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  • Variation in Metal Tolerance Associated with Population Exposure History in Southern Toads (Anaxyrus terrestris)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-12-13
    R. Wesley Flynn, Cara N. Love, Austin Coleman, Stacey L. Lance

    Human activities have radically shaped the global landscape, affecting the structure and function of ecosystems. Habitat loss is one of the most visible changes to the landscape and a primary driver of species declines; however, anthropogenic environmental contamination also threatens population persistence, but is not as readily observed. Aquatic organisms are especially susceptible to chemical perturbations, which can negatively impact survival and fitness related traits. Some populations have evolved tolerance to chemical stressors, which could mitigate the consequences associated with contamination. Amphibians are experiencing global declines due to multiple stressors and are particularly at risk to aquatic chemical stressors due to their permeable skin and reliance on wetlands for reproduction and larval development. However, amphibians also have substantial plasticity in response to environmental variation. We designed our study to examine whether tolerance to heavy metals is greater in Southern toad (Anaxyrus terrestris) larvae from wetlands with a history of contamination. Considering many of the most common trace elements elicit acute toxicity by disrupting osmotic- and ionic-regulation, we hypothesized that alterations to these aspects of physiology resulting from multigenerational exposure to trace element mixtures would be the most likely routes by which tolerance would evolve. We used copper (Cu) as a proxy for heavy metal exposure because it is a widely distributed aquatic stressor known to cause osmotic stress that can also cause mortality at levels commonly encountered in the environment. We found considerable within and among population variation in Cu tolerance, as measured by time to death. Larvae from populations living in sites contaminated with mixtures of heavy metals associated with coal fly ash were no more tolerant to Cu than those from reference sites. However, larvae from a population inhabiting a constructed wetland complex with high Cu levels were significantly more tolerant; having half the risk of mortality as reference animals. This wetland complex was created < 20 years ago, thus if elevated Cu tolerance in this population is due to selection in the aquatic habitat, such adaptation may occur rapidly (i.e. ~10 generation). Our results provide evidence that amphibians may be able to evolve tolerance in response to trace element contamination, though such tolerance may be specific to the combination of contaminants present.

  • Predicting cadmium toxicity with the kinetics of phytochelatin induction in a marine diatom
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-12-11
    Yun Wu, Yue Yuan, Hezhong Yuan, Wei Zhang, Li Zhang

    Phytochelatin (PC) synthesis is thought to be a rapid and specific response to metal exposure in marine phytoplankton, but its potential as a predictor of metal toxicity is far from conclusive. Thus this research examines the bioaccumulation, PC induction, and toxicity of Cadmium (Cd) in Thalassiosira weissflogii, a coastal diatom under varying nutrient conditions. Nitrogen limitation strongly inhibited Cd uptake and PC induction at the same [Cd2+] level, and increased metal sensitivity. Conversely, phosphorus limitation had little influence on Cd accumulation and PC induction, yet also enhanced metal effect on growth. Differential growth inhibitions were correlated with [Cd2+], intracellular Cd concentration, PC concentration, the kinetics of Cd uptake and PC induction, respectively. It was found that stronger interrelations existed between kinetic rates (both Cd uptake and PC synthesis) and Cd sensitivity than between the static concentrations (Cd and PC) and growth inhibition. Moreover, according to the calculated median inhibition concentration (IC50), median effective uptake rate of Cd, as well as median effective induction rate of PCs, the latter two showed the smallest variation when nutrients were varied (1.4–1.9 fold). Our study set out the first step toward considering the use of PC synthesis kinetics to predict metal toxicity for phytoplankton.

  • Transcriptional and physiological responses of Dunaliella salina to cadmium reveals time-dependent turnover of ribosome, photosystem, and ROS-scavenging pathways
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-12-07
    Qing-Ling Zhu, Sai-Nan Guo, Fang Wen, Xiao-Lin Zhang, Cheng-Cheng Wang, Lan-Fang Si, Jia-Lang Zheng, Jianhua Liu

    Effects on short-term (6 h) and long-term (96 h) exposure to cadmium (Cd) at 0.1, 0.5 and 2.5 mg/L in microalga Dunaliella salina were assessed using both physiological end points and gene expression analysis. Different physiological responses between the short-term and long-term exposures were observed. Upon 6 h after Cd exposure, lipid peroxidation and cell ultrastructure remained unchanged, while contents of chlorophyll a, chlorophyll b, carotenoids were increased at 0.5 and 2.5 mg/L Cd. Contrarily, 96 h after Cd exposure, lipid peroxidation levels were increased, while pigments content was decreased, and damaged cell ultrastructure was apparent at 2.5 mg/L Cd. Activities of antioxidant enzymes (APX, SOD, GST, GPX, and GR) changed differently both at 6 h and 96 h after Cd exposure. Upon 6 h after Cd exposure, SOD and GST activity increased at all three doses, GR and GPX activity increased at 0.5 mg/L Cd while APX activity increased at 0.1 mg/L Cd. Contrarily, 96 h after Cd exposure, activities of all the antioxidant enzymes increased both at 0.1 and 0.5 mg/L Cd; but there was a decrease in SOD and GR activity in D. salina exposed to 2.5 mg/L Cd. RNA-seq and qRT-PCR analyses indicated that genes involved in ROS-scavenge, photosystem, and ribosome functions were differentially expressed. The most significantly enriched function was the ribosome, in which more than 30 ribosome genes were up-regulated at 6 h but down-regulated at 96 h after Cd exposure at 2.5 mg/L. Our study indicated for the first time that genes encoding ribosomal proteins are the primary target for Cd in microalgae, which allowed gaining new insights into temporal dynamics of toxicity and adaptive response pathways in microalgae exposed to metals.

  • Oxidative damage induced by copper in testis of the red swamp crayfish Procambarus clarkii and its underlying mechanisms
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-12-06
    Dan Zhao, Xiaona Zhang, Xuefu Li, Shaoguo Ru, Yanwen Wang, Jinbin Yin, Dasheng Liu

    Copper (Cu) is one of the most widespread environmental pollutants and is known to exert multiple toxic effects including reproductive toxicity. In this study, we investigated the toxic effect of Cu on reproduction of the red swamp crayfish (Procambarus clarkii), an economic crustacean species, by exposing adult male crayfish to 0.03 and 3.00 mg/L Cu2+ for 7 days. The results showed that Cu2+ exposure induced oxidative stress accompanied by elevated reactive oxygen species (ROS) and malondialdehyde (MDA) levels in testes, and resulted in decreased sperm quality and abnormal testicular structures with apoptotic germ cells and vacuolisation in Sertoli cells. To reveal the molecular mechanism of Cu2+-induced oxidative damage in crayfish testes, we sequenced, assembled and annotated the transcriptome for crayfish testes, using the Illumina sequencing approach. After the 3.00 mg/L Cu2+ treatment, 6,745 genes with differentially expressed profile were identified, of which many genes were involved in cellular response to ROS based on Gene Ontology enrichment analysis. Further, KEGG analysis demonstrated that genes with up-regulated expression levels significantly enriched in mitochondria oxidative phosphorylation pathway, suggesting disturbed mitochondrial electron transport chain was probably a main source of Cu2+-induced ROS production in testes. This study represented the first use of transcriptome to investigate the toxic effect of Cu2+ on male crayfish reproduction, and the pathways identified underlying Cu2+ toxicity at molecular level provide a novel insight into the reproductive toxicity of Cu in crustaceans.

  • QSAR for baseline toxicity and classification of specific modes of action of ionizable organic chemicals in the zebrafish embryo toxicity test
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-12-05
    Nils Klüver, Kai Bittermann, Beate I. Escher

    The fish embryo toxicity (FET) test with the zebrafish Danio rerio is widely used to assess the acute toxicity of chemicals thereby serving as animal alternative to the acute fish toxicity test. The minimal toxicity of neutral chemicals in the FET can be predicted with a previously published Quantitative Structure-Activity Relationship (QSAR) based on the liposome-water partition coefficient Klipw. Such a QSAR may serve to plan toxicity testing and to evaluate whether an observed effect is caused by a specific mode of action (MoA). The applicability domain of this QSAR was extended to ionizable organic chemicals (IOC) without any modification of slope and intercept simply by replacing the Klipw with the speciation-corrected liposome-water distribution ratio (Dlipw(pH)) as descriptor for the uptake into the embryo. FET LC50 values of IOCs were extracted from an existing FET database and published literature. IOCs were selected that are present concomitantly as neutral and charged, species, i.e., acids with an acidity constant pKa <10 and bases with pKa >5. IOCs were grouped according to their putative MoA of acute aquatic toxicity. The toxic ratios (TR) in the FET were derived by of the experimental FET-LC50 in comparison with the baseline toxicity QSAR. Baseline toxicants were confirmed to align well with the FET baseline toxicity QSAR (TR < 10). Chemicals identified to act as specific or reactive chemicals with the toxic ratio analysis in the FET test (TR > 10) were generally consistent with MoA classification for acute fish toxicity with a few exceptions that were suspected to have had issues with the stability of the pH during testing. One critical aspect for the effect analysis of ionizable chemicals is the pH, since the difference between pH and pKa determines the speciation and thereby the Dlipw(pH).

  • In vivo effects of serotonin and fluoxetine on cardio-ventilatory functions in the shore crab Carcinus maenas (L. 1758)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-12-05
    Alexandrine Robert, Tiphaine Monsinjon, Romain Péden, Virginie Rasoamampianina, Jean-Claude Le Mével, Thomas Knigge

    Serotonin (5-HT) takes a key position in regulating vital functions, such as cardio-ventilatory activity, locomotion and behaviour. Selective serotonin reuptake inhibitors (SSRIs) modulate the serotonergic system and thus affect these functions. Rhythmic behaviours, such as cardio-ventilatory activity, are controlled by central pattern generators, which in turn are regulated by 5-HT. In crustaceans, 5-HT also regulates the synthesis and secretion of crustacean hyperglycaemic hormone, a pleiotropic hormone involved in the mobilisation and release of glucose into the haemolymph, thus stimulating the animal’s activity. As a matter of consequence, SSRIs may affect cardio-ventilatory activity. In order to examine how the SSRIs affect fundamental physiological parameters based on rhythmic behaviour in decapods, cardio-respiratory activity in the shore crab Carcinus maenas was assessed after pericardial injection of a single dose of either 0.5 μM, 0.75 μM or 1 µM fluoxetine, respectively. Simultaneous recordings of heart and scaphognathite movements in both brachial chambers were conducted by measuring impedance changes in the respective body compartments. Injection of 5-HT had an immediate effect on cardio-ventilatory activities and strongly upregulated both cardiac and ventilatory activities. Fluoxetine showed similar effects, entailing moderate tachycardia and increased ventilation rates. Compared to 5-HT, these effects were delayed in time and much less pronounced. Metabolism of fluoxetine into the active compound nor-fluoxetine might account for the delayed action, whereas compensatory regulation of cardio-ventilatory frequencies and amplitudes are likely to explain the attenuation of the responses compared to the strong and immediate increase by 5-HT. Overall, the results suggest increased 5-HT levels in invertebrates following fluoxetine exposure, which are able to disturb physiological functions regulated by 5-HT, such as cardiac and respiratory activity.

  • Excess copper promotes photoinhibition and modulates the expression of antioxidant-related genes in Zostera muelleri
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-12-05
    Pimchanok Buapet, Nasim Shah Mohammadi, Mathieu Pernice, Manoj Kumar, Unnikrishnan Kuzhiumparambil, Peter J. Ralph

    Copper (Cu) is an essential micronutrient for plants and as such is vital to many metabolic processes. Nevertheless, when present at elevated concentrations, Cu can exert toxic effects on plants by disrupting protein functions and promoting oxidative stress. Due to their proximity to the urbanised estuaries, seagrasses are vulnerable to chemical contamination via industrial runoff, waste discharges and leachates. Zostera muelleri is a common seagrass species that forms habitats in the intertidal areas along the temperate coast of Australia. Previous studies have shown the detrimental effects of Cu exposure on photosynthetic efficiency of Z. muelleri. The present study focuses on the impacts of sublethal Cu exposure on the physiological and molecular responses. By means of a single addition, plants were exposed to 250 and 500 µg Cu L-1 (corresponding to 3.9 and 7.8 µM, respectively) as well as uncontaminated artificial seawater (control) for 7 days. Chlorophyll fluorescence parameters, measured as the effective quantum yield ( φ PSII), the maximum quantum yield (Fv/Fm) and non-photochemical quenching (NPQ) were assessed daily, while Cu accumulation in leaf tissue, total reactive oxygen species (ROS) and the expression of genes involved in antioxidant activities and trace metal binding were determined after 1, 3 and 7 days of exposure. Z. muelleri accumulated Cu in the leaf tissue in a concentration-dependent manner and the bioaccumulation was saturated by day 3. Cu exposure resulted in an acute suppression of φ PSII and Fv/Fm. These two parameters also showed a concentration- and time-dependent decline. NPQ increased sharply during the first few days before subsequently decreasing towards the end of the experiment. Cu accumulation induced oxidative stress in Z. muelleri as an elevated level of ROS was detected on day 7. Lower Cu concentration promoted an up-regulation of genes encoding Cu/Zn-superoxide dismutase (Cu/Zn-sod), ascorbate peroxidase (apx), catalase (cat) and glutathione peroxidase (gpx), whereas no significant change was detected with higher Cu concentration. Exposure to Cu at any concentration failed to induce regulation in the expression level of genes encoding metallothionein type 2 (mt2), metallothionein type 3 (mt3) and cytochrome c oxidase copper chaperone (cox17). It is concluded that chlorophyll fluorescence parameters provide timely probe of the status of photosynthetic machinery under Cu stress. In addition, when exposed to a moderate level of Cu, Z. muelleri mitigates any induced oxidative stress by up-regulating transcripts coding for antioxidant enzymes.

