Oxidative and interactive challenge of cadmium and ocean acidification on the smooth scallop Flexopecten glaber Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-08 Alessandro Nardi, Maura Benedetti, Daniele Fattorini, Francesco Regoli
Effects of domestic effluent discharges on mangrove crab physiology: integrated energetic, osmoregulatory and redox balances of a key engineer species Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-06 Dimitri Theuerkauff, Georgina A. Rivera-Ingraham, Yann Mercky, Mathilde Lejeune, Elliott Sucré, Jehan-Hervé Lignot
Mangroves are increasingly used as biofiltering systems of (pre-treated) domestic effluents. However, these wastewater discharges may affect local macrofauna. This laboratory study investigates the effects of wastewater exposure on the mangrove spider crab Neosarmatium meinerti, a key engineering species which is known to be affected by waste waters in effluent-impacted areas. These effects were quantified by monitoring biological markers of physiological state, namely oxygen consumption, the branchial cavity ventilation rate, gill physiology and morphology, and osmoregulatory and redox balance. Adults acclimated to clean seawater (SW, 32 ppt) and freshwater (FW, ∼0 ppt) were compared to crabs exposed to wastewater for 5 hours (WW, ∼0 ppt). Spider crabs exposed to WW increased their ventilation and whole-animal respiration rates by 2- and 3-fold respectively, while isolated gill respiration increased in the animals exposed to FW (from 0.5 to 2.3 and 1.1 nmol O2 min−1 mgDW−1 for anterior and posterior gills, respectively) but was not modified in WW-exposed individuals. WW exposure also impaired crab osmoregulatory capacity; an 80 mOsm.kg−1 decrease was observed compared to FW, likely due to decreased branchial NKA activity. ROS production (DCF fluorescence in hemolymph), antioxidant defenses (superoxide dismutase and catalase activities) and oxidative damage (malondialdehyde concentration) responses varied according to animal gender. Overall, this study demonstrates that specific physiological parameters must be considered when focusing on crabs with bimodal breathing capacities. We conclude that spider crabs exposed to WW face osmoregulatory imbalances due to functional and morphological gill remodeling, which must rapidly exhaust energy reserves. These physiological disruptions could explain the ecological changes observed in the field.
Effects of lanthanum on Microcystis aeruginosa: Attention to the changes in composition and content of cellular microcystins Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-06 Fei Shen, Lihong Wang, Qing Zhou, Xiaohua Huang
Algal blooms threaten human health and aquatic ecosystem through the production of microcystins (MCs) by toxic strains. The accumulation of rare earth elements (REEs) in water affects the growth and physiological activities of algae. However, whether or how REEs affect cellular microcystins (MCs) is largely unknown. In this study, the effects of lanthanum ion [La(III)], a type of REE, on the MCs in Microcystis aeruginosa were investigated, and the mechanism of the effect was analyzed using ecological stoichiometry. The different concentrations of La(III) were selected to correlate environmental pollution status. Low-dose La(III) (0.2, 2.0, and 4.0 μM) exposure increased the total content of MCs and the percentage contents of microcystin-YR (MC-YR) and microcystin-LW (MC-LW) and decreased the percentage content of microcystin-LR (MC-LR). High-dose La(III) (8.0, 20, 40, and 60 μM) exposure decreased the total content of the MCs, increased the percentage content of MC-LR, and decreased the percentage contents of MC-YR and MC-LW. The changes in the total MCs content were positively associated with the ratios of C:P and N:P in algal cells. The composition of MCs was dependent on the ratio of C:N in algal cells; for example, the percentage content of MC-LR decreased and the percentage content of MC-YR and MC-LW increased as the ratio of C:N in algal cells increased. In conclusion, La(III) could affect the content and composition of MCs via changes in the growth and chlorophyll-a content of Microcystis aeruginosa, and these effects depended on the ratios of C:P, N:P, and C:N in Microcystis aeruginosa. Such changes may influence the toxicity of Microcystis blooms. The results provides a new insight into the mechanism of REEs effects on algal toxins and provide references for evaluating environmental risks of REEs pollution in aquatic ecosystems.
