observed effect concentrations (NOEC and LOEC) exceed expected environmental concentrations, with effects only in the highest concentrations tested and the longest exposure times. Duckweed exposed to TFM indicated 7-day LOECs ≥4.88 mg/L for mean specific growth rate and yield, with the half maximal effective concentration (EC50) > 9.74 mg/L. For duckweed exposed to niclosamide, 7-day LOECs for mean specific growth rate and yield ranged from 0.271 to 0.569 mg/L, with the half maximal inhibitory concentration (IC50) 0.725 mg/L or greater depending on the parameter measured. For midge larvae exposed to niclosamide-dosed sediment, the LOEC values based on survival and growth were 26.2 mg/kg and >82.1 mg/kg, respectively, and the EC50 based on survival was 49.6 mg/kg. Based on these data, deleterious effects on aquatic plants and benthic invertebrates are unlikely to result from use of TFM and niclosamide for lamprey control, given that the effect concentrations are in excess of the expected environmental concentrations.

Embryonic toxicity of 3,4-dichloroaniline (3,4-DCA) on Javanese medaka (Oryzias javanicus Bleeker, 1854)

Early-life exposure to toxic chemicals causes irreversible morphological and physiological abnormalities that may last for a lifetime. The present study aimed to determine the toxicity effect of 3,4-Dichloroaniline (3,4-DCA) on Javanese medaka (Oryzias javanicus) embryos. Healthy embryos were exposed to various 3,4-DCA concentrations for acute toxicity (5, 10, 25, 50, and 100 mg.L−1) and sublethal toxicity (0.10, 0.50, 1.25, 2.50, and 5.00 mg.L−1) for 96 h and 20 days respectively. Acute toxicity test revealed that the median lethal concentration (96h-LC50) was 32.87 mg.L−1 (95 % CI = 27.90–38.74, R2 = 0.95). Sublethal exposure revealed that 1.25 mg.L-1 at 3 days post-exposure (3 dpe) has a significant lower heartrate (120 ± 12.3 beats/min., p < 0.01), while at 7 dpe those exposed to 5 mg.L−1 (141.8 ± 8.3 beats/min) had significantly (p < 0.01) lower heart rate compared to other treatments. Likewise, at 13 dpe, 5.00 mg.L−1 (110.4 ± 17.3 beats/min) and 2.5 mg.L-1 (130.4 ± 8.3 beats/min) were significantly lower (p < 0.001) compared to control. None of the embryos in 5.00 mg.L−1 and 2.50 mg.L-1 treatment groups survived at the end of the experiment. The results indicated a concentration-dependent response. The lowest observed effect concentration (LOEC) that exerted developmental deformities was 0.5 mg.L−1. Javanese medaka embryo have low sensitivity to acute toxicity of 3,4-DCA, but developmental abnormalities at sublethal concentrations were observed.

제브라피쉬 초기배아발생단계의 기형현상을 이용한 만성 NOEC의 예측방법 개발

This study has developed a new simplicity toxicity assessment method that can predict the chronic NOEC (No Observed Effect Concentration) value rapidly by observing the morphological abnormality at the low concentration area in the early embryonic development stage of Danio rerio. As a result, the acute LOEC (Lowest Observed Effect Concentration) values of Camptothecin, Camphor and Curcumin were calculated as 9.3 nM, 1248.4 μM and 18.3 μM, respectively. The morphological anomalies were observed to yolk sac edema (YSE), pericardial edema (PE), black yolk (BY), bent spine (BS), albinism (A), dyed yellow yolk (DY), collapse symptoms of fertilized embryo tissue (CPFE), no heartbeat (NHB), reduced heart rate (RHR), hatching delay (HD), short body length (SBL). And acute NOEC values were classified into A-type and B-type depending on the presence or absence of morphological anomalies. A-type morphological anomalies were observed at 6.2 nM, 832.3 μM and 9.2 μM, similar to the area near acute LOEC except for albinism (A), dyed yellow yolk (DY), collapse symptoms of fertilized embryo tissue (CPFE), and no heartbeat (NHB). On the other hand, morphological anomalies of B-type did not occur at all in 0.4, 4.0, and 0.1 within 4 days, and the acute NOEC values of B-type were consistent with the chronic NOEC values at 32 days. This means that the concentration without any deformity in acute toxicity test during 4 days is consistent with the chronic NOEC value. That is, it is also a means to quickly calculate chronic NOEC using the acute NOEC value through the presence or absence of morphological abnormality in the Danio rerio embryo development stage of short term.