  • Immunotoxic effects of 4-nonylphenol on Clarias gariepinus: cytopathological changes in hepatic melanomacrophages
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-12-03
    Alaa El-Din H. Sayed, Mahmoud Abd-Elkareem, Nasser S. Abou Khalil

    Melanomacrophage centres (MMCs) play a key role in the immune response in fish. They are considered sensitive bio-monitoring structures with roles in the assessment of toxicant impacts. The aim of this study was to examine the potential histopathological effect of 4-nonylphenol (4-NP) on hepatic MMCs in Clarias gariepinus. To achieve this objective, adult male fish were divided randomly and equally into two groups: a control group and a group that was exposed to 4-NP (dissolved in water at a dose of 0.1 mg/L) for 21 days. The 4-NP-intoxicated hepatic MMCs contained numerous necrotic macrophages. Superoxide dismutase 2 was immuno-expressed in the hepatic MMCs in both groups, with no significant difference. Histomorphometric examination revealed that the sizes and numbers of MMCs were dramatically higher in the livers of 4-NP-exposed C. gariepinus than in control fish. Following 4-NP challenge, in the liver, the abundance of lipofuscin and haemosiderin pigments increased, and single-pigmented macrophages, aggregated groups of deformed red blood cells (RBCs) and macrophages were present near blood vessels and hepatic sinusoids. These results reveal that 4-NP exerts immunological effects on hepatic MMCs in C. gariepinus and support the utility of MMCs as a cytological biomarker for aquatic exposure to 4-NP.

  • Investigating tissue bioconcentration and the behavioural effects of two pharmaceutical pollutants on sea trout (Salmo trutta) in the laboratory and field
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-12-01
    Erin S. McCallum, Anna Sundelin, Jerker Fick, Anders Alanärä, Jonatan Klaminder, Gustav Hellström, Tomas Brodin

    Pharmaceuticals entering aquatic ecosystems via wastewater effluents are of increasing concern for wild animals. Because some pharmaceuticals are designed to modulate human behaviour, measuring the impacts of exposure to pharmaceuticals on fish behaviour has become a valuable endpoint. While laboratory studies have shown that pharmaceuticals can affect fish behaviour, there is a lack of understanding if behaviour is similarly affected in natural environments. Here, we exposed sea trout (Salmo trutta) smolts to two concentrations of two pharmaceutical pollutants often detected in surface waters: temazepam (a benzodiazepine, anxiolytic) or irbesartan (an angiotensin II receptor blocker, anti-hypertensive). We tested the hypothesis that changes to behavioural traits (anxiety and activity) measured in laboratory trials following exposure are predictive of behaviour in the natural environment (downstream migration). Measures of anxiety and activity in the laboratory assay did not vary with temazepam treatment, but temazepam-exposed fish began migrating faster in the field. Activity in the laboratory assay did predict overall migration speed in the field. In contrast to temazepam, we found that irbesartan exposure did not affect behaviour in the laboratory, field, or the relationship between the two endpoints. However, irbesartan was also not readily taken up into fish tissues (i.e. below detection levels in the muscle tissue), while temazepam bioconcentrated (bioconcentration factor 7.68) rapidly (t1/2 < 24 h). Our findings add to a growing literature showing that benzodiazepine pollutants can modulate fish behaviour and that laboratory assays may be less sensitive at detecting the effects of pollutants compared to measuring effects in natural settings. Therefore, we underscore the importance of measuring behavioural effects in the natural environment.

  • Physiological insights into largemouth bass (Micropterus salmoides) survival during long-term exposure to high environmental ammonia
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-30
    Nathan Egnew, Nilima Renukdas, Yathish Ramena, Amit K. Yadav, Anita M. Kelly, Rebecca T. Lochmann, Amit Kumar Sinha

    Waterborne ammonia is an environmental pollutant that is toxic to all aquatic animals. However, ammonia induced toxicity as well as compensatory mechanisms to defend against high environmental ammonia (HEA) are not well documented at present for largemouth bass (Micropterus salmoides), a high value fish for culture and sport fisheries in the United States. To provide primary information on the sensitivity of this species to ammonia toxicity, a 96 h-LC50 test was conducted. Thereafter, responses at physiological, ion-regulatory and transcript levels were determined to get insights into the underlying adaptive strategies to ammonia toxicity. For this purpose, fish were progressively exposed to HEA (8.31 mg/L representing 25% of 96 h-LC50) for 3, 7, 14, 21 and 28 days. Temporal effects of HEA on oxygen consumption rate (MO2), ammonia and urea dynamics, plasma ions (Na+, Cl− and K+), branchial Na+/K+-ATPase (NKA) and H+-ATPase activity, muscle water content (MWC), energy store (glycogen, lipid and protein) as well as branchial mRNA expression of Rhesus (Rh) glycoproteins were assessed. Probit analysis showed that 96 h-LC50 of (total) ammonia (as NH4HCO3) at 25 °C and pH 7.8 was 33.24 mg/L. Results from sub-lethal end-points shows that ammonia excretion rate (Jamm) was strongly inhibited after 7 days of HEA, but was unaffected at 3, 14 and 21 days. At 28 days fish were able to increase Jamm efficiently and concurrently, plasma ammonia re-established to the basal level. Urea production was increased as evidenced by a considerable elevation of plasma urea, but urea excretion rate remained unaltered. Expression of Rhcg isoform (Rhcg2) mRNA was up-regulated in parallel with restored or increased Jamm, suggesting its ammonia excreting role in largemouth bass. Exposure to HEA also displayed pronounced augmentations in NKA activity, exemplified by a rise in plasma [Na+]. Furthermore, [K+], [Cl−] and MWC homeostasis were disrupted followed by recovery to the control levels. H+-ATPase activity was elevated but NKA did not appear to function preferentially as a Na+/NH4+-ATPase. From 14 days onwards MO2 was depressed, potentially an attempt towards minimizing catabolism. Glycogen content in liver and muscle were temporarily depleted, whereas a remarkable increment in protein was evident at the last exposure period. Overall, these data suggest that ammonia induced toxicity can disturb several biological processes in largemouth bass, however, it can adapt to the long-term sub-lethal ammonia concentrations by activating various components of ammonia excretory, ion-regulatory and metabolic pathways.

  • The responses of Oncorhynchus mykiss coping with BDE-47 stress via PXR-mediated detoxification and Nrf2-mediated antioxidation system
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-30
    Chunchen Liu, Boyuan Wang, Bin Zhou, Xiaoyang Jian, Xinxin Zhang, You Wang

    The low brominated polybrominated diphenyl ether (PBDE) 2,2’,4,4’-tetrabromodiphenyl ether (BDE-47) is ubiquitous in the marine environment. To elucidate the stress response and possible mechanisms underlying BDE-47, the rainbow trout fish Oncorhynchus mykiss were selected and orally fed bait with BDE-47 concentrations of 50 ng/g and 500 ng/g. BDE-47 was found to be mainly accumulated in head kidney and caused lipid peroxidation after prolonged exposure. We studied the detoxification system genes pregnane X receptor (PXR) and downstream genes (cytochrome 3 A, CYP3 A; glutathione S-transferase, GST) and their corresponding enzyme activity and found that the above indicators in the treatment groups increased first and then decreased with time, while the 500 ng/g group showed more significant changes. Further, the antioxidant system gene expression levels of the NF-E2-related factor 2 (Nrf2) and downstream genes (superoxide dismutase, SOD; catalase, CAT) were found significantly up-regulated with concentration and time. The change in the enzyme activity of SOD and CAT showed the same tendency as that of indicators of detoxifying system. The results showed that BDE-47 can accumulated in head kidney and caused activate and fast increase of genes and enzymes of detoxification and antioxidant system in the short-term and then damage the response systems in longer times. After Pearson correlation analysis, the Integrated Biomarker Response (IBR) Index was established with malondialdehyde (MDA) content; PXR, Nrf2, SOD, and CAT gene expression; and CYP3 A, GST, and CAT enzymatic activity, which were significantly related to BDE-47 bioaccumulation (P < 0.5). The IBR value can indicate the ecotoxicological responses of the head kidney to different BDE-47 concentrations exposure, but the high activity of the antioxidant system might obscure the damage of the detoxification system.

  • Behavioral Consequences of Dietary Exposure to Crude Oil Extracts in the Siamese Fighting Fish (Betta splendens)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-29
    Naim M. Bautista, Tanushri Pothini, Kelly Meng, Warren W. Burggren

    Uptake by fishes of crude oil and its polycyclic aromatic hydrocarbons (PAHs) components occurs via gills, dietary intake, or diffusion through the skin. Dietary exposure to crude oil and its components is environmentally relevant, and induces physiological and morphological disruptions in fish. However, the impacts of crude oil on fish social and reproductive behaviors and thus the possible influences on reproductive success are poorly understood. As a part of their intraspecific interactions, male Siamese fighting fish (Betta splendens) exhibit highly stereotypic behavioral and territorial displays. This makes this species a tractable model for testing crude oil effects on behavior. After 2 weeks of acclimation at 29 °C, male adult betta fish were divided into three groups and fed for 4 weeks with food spiked with water (control), low oil concentrations or high oil concentrations (∑Total PAH concentrations 340, 3960 or 8820 ng/g dw, respectively) to determine subsequent alterations in behavioral displays. Compared with control fish, the aggressive display of “opercular flaring” was significantly increased (P < 0.03, n = 14-16) in oil-exposed fish. Bubble nest building, as well as testis and brain mass, were significantly reduced in treated fish (P < 0.05). Hematocrit of treated groups was increased significantly (P < 0.02) from 21% in control fish to ~27% in both oil exposure groups. Dietary exposure over a 4-week period to low, relevant levels of crude oil thus leads to an increase in aggressive behavioral displays, a decrease in reproductive activity and additional morphological changes.

  • Altered non-reproductive behavior and feminization caused by developmental exposure to 17α-ethinylestradiol persist to adulthood in three-spined stickleback (Gasterosteus aculeatus)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-28
    Tove Porseryd, Josefine Larsson, Martin Kellner, Tomas Bollner, Patrik Dinnétz, Inger Porsch Hällström

    The synthetic estrogen 17α-ethinylestradiol (EE2), ubiquitous in the aquatic environment and commonly detected in sewage effluents, interferes with the endocrine system in multiple ways. Exposure during sensitive windows of development causes persistent effects on fertility, reproductive and non-reproductive behavior in mammals and fish. In the present study, three-spined stickleback (Gasterosteus aculeatus) were exposed to nominal 0 and 20 ng/L EE2 from fertilization to 7 weeks post-hatch. After 8 months of remediation in clean water three non-reproductive behaviors, not previously analyzed in developmentally EE2-exposed progeny of wild-caught fish, were evaluated. Chemical analysis revealed that the nominal 0 and 20 ng/L exposure contained 5 and 30 ng/L EE2, respectively. Therefore, the use of control fish from previous experiments was necessary for comparisons. Fish exposed during development showed significant concentration-dependent reduction in anxiety-like behavior in the scototaxis (light/dark preference) test by means of shorter latency to first entrance to the white compartment, more visits in white, and longer total time in white compared to unexposed fish. In the novel tank test, developmental exposure significantly increased the number of transitions to the upper half of the aquaria. Exposure to EE2 during development did not alter shoal cohesion in the shoaling test compared with unexposed fish but fish exposed to 30 ng/L EE2 had significantly longer latency to leave the shoal and fewer transitions away from the shoal compared to fish exposed to 5 ng/L EE2. Skewed sex ratio with more females, sex reversal in genetic males as well as intersex in males was observed after exposure to 30, but not 5 ng/L EE2. In conclusion, EE2 exposure during development in three-spined stickleback resulted in persistent effects on anxiety-like behaviors. These long-term effects from developmental exposure are likely to be of higher relevance for natural populations than are short-term effects from adult exposure.

  • Investigating a Transcriptomic Approach on Marine Mussel Hemocytes Exposed to Carbon Nanofibers: an in vitro/in vivo Comparison
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-27
    Andrew Barrick, Nicolas Manier, Pierre Lonchambon, Emmanuel Flahaut, Nisrine Jrad, Catherine Mouneyrac, Amélie Châtel

    Manufactured nanomaterials are an ideal test case of the precautionary principle due to their novelty and potential environmental release. In the context of regulation, it is difficult to implement for manufactured nanomaterials as current testing paradigms identify risk late into the production process, slowing down innovation and increasing costs. One proposed concept, namely safe(r)-by-design, is to incorporate risk and hazard assessment into the design process of novel manufactured nanomaterials by identifying risks early. When investigating the manufacturing process for nanomaterials, differences between products will be very similar along key physicochemical properties and biological endpoints at the individual level may not be sensitive enough to detect differences whereas lower levels of biological organization may be able to detect these variations. In this sense, the present study used a transcriptomic approach on Mytilus edulis hemocytes following an in vitro and in vivo exposure to three carbon nanofibers created using different production methods. Integrative modeling was used to identify if gene expression could be in linked to physicochemical features. The results suggested that gene expression was more strongly associated with the carbon structure of the nanofibers than chemical purity. With respect to the in vitro/in vivo relationship, results suggested an inverse relationship in how the physicochemical impact gene expression.