Effects of copper and butyltin compounds on the growth, photosynthetic activity and toxin production of two HAB dinoflagellates : the planktonic Alexandrium catenella and the benthic Ostreopsis cf. ovata Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-06 Douglas Couet, Olivier Pringault, Chrystelle Bancon-Montigny, Nicolas Briant, Françoise Elbaz Poulichet, Sophie Delpoux, Ons Kéfi-Daly Yahia, BenGharbia Hela, M’Rabet Charaf, Fabienne Hervé, Georges Rovillon, Zouher Amzil, Mohamed Laabir
Controlled laboratory experiments were conducted to test the effects of copper (Cu2+) and butyltins (BuT) on the growth, photosynthetic activity and toxin content of two HABs (Harmful Algal Blooms) dinoflagellates, the planktonic Alexandrium catenella and the benthic Ostreopsis cf. ovata. Microalgae were exposed to increasing concentrations of Cu2+ (10−4 to 31 nM) or BuT (0.084 to 84 nM) for seven days. When considering the growth, EC50 values were 0.16 (±0.09) nM and 0.03 (±0.02) nM of Cu2+ for A. catenella and O. cf. ovata, respectively. Regarding BuT, EC50 was 14.2 (±6) nM for O. cf. ovata, while A. catenella growth inhibition appeared at BuT concentrations ≥27 nM. Photosynthetic activity of the studied dinoflagellates decreased with increasing Cu and BuT concentrations. For O. cf. ovata, the response of this physiological parameter to contamination was less sensitive than the biomass. Cu exposure induced the formation of temporary cysts in both organisms that could resist adverse conditions. The ovatoxin-a and -b concentrations in O. cf. ovata cells increased significantly in the presence of Cu. Altogether, the results suggest a better tolerance of the planktonic A. catenella to Cu and BuT. This could result in a differentiated selection pressure exerted by these metals on phytoplankton species in highly polluted waters. The over-production of toxins in response to Cu stress could pose supplementary health and socio-economic threats in the contaminated marine ecosystems where HABs develop.
Effects of ocean acidification on copepods Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-05 Minghua Wang, Chang-Bum Jeong, Young Hwan Lee, Jae-Seong Lee
Ocean acidification (OA) leads to significant changes in seawater carbon chemistry, broadly affects marine organisms, and considered as a global threat to the fitness of marine ecosystems. Due to the crucial role of copepods in marine food webs of transferring energy from primary producers to higher trophic levels, numerous studies have been conducted to examine the impacts of OA on biological traits of copepods such as growth and reproduction. Under OA stress, the copepods demonstrated species-specific and stage-dependent responses. Notably, different populations of the same copepod species demonstrated different sensitivities to the increased pCO2. In copepods, the deleterious effects of OA are also reinforced by other naturally occurring co-stressors (e.g., thermal stress, food deprivation, and metal pollution). Given that most OA stress studies have focused on the effects of short-term exposure (shorter than a single generation), experiments using adults might have underestimated the damaging effects of OA and the long-term multigenerational exposure to multiple stressors (e.g., increased pCO2 and food shortage) will be required. Particularly, omics-based technologies (e.g., genomics, proteomics, and metabolomics) will be helpful to better understand the underlying processes behind biological responses (e.g., survival, development, and offspring production) at the mechanistic level which will improve our predictions of the responses of copepods to climate change stressors including OA.