Zinc chloride influences embryonic development, growth, and Gh/Igf-1 gene expression during the early life stage in zebrafish (Danio rerio)

Although zinc is an essential element for organisms, excess zinc exposure is harmful. We assessed the possible negative influence of zinc (Zn) on the freshwater fish Danio rerio during its early life stage by using Organization for Economic Cooperation and Development test guideline no. 210. Lethality of Zn after hatching occurred in a concentration dependent manner. The LC50 and lowest observed effect concentration of mortality values in the present toxicity assay were 2.31 mg/L (95% confidence limit: 1.81–3.05) and 1.5 mg/L, respectively. These values were close to the reported concentration recorded in aquatic environments. Growth inhibition was observed at 15 and 30 days post-hatching with Zn exposure of 1.5 mg/L. In general, the growth hormone (Gh)/insulin-like growth factor-I (Igf-1) axis is important for growth in fishes, and Zn exposure induced a significant reduction of igf-1 expression at the concentration that caused growth inhibition. These findings suggest that the observed growth inhibition was induced by the suppression of igf-1 expression. In addition, these results suggest that by examining gene expression on the Gh/Igf-1 axis, it may be possible to predict growth suppression by chemical exposure.

Comparative Assessment of the Sensitivity of Fish Early-Life Stage, Daphnia, and Algae Tests to the Chronic Ecotoxicity of Xenobiotics: Perspectives for Alternatives to Animal Testing.

No-observed-effect concentrations (NOECs) are used in environmental hazard classification and labeling of chemicals and their environmental risk assessment. They are typically obtained using standard tests such as the fish early-life stage (FELS) toxicity test, the chronic Daphnia reproduction test, and the algae growth inhibition test. Given the demand to replace and reduce animal tests, we explored the impact of the FELS toxicity test on the determination of effect concentrations by comparing the FELS toxicity test and the Daphnia and algae acute or chronic toxicity tests. Lowest-observed-effect concentrations (LOECs) were used instead of NOECs for better comparison with median lethal or effect concentration data. A database of FELS toxicity data for 223 compounds was established. Corresponding Daphnia and algae toxicity tests were identified using established databases (US Environmental Protection Agency ECOTOX, Organisation for Economic Co-operation and Development QSAR Toolbox, eChemPortal, EnviroTox, and OpenFoodTox). Approximately 9.5% of the investigated compounds showed a 10-fold higher sensitivity with the FELS toxicity test in comparison with the lowest effect concentrations obtained with any of the other tests. Some of these compounds have been known or considered as endocrine disrupting, or are other non-narcotic chemicals, indicating that the higher sensitivity in the FELS toxicity test is related to a specific mechanism of action. Targeting these mechanisms by alternative test systems or endpoints, using fish embryos for instance, may allow reduction or replacement of the FELS toxicity test or may allow us to prioritize compounds for conduction of the FELS toxicity test. Environ Toxicol Chem 2019;39:30-41. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Silver nanoparticle toxicity effect on the seagrass Halophila stipulacea.