  • Physiological and biochemical effect of silver on the aquatic plant Lemna gibba L.: evaluation of commercially available product containing colloidal silver
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-27
    Martina Varga, Janja Horvatić, Lara Barišić, Zdenko Lončarić, Maja Dutour Sikirić, Ina Erceg, Aleksandra Kočić, Ivna Štolfa Čamagajevac

    This paper aims to evaluate the effects of a product containing colloidal silver in the aquatic environment, using duckweed Lemna gibba as a model plant. Therefore, growth parameters, photosynthetic pigments content and protein content as physiological indices were evaluated. Changes in the content of non-enzymatic antioxidants and activity of several antioxidant enzymes, alongside with the accumulation of hydrogen peroxide and lipid peroxidation end-products were assessed to explore the potential of colloidal silver to induce oxidative stress. The commercially available colloidal silver product contained a primary soluble form of silver. The treatment with colloidal silver resulted in significant physiological and biochemical changes in L. gibba plants and a consequent reduction of growth. Accumulation of silver caused altered nutrient balance in the plants as well as a significant decrease in photosynthetic pigments content and protein concentration. The antioxidative response of L. gibba plants to treatment with colloidal silver was inadequate to protect the plants from oxidative stress caused by metal accumulation. Silver caused concentration-dependent and time-dependent hydrogen peroxide accumulation as well as the elevation of lipid peroxidation levels in L. gibba plants. The use of commercially available products containing colloidal silver, and consequent accumulation of silver, both ionic and nanoparticle form in the environment, represents a potential source of toxicity to primary producers in the aquatic ecosystem.

  • Primary green turtle (Chelonia mydas) skin fibroblasts as an in vitro model for assessing genotoxicity and oxidative stress
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-26
    Kimberly A. Finlayson, Frederic D.L. Leusch, Jason P. van de Merwe

    Little is known about the effects of contaminants that accumulate in sea turtles. When in vivo exposure studies have ethical and logistical barriers, as is the case with sea turtles, in vitro tools can provide important information on the effects of contaminants. Several in vitro studies have assessed cytotoxicity of contaminants to sea turtles cells, however to gain a more refined mechanistic understanding of the effects of contaminants, sub-lethal effects also require investigation. Considering the complex mixture of contaminants that sea turtles are potentially exposed to, high throughput testing methods are necessary so that a large number of contaminants (and mixtures) can be rapidly tested. This study examined oxidative stress (reactive oxygen species production) and genotoxicity (micronucleus formation) in primary green turtle skin fibroblasts in response to 16 organic and inorganic contaminants found in coastal environments. Significant induction of oxidative stress was found with Cu, Co, Cr, and Hg. Significant effects on genotoxicity were found with Cu, Co, Cr, Hg, Pb and metolachlor. Effect concentrations from the bioassays were used in a simple risk assessment of turtles worldwide using accumulation values from the literature to identify populations at risk. Cu, Co, Cr and Hg were identified as posing the biggest threat to sea turtles. This study demonstrated the validity of using primary turtle cell cultures in the assessment of risk associated with a large number of contaminants using a high-throughput toxicity testing format.

  • Individual variation in aquatic toxicology: not only unwanted noise
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-26
    Mikko Nikinmaa, Katja Anttila

    The mean value of any parameter and its changes are usually discussed, when ecotoxicological studies are carried out. However, also the variation of any parameter and its changes can be important components of the responses to environmental contamination. Although the homogeneity of variances is commonly tested, testing is done for the use of correct statistical methods, not because of exploring the possibility that variability and its changes could be important components of environmental responses. We evaluated recent aquatic toxicological literature and found that in the majority of articles indicating that homogeneity of variances was tested and giving the result of testing, the assumption of homogeneity was not fulfilled. Further, it was observed that in some studies experimental treatment clearly affected the variability. In this commentary we discuss the reasons for variability: measurement errors, experimental design, genetic heterogeneity and phenotypic plasticity, and conclude that even after accounting for experimental design and genetic makeup significant variability remains. This plasticity may change in environmental responses as suggested by a hypothetical example, and as confirmed by experimental data. As a consequence, the changes of variability can be significant, even when the means do not differ. Because of this, variability and its changes should always be analysed and reported. This will be easy, since the datasets are exactly the same for comparing the variances and means, and as normally variances are tested for homogeneity. It is likely that much new information about the responses of organisms to environmental contamination will be obtained. However, the present journal practices tend to discourage one from concentrating on anything but the mean. In contrast, we think it is imperative that variability is always included as an endpoint in data analysis in the future.

  • Estrogenic activity of multicyclic aromatic hydrocarbons in rainbow trout (Oncorhynchus mykiss) in vitro assays
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-26
    Richard C. Kolanczyk, Jeffrey S. Denny, Barbara R. Sheedy, Patricia K. Schmieder, Mark A. Tapper

    A representative group of multicyclic aromatic hydrocarbons (MAHC) which can be further classified as bridged-ring (bridged-MAHC) or fused-ring (fused-MAHC) were examined for their ability to interact with the estrogen receptor of rainbow trout (rtER) in a hepatic cytosolic estrogen receptor competitive binding assay (cyto rtERαβ) and the vitellogenin (Vtg) mRNA gene activation liver slice assay. All five fused-MAHCs; naphthalene (NAFT), fluorene (FE), Fluoranthene (FAT), pyrene (PY), and 9,10-dihydroanthracene (DAC) had no estrogenic activity in the in vitro assays used. Five of the eight bridged-MAHCs; triphenylethylene (3PE), o-terphenyl (OTP), triphenylmethane (TPM), 1,1-diphenylethylene (DPE), and cis-stilbene (CSB) were positive in the rtER-binding assay. The additional three bridged-MAHC’s; trans-stilbene (TSB), tetraphenylethylene (4PE), and 4,4-di-tertbutylphenyl (DtBB) were determined to be non-binders due to isomeric configuration, solubility limitation, and possible steric hinderance. It is possible that the bridged-MAHCs bind to the rtER through a proposed aromatic-aromatic stacking (π-π interaction) facilitated by perpendicular ring orientation achieved through free rotation of the bridged rings. The fused-ring structures are locked in a planar configuration which doesn’t allow for rotation of rings perpendicular to one another. This first report of the rtER-binding of bridged-MAHCs in fish demonstrates binding for a class of chemicals normally not thought of as having an affinity for the estrogen receptor and further supports the versatility or promiscuity of ER ligand selectivity.

  • Neurotoxicological effects induced by up-regulation of miR-137 following triclosan exposure to zebrafish (Danio rerio)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-22
    Jinfeng Liu, Chenyan Xiang, Wenhao Huang, Jingyi Mei, Limei Sun, Yuhang Ling, Caihong Wang, Xuedong Wang, Randy A. Dahlgren, Huili Wang

    Triclosan (TCS) is a prevalent anthropogenic contaminant in aquatic environments and its chronic exposure can lead to a series of neurotoxic effects in zebrafish. Both qRT-PCR and W-ISH identified that TCS exposure resulted in significant up-regulation of miR-137, but downregulation of its regulatory genes (bcl11aa, MAPK6 and Runx1). These target genes are mainly associated with neurodevelopment and the MAPK signaling pathway, and showed especially high expression in the brain. After overexpression or knockdown treatments by manual intervention of miR-137, a series of abnormalities were induced, such as ventricular abnormality, bent spine, yolk cyst, closure of swim sac and venous sinus hemorrhage. The most sensitive larval toxicological endpoint from intervened miR-137 expression was impairment of the central nervous system (CNS), ventricular abnormalities and notochord curvature. Microinjection of microRNA mimics or inhibitors of miR-137 both caused zebrafish malformations. The posterior lateral line neuromasts became obscured and decreased in number in intervened miR-137 groups and TCS-exposure groups. Up-regulation of miR-137 led to more severe neurotoxic effects than its down-regulation. Behavioral observations demonstrated that both TCS exposure and miR-137 over-expression led to inhibited hearing or vision sensitivity. HE staining indicated that hearing and vision abnormalities induced by long-term TCS exposure originated from CNS injury, such as reduced glial cells and loose and hollow fiber structures. The findings of this study enhance our mechanistic understanding of neurotoxicity in aquatic animals in response to TCS exposure. These observations provide theoretical guidance for development of early intervention treatments for nervous system diseases.

  • Mesohaline conditions represent the threshold for oxidative stress, cell death and toxin release in the cyanobacterium Microcystis aeruginosa
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-22
    Cliff Ross, B.Christopher Warhurst, Amber Brown, Chase Huff, Judith D. Ochrietor

    As aquatic ecosystems become increasingly affected by hydrologic alterations, drought and sea level rise a need exists to better understand the biological effects of elevated salinity on toxigenic cyanobacteria such as Microcystis aeruginosa. This study investigated the impacts of oligohaline/low mesohaline conditions and exposure time on selected physiological and biochemical responses in M. aeruginosa including cell viability, oxidative stress, antioxidant responses, in addition to microcystin synthesis and release into the surrounding environment. M. aeruginosa was able to grow in most test salinity treatments (1.4 - 10 ppt), as supported by cell abundance data and chlorophyll-a (chl-a) concentrations. Physiological data showed that after certain salinity thresholds (~7ppt) were surpassed, salt stress had cascading effects, such as increased ROS production and lipid peroxidation, potentiating the decline in cellular viability. Furthermore, elevated salinity induced oxidative stress which was concomitant with a decrease in cell abundance, chl-a concentration and photochemical efficiency in the 7-10 ppt treatments. M. aeruginosa did not synthesize microcystins (MCs) in response to increased saline conditions, and mcy-D expression was not correlated with either salinity treatment or extracellular MC concentrations, indicating that salinity stress could inhibit toxin production and that released toxins were likely synthesized prior to exposure. Additionally, extracellular MC concentrations were not correlated with decreased cellular integrity, as evidenced by SYTOX analyses, suggesting that toxins may be released through mechanisms other than cellular lysis. Results from this study support that M. aeruginosa can survive with limited negative impacts to cellular structure and function up to a certain threshold between 7-10 ppt. However, after these thresholds are surpassed, there is radical decline in cell health and viability leading to toxin release. This work underscores the importance of understanding the balance between ROS production and antioxidant capacities when assessing the fate of M. aeruginosa under mesohaline conditions.

  • The influence of short-term experimental fasting on biomarker responsiveness in oil WAF exposed mussels
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-20
    E. Blanco-Rayón, L. Guilhermino, M. Irazola, A.V. Ivanina, I.M. Sokolova, U. Izagirre, I. Marigómez

    Mussels are widely used in toxicological experimentation; however, experimental setups are not standardized yet. Although there is evidence of changes in biomarker values during food digestion and depending on the mussel nutritive status, the mode of feeding differs among toxicological experiments. Typically, mussels are fed with different diets in different long-term experiments, while fasting is the most common approach for short-term studies. Consequently, comparisons among experiments and reliable interpretations of biomarker results are often unfeasible. The present investigation aimed at determining the influence of fasting (against feeding with Isochrysis galbana) on biomarkers and their responsiveness in mussels exposed for 96 h to the water accommodated fraction (WAF) of a heavy fuel oil (0%, 6.25%, 12.5% and 25% WAF in sea water). PAH tissue levels in digestive gland and a battery of biomarkers were compared. WAF exposure led to decrease of cytochrome-C-oxidase activity, modulated glutathione-S-transferase activity, augmented lipid peroxidation, inhibited acetyl cholinesterase (AChE) activity, and led to lysosomal enlargement (VvLYS and S/VLYS) and membrane destabilisation, lipofuscin accumulation, and histopathological alterations (VvBAS, MLR/MET and CTD ratio) in the digestive gland epithelium; and were integrated as IBR/n (biological response index). Overall, no significant changes were recorded in AChE activity, S/VLYS and CTD ratio in any experimental treatment, while all the other biomarkers showed significant changes depending on the fasting/feeding condition, the exposure to WAF and/or their interaction. As a result, the integrated biomarker index IBR/n was higher at increasing WAF exposure levels both in fasted and fed mussels albeit the response was more marked in the latter. The response profiles were qualitatively similar between fasted and fed mussels but quantitatively more pronounced in fed mussels, especially upon exposure to the highest concentration (25% WAF). Therefore, it is highly recommended that mussels are also supplied with food during short-term, like during long-term toxicological experiments. This practice would avoid the interference of fasting with biological responses elicited by the tested chemicals and allow for reliable comparison with data obtained in long-term experiments and monitoring programmes.

  • Toxicokinetics and bioaccumulation of polycyclic aromatic compounds in wood frog tadpoles (Lithobates sylvaticus) exposed to Athabasca oil sands sediment
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-17
    J.C. Bilodeau, J.M. Gutierrez Villagomez, L.E. Kimpe, P.J. Thomas, B.D. Pauli, V.L. Trudeau, J.M. Blais

    We performed accumulation-elimination experiments of polycyclic aromatic compounds (PACs) in wood frog tadpoles (Lithobates sylvaticus) using river sediment from Canada’s Athabasca oil sands region. The PACs in wood frog tadpoles were ~2x higher on average when the animals were in direct contact with PAC-contaminated sediment than when they were separated from the sediment with a screen and exposed only to aqueous PACs. These results suggest that sediment exposure/ingestion contributes as much to PAC accumulation in tadpoles as exposure via aqueous pathways. Alkyl-substituted PAC concentrations in exposed tadpoles exceeded those of the unsubstituted (parent) PACs by about 10 × . Bioaccumulation factors ranged between 0.01 and 4.93, with parent PACs having higher bioaccumulation factors than alkylated PACs. Wood frog tadpoles efficiently eliminated and metabolized most parent and alkyl-substituted PACs, though some compounds (e.g., C4-naphthalenes) had higher bioaccumulation potential and may serve as effective markers of exposure. Here we present a comprehensive analysis of the toxicokinetics and bioaccumulation of PACs (52 analytes) in amphibian larvae, and highlight the importance of sediment exposure when considering the bioaccumulation and potential biological impact of PACs in benthic and epibenthic organisms.