Title: Vitamin C attenuates biochemical and genotoxic damage in common carp (Cyprinus carpio) upon joint exposure to combined toxic doses of fipronil and buprofezin insecticides Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-05 Madiha Ghazanfar, Sana Shahid, Irfan Zia Qureshi
Feeding inhibition in Corbicula fluminea (O.F. Muller, 1774) as an effect criterion to pollutant exposure: perspectives for ecotoxicity screening and refinement of chemical control Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-04 Bruno Branco Castro, Carlos Silva, Inês Patrunilho Efe Macário, Bruno Oliveira, Fernando Gonçalves, Joana Luísa Pereira
Bivalves are commonly used in biomonitoring programs to track pollutants. Several features, including its filter-feeding abilities, cumulatively argue in favour of the use of the Asian clam (Corbicula fluminea) as a biosentinel and an ecotoxicological model. Filtration in bivalves is very sensitive to external stimuli and its control is dictated by regulation of the opening/closure of the valves, which may be used as an avoidance defence against contaminants. Here, we investigate the filter-feeding behaviour of the Asian clam as an endpoint for assessing exposure to pollutants, driven by two complementary goals: (i) to generate relevant and sensitive toxicological information based on the ability of C. fluminea to clear an algal suspension, using the invasive species as a surrogate for native bivalves; (ii) to gain insight on the potential of exploring this integrative response in the refinement of chemical control methods for this pest. Clearance rates and proportion of algae removed were measured using a simple and reproducible protocol. Despite some variation across individuals and size classes, 50–90% of food particles were generally removed within 60–120 min by clams larger than 20 mm. Removal of algae was sensitive to an array of model contaminants with biocide potential, including fertilizers, pesticides, metals and salts: eight out of nine tested substances were detected at the μg l−1 or mg l−1 range and triggered valve closure, decreasing filter-feeding in a concentration-dependent manner. For most toxicants, a good agreement between mortality (96 h − LC50 within the range 0.4–5500 mg l−1) and feeding (2 h − IC50 within the range 0.005–2317 mg l−1) was observed, demonstrating that a 120-min assay can be used as a protective surrogate of acute toxicity. However, copper sulphate was very strongly avoided by the clams (IC50 = 5.3 μg l−1); on the contrary, dichlorvos (an organophosphate insecticide) did not cause feeding depression, either by being undetected by the clams’ chemosensors and/or by interfering with the valve closure mechanism. Such an assay has a large potential as a simple screening tool for industry, environmental agencies and managers. The ability of dichlorvos to bypass the Asian clam’s avoidance strategy puts it in the spotlight as a potential agent to be used alone or combined with others in eradication programs of this biofouler in closed or semi-closed industrial settings.
Copper induces expression and methylation changes of early development genes in Crassostrea gigas embryos Aquat. Toxicol. (IF 4.129) Pub Date : 2018-01-03 Rossana Sussarellu, Morgane Lebreton, Julien Rouxel, Farida Akcha, Guillaume Rivière
Copper contamination is widespread along coastal areas and exerts adverse effects on marine organisms such as mollusks. In the Pacific oyster, copper induces severe developmental abnormalities during early life stages; however, the underlying molecular mechanisms are largely unknown. This study aims to better understand whether the embryotoxic effects of copper in Crassostrea gigas could be mediated by alterations in gene expression, and the putative role of DNA methylation, which is known to contribute to gene regulation in early embryo development.For that purpose, oyster embryos were exposed to 4 nominal copper concentrations (0.1, 1, 10 and 20 μg L−1 Cu2+) during early development assays. Embryotoxicity was monitored through the oyster embryo-larval bioassay at the D-larva stage 24 h post fertilization (hpf) and genotoxicity at gastrulation 7 hpf. In parallel, the relative expression of 15 genes encoding putative homeotic, biomineralization and DNA methylation proteins was measured at three developmental stages (3 hpf morula stage, 7 hpf gastrula stage, 24 hpf D-larvae stage) using RT-qPCR. Global DNA content in methylcytosine and hydroxymethylcytosine were measured by HPLC and gene-specific DNA methylation levels were monitored using MeDIP-qPCR.A significant increase in larval abnormalities was observed from copper concentrations of 10 μg L−1, while significant genotoxic effects were detected at 1 μg L−1 and above. All the selected genes presented a stage-dependent expression pattern, which was impaired for some homeobox and DNA methylation genes (Notochord, HOXA1, HOX2, Lox5, DNMT3b and CXXC-1) after copper exposure. While global DNA methylation (5-methylcytosine) at gastrula stage didn’t show significant changes between experimental conditions, 5-hydroxymethylcytosine, its degradation product, decreased upon copper treatment. The DNA methylation of exons and the transcript levels were correlated in control samples for HOXA1 but such a correlation was diminished following copper exposure. The methylation level of some specific gene regions (HoxA1, Hox2, Engrailed2 and Notochord) displayed changes upon copper exposure. Such changes were gene and exon-specific and no obvious global trends could be identified. Our study suggests that the embryotoxic effects of copper in oysters could involve homeotic gene expression impairment possibly by changing DNA methylation levels.
Toxicokinetic and toxicodynamic of depleted uranium in the zebrafish, Danio rerio Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-30 Olivier Simon, Béatrice Gagnaire, Virginie Camilleri, Isabelle Cavalié, Magali Floriani, Christelle Adam-Guillermin
This study investigated the accumulation pattern and biological effects (genotoxicity and histopathology) to adult zebrafish (male and female) exposed to a nominal waterborne concentration of 20 μg L−1 of depleted uranium (DU) for 28 days followed by 27 days of depuration. Accumulation pattern showed that (i) DU accumulated in brain, (ii) levels in digestive tract were higher than those measured in gills and (iii) levels remained high in kidney, brain and ovary despite the 27 days of depuration period. Genotoxicity, assessed by comet assay, was significant not only during DU exposure, but also during depuration phase. Gonads, in particular the testes, were more sensitive than gills. The histology of gonads indicated severe biological damages in males. This study improved knowledge of ecotoxic profile of uranium, for which a large range of biological effects has already been demonstrated.