Information on silver nanoparticle (AgNP) phytotoxicity on seagrasses is provided for the first time. Toxic effects of environmentally relevant AgNP concentrations on Halophila stipulacea were assessed to identify sensitive biomarkers, to determine threshold effect concentrations and to evaluate potential risks. Potential alterations in the cytoskeleton, endoplasmic reticulum, cell ultrastructure and viability, oxidative stress parameters and elongation in H. stipulacea leaves exposed to AgNP concentrations ranging from 0.0002 to 0.2mgL-1 for 8 days were examined. The first signs of actin filament (AF) response in differentiating cells, exhibiting disorientation and slight bundling, were observed on the 4th day at 0.0002mgL-1, while at the end of the experiment and at the higher concentrations, AFs were extremely bundled. Endoplasmic reticulum was affected in meristematic and differentiating cells; massive aggregations and loss of the "grainy" structure were observed, initially on the 6th day at 0.002mgL-1. Effects on microtubules were detected on the last day at 0.2mgL-1. An increase in H2O2 levels on the 4th and/or 6th day even at 0.0002mgL-1 was followed by a decrease on, or up to the last day. On the 6th day at the lowest concentration, elevated malondialdehyde content, and superoxide dismutase and peroxidase activity were detected, indicating oxidative damage and antioxidant defense mechanism activation. Dead epidermal cells mainly occurred at 0.02 and 0.2mgL-1, while no dead vein cells were detected. A significant inhibition in leaf elongation was observed only at 0.2mgL-1. Therefore, AF disturbance in differentiating leaf cells, being a susceptible response parameter, could be regarded as an early warning indicator of risk posed by AgNPs to H. stipulacea meadows, while most of the remaining parameters examined also constitute useful biomarkers. The lowest observed effect concentration (0.0002mgL-1), being within the range of environmentally relevant AgNPs concentrations, suggests the possibility of negative impacts of AgNPs on seagrass health. A risk quotient of 1.33 was calculated, indicating that AgNPs may pose a significant potential risk to the coastal environment. The data presented highlight the importance of future research to further investigate the seagrass-AgNP interactions, stress the need for a refinement of the environmental risk assessment of AgNPs and could be utilized for the design of biomonitoring programs for rational management of the coastal environment.

Comparison of thromboelastography versus conventional coagulation tests in simulated Crotalus atrox envenomation using human blood

IntroductionPit viper bites are a source of significant morbidity and mortality. Pit viper bites can cause venom-induced consumptive coagulopathy (VICC), typically evaluated with laboratory-based conventional coagulation tests (CCTs). However, CCTs require a laboratory and average 1 h to conduct. Thromboelastography (TEG) provides real-time, point-of-care tests of coagulation that are fast and require no separate laboratory facilities, which could be advantageous in both hospital and austere settings. However, the relative efficacy of TEG versus CCTs was unclear, particularly at low venom concentrations. Therefore, the objectives of this study were to test human blood with various concentrations of pit viper venom using CCTs and TEG to determine dose-dependent changes, lowest observed effect concentration (LOEC), and sensitivity to detecting samples out of normal diagnostic range. MethodsBlood samples from 20 volunteers were mixed with varying concentrations of western diamond back rattlesnake (Crotalus atrox) venom based on the mouse LD50IV (none, 0.5%, 1%, 2%, 33%, 66%, and 100% LD50IV). Samples were split and assessed with both CCTs including prothrombin time (PT), international normalized ratio (INR), partial thromboplastin time (PTT), fibrinogen, and D-dimer, along with TEG measures of reaction time (R), kinetic time (K), rate of clot formation (α-angle), and clot strength (MA). Data were analyzed as dose-dependent concentration-based changes in raw values and in percent of samples exceeding diagnostic thresholds using ANOVA and nonparametric statistics at the p < .05 threshold. ResultsAll evaluations showed significant concentration-dependent changes, and 100% of samples exceeded diagnostic thresholds at 33%LD50IV and above, save D-dimer. At 0.5%LD50IV, R, K, α-angle, PT, and INR were significantly different from controls, and at 1%LD50IV, mean values exceeded diagnostic thresholds for R, K, α-angle, MA, PT, and INR, but not for PTT, D-dimer, or fibrinogen. At 2%LD50IV, 100% of samples were out of normal range for K, α-angle, and PT. ConclusionTEG is effective in coagulopathy evaluations of in vitro simulated pit viper envenomation. At low venom concentrations, TEG performed as well or better than the majority of CCTs. These findings provide empirical evidence supporting the use of TEG to rapidly and accurately evaluate VICC.