  • Is the presence of Central European strains of Raphidiopsis (Cylindrospermopsis) raciborskii a threat to a freshwater fish? An in vitro toxicological study in common carp cells
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-17
    Halina Falfushynska, Oksana Horyn, Agnieszka Brygider, Olga Fedoruk, Bogdan Buyak, Dmytro Poznansky, Barbara Poniedziałek, Mikołaj Kokociński, Piotr Rzymski

    As yet European strains of Raphidiopsis raciborskii (previously Cylindrospermopsis raciborskii) have not been found to produce known cyanotoxins although their extracts have caused adverse effects in mammals, as shown using in vitro and in vivo experimental models. The present study investigated whether strains isolated from Western Poland and Ukraine can affect fish cells using in vitro exposures of hepatocytes and red blood cells (RBC), and brain homogenates obtained from common carp (Cyprinus carpio) to 1.0% and 0.1% extracts of 7 strains. The studied extracts evoked different responses of catalase activity in hepatocytes with both increase and decrease observed under low and high concentrations. The cellular thiol pool was also altered with most extracts inducing a decrease in the activity of glutathione-S-transferase, and Ukrainian strains leading to an increase in glutathione level and a decrease in metallothionein content. All the studied extracts induced comparable reactive oxygen species formation, lipid peroxidation, protein carbonylation and DNA fragmentation in hepatocytes, and all but one increased the activity of caspase-3. Only one extract caused lysosomal membrane destabilization as measured by neutral red retention in RBC. In contrast to extracts of Ukrainian isolates, exposure of brain homogenates to extracts of Polish strains induced an increase in acetylcholinesterase activity suggesting the neurotoxic action of their exudates. The results indicate that both Polish and Ukrainian strains of R. raciborskii may pose a toxicological risk to freshwater fish, and further, that Polish strains may produce compound(s) evoking neurotoxic effects.

  • Transcriptomic analysis revealing hepcidin expression in Oryzias melastigma regulated through the JAK-STAT signaling pathway upon exposure to BaP
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-16
    Qian Cui, Fang-Yi Chen, Min Zhang, Hui Peng, Ke-Jian Wang

    Our previous study revealed that an antimicrobial peptide hepcidin, can be significantly up-regulated either with LPS challenge or upon exposure to Benzo[a]pyrene (BaP) in red sea bream, but the molecular mechanism involved in whether the transcriptional expression of hepcidin induced by LPS or BaP is regulated through a similar signaling pathway is not yet known. To elucidate the underlying molecular mechanism, the marine model fish Oryzias melastigma was exposed to 1 μg/L BaP as well as challenged with 5 μg of LPS per fish. Samples at 3 h post-LPS challenge, and 2 d and 3 d post-BaP exposure were separately collected for transcriptome analysis. General analysis of the predicted immune-associated unigenes based on the transcriptomic data showed that the percentages of modulated immune-associated genes were 7% with LPS challenge, and 3% and 7% with BaP exposure at 2 and 3 days, respectively. Genes involved in functions like antimicrobial activity, neutrophil activation, and leukocyte chemotaxis were up-regulated with LPS challenge, whereas more than half of the immune associated genes including the KLF family were down-regulated upon BaP exposure, indicating a difference in the modulated immune genes between LPS challenge and BaP exposure. Specific comparative analyses of the immune-associated signal pathways NOD, TOLL, NF-κB and JAK-STAT with LPS challenge or upon exposure to BaP, indicated that most of the modulated genes in association with the NOD, TOLL and NF-κB pathways were induced with LPS challenge but only a few after exposure to BaP, suggesting that BaP exposure was generally not associated with any of the three signal pathways. Interestingly, further transcriptomic analysis revealed that 5 of the 8 modulated genes associated with the JAK-STAT pathway were down-regulated, while 2 inhibiting genes were up-regulated after BaP exposure for 2 days whereas LPS challenge resulted in only less than half modulated, suggesting the possibility of down-regulation caused by BaP exposure through JAK-STAT pathway. Further testing using an EPC cell culture demonstrated that expression of the hepcidin1 gene was less involved in the known signal pathways, such as c/EBP, BMP, and NF-κB, but instead mostly in association with the JAK-STAT pathway upon BaP exposure.

  • Evaluation of microcystin-LR absorption using an in vivo intestine model and its effect on zebrafish intestine
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-15
    Jian Li, Chuanyue Chen, Tongzhou Zhang, Wanjing Liu, Li Wang, Yuanyuan Chen, Lei Wu, Abeer M. Hegazy, El-Sayed AF, Xuezhen Zhang

    Microcystin-LR (MC-LR) is regarded as one of the most toxic microcystins (MCs) isoforms. Microcystins could cause multiple organs dysfunction, and more attention has been drawn to the toxic effects on the gastrointestinal disorder. By using ex vivo everted gut sac model in 6 fish (Carassius auratus, Megalobrama amblycephala, Hypophthalmichthys molitrix, Aristichthys nobilis, Ctenopharyngodon idellus and Cyprinus carpio) and determining the accumulation of MC-LR in zebrafish intestine, we found a dose-dependent manner in the absorption and accumulation of MC-LR. Until now, little studies have been reported concerning the gut microbiota composition caused by different MC-LR exposure. The present study is the first time characterized the phylogenetic composition and taxonomic of the bacterial communities growth in the intestines of zebrafish treated with MC-LR using 16S rRNA pyrosequencing. After 30 days of treatment with 0, 1, 5 or 20 μg/L MC-LR, the alpha and beta diversity did not generate significant differences, indicating the existence of a core microbiota. However, db-RDA analysis showed that treatment with 20 μg/L MC-LR changed the characteristics of high abundances microbiota. The expression of Oatp2b1, stress related enzyme activities in gut and their associations with gut microbiota were also determined. The identified phylotypes including Actinobacteria, Lactobacillus and some opportunistic pathogens highlight the increasing risks of pathogen invasion and recovery tendency via potential probiotics resistance in zebrafish exposed to MC-LR.

  • Real-time CO2 uptake/emission measurements as a tool for early indication of toxicity in Lemna-tests
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-15
    Vesna Peršić, Tamara Đerđ, Martina Varga, Branimir Hackenberger Kutuzović

    This paper presents an application of continuous monitoring of the emission and uptake rate of CO2 in Lemna toxicity test. On a real-time basis, the CO2 concentration data were collected by the Arduino platform-based respiratory activity measuring system (ResTox) and reported as CO2 concentration dynamic curves. The results of CO2 measurements demonstrated that tested metals (Co, Cu, Hg, and Cd), as well as herbicides (nicosulfuron, diquat, and tembotrione), stimulated the CO2 exchange rates at low doses, while at high doses CO2 exchange rates were inhibited. The addition of higher concentrations of clopyralid stimulated photosynthetic activity and caused a higher increase in respiration rates indicating its mode of action as auxin mimic herbicide. The results obtained underline the necessity of considering other biological endpoints like continuous measurements of gas exchange from the very beginning of exposure to toxicants. Simultaneous measurements of real-time CO2 concentrations, as the primary effect of toxicant mode of action, and processes that are supported by carbon flux, as the secondary effect or endpoint, are needed to relate actual and substrate-induced or inhibited respiration and photosynthesis to those processes. Therefore, continuous measurements of CO2 exchange rates can be implemented for the initial screening of potential toxicity to give valuable information that is needed for further examination of toxicity mechanisms and risk assessment.

  • Impact of an immunosuppressive human pharmaceutical on the interaction of a bacterial parasite and its invertebrate host
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-14
    Lisa Schlüter-Vorberg, Anja Coors

    The interaction of pollutants and pathogens may result in altered and often enhanced effects of the chemical, the biotic stressor or both. These interaction effects cannot be reliably predicted from the toxicity of the chemical or the virulence of the pathogen alone. While standardized detection methods for immunotoxic effects of chemicals exist with regard to human health, employing host-resistance assays with vertebrates, such standardized test systems are completely lacking for invertebrate species and no guidance is available on how immunotoxic effects of a chemical in invertebrates could be definitively identified. In the present study, we investigated the impact of the immunosuppressive pharmaceutical cyclosporine A (CsA) on the invertebrate host-pathogen system Daphnia magna – Pasteuria ramosa. CsA is a calcineurin-inhibitor in vertebrates and also known to have antibiotic as well as antifungal properties. Juvenile D. magna were exposed to CsA for 21 days with or without additional pathogen challenge during the first 72 h of exposure. Long-term survival of the host D. magna was synergistically impacted by co-exposure to the chemical and the pathogen, expressed e.g. in significantly enhanced hazard ratios. Additionally, enhanced virulence of the pathogen upon chemical co-exposure was expressed in an increased proportion of infected hosts and an increased speed of Pasteuria-induced host sterilization. In contrast, effects on reproduction were additive in Pasteuria-challenged, but finally non-infected D. magna. The enhancing effects of CsA occurred at and below 3 µg/L, which was in the absence of the pathogen the lowest concentration significantly impacting the standard toxicity endpoint ‘reproduction’ in D. magna. Hence, the present study provides evidence that a pharmaceutical intended to suppress the human immune system can also suppress disease resistance of an aquatic invertebrate organism at otherwise non-toxic concentrations. Plausible ways of direct interactions of CsA with the host’s immune system are discussed, e.g. interference with phagocytosis or Toll-like receptors. Experimental verification of such a direct interference would be warranted to support the strong evidence for immunotoxic activity of CsA in invertebrates. While it remains open whether CsA concentrations in the environment are high enough to trigger adverse effects in environmental organisms, our findings highlight the need to consider immunotoxicity in an environmental risk assessment, and to develop suitable standardized methods for this purpose.

  • Subcellular accumulation and source of O2•– and H2O2 in submerged plant Hydrilla verticillata (L.f.) Royle under NH4+-N stress condition
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-13
    Kai Zhuang, Danlu Shi, Zhubing Hu, Fuliu Xu, Yahua Chen, Shen Zhenguo

    In this study, the effects of excess NH4+-N on the subcellular accumulation of O2•– and H2O2 in submerged plant Hydrilla verticillata (L.f.) Royle were investigated using both histochemical and cytochemical methods. Treatments with ≥ 2.00 and ≥ 5.00 mg L-1 NH4+-N for 5 d significantly increased production of O2•– and H2O2, respectively. The activities of plasma membrane-bound NADPH (nicotinamide adenine dinucleotide phosphate) oxidases and antioxidant enzymes (superoxide dismutase, peroxidase, ascorbate peroxidase, catalase, dehydroascorbate reductase and glutathione reductase) were also increased correspondingly. This study also provides the first cytochemical evidence of subcellular accumulation of O2•– and H2O2 in the submerged plants. In the leaves of H. verticillata treated with 20.0 mg L-1 NH4+-N, O2•– dependent DAB precipitates were found primarily on the inner side of the plasma membrane, extracellular space and chloroplasts. H2O2-CeCl3 precipitates were mainly localized on the inner side of the plasma membrane and extracellular space of the mesophyll cells. Treatments with the inhibitors of NADPH oxidase (diphenylene iodonium and imidazole) indicate that NH4+-N-induced production of O2•– and H2O2 in H. verticillata leaves may involve plasma membrane-bound NADPH oxidase. Moreover, low-light treatment decreased NH4+-induced O2•– production, suggesting that alterations in the photosynthetic electron transfer chain due to NH4+ toxicity could lead to O2•– production.

  • Profiling microRNA expression in Atlantic killifish (Fundulus heteroclitus) gill and responses to arsenic and hyperosmotic stress
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-12
    Britton C. Goodale, Thomas H. Hampton, Emily N. Ford, Craig E. Jackson, Joseph R. Shaw, Bruce A. Stanton, Benjamin L. King

    The Atlantic killifish (Fundulus heteroclitus), native to estuarine areas of the Atlantic coast of the United States, has become a valuable ecotoxicological model as a result of its ability to acclimate to rapid environmental changes and adapt to polluted habitats. MicroRNAs (miRNAs) are highly conserved small RNAs that regulate gene expression and play critical roles in stress responses in a variety of organisms. Global miRNA expression in killifish and the potential roles miRNA have in environmental acclimation have yet to be characterized. Accordingly, we profiled miRNA expression in killifish gill for the first time and identified a small group of highly expressed, well-conserved miRNAs as well as 16 novel miRNAs not yet identified in other organisms. Killifish respond to large fluctuations in salinity with rapid changes in gene expression and protein trafficking to maintain osmotic balance, followed by a secondary phase of gene and protein expression changes that enable remodeling of the gills. Arsenic, a major environmental toxicant, was previously shown to inhibit gene expression responses in killifish gill, as well the ability of killifish to acclimate to a rapid increase in salinity. Thus, we examined the individual and combined effects of salinity and arsenic on miRNA expression in killifish gill. Using small RNA sequencing, we identified 270 miRNAs expressed in killifish, and found that miR-135b was differentially expressed in response to arsenic and at 24 hours following transfer to salt water. Predicted targets of miR-135b are involved in ion transport, cell motility and migration, GTPase mediated signal transduction and organelle assembly. Consistent with previous studies of these two environmental stressors, we found a significant interaction (i.e., arsenic dependent salinity effect), whereby killifish exposed to arsenic exhibited an opposite response in miR-135b expression at 24 h post hyperosmotic challenge compared to controls. By examining mRNA expression of predicted miRNA targets during salinity acclimation and arsenic exposure, we found that miR-135b targets were significantly more likely to decrease during salinity acclimation than non-targets. Our identification of a significant interaction effect of arsenic and salinity on miR-135b expression supports the hypothesis that arsenic alters upstream regulators of stress response networks, which may adversely affect the killifish response to osmotic stress. The characterization of miRNAs in this ecotoxicological model will be a valuable resource for future studies investigating the role of miRNAs in response to environmental stress.