Novel approach for evaluating pharmaceuticals toxicity using Daphnia model: analysis of the mode of cytochrome P450-generated metabolite action after acetaminophen exposure Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-30 Ryeo-Ok Kim, Min-A Jo, Jinhaeng Song, Il-Chan Kim, Seokjoo Yoon, Woo-Keun Kim
Because of its widespread use, the pharmaceutical acetaminophen (APAP) is frequently detected in aquatic environments. APAP can have serious physiological effects, such as reduced reproduction, low growth rates, and abnormal behavior, in aquatic organisms. However, the methods available for evaluation of the aquatic toxicity of APAP are of limited usefulness. The present study aimed to develop reliable and sensitive markers for evaluation of APAP toxicity using Daphnia as a model organism. We focused on N-acetyl-p-benzoquinoneimine (NAPQI) production from APAP via cytochrome P450 metabolism because NAPQI causes APAP toxicity. Daphnia magna were exposed to APAP (0, 50, or 100 mg/L for 12 h or 24 h), and the total metabolites were extracted and analyzed for NAPQI. Direct detection of NAPQI was difficult because of its high reactivity, and its peak was close to that for APAP. Therefore, we tried to identify molecular and biochemical indicators associated with NAPQI generation, elimination, and its interactions with macromolecules. We identified changes in CYP370A13 gene expression, glutathione depletion, inhibition of thioredoxin reductase activity, and production of reactive oxygen species as indicators of D. magna exposure to APAP. These indicators could be used to develop sensitive and accurate techniques to evaluate the environmental toxicity of APAP.
The protective role of multixenobiotic resistance (MXR)-mediated ATP-binding cassette (ABC) transporters in biocides-exposed rotifer Brachionus koreanus Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-30 Young Hwan Lee, Hye-Min Kang, Min-Sub Kim, Jin-Sol Lee, Chang-Bum Jeong, Jae-Seong Lee
The effect of chlorpyrifos on salinity acclimation of juvenile rainbow trout (Oncorhynchus mykiss) Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-28 Bagher Mojazi Amiri, Elvis Genbo Xu, Allison Kupsco, Marissa Giroux, Mahbubeh Hoseinzadeh, Daniel Schlenk
As a part of their unique life cycle, most salmonids undergo a transition from fresh water to salt water requiring various adjustments in metabolism, osmoregulation and ion regulation. Exposure to pesticides may affect the acclimation of juvenile salmonids to salt water during downstream migration to estuaries. Using the Caspian Sea as a model waterbody, the present study aimed to determine how the toxicity of the organophosphate pesticide chlorpyrifos (CPF) impacts saline acclimation of rainbow trout (Oncorhynchus mykiss). We pre-exposed 4-month-old fish to nominal concentrations of 0, 20, 40, 80, 160 μg/L of CPF for seven days, and then gradually to salinity (12ppt) for another seven days. Mortality, levels of cortisol, T3 and T4 in serum, and expression of genes involved in gill ion transport (Na+/K+ATPase α1a and α1b) and liver xenobiotic detoxification (Glutathione-S-Transferase pi, GST) were measured at day fourteen. Cortisol concentrations in serum were not changed by CPF exposure in freshwater, but serum T3 increased up to three fold relative to controls in freshwater. Following salinity acclimation, T3 and T4 concentrations in the serum were both increased up to 2.5 and 8.8 fold in animals treated with CPF followed by saltwater. Na+/K + ATPase α1a and α1b mRNA in gill were unchanged by CPF treatment in freshwater but trended higher in CPF-treated animals after salinity acclimation. Hepatic mRNA of GST was significantly increased following exposure to CPF but was unchanged after saltwater exposure. Although saltwater treatment reduced the acute lethality of CPF, changes in T3/T4 suggest sublethal impacts may occur in CPF-treated fish after they acclimate to Caspian seawater.