Genotoxicity response of Vicia faba seedlings to cadmium in soils as characterized by direct soil exposure and micronucleus test.

To overcome the drawbacks of the Vicia faba root tip micronucleus test in soil using the solution extract method, we conducted a potting experiment by direct soil exposure. Cadmium was spiked into 3 typical soils (brown soil, red soil, and black soil) to simulate environmental concentrations (0.625, 1.25, 2.5, 5, and 10 mg kg-1). Multiple Vicia faba tissues (primary root tips, secondary root tips, and leaf tips) were sampled, and mitotic index (MI), chromosome aberration frequency (CA), and micronucleus frequency (MN) were used as endpoints after a seedling period of 5 days. The results showed a response between Cd concentrations and multiple sampling tissues of Vicia faba, and the secondary root tips responded to Cd stress the most, followed by primary root tips and leaf tips. Soil physicochemical properties (e.g., pH, total phosphorus, total organic carbon, etc.) influenced the genotoxicity of Cd, and pH was the dominant factor, which resulted in the genetic toxicity response of Cd in soils in the order: red soil > brown soil > black soil. The lowest observable effect concentration (LOEC) of Cd was 1.25 mg kg-1 for both brown soil and red soil and 2.5 mg kg-1 for black soil. In view of this, we suggested that soil properties should be considered in evaluating genotoxicity risk of Cd in soil, especially with soil pH range, and the secondary root tips should be taken as suitable test tissues in the MN test due to its more sensible response feature to Cd stress in soil.

Toxicity of microbial insecticides toward the non-target freshwater insect Chironomus xanthus.

Commercial formulations based on Bacillus thuringiensis subs. kurstaki (Btk) and Beauveria bassiana (Bb) are commonly used microbial insecticides in Brazil and other tropical regions. However, and despite being considered environmentally friendly, their use generates concerns regarding possible adverse ecological effects in freshwater ecosystems. Here, we evaluate the effects of these bioinsecticides on the tropical aquatic dipteran Chironomus xanthus under laboratory conditions. After laboratory exposures to these compounds 48-h median lethal concentration (LC50 ) values of 1534 μg a.i./L for Btk and of 6.35 μg a.i./L for Bb were estimated. Chronic assays revealed different sublethal effects: Btk-based bioinsecticide exposure reduced C. xanthus growth [lowest observed effect concentration (LOEC) was 126 μg a.i./L for head width], decreased emergence rate (LOEC = 8 μg a.i./L) and increased immunological response (LOEC = 50 μg a.i./L) measured as total hemocyte count in larvae hemolymph. Exposure to low concentrations of Bb-based insecticide also reduced C. xanthus growth (LOEC = 0.07 μg a.i./L for larvae body length measurements), and emergence rate (LOEC = 0.28 μg a.i./L), despite no clear effects on the total hemocyte counts. Our results suggest that low concentrations of Btk and Bb bioinsecticides are toxic to C. xanthus. Given their widespread use and occurrence in tropical freshwater systems, research is needed to evaluate the potential effects of these compounds concerning natural freshwater insect communities and ecosystem functioning. © 2019 Society of Chemical Industry.

Symbiosis between Rhizobium leguminosarum bv. trifolii strain TA1 and a white clover cultivar benefits clover tolerance to cadmium toxicity