  • Fate of four phthalate esters with presence of Karenia brevis: uptake and biodegradation
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-12
    Cuizhu Sun, Ge Zhang, Hao Zheng, Ning Liu, Mei Shi, Xianxiang Luo, Lingyun Chen, Fengmin Li, Shugang Hu

    Phthalate esters (PAEs), one class of the most frequently detected endocrine-disrupting chemicals (EDCs) in marine environment, have aroused wide public concerns because of their carcinogenicity, teratogenicity, and mutagenicity. However, the environmental fate of PAEs in the occurrence of harmful algal blooms remains unclear. In this research, four PAEs regarded as priority control pollutants with different alkyl chains, i.e., dimethyl phthalate (DMP), diethyl phthalate (DEP), diallyl phthalate (DAP), and dipropyl phtalate (DPrP) were selected as models to investigate toxicity, uptake, and degradation of PAEs in seawater grown with K. brevis, one of the common harmful red tide species. The 96-h median effective concentration (96h-EC50) values followed the order of DMP (over 50 mg L-1) > DEP (39.6 mg L-1) > DAP (33.5 mg L-1) > DPrP (23.9 mg L-1), and the bio-concentration factors (BCFs) were positively correlated to the alkyl chain length. These results indicate that the toxicity of PAEs and their accumulation in K. brevis increased with increasing alkyl chains, due to the higher lipophicity of the longer chain PAEs. With growth of K. brevis for 96 h, the content of DMP, DEP, DAP, and DPrP decreased by 93.3%, 68.2%, 57.4% and 46.7%, respectively, mainly attributed to their biodegradation by K. brevis, accounting for 87.1%, 61%, 46%, 40% of their initial contents, respectively. It was noticed that abiotic degradation had little contribution to the total reduction of PAEs in the algal cultivation systems. Moreover, five metabolites were detected in the K. brevis when exposed to DEP including dimethyl phthalate (DMP), monoethyl phthalate (MEP), mono-methyl phthalate (MMP), phthalic acid (PA), and protocatechuic acid (PrA). While when exposed with to DPrP, one additional intermediate compound diethyl phthalate (DEP) was detected in the cells of K. brevis in addition to the five metabolites mentioned above. These results confirm that the main biodegradation pathways of DEP and DPrP by K. brevis included de-esterification, demethylation or transesterification. These findings will provide valuable evidences for predicting the environmental fate and assessing potential risk of PAEs in the occurrence of harmful algal blooms in marine environment.

  • Copper exposure and seawater acidification interaction: Antagonistic effects on biomarkers in the zooxanthellate scleractinian coral Mussismilia harttii
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-10
    Laura Fernandes Barros Marangoni, Marina Marinho de Azevedo Novazzi Pinto, Joseane Aparecida Marques, Adalto Bianchini

    Coral reefs are threatened by global and local impacts, such as ocean acidification (OA) and metal contamination. Toxicity of metals, such as copper (Cu), is expected to be enhanced with OA. However, the interaction between these environmental stressors is still poorly evaluated. In the present study, the interactive effects of seawater acidification and increasing Cu concentrations were evaluated in a zooxanthellate scleractinian coral (Mussismilia harttii), using biochemical biomarkers involved in the coral calcification process and the photosynthetic metabolism of endosymbionts. Corals were kept under control conditions (no seawater acidification and no Cu addition in seawater) or exposed to combined treatments of reduced seawater pH (8.1, 7.8, 7.5 and 7.2) and environmentally relevant concentrations of dissolved Cu (measured: 1.0, 1.6, 2.3 and 3.2 µg/L) in a mesocosm system. After 15- and 35-days exposure, corals were analyzed for photochemical efficiency (Fv/Fm), chlorophyll a content, Ca-ATPase and carbonic anhydrase (CA) activity. Results showed that 76% of the interactions between reduced seawater pH and increasing Cu concentrations were antagonistic. Only 24% of these interactions were additive or synergistic. In general, the combination of stressors had no significant deleterious effects in the photosynthetic metabolism of endosymbionts or Ca-ATPase activity. In fact, the lowest dissolved Cu concentration tested had a consistent positive effect on Ca-ATPase activity in corals facing any of the reduced seawater pH conditions tested. In turn, potentially deleterious effects on acid-base balance in M. harttii, associated with changes in CA activity, were intensified by the combination of stressors. Findings reported here indicate that Cu toxicity in future OA scenarios can be less severe than previously suggested in this coral holobiont.

  • Dichlorprop induced structural changes of LHCⅡ chiral macroaggregates associated with enantioselective toxicity to Scnedesmus obliquus
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-06
    Hui Chen, Chensi Shen, Zunwei Chen, Babar Aijaz Ali, Yuezhong Wen
  • Response of natural phytoplankton communities exposed to crude oil and chemical dispersants during a mesocosm experiment
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-06
    Laura Bretherton, Manoj Kamalanathan, Jennifer Genzer, Jessica Hillhouse, Samantha Setta, Yue Liang, Chris M. Brown, Chen Xu, Julia Sweet, Uta Passow, Zoe V. Finkel, Andrew J. Irwin, Peter H. Santschi, Antonietta Quigg

    During the 2010 Deepwater Horizon oil spill, the chemical dispersant Corexit was applied over vast areas of the Gulf of Mexico. Marine phytoplankton play a key role in aggregate formation through the production of extracellular polymeric materials (EPS), an important step in the biological carbon pump. This study examined the impacts of oil and dispersants on the composition and physiology of natural marine phytoplankton communities from the Gulf of Mexico during a 72-hour mesocosm experiment and consequences to carbon export. The communities were treated using the water accommodated fraction (WAF) of oil, which was produced by adding Macondo surrogate oil to natural seawater and mixed for 24 hours in the dark. A chemically enhanced WAF (CEWAF) was made in a similar manner, but using a mixture of oil and the dispersant Corexit in a 20:1 ratio as well as a diluted CEWAF (DCEWAF). Phytoplankton communities exposed to WAF showed no significant changes in PSII quantum yield (Fv/Fm) or electron transfer rates (ETRmax) compared to Control communities. In contrast, both Fv/Fm and ETRmax declined rapidly in communities treated with either CEWAF or DCEWAF. Analysis of other photophysiological parameters showed that photosystem II (PSII) antenna size and PSII connectivity factor were not altered by exposure to DCEWAF, suggesting that processes downstream of PSII were affected. The eukaryote community composition in each experimental tank was characterized at the end of the 72 h exposure time using 18S rRNA sequencing. Diatoms dominated the communities in both the control and WAF treatments (52 and 56% relative abundance respectively), while in CEWAF and DCEWAF treatments were dominated by heterotrophic Euglenozoa (51 and 84% respectively). Diatoms made up the largest relative contribution to the autotrophic eukaryote community in all treatments. EPS concentration was four times higher in CEWAF tanks compared to other treatments. Changes in particle size distributions (a proxy for aggregates) over time indicated that a higher degree of particle aggregation occurred in both the CEWAF and DCEWAF treatments than the WAF or Controls. Our results demonstrate that chemically dispersed oil has more negative impacts on photophysiology, phytoplankton community structure and aggregation dynamics than oil alone, with potential implications for export processes that affect the distribution and turnover of carbon and oil in the water column.

  • Parental transfer of ethylhexyl methoxy cinnamate and induced biochemical responses in zebrafish
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-03
    Ranran Zhou, Guanghua Lu, Zhenhua Yan, Runren Jiang, Jie Shen, Xuhui Bao

    Ethylhexyl methoxy cinnamate (EHMC) is one of the major organic ultraviolet (UV) filter pollutants in the environment. The purpose of this study was to investigate the parental transfer of EHMC and induced biochemical responses in zebrafish (Danio rerio). Zebrafish embryos were exposed to EHMC solution (1, 10, and 100 μg/L) for 4 months until sexual maturation. Then male and female parents were paired to lay eggs. F1 generations were divided into 2 categories: with and without continued EHMC exposure. EHMC was detected in both F0 parents and F1 eggs, indicating that EHMC can accumulate in zebrafish and transfer to offspring through reproduction. The hatching rate decreased and malformation rate increased significantly among parents and progeny embryos in the high concentration exposure group. For 40 dpf (days post-fertilisation) F0 generations, estradiol hormone and vitellogenin (Vtg) contents, the expression levels of Vtg1, P450 aromatase (Cyp19a and Cyp19b), 17β-hydroxysteroid dehydrogenase (Hsd17b1, Hsd17b3), estrogen receptor-alpha and progesterone receptor in all concentration groups decreased significantly, while androgen receptor increased significantly in 10 and 100 μg/L exposure groups compared with the corresponding control group, showing anti-estrogen and androgen effects. For 120 dpf F0 generations, acetylcholinesterase activity was significantly decreased and glutathione and malondialdehyde levels, superoxide dismutase, catalase and glutathione reductase activities were significantly increased in all treatment groups compared with the corresponding control group. In addition, F1 offspring with or without continued exposure to EHMC suffered similar or stronger oxidative stress compared with their parents. DNA breakage and apoptosis also occurred in 120 dpf parental liver cells in all treatment groups as a result of oxidative damage. Results suggested that EHMC have transfer effects between parents and offspring, which may cause negative effects on growth and development of zebrafish and induce biochemical responses in both parents and offspring.

  • Long-chain polyunsaturated fatty acid biosynthesis and its response to cadmium exposure in silver pomfret
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-03
    Kai Liao, Zhaoshou Ran, Ran Meng, Jilin Xu, Jiayi Cao, Xiaorong Xu, Yajun Wang, Shanliang Xu, Xiaojun Yan

    Despite a close interaction between cadmium (Cd) and long-chain polyunsaturated fatty acid (LC-PUFA) metabolism, the influence of Cd exposure on the endogenous synthesis of LC-PUFA has received little attention. In the present study, we hypothesized that Cd exposure would affect the synthesis of LC-PUFA in the marine fish silver pomfret (Pampus argenteus). Therefore, the molecular basis of LC-PUFA biosynthesis and regulation was investigated as the first step to understanding the mechanisms underpinning the effects of Cd exposure. Thereafter, transcriptional regulation of the genes that participate in LC-PUFA biosynthesis and regulation by Cd exposure were also explored. Our results showed that fatty acyl desaturase 2 (Fads2) and elongases of very long-chain fatty acids 5 (Elovl5), two key enzymes involved in LC-PUFA biosynthesis, enabled silver pomfret to biosynthesize 20:3n–6 and 20:4n–3 from 18:2n-6 and 18:3n-3. The results also raise the possibility that silver pomfret may have the ability to produce docosahexaenoic acid (DHA, 22:6n-3) from endogenous eicosapentaenoic acid (EPA, 20:5n-3). The expression of silver pomfret fads2 and elovl5 was transcriptionally regulated by the peroxisome proliferator activated receptor α (Pparα). The expression of fads2, elovl5 and pparα in the brain was significantly increased in response to Cd exposure. In addition, Cd exposure significantly reduced the DHA concentration and significantly increased the malondialdehyde concentration in the brain of silver pomfret. Cd exposure likely increases brain-specific DHA synthesis from EPA by transcriptionally activating fads2 and elovl5 via Pparα in silver pomfret. This regulation may be a coping mechanism for the reduction of DHA caused by Cd-oxidative stress in the brains of silver pomfret.

  • Divergent gene expression in the gills of juvenile turbot (Psetta maxima) exposed to chronic severe hypercapnia indicates dose-dependent increase in intracellular oxidative stress and hypoxia
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-11-03
    Bernd. T. Hermann, Sven Würtz, Klaus H. Vanselow, Carsten Schulz, Kevin T. Stiller

    Elevated concentrations of carbon dioxide are a common stressor for fish and other aquatic animals. In particular, intensive aquaculture can impose prolonged periods of severe environmental hypercapnia, manifold exceeding CO2 concentrations of natural habitats. In order to cope with this stressor, gills are essential and constitute the primary organ in the acclimatization process. Yet, despite a general understanding of changes in ion regulation, not much is known with regard to other cellular mechanisms. In this study, we apply RT-qPCR to investigate changes in the expression of several genes associated with metabolism, stress and immunity within gills of juvenile turbot (Psetta maxima) after an eight-week exposure to different concentrations of CO2 (low = ~3000 μatm, medium = ~15000 μatm and high = ~25000 μatm CO2). Histological examination of the gill tissue only found a significant increase of hypertrophied secondary lamella in the highest tested treatment level. gene expression results, on the other hand, implied both, mutual and dose-dependent transcriptional adjustments. Comparable up-regulation of IL-1ß, LMP7 and Grim19 at medium and high hypercapnia indicated an increase of reactive oxygen species (ROS) within gill cells. Simultaneous increase in Akirin and PRDX transcripts at medium CO2 indicated enhanced anti-oxidant activity and regulation of transcription, while reduced mRNA concentrations of COX, EF1α and STAT2 at high CO2 denoted suppressed protein synthesis and reduced metabolic capacity. In addition to upregulated DFAD and ApoE expression, implying compensating repair measures, gills exposed to the highest tested treatment level seemed to operate close to or even beyond their maximum capacity. Thus, fitting the model of capacity limitation, our results provide evidence for accretive intracellular hypoxia and oxidative stress in the gills of turbot, dependent on the level of environmental hypercapnia. Further, genes, such as COX, may be valuable biomarkers when attempting to discriminate between a successful and an overpowered stress response.