Multixenobiotic resistance in Mytilus edulis: molecular and functional characterization of an ABCG2- type transporter in hemocytes and gills Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-28 Yosra Ben Cheikh, Benoit Xuereb, Céline Boulangé-Lecomte, Frank Le Foll
Among the cellular protection arsenal, ABC transporters play an important role in xenobiotic efflux in marine organisms. Two pumps belonging to B and C subfamily has been identified in Mytilus edulis. In this study, we investigated the presence of the third major subtype ABCG2/BCRP protein in mussel tissues. Transcript was expressed in hemocytes and with higher level in gills. Molecular characterization revealed that mussel ABCG2 transporter shares the sequence and organizational structure with mammalian and molluscan orthologs. Overall identity of the predicted amino acid sequence with corresponding homologs from other organisms was between 49% and 98%. Moreover, protein efflux activity was demonstrated using a combination of fluorescent allocrites and specific inhibitors. The accumulation of bodipy prazosin and pheophorbide A was heterogeneous in gills and hemocytes. Most of the used blockers enhanced probe accumulation at different levels, most significantly for bodipy prazosin. Moreover, Mrp classical blocker MK571 showed a polyspecificity. In conclusion, our data demonstrate that several ABC transporters contribute to MXR phenotype in the blue mussel including ABCG2 that forms an active pump in hemocytes and gills. Efforts are needed to distinguish between the different members and to explore their single function and specificity towards allocrites and chemosensitizers.
Role of mTOR in autophagic and lysosomal reactions to environmental stressors in molluscs Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-28 Susanna Sforzini, Michael N. Moore, Caterina Oliveri, Anna Volta, Awadhesh Jha, Mohamed Banni, Aldo Viarengo
Lysosomal membrane stability (LMS) has been used in various organisms as a very sensitive biomarker of stress. However, despite the abundance of data about regulation of the autophagic process in mammals, in the invertebrates there is only limited mechanistic understanding. Marine mussels (Mytilus galloprovincialis Lam.) are bivalve molluscs, widely used as models in ecotoxicology and as environmental bioindicators of sea water quality. In order to elucidate this fundamental process, in the present study, mussels were exposed for 3 days to a “priority”, ubiquitous environmental contaminant, benzo[a]pyrene (B[a]P) at different concentrations (i.e. 5, 50, 100 μg/L seawater). B[a]P accumulated in lysosomes of digestive tubule epithelial cells (digestive cells) and in enlarged lipid-rich lysosomes (autolysosomes) as detected by immunofluorescence and UV-fluorescence. B[a]P also activated the autophagic process with a marked decrease of LMS and concurrent increase in lysosomal/cytoplasmic volume ratio. Dephosphorylation of mTOR contributes to increased lysosomal membrane permeability and induced autophagy. B[a]P induced a decrease in phosphorylated (active form) mTOR. The probable role of mTOR in cell signalling and the regulation of the cellular responses to the contaminants has been also confirmed in a field study, where there was significant inactivation of mTOR in stressed animals. Statistical and network modelling supported the empirical investigations of autophagy and mTOR; and was used to integrate the mechanistic biomarker data with chemical analysis and DNA damage.