ABSTRACT New Zealand pastoral productivity relies heavily on biological nitrogen (N) fixation from rhizobia bacteria. Cadmium (Cd), present in pasture soils as an impurity in phosphate fertilisers, may have toxic effects on both plant growth and rhizobia activity. Effects of Cd on growth of seedlings of a white clover cultivar ‘Grasslands Tribute’, in the absence and presence of the N2-fixing Rhizobium leguminosarum bv. trifolii strain TA1, were assessed in vermiculite microcosm assays. The lowest observable effect concentrations resulting in significantly lower white clover shoot weights than those grown without Cd were 0.07 mg Cd kg−1 (measured as Ca(NO3)2-extractable Cd, Cdextractable) in the absence of Rhizobium, and 2.33 mg Cdextractable kg−1 for Rhizobium-inoculated seedlings. Shoot N content was unaffected in white clover exposed to <5 mg Cdextractable kg−1. The results indicate symbiosis with Rhizobium strain TA1 conferred tolerance to white clover ‘Grasslands Tribute’ against Cd toxicity, and that this symbiosis is unlikely to be adversely affected by Cd concentrations reported (<0.003 mg Cdextractable kg−1) in New Zealand pasture soils.

Geophagus brasiliensis (Teleostei: Cichlidae) as an indicator of toxicity of ornamental stone processing wastes

Massive exploitation of geological resources may lead to environmental issues due to the inadequate disposal of the processing wastes, which are potentially hazard to terrestrial and aquatic environments. To evaluate the toxic effects ornamental stones processing wastes (OSPW), Geophagus brasiliensis fish were contaminated with different concentrations of OSPW (250, 500, 750 and 1000 mg/L). The contaminated aquarium water showed increased total hardness and Ca, Na, K, Mg and Mn content, which lead to bioconcentration of Na+, K+ and Mg2+ in G. brasiliensis gills. The highest concentration of OSPW induced slight to moderate histopathological lesions in gills of exposed fish, such as structural detachment, hyperplasia of the lamellar epithelium and incomplete fusion of several lamellae. Micronucleus and comet assays revealed a dose-dependent genotoxic damage in fish exposed to the contaminant. The biochemical analysis revealed a slight increase in catalase and reduction in superoxide dismutase activities in exposed fish, indicating that OSPW affects the oxidative stress of G. brasiliensis. The no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) parameters indicate that low concentrations of OSPW (even under 250 mg/L) may be detrimental to exposed organisms by causing oxidative damage. This study demonstrates the toxic potential of OSPW in G. brasiliensis, even in short-term exposure, revealing some morphologic and molecular parameters that may be used as biomarkers in monitoring aquatic ecosystems contaminated with this effluent.

Chronic effects of fire suppressors on the reproduction of the copepod Nitocra sp.

Fire suppressors are widely used in firefighting and their chemical composition may present a mixture of perfluorochlorinated surfactants (PFCs), including the perfluorooctane sulfonate (PFOS) which has been internationally banned due to its classification as a persistent organic pollutant (POP). PFCs have been found in environmental matrices and soft tissues of organisms, but the potential effect of such compounds on marine organisms has been overlooked. Here, it was evaluated whether the chronic exposures (i.e., seven days) to the fire suppressors Ageofoam, Cold Fire, Kidde and Argus could affect the reproduction of the copepod Nitocra sp. The tested concentrations consisted of those recommended on the products’ manuals and those ranging between 0.0001% and 1%. For each compound, the effective concentrations to 50% exposed organisms (EC50) and the lowest observed effect concentrations (LOEC) were estimated. All the fire suppressors exhibited high toxicity, causing fecundity reduction. At the recommended dilutions, 100% lethality occurred for all compounds. The EC50 values ranged from 0.00817% - Ageofoam - to 0.03081% - Argus. The LOECs ranged from 0.001% - Ageofoam - to 0.1% - Argus and Kidde; and were much lower than the concentrations recommended for commercial use. The fire suppressors showed high toxicity to the copepod, reducing the reproduction rates, even in very low concentrations, suggesting that the release of such substances in the estuary caused severe effects to the environment. This assessment provides subsides to the environmental regulation of fire suppressors in Brazil, because these compounds do not have national regulations for their use and disposal.