  • Accumulation, metabolite and active defence system responses of fluoxetine in zebrafish embryos: Influence of multiwalled carbon nanotubes with different functional groups
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-30
    Zhenhua Yan, Hongwei Sun, Runren Jiang, Huike Dong, Haohan Yang, Jianchao Liu, Guanghua Lu, Yong Ji

    Studies on the bioavailability of organic contaminants adsorbed to nanomaterials are increasing. In this study, we investigated the interaction between fluoxetine (FLX) and three multiwalled carbon nanotubes (MWCNTs) with different functional groups in zebrafish (Danio rerio) embryos, focusing on the FLX accumulation, the formation of the metabolite norfluoxetine (NFLX), and the active defence system responses. The accumulation of FLX in zebrafish was intensified by MWCNTs (46-99%), which simultaneously facilitated the formation of the metabolite NFLX by 23-167%. The consistent enhancement revealed that the absorbed FLX is bioavailable in zebrafish. Moreover, the coexisting MWCNTs further promoted the influences of FLX on the active defence system in zebrafish (e.g. antioxidant and metabolic function), eliciting the defence function. The influences of MWCNTs on the bioavailability of FLX in zebrafish could be ordered as OH-MWCNTs > COOH-MWCNTs > pristine MWCNTs. The release of FLX from MWCNTs in biofluids may partially contribute to these significant alterations. In particular, MWCNTs themselves may also modulate the bioavailability of FLX in zebrafish by downregulating the gene expression of membrane ATP-binding cassette transporter (abcb4). These findings demonstrated that MWCNTs increased the bioavailability of FLX in zebrafish, especially the functionalized MWCNTs. The production of metabolites may be a useful bio-endpoint to evaluate the bioavailability of adsorbed contaminants on nanomaterials.

  • Generation of a Tg(cyp1a-12DRE:EGFP) transgenic zebrafish line as a rapid in vivo model for detecting dioxin-like compounds
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-30
    Chao Shen, Yixi Zhou, Jinpeng Ruan, Yung-Jen Chuang, Chonggang Wang, Zhenghong Zuo

    Dioxin-like compounds (DLCs) are extremely stable toxic organic compounds and can cause serious health risks. To develop a convenient biomonitoring tool for the detection of DLCs in the environment, we generated a transgenic line—Tg(cyp1a-12DRE:EGFP)—with a zebrafish cyp1a promoter recombined with multiple dioxin-responsive elements (DREs) that drive EGFP expression. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)-induced EGFP expression was observed in the head cartilage (most sensitive), gut, otic vesicle, pectoral fin bud and eye of larvae. The lowest observed effect concentration of TCDD was estimated to be approximately 1 ng/L. Compared with existing zebrafish lines, our transgenic fish displayed comparable or even higher detection sensitivity to DLCs and could serve as an improved and rapid assay in an in vivo context. The Tg(cyp1a-12DRE:EGFP) transgenic zebrafish line also had higher stability for inducing EGFP expression (nearly 100% of our zebrafish induced EGFP at approximately 1 ng/L TCDD) than other lines. In addition, Tg(cyp1a-12DRE:EGFP) zebrafish could serve as a convenient and straightforward tool to assess potential cranial malformations and related health effects.

  • Waterborne and diet-related effects of inorganic and organic fungicides on the insect leaf shredder Chaetopteryx villosa (Trichoptera)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-29
    M. Konschak, J.P. Zubrod, P. Baudy, D. Englert, B. Herrmann, R. Schulz, M. Bundschuh

    It is well-documented that fungicides can affect crustacean leaf shredders via two effect pathways, namely waterborne exposure and their diet (i.e., via dietary uptake of fungicides adsorbed to leaf material and an altered microorganism-mediated food quality). As a consequence of different life history strategies, the relevance of these effect pathways for aquatic shredders belonging to other taxonomic classes, for instance insects, remains unclear. Therefore, we investigated waterborne and diet-related effects in larvae of the caddisfly leaf shredder Chaetopteryx villosa (Insecta: Trichoptera) and compared our observations to previous reports on effects in adults of the crustacean leaf shredder Gammarus fossarum (Malacostraca: Amphipoda). We assessed acute waterborne effects of an organic fungicide mixture (OFM) and the inorganic fungicide copper (Cu) on the leaf consumption (n = 30) of the fourth-/fifth-instar larvae of C. villosa and their food choice (n = 49) when offered leaf material, which was either conditioned in presence or in absence of the respective fungicide(s). Moreover, the larval leaf consumption (n = 50) and physiological fitness (i.e., growth as well as lipid and protein content) were examined after subjecting C. villosa for 24 days towards the combination of both effect pathways at environmentally relevant concentrations. G. fossarum and C. villosa exhibited similar sensitivities and the same effect direction when exposed to the OFM (either waterborne or dietary pathways). Both shredders also showed the same effect direction when exposed to dietary Cu, while with regards to mortality and leaf consumption C. villosa was less sensitive to waterborne Cu than G. fossarum. Finally, as observed for G. fossarum, the combined exposure to OFM over 24 days negatively affected leaf consumption and the physiology (i.e., growth and lipid reserves) of C. villosa. While no combined Cu effects were caused on larval leaf consumption, contrasting to the observations for G. fossarum, the physiology of both shredders was negatively affected, despite partly differing effect sizes and directions. Our results suggest that C. villosa and G. fossarum seem to be of comparable sensitivity towards waterborne and diet-related organic fungicide exposure, whereas the trichopteran is less sensitive to Cu-based waterborne fungicide exposure. However, when both pathways act jointly, organic and inorganic fungicides can affect the physiology of shredder species with completely different life history strategies. As caddisflies represent a subsidy for terrestrial consumers, these observations indicate that fungicide exposure might not only affect aquatic ecosystem functioning but also the flux of energy across ecosystem boundaries.

  • Body size-dependent interspecific tolerance to cadmium in the marine rotifer Brachionus spp. and their molecular responses to cadmium
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-29
    Hye-Min Kang, Jin-Sol Lee, Young Hwan Lee, Min-Sub Kim, Heum Gi Park, Chang-Bum Jeong, Jae-Seong Lee

    Although several studies have reported on different interspecific sensitivities in response to various toxicants, the response mechanisms are still poorly understood. Here, we investigate the interspecific toxicity of cadmium (Cd) and its mechanism using three marine rotifer Brachionus spp. that are distinguishable by body size, which is considered the most significant indicator of phenotypic difference. The body sizes of B. plicatilis, B. koreanus, and B. rotundiformis are significantly different throughout their life cycles (egg, neonate, and adult), with the smaller rotifer exhibiting higher sensitivity to Cd. To investigate the mechanisms that result in body size-dependent tolerance to Cd, metabolic and Cd bioaccumulation rates were investigated. Both rates have shown a significant correlation with body size, indicating that body size and its variables are important factors in determining Cd tolerance in Brachionus spp. In addition, similar patterns that further explain body size-dependent tolerance are shown in the phosphorylation status of mitogen-activated protein kinases, reactive oxygen species level, and antioxidant enzymatic activities. Our study provides valuable insight into size- and species-dependent toxicity mechanisms of species in the same genus.

  • Constant exposure to environmental concentrations of the antifouling biocide Sea-Nine retards growth and reduces acetylcholinesterase activity in a marine mysid
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-29
    Jeong Wan Do, Niamul Haque, Hyun-Jeong Lim, Byung Hwa Min, Do-Hee Lee, Jung-Hoon Kang, Moonkoo Kim, Jee-Hyun Jung, Jae-Sung Rhee

    Sea-Nine (4,5-dichloro-2-n-octyl-4-isothiazoline3-one; DCOIT) antifoulant has been widely used owing to its broad spectrum of biocide activity against major fouling organisms. In this study, several physiological parameters of a marine mysid were analyzed upon exposure to sublethal environmental concentrations (1 and 100 ng L-1) of Sea-Nine in two exposure conditions, intermittent (weekly; once per week) and constant (daily; once per 24 h) exposure, for 4 weeks. In both experimental conditions, growth retardation, acetylcholinesterase (AChE) activity, glutathione S-transferase (GST) activity, and number of newborn juveniles as second generation, together with their survival were measured. Morphometric parameters of total body, antennal scale, exopod, endopod, and telson were significantly retarded by 22%, 14%, 13%, and 24%, respectively, by daily exposure to 100 ng L-1 Sea-Nine for 4 weeks. Significant inhibition of AChE activity was observed at week 4 in the 100 ng L-1 daily Sea-Nine-exposed groups, whereas no significant GST activity was measured at the same experimental conditions. Inhibition of AChE activity would be associated with impairment of cholinergic system and may adversely modulate growth parameters of the mysid. The number of newly hatched juveniles from females that were exposed daily to 100 ng L-1 Sea-Nine was significantly lower than that of the control. Although no significant differences were observed between survival percentages of newborn juveniles for 30 days, mortality (NOEC and LC50) increased in the surviving offspring from the 100 ng L-1-exposed 1st generation of mysids. These findings suggested that constant exposure to Sea-Nine has detrimental effects on the growth parameters of marine mysids with inhibition of AChE activity.

  • Characterization of brain acetylcholinesterase of bentonic fish Hoplosternum littorale: Perspectives of application in pesticides and metal ions biomonitoring
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-26
    Marlyete Chagas de Araújo, Caio Rodrigo Dias de Assis, Kaline Catiely Campos Silva, Kelma Sirleide de Souza, Rafael Souto de Azevedo, Maria Helena Menezes Estevam Alves, Luciano Clemente da Silva, Valdir Luna da Silva, Mônica Lúcia Adam, Luiz Bezerra de Carvalho Junior, Ranilson de Souza Bezerra, Maria Betânia Melo de Oliveira

    Acetylcholinesterase (AChE; EC is a serine hydrolase, whose main function is to modulate neurotransmission at cholinergic synapses. It is, therefore, the primary target of some pesticides and heavy metals. Its inhibition in aquatic organisms has been used as an indicator of the presence of these pollutants in water bodies. The present study aimed to characterize physicochemical and kinetic parameters of brain AChE in the benthic fish Hoplosternumlittorale and to analyze the in vitro effects of pesticides (dichlorvos, diazinon, chlorpyrifos, parathion-methyl, temephos, carbaryl, carbofuran, aldicarb, diflubenzuron, novaluron and pyriproxyfen) and metal ions (As3+, Cd2+, Cu2+, Fe2+, Mn2+, Mg2+, K+, Pb2+, Hg2+, Zn2+) investigating the potential of this enzyme as environmental biomarker based on current regulations. Specific substrates and inhibitors have indicated AChE to be the predominant cholinesterase (ChE) in the brain of H. littorale. Peak activity was observed at pH 8.0 and 30 °C. The enzymatic activity is otherwise moderately thermostable (≈ 50% activity at 45 °C). The enzyme can reduce the activation energy of acetylthiocholine hydrolysis reaction to 8.34 kcal mol-1 while reaching a rate enhancement of 106. Among the pesticides under study, dichlorvos presented an IC50 value below the maximum concentrations allowed by legislation. This study presents the first report on the inhibition of brain AChE activity from Siluriformes by the pesticides novaluron and pyriproxyfen. Mercury ion also exerted a strong inhibitory effect on its enzymatic activity. The H. littorale enzyme thus has the potential to function as an in vitro biomarker for the presence of the pesticide dichlorvos as well as mercury in areas of mining and industrial discharge.

  • Interaction of environmental contaminants with zebrafish (Danio rerio) multidrug and toxin extrusion protein 7 (Mate7/Slc47a7)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-25
    Jovica Lončar, Tvrtko Smital

    Zebrafish Mate7 belongs to solute carrier protein superfamily and specifically to subfamily of multidrug and toxin extruders. It is co-orthologous to mammalian Mates, and is ubiquitously expressed in zebrafish tissues with the highest expression in kidney. It has been shown to interact with both endogenous (steroid hormones) and xenobiotic compounds (pharmaceuticals), implying a role in efflux of toxic compounds. The objective of our study was to analyse interaction of environmental contaminants with zebrafish Mate7 using a newly developed high throughput screening (HTS) Mate7 assay. A full-length zebrafish mate7 sequence was obtained from zebrafish cDNA originating from male kidney, and a stable expression of Mate7 in genetically engineered HEK293 Flp-In cells was achieved. Stable Mate7 transfectants were then used for development and optimization of a new HTS cellular uptake protocol, with DAPI and ASP + as model fluorescent substrates. The developed assay was used for identifying zebrafish Mate 7 interactors and discerning the type of interaction. A series of 89 diverse environmental contaminants, including industrial chemicals, pesticides, and pharmaceuticals, was tested and highly effective Mate7 interactors were identified in all of the aforementioned groups. Some of the inhibitors identified could be of environmental concern because they may potentially impair Mate7 efflux function, lowering the fish defence capacity against environmental contaminants, or interfering with transport of yet unidentified physiological substrates. In addition, we found significant differences between zebrafish Mate7 and mammalian Mates’ substrate preferences, a finding that should be taken into consideration when using zebrafish as a model organism in toxicokinetic studies.