Assessment of fipronil toxicity to the freshwater midge Chironomus riparius: Molecular, biochemical, and organismal responses

Fipronil is a phenylpyrazole insecticide that entered the market to replace organochlorides and organophosphates. Fipronil impairs the regular inhibition of nerve impulses that ultimately result in paralysis and death of insects. Because of its use as a pest control, and due to runoff events, fipronil has been detected in freshwater systems near agricultural areas, and therefore might represent a threat to non-target aquatic organisms. In this study, the toxicity of fipronil to the freshwater midge Chironomus riparius was investigated at biochemical, molecular, and whole organism (e.g. growth, emergence, and behavior) levels.At the individual level, chronic (28 days) exposure to fipronil resulted in reduced larval growth and emergence with a lowest observed effect concentration (LOEC) of 0.081 μg L−1. Adult weight, which is directly linked to the flying performance and fecundity of midges, was also affected (LOEC = 0.040 μg L−1). Additionally, behavioral changes such as irregular burrowing behavior of C. riparius larvae (EC50 = 0.084 μg L−1) and impairment of adult flying performance were observed. At a biochemical level, acute (48 h) exposure to fipronil increased cellular oxygen consumption (as indicated by the increase of electron transport system (ETS) activity) and decreased antioxidant and detoxification defenses (as suggested by the decrease in catalase (CAT) and glutathione S-transferase (GST) activities). Exposure to fipronil also caused alterations in the fatty acid profile of C. riparius, since high levels of stearidonic acid (SDA) were observed. A comparison between exposed and non-exposed larvae also revealed alterations in the expression of globins, cytoskeleton and motor proteins, and proteins involved in protein biosynthesis. These alterations may aid in the interpretation of potential mechanisms of action that lead to the effects observed at the organism level.Present results show that environmentally relevant concentrations of fipronil are toxic to chironomid populations which call for monitoring of phenylpyrazole insecticides and of their ecological effects in freshwaters. Present results also emphasize the importance of complementing ecotoxicological data with molecular approaches such as proteomics, for a better interpretation of the mode of action of insecticides in aquatic invertebrates.

Lethal and sublethal toxicity assessment of Bacillus thuringiensis var. israelensis and Beauveria bassiana based bioinsecticides to the aquatic insect Chironomus riparius

Despite being considered environmentally safe, a deeper environmental risk assessment is needed for microbial insecticides; special attention should be devoted to their sublethal toxicity to non-target species.This study evaluated effects of VectoBac® 12AS - VB (based on the bacterium Bacillus thurigiensis var. israelensis) and Naturalis®-L - NL (based on the fungus Beauveria bassiana) on the aquatic insect Chironomus riparius life-history and biochemical responses.Acute tests estimated a 48 h-LC50 (median lethal concentration) of 1.85 μg/L (VB) and 34.7 mg/L (NL). Under sublethal exposure, VB decreased adults' emergence (LOEC – lowest observed effect concentration of 80 ng/L) while NL impaired larval growth (LOEC of 0.32 mg/L) and delayed emergence (LOEC of 2 mg/L for males and 0.8 mg/L for females). Despite not being monotonic, phenoloxidase activity increased (LOEC of 20 ng/L (VB) and 2 mg/L (NL)), suggesting activation of the immune system. There were no indications of oxidative damage nor neurotoxicity. Catalase activity was stimulated with all VB treatments, possibly associated with detoxification of immune response products. Under NL exposure, glutathione-S-transferase activity increased but did not show a dose-dependent response and, total glutathione decreased in the highest concentration. Exposure to both formulations caused the increase in protein content, while carbohydrate and lipids were not altered.This study revealed the susceptibility of C. riparius to VB and NL at concentrations below the ones recommended for field application, with potential population-level effects. These results add important information for the risk assessment of these microbial insecticides in aquatic ecosystems, considering relevant sublethal endpoints and raising concern about the adverse effects on non-target aquatic organisms.