  • The evolution and origin of tetrodotoxin acquisition in the blue-ringed octopus (genus Hapalochlaena)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-24
    Brooke L. Whitelaw, Ira R. Cooke, Julian Finn, Kyall Zenger, J.M. Strugnell

    Tetrodotoxin is a potent non-proteinaceous neurotoxin, which is commonly found in the marine environment. Synthesised by bacteria, tetrodotoxin has been isolated from the tissues of several genera including pufferfish, salamanders and octopus. Believed to provide a defensive function, the independent evolution of tetrodotoxin sequestration is poorly understood in most species. Two mechanisms of tetrodotoxin resistance have been identified to date, tetrodotoxin binding proteins in the circulatory system and mutations to voltage gated sodium channels, the binding target of tetrodotoxin with the former potentially succeeding the latter in evolutionary time. This review focuses on the evolution of tetrodotoxin acquisition, in particular how it may have occurred within the blue-ringed octopus genus (Hapalochlaena) and the subsequent impact on venom evolution.

  • Developmental exposure to environmentally relevant concentrations of bifenthrin alters transcription of mTOR and ryanodine receptor-dependent signaling molecules and impairs predator avoidance behavior across early life stages in inland silversides (Menidia beryllina)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-24
    Daniel F. Frank, Susanne M. Brander, Simone Hasenbein, Danielle J. Harvey, Pamela J. Lein, Juergen Geist, Richard E. Connon

    Altered transcription of calcium-dependent signaling cascades involving the ryanodine receptor (RyR) and mechanistic target of rapamycin (mTOR) in response to environmental exposures have been described in model vertebrates, including zebrafish, while the relevance for wild fishes remains unknown. To address this knowledge gap, we exposed the euryhaline model Menidia beryllina (inland silversides) to the insecticide bifenthrin, a known modulator of calcium signaling. The main objectives of this study were to determine: (1) whether exposure of developing silversides to environmentally relevant concentrations of bifenthrin alters their behavior; and (2) whether behavioral changes correlate with altered expression of genes involved in RyR and mTOR-dependent signaling pathways. At six hours post fertilization (hpf), inland silversides were exposed to bifenthrin at 3, 27 and 122 ng/L until 7 days post fertilization (dpf, larvae hatched at 6dpf), followed by a 14-day recovery period in uncontaminated water. Transcriptional responses were measured at 5, 7 and 21 dpf; locomotor behavior following external stimuli and response to an olfactory predator cue were assessed at 7 and 21 dpf. Bifenthrin elicited significant non-monotonic transcriptional responses in the majority of genes examined at 5 dpf and at 21 dpf. Bifenthrin also significantly altered predator avoidance behavior via olfactory mechanisms with main effects identified for animals exposed to 3 and 27 ng/L. Behavioral effects were not detected in response to visual stimuli during acute exposure, but were significant in the predator-cue assessment following the recovery period, suggesting delayed and long-term effects of early developmental exposures to bifenthrin. Our findings demonstrate that at picomolar (pM) concentrations, which are often not represented in ecotoxicological studies, bifenthrin perturbs early development of inland silversides. These developmental impacts are manifested behaviorally at later life stages, specifically as altered patterns of predator avoidance behavior, which have been correlated with population decline. Collectively, these data suggest that bifenthrin may be negatively impacting wild fish populations.

  • Copper inhibits hatching of fish embryos via inducing reactive oxygen species and down-regulating Wnt signaling
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-24
    YanJun Zhang, RuiTao Zhang, HaoJie Sun, Qi Chen, XueDong Yu, Ting Zhang, Ming Yi, Jing-Xia Liu

    The copper ion (Cu2+) has been reported to suppress the hatching of fish. However, little is known about the underlying mechanism. In this study, copper nanoparticles (CuNPs) and Cu2+ were shown to significantly suppress hatching of zebrafish in a dosage-dependent manner, and reactive oxygen species (ROS) scavengers NAC (N­acetylcysteine) & GSH (reduced glutathione) and Wnt signaling agonist BIO (6­Bromoindirubin­3’­oxime) significantly alleviated the suppressing effects of Cu2+ and CuNPs on egg hatching. Mechanistically, NAC, GSH, and BIO recovered the egg hatching in copper-treated group via increasing the embryonic motility rather than stimulating the expression and secretion of hatching enzymes before hatching. Additionally, no significant difference in egg hatching was observed between the control and Cu2+-treated group at 72 hpf (hours post fertilization) in cox17 mutant embryos, in which little ROS was producd after copper stimulation. This may be the first report that Cu2+ and CuNPs suppress embryonic motility and the subsequent hatching via inducing ROS and at the same time down-regulating Wnt signaling in fish embryos.

  • Neonicotinoid insecticides are potential substrates of the multixenobiotic resistance (MXR) mechanism in the non-target invertebrate, Dreissena sp
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-23
    Ágnes Vehovszky, Anna Farkas, Vivien Csikós, András Székács, Mária Mörtl, János Győri

    Mussels are among the most frequently used invertebrate animals in aquatic toxicology to detect toxic exposure in the environment. The presence and activity of a cellular defence system, the multixenobiotic resistance (MXR) mechanism, was also established in these organisms. In isolated gill tissues of dreissenid mussels (D. bugensis) the MXR activity was assayed after treatment by commercially available insecticides (formulated products) which contain neonicotinoids as their active ingredients: Actara (thiamethoxam), Apacs (clothianidin), Calypso (thiacloprid) and Kohinor (imidacloprid), respectively. While applying the accumulation assay method, 0.5 μM rhodamine B was used as model substrate and 20 μM verapamil as model inhibitor of the MXR mechanism. In acute (in vitro) experiments when isolated gills were co-incubated in graded concentrations of insecticides and rhodamine B simultaneously, Calypso and Kohinor treatment resulted increasing rhodamine accumulation. Chemical analysis of gills in vitro incubated in insecticides demonstrated higher tissue concentrations of thiamethoxam, clothianidin and thiacloprid in the presence of verapamil suggesting that the active ingredients of Actara, Apacs and Calypso are potential substrates of the MXR mediated cellular efflux. In contrast, verapamil did significantly alter the accumulated imidacloprid concentrations in gills, suggesting that the active component of Kohinor is not transported by the MXR mechanism. Chronic (in vivo) exposures of the intact animals in lower, 1, 10 mg/L concentration of neonicotinoid products, resulted in a decreased level of both rhodamine accumulation and verapamil inhibition by the 12th-14th days of treatment. These results suggest an enhancement of MXR activity (chemostimulation), building up gradually in the animals exposed to Actara, Apacs and Kohinor, respectively. Neonicotinoid-type insecticides are generally considered as selective neurotoxins for insects, targeting the nicotinic type acetylcholine receptors (nAChRs) in their central nervous system. Our present results provide the first evidences that neonicotinoid insecticides are also able to alter the transmembrane transport mechanisms related to the MXR system.

  • Differential nickel-induced responses of olfactory sensory neuron populations in zebrafish
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-23
    Maurizio Lazzari, Simone Bettini, Liliana Milani, Maria Gabriella Maurizii, Valeria Franceschini

    The olfactory epithelium of fish includes three main types of olfactory sensory neurons (OSNs). Whereas ciliated (cOSNs) and microvillous olfactory sensory neurons (mOSNs) are common to all vertebrates, a third, smaller group, the crypt cells, is exclusive for fish. Dissolved pollutants reach OSNs, thus resulting in impairment of the olfactory function with possible neurobehavioral damages, and nickel represents a diffuse olfactory toxicant. We studied the effects of three sublethal Ni2+ concentrations on the different OSN populations of zebrafish that is a widely used biological model. We applied image analysis with cell count and quantification of histochemically-detected markers of the different types of OSNs. The present study shows clear evidence of a differential responses of OSN populations to treatments. Densitometric values for Gα olf, a marker of cOSNs, decreased compared to control and showed a concentration-dependent effect in the ventral half of the olfactory rosette. The densitometric analysis of TRPC2, a marker of mOSNs, revealed a statistically significant reduction compared to control, smaller than the decrease for Gα olf and without concentration-dependent effects. After exposure, olfactory epithelium stained with anti-calretinin, a marker of c- and mOSNs, revealed a decrease in thickness while the sensory area appeared unchanged. The thickness reduction together with increased densitometric values for HuC/D, a marker of mature and immature neurons, suggests that the decrements in Gα olf and TRPC2 immunostaining may depend on cell death. However, reductions in the number of apical processes and of antigen expression could be a further explanation. We hypothesize that cOSNs are more sensitive than mOSNs to Ni2+ exposure. Difference between subpopulations of OSNs or differences in water flux throughout the olfactory cavity could account for the greater susceptibility of the OSNs located in the ventral half of the olfactory rosette. Cell count of anti-TrkA immunopositive cells reveals that Ni2+ exposure does not affect crypt cells. The results of this immunohistochemical study are not in line with those obtained by electro-olfactogram.

  • Different crystalline forms of titanium dioxide nanomaterial (rutile and anatase) can influence the toxicity of cooper in golden mussel Limnoperna fortunei?
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-22
    Silvana Manske Nunes, Marcelo Estrella Josende, Michael González-Durruthy, Caroline Pires Ruas, Marcos Alexandre Gelesky, Luis Alberto Romano, Daniele Fattorini, Francesco Regoli, José Maria Monserrat, Juliane Ventura-Lima

    Although some studies have showed the effects of different crystalline structures of nTiO2 (anatase and rutile) and their applicability in several fields, few studies has analyzed the effect of coexposure with other environmental contaminants such as copper. Thus, the objective of this study was to evaluate if the coexposure to nTiO2 (nominal concentration of 1 mg/L; anatase or rutile) can increase the incorporation and toxic effect induced by Cu (nominal concentration of 56 μg/L) in different tissues of Linmoperna fortunei after 120 h of exposure. Our results showed that the coexposure increased the accumulation of Cu in the gills and adductor muscle independently of the crystalline form and can positively or negatively modulate the antioxidant system, depending on the tissue analyzed. However, exposure only to rutile nTiO2 induced damage in the adductor muscle evidenced by the infiltration of hemocytes in this tissue. Additionally, histomorphometric changes based on fractal dimension analysis showed that coexposure to both forms of nTiO2 induced damage in the same tissue. These results suggest that both crystalline forms exhibited toxicity depending on the analyzed tissue and that coexposure of nTiO2 with Cu may be harmful in L. fortunei, indicating that increased attention to the use and release of nTiO2 in the environment is needed to avoid deleterious effects in aquatic biota.

  • Exposure of male tilapia (Oreochromis niloticus) to copper by intraperitoneal injection: DNA damage and larval impairment
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-21
    Gustavo Souza Santos, Giovano Neumann, Cristian Zwetzch do Nascimento, Cinthia Eloise Domingues, Sandro Xavier Campos, Robie Allan Bombardelli, Marta Margarete Cestari

    The present work aimed to assess the genotoxic effects of intraperitoneally injected copper in males of O. niloticus, and to investigate its association with eventual changes in the quality of the gametes and in the generation of offspring abnormalities. Thus, to evaluate DNA damage, the alkaline comet assay was performed in sperm and blood; sperm parameters were analyzed to determine the quality of the gametes, and the incidence of morphological abnormalities of larvae, originated from eggs fertilized by males exposed to copper, was used as a measure of reproductive impairment. Male fish were exposed to three doses (1 mg/kg, 2 mg/kg, 4 mg/kg) of copper sulfate via intraperitoneal injection and observed after 96 h of exposure. We found that the quality of gametes was not affected by copper, as indicated by the lack of differences in sperm parameters between the exposed and the control groups. Nonetheless, copper induced an increase in sperm DNA damage at all tested doses. Taking into consideration the total number of abnormalities, larvae presented a higher proportion of morphological abnormalities at all the tested doses. Considering the morphological abnormalities separately, the 2 mg/kg and 4 mg/kg groups presented significantly higher frequencies of arrested development and spinal abnormalities than the control group. This work suggests that intraperitoneally injected copper is an inductor of DNA breakage in germ cells of O. niloticus males. Copper induces the formation of larval morphological abnormalities, causing reproductive impairment to this species. The fact that copper did not induce alterations on sperm parameters indicates that the parental genotoxic effects are inheritable to the offspring.

  • Acute toxic effects of zinc oxide nanoparticles on Hydra magnipapillata
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-21
    Ade Yamindago, Nayun Lee, Seonock Woo, Hyosun Choi, Ji Young Mun, Seok-Won Jang, Sung Ik Yang, Friederike Anton-Erxleben, Thomas C.G. Bosch, Seungshic Yum

    Zinc oxide nanoparticles (ZnO NPs) are increasingly used in various products as coating and additive materials for household goods, personal-care products, and drug delivery systems. Because of their broad applications, the potential risks to nontarget organisms associated with their input into aquatic environments have generated much concern. We investigated the acute toxicity, morphological responses, and potential impact on physiology and metabolism in polyps exposed to spherical ZnO NPs of either 20 nm (ZnO NP20) or 100 nm (ZnO NP100). The median lethal concentrations (LC50) of ZnO NP20 were 55.3, 8.7, and 7.0 μg/mL after exposure for 48, 72, and 96 h, respectively; and those of ZnO NP100 were 262.0, 14.9, and 9.9 μg/mL, respectively. The morphological responses of the hydra polyps to a range of ZnO NP concentrations suggest that ZnO NPs may negatively affect neurotransmission in Hydra. ZnO NPs may also induce abnormal regeneration in the polyps by affecting the expression of several genes related to the Wnt signaling pathway. The presence of ZnO NP20 in the hydra tissue was confirmed with electron microscopy. A Gene Ontology analysis of the genes differentially expressed in hydra polyps after exposure to ZnO NP20 for 12 or 24 h revealed changes in various processes, including cellular and metabolic process, stress response, developmental process, and signaling. A KEGG pathway analysis of hydra polyps after exposure of ZnO NP20 or ZnO NP100 for 12 or 24 h demonstrated various changes, including in the DNA replication and repair, endocytosis, lysosomes, Wnt signaling, and natural killer-cell-mediated cytotoxicity pathways, suggesting the mechanisms that maintain cellular homeostasis in response to ZnO NPs. Progesterone-mediated oocyte maturation was also affected by the ZnO NPs nanoparticles, suggesting that they are potential endocrine disruptors. This study should increase our concern regarding the dispersal of ZnO NPs in aquatic environments.

  • Hepatic metabolite profiling of polychlorinated biphenyl (PCB)-resistant and sensitive populations of Atlantic killifish (Fundulus heteroclitus)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-16
    Lilah Glazer, Melissa C. Kido Soule, Krista Longnecker, Elizabeth B. Kujawinski, Neelakanteswar Aluru

    Atlantic killifish inhabiting polluted sites along the east coast of the U.S. have evolved resistance to toxic effects of contaminants. One such contaminated site is the Acushnet River estuary, near New Bedford Harbor (NBH), Massachusetts, which is characterized by very high PCB concentrations in the sediments and in the tissues of resident killifish. Though killifish at this site appear to be thriving, the metabolic costs of survival in a highly contaminated environment are not well understood. In this study we compared the hepatic metabolite profiles of resistant (NBH) and sensitive populations (Scorton Creek (SC), Sandwich, MA) using a targeted metabolomics approach in which polar metabolites were extracted from adult fish livers and quantified. Our results revealed differences in the levels of several metabolites between fish from the two sites. The majority of these metabolites are associated with one-carbon metabolism, an important pathway that supports multiple physiological processes including DNA and protein methylation, nucleic acid biosynthesis and amino acid metabolism. We measured the gene expression of DNA methylation (DNA methyltransferase 1, dnmt1) and demethylation genes (Ten-Eleven Translocation (TET) genes) in the two populations, and observed lower levels of dnmt1 and higher levels of TET gene expression in the NBH livers, suggesting possible differences in DNA methylation profiles. Consistent with this, the two populations differed significantly in the levels of 5-methylcytosine and 5-hydroxy methylcytosine nucleotides. Overall, our results suggest that the unique hepatic metabolite signatures observed in NBH and SC reflect the adaptive mechanisms for survival in their respective habitats.

  • Metabolomic alterations and oxidative stress are associated with environmental pollution in Procambarus clarkii
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-13
    Ricardo Fernández-Cisnal, Miguel A. García-Sevillano, Tamara García-Barrera, José L. Gómez-Ariza, Nieves Abril
  • Environmentally-relevant mixture of pharmaceutical drugs stimulates sex-steroid hormone production and modulates the expression of candidate genes in the ovary of juvenile female rainbow trout
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-13
    Mélodie Schmitz, Mahaut Beghin, Syaghalirwa N.M. Mandiki, Katherine Nott, Michaël Gillet, Sébastien Ronkart, Christelle Robert, Sébastien Baekelandt, Patrick Kestemont
  • Interaction between 1,2-benzisothiazol-3(2H)-one and microalgae: growth inhibition and detoxification mechanism
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-10
    WANG Xiao-Xiong, ZHANG Tian-Yuan, DAO Guo-Hua, HU Hong-Ying

    Isothiazolinones, such as 1,2-benzisothiazol-3(2 H)-one (BIT), are widely used as biocides for bacterial growth control in many domestic and industrial processes. Despite their advantages as biocides, they are highly toxic and pose a potential risk to the environment. This study investigated the inhibition process and detoxification mechanism involved in microalgal survival and growth recovery after BIT poisoning. BIT could seriously inhibit the growth of Scenedesmus sp. LX1, Chlorella sp. HQ, and Chlamydomonas reinhardtii with half maximal effective concentrations at 72 h (72h-EC50) of 1.70, 0.41, and 1.16 mg/L, respectively. The primary inhibition mechanism was the BIT-induced damage to microalgal photosynthetic systems. However, the inhibited strains could recover when their growth was not completely inhibited. The influence of this inhibiting effect on subsequent algal regrowth was negligible or weak. BIT consumption was the primary reason for their recovery. Notably, algae did not die even if their growth was completely inhibited. If the BIT concentration did not exceed a certain high level, then the inhibited algae could recover their growth relatively well. Microalgal generation of reduced glutathione (GSH) and the oxygen radical scavenging enzymes, superoxide dismutase (SOD) and catalase (CAT), played a key role in detoxification against BIT poisoning.

  • Effects of environmentally relevant metformin exposure on Japanese medaka (Oryzias latipes)
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-09
    Erin Ussery, Kristin N. Bridges, Zacharias Pandelides, Andrea E. Kirkwood, Dario Bonetta, Barney J. Venables, John Guchardi, Douglas Holdway

    Metformin is one of the most prevalent pharmaceuticals in both surface and waste waters, yet little is known about the bioavailability and/or effects of developmental exposure on early life stage (ELS) fish. Here, we demonstrate that embryo-larval stages of medaka are capable of taking up metformin from the aquatic environment, provided exposure occurs prior to chorion hardening (~6-hpf). Once transferred to clean water, ELS medaka are able to completely depurate metformin in < 24-hours. Furthermore, ELS medaka exposed to a range of relevant concentrations of waterborne metformin (from 6 hpf through 28-days post hatch) had significantly reduced growth metrics, altered metabolomes, and changes in the expression of genes associated with cell growth. The range of concentrations investigated were 1.0, 3.2, 10, 32, and 100 µg · L-1. To examine effects of chronic, low level metformin exposure across the full medaka life-cycle, we exposed newly fertilized embryos to 3.2 µg · L-1 waterborne metformin for 165-days. The weight and length of adult fish were examined, as were effects on the production of some steroid hormones, specifically a significant increase (control females: 0.161 ± 0.023 pg/mg; metformin treated females: 3.42 ± 0.543) in the production of 11-ketotestosterone was observed in adult female medaka. Collectively, these results suggest that current environmental exposure scenarios may be sufficient to cause effects on developing fish.

  • The stresses of allelochemicals isolated from culture solution of diatom Phaeodactylum tricornutum Bohlin on growth and physiology of two marine algae
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-09
    Qiaona Xue, Rui Wang, Wenjing Xu, Jiangtao Wang, Liju Tan

    The allelopathic effects of extracts isolated from the culture filtrate of diatom Phaeodactylum triconutum Bohlin on typical marine microalgae Prorocentrum donghaiense Lu and Dunaliella salina Teodoresco were investigated by determining different physiological and biochemical parameters, such as growth rate, membrane systems and esterase activity under controlled laboratory conditions. The growth of P. donghaiense was significantly inhibited immediately after exposure to the allelochemicals, while the algae density of D. salina was less sensitive. Chlorophyll-a content, membrane systems, as well as esterase activity were simultaneously investigated by flow cytometry with particular fluorescent markers and exhibited changeable sensitivities. The results demonstrated that the membrane systems of P. donghaiense were suppressed by the allelochemicals directly, causing loss of integrity and membrane penetration. Esterase activity was the most sensitive indicator as that of P. donghaiense cells significantly increased in short time and was inhibited subsequently. However, the membrane of D. salina remained intact still after exposure to the extracts and the esterase activity was only inhibited on last day during experiment period. Membrane potential and chlorophyll-a content of the two marine algae also showed somewhat different changes, as that of P. donghaiense cells were impaired after 5 day exposure to all volume conditions while these two characteristics of D. salina was only suppressed by exposure to high volume of the allelochemicals on day 6. The present results indicated that the inhibition of culture filtrate of P. triconutum on P. donghaiense was algicidal whereas the effect on D. salina appeared to be algistatic.

  • Assessment of Adverse Outcome of Excel Mera 71 in Anabas testudineus by Histological and Ultrastructural Alterations
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-03
    Palas Samanta, Sandipan Pal, Tarakeshwar Senapati, Aloke Kumar Mukherjee, Apurba Ratan Ghosh

    Present study was designed to evaluate the adverse effect of glyphosate-based herbicide, Excel Mera 71 in Anabas testudineus on comparative basis under field and laboratory conditions. Field (750 g/acre) and laboratory (17.2 mg/L) experiments were performed for a period of 30 days. For field experiment special type of cages were prepared. Fish gill, liver, and kidney were analyzed for histology and ultrastructural responses. A significant increment in morphometric indices (DTC) was observed in gill, liver and kidney of A. testudineus under laboratory condition (p < 0.05) and responses showed the degree of pathogenicity in the order of liver > kidney > gills. However, under field study significant increase in DTC value was observed in gill and liver (p < 0.05). Among the scanning electron microscopic (SEM) observations necrosis and loss of microridges, and damage in stratified epithelial cells were prominent in gill, although higher prevalence of alterations was observed under laboratory study than field study. Additionally, transmission electron microscopic (TEM) observations also depicted higher prevalence of pathological lesions under laboratory study compared with field observation. Among the TEM observations damage in chloride and pavement cells, degenerative mitochondria and nucleus (in gill); severe vacuolation, necrosed nucleus and vesiculated network in case of liver and degenerated epithelial cells, cytoplasmic vacuolation, and damage in proximal convoluted tubules (PCT) in case of kidney were prominent. Therefore, these findings demonstrated that Excel Mera 71 induces significant damage in tissues of A. testudineus and these responses might be considered as biomarkers for monitoring herbicidal toxicity on fish in aquatic body.

  • Natural variability and modulation by environmental stressors of global genomic cytosine methylation levels in a freshwater crustacean, Gammarus fossarum
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-10-02
    Pauline Cribiu, Arnaud Chaumot, Olivier Geffard, Jean-Luc Ravanat, Thérèse Bastide, Nicolas Delorme, Hervé Quéau, Sylvain Caillat, Alain Devaux, Sylvie Bony

    To improve the assessment of aquatic organism responses to environmental stressors, there is an interest in studying epigenetic marks in addition to other validated biomarkers. Indeed, the epigenetic marks may be influenced by the surrounding environment. Non-model invertebrates such as gammarids are sentinel organisms representative of the diversity of natural stream communities. Despite their ecologically relevance, the epigenetic responses have been to date poorly documented in these species. The present study explores the measurement of the global cytosine methylation level in the genome of the freshwater crustacean Gammarus fossarum. In a first step, natural variability of global cytosine methylation level (basal level) was assessed by studying the effect of sex, age and sampling site of organisms. Results showed a significant effect of age and sampling site. In a second step, effects of water temperature and food starvation were studied. For both factors, a hypermethylation was observed after 1 month of exposure. In a third step, gammarids were exposed to a range of environmentally relevant cadmium concentrations (0.05-5 µg/L) in order to assess the effect of a chemical stress. Whatever the cadmium concentration used, a significant hypomethylation was observed after 14 days followed by a trend for hypermethylation after 1 month of exposure. These results are the first ones dealing with the 5C-methylation status in gammarids. The results constitute potential markers of environmental stresses in relevant sentinel species widely used in ecotoxicological studies.

  • Characterization of AHR1 and its Functional Activity in Atlantic Sturgeon and Shortnose Sturgeon
    Aquat. Toxicol. (IF 3.884) Pub Date : 2018-09-29
    Nirmal K. Roy, Melissa DellaTorre, Allison Candelmo, R. Christopher Chambers, Ehren Habeck, Isaac Wirgin

    Sturgeon species are imperiled world-wide by a variety of anthropogenic stressors including chemical contaminants. Atlantic sturgeon, Acipenser oxyrinchus, and shortnose sturgeon, Acipenser brevirostrum, are largely sympatric acipenserids whose young life-stages are often exposed to high levels of benthic-borne PCBs and PCDD/Fs in large estuaries along the Atlantic Coast of North America. In previous laboratory studies, we demonstrated that both sturgeon species are sensitive to early life-stage toxicities from exposure to environmentally relevant concentrations of coplanar PCBs and TCDD. The sensitivity of young life-stages of fishes to these contaminants varies among species by three orders of magnitude and often is due to variation in the structure and function of the aryl hydrocarbon receptor (AHR) pathway. Unlike mammals, fishes have two forms of AHR (AHR1 and AHR2) with AHR2 usually being more highly expressed across tissues and functional in mediating toxicities. Based on previous studies in white sturgeon, A. transmontanus, we hypothesized that sturgeon taxa are unusually sensitive to these contaminants because of higher levels of expression and functional activity of AHR1 than in other fish taxa. To address this possibility, we characterized AHR1 in both Atlantic Coast sturgeon species, evaluated its’ in vivo expression in young life-stages and in multiple tissues of shortnose sturgeon, and tested its ability to drive reporter gene expression in AHR-deficient cells treated with graded doses of PCB126 and TCDD. Similar to white sturgeon and lake sturgeon, AHR1 amino acid sequences in Atlantic sturgeon and shortnose sturgeon were more similar to mammalian AHRs and avian AHR1s than to AHR1 in other fishes, suggesting their greater functionality in sturgeon species than in other fishes. Exposure to graded doses of coplanar PCBs and TCDD usually failed to significantly induce AHR1 expression in young life-stages or most tissues of shortnose sturgeon. However, in reporter gene assays, AHR1 drove higher levels of gene expression than AHR2 alone, but their binary combination failed to drive higher levels of expression than either AHR alone. In total, our results suggest that AHR1 may be more functional in sturgeon species than in other fishes, but probably does not explain their heightened sensitivity to these contaminants.

Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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