Soil copper uptake by land snails: A semi-field experiment with juvenile Cantareus aspersus snails

There is currently limited scientific evidence linking soil copper and land snails, although these invertebrates are important players in terrestrial ecosystems. In the present study, Cantareus aspersus juveniles, were exposed in two successive phases of 30 days each, to soil spiked with increasing concentrations of copper sulfate. Copper concentrated preferentially and in a dose-dependent manner in the hepatopancreas. In the case of specimens previously exposed to Cu-spiked soils, Cu retention kinetics were independent from the effects of a new exposure event. There was no effect on shell growth, but significant mortality was observed at 60 days. The no observed effect concentration and the lowest observed effect concentration for mortality in snails, were ˜ 41 and 54 mg, respectively, per grams dry weight in the hepatopancreas. The results demonstrate, for the first time, that terrestrial gastropods can accumulate soil Cu autonomously from dietary uptake.

Toxicity and Subcellular Fractionation of Yttrium in Three Freshwater Organisms: Daphnia magna, Chironomus riparius, and Oncorhynchus mykiss.

The demand for rare earth elements (REEs) has increased since the 1990s leading to the development of many mining projects worldwide. However, less is known about how organisms can handle these metals in natural aquatic systems. Through laboratory experiments, we assessed the chronic toxicity and subcellular fractionation of yttrium (Y), one of the four most abundant REEs, in three freshwater organisms commonly used in aquatic toxicology: Daphnia magna, Chironomus riparius, and Oncorhynchus mykiss. In bioassays using growth as an end point, C. riparius was the only organism showing toxicity at Y exposure concentrations close to environmental ones. The lowest observable effect concentrations (LOECs) of Y assessed for D. magna and O. mykiss were at least 100 times higher than the Y concentration in natural freshwater. A negative correlation between Y toxicity and water hardness was observed for D. magna. When exposed to their respective estimated LOECs, D. magna bioaccumulated 15–45 times more Y than the other two organisms exposed to their own LOECs. This former species sequestered up to 75% of Y in the NaOH-resistant fraction, a putative metal-detoxified subcellular fraction. To a lesser extent, C. riparius bioaccumulated 20–30% of Y in this detoxified fraction. In contrast, the Y subcellular distribution in O. mykiss liver did not highlight any notable detoxification strategy; Y was accumulated primarily in mitochondria (ca. 32%), a putative metal-sensitive fraction. This fraction was also the main sensitive fraction where Y accumulated in C. riparius and D. magna. Hence, the interaction of Y with mitochondria could explain its toxicity. In conclusion, there is a wide range of subcellular handling strategies for Y, with D. magna accumulating high quantities but sequestering most of it in detoxified fractions, whereas O. mykiss tending to accumulate less Y but in highly sensitive fractions.

Behavioral effects of citalopram, tramadol, and binary mixture in zebrafish (Danio rerio) larvae

Pharmaceuticals are emerging as environmentally problematic compounds. As they are often not appropriately removed by sewage treatment plants, pharmaceutical compounds end up in surface water environments worldwide at concentrations in the ng to μg L−1 range. There is a need to further explore single compound and mixture effects using e.g. in vivo test model systems. We have investigated, for the first time, behavioral effects in larval zebrafish (Danio rerio) exposed to a binary mixture of an antidepressant drug (citalopram) and a synthetic opioid (tramadol). Citalopram and tramadol have a similar mode of action (serotonin reuptake inhibition) and are known to produce drug-drug interactional effects resulting in serotonin syndrome (SS) in humans. Zebrafish embryo-larvae were exposed to citalopram, tramadol and 1:1 binary mixture from fertilization until 144 h post-fertilization. No effects on heart rate, spontaneous tail coiling, or death/malformations were observed in any treatment at tested concentrations. Behavior (hypoactivity in dark periods) was on the other hand affected, with lowest observed effect concentrations (LOECs) of 373 μg L−1 for citalopram, 320 μg L−1 for tramadol, and 473 μg L−1 for the 1:1 mixture. Behavioral EC50 was calculated to be 471 μg L−1 for citalopram, 411 μg L−1 for tramadol, and 713 μg L−1 for the 1:1 mixture. The results of this study conclude that tramadol and citalopram produce hypoactivity in 144 hpf zebrafish larvae. Further, a 1:1 binary mixture of the two caused the same response, albeit at a higher concentration, possibly due to SS.