Microplastics have a more profound impact than elevated temperatures on the predatory performance, digestion and energy metabolism of an Amazonian cichlid Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-26 Bin Wen, Nan Zhang, Shi-Rong Jin, Zai-Zhong Chen, Jian-Zhong Gao, Ying Liu, Han-Peng Liu, Zhe Xu
Knowledge on the impacts of microplastics (MPs) pollution on freshwater environments and biota remains limited. Meanwhile, freshwater ecosystems have been threatened by elevated temperatures caused by climate change. To date, no information exists on how MPs—especially under elevated temperature conditions—affect predatory performance, digestive processes and metabolic pathways in freshwater organisms. Here, we examined MPs, elevated temperature and their combined effects on juveniles (0+ group) of an Amazonian cichlid, the discus fish (Symphysodon aequifasciatus). For 30 days, fish were exposed to ambient or elevated temperatures (i.e., 28 or 31 °C) in the absence or presence of MPs (i.e., 0 or 200 μg/L). The following metrics were quantified: MPs accumulation; predatory performance; and biomarkers involved in neurotransmission, digestion and energy production. The results showed that survival rate and body length were not affected by MPs, elevated temperatures or their combination. Elevated temperatures resulted in an increase in MP concentrations in fish bodies. Exposure to MPs decreased the post-exposure predatory performance (PEPP) at ambient temperatures but not at elevated temperatures. Elevated temperatures, however, had no effect on the PEPP but antagonistically interacted with MPs, leading to similar predatory performances under present and future conditions. Acetylcholinesterase (AChE) activity was only affected by MPs and decreased in the presence of MPs, indicating adverse effects in nervous and neuromuscular function and, thus, potentially in predatory performance. Trypsin activity was only influenced by MPs and decreased during exposure to MPs. Elevated temperatures or MPs alone increased the amylase activity but interacted antagonistically. Lipase activity was not influenced by either of the two stressors. In contrast, alkaline phosphatase (ALP) activity was affected by MPs or elevated temperatures alone and decreased with both stressors. Such results indicate deficits in the digestive capabilities of early-stage S. aequifasciatus under elevated temperature conditions and especially during exposure to MPs. Electron transport system (ETS) activity was not influenced by either of the two stressors. Both elevated temperatures and MPs alone increased LDH activity; however, the interaction between the two stressors cancelled activity but was still higher than activity in present conditions. Citrate synthase (CS) activity decreased with elevated temperature but increased during exposure to MPs. Cytochrome c oxidase (COX) activity was only influenced by MPs and increased in the presence of MPs. Thus, S. aequifasciatus juveniles exposed to elevated temperatures and MPs not only relied on anaerobic glycolysis for energy production but also depended on aerobic metabolism in the presence of MPs. Overall, these findings suggested that MPs showed a greater impact than elevated temperatures on the predatory performance, digestion and energy production of S. aequifasciatus. Nevertheless, juvenile survival and growth were minimally impacted, and thus, S. aequifasciatus could cope with near-future temperature increases and MP exposure.
Effects of triphenyl phosphate on growth, reproduction and transcription of genes of Daphnia magna Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-23 Siliang Yuan, Han Li, Yao Dang, Chunsheng Liu
The additive flame retardant triphenyl phosphate (TPHP) has been frequently detected in environments and biota. Evidences indicate that TPHP has potential risks to aquatic organisms. Seldom has been reported about its chronic effects to aquatic organism at low trophic levels, such as Cladocera. In the present study, <12 h old Daphnia magna (D. magna) were exposed to 0, 5, 50 or 500 μg/L TPHP for 21 days to investigate the chronic effects of TPHP on body length, fecundity and survival. Meanwhile, D. magna PCR arrays were used to evaluate the transcriptional responses of 155 genes involved in 40 pathways. Exposure to 500 μg/L TPHP for 21 days significantly decreased the body lengths of both F0 and F1 generation and inhibited the fecundity of F0 generation. Results of RT-qPCR showed that the expressions of 76 genes involved in 15 pathways were significantly altered after exposure to 500 μg/L TPHP for 21 days. The significantly altered pathways related to genetic information processing, cellular process and metabolism might be responsible for the observed effects of TPHP. Overall, our results showed that chronic exposure to TPHP caused developmental and reproductive toxicities to D. magna.
A glyphosate micro-emulsion formulation displays teratogenicity in Xenopus laevis Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-24 P. Bonfanti, M. Saibene, R. Bacchetta, P. Mantecca, A. Colombo
Glyphosate is the active ingredient in broad-spectrum herbicide formulations used in agriculture, domestic area and aquatic weed control worldwide. Its market is growing steadily concurrently with the cultivation of glyphosate-tolerant transgenic crops and emergence of weeds less sensitive to glyphosate. Ephemeral and lentic waters near to agricultural lands, representing favorite habitats for amphibian reproduction and early life-stage development, may thus be contaminated by glyphosate based herbicides (GBHs) residues. Previous studies on larval anuran species highlighted increased mortality and growth effects after exposure to different GBHs in comparison to glyphosate itself, mainly because of the surfactants such as polyethoxylated tallow amine present in the formulations. Nevertheless, these conclusions are not completely fulfilled when the early development, characterized by primary organogenesis events, is considered. In this study, we compare the embryotoxicity of Roundup® Power 2.0, a new GBH formulation currently authorized in Italy, with that of technical grade glyphosate using the Frog Embryo Teratogenesis Assay–Xenopus (FETAX). Our results evidenced that glyphosate was not embryolethal and only at the highest concentration (50 mg a.e./L) caused edemas. Conversely, Roundup® Power 2.0 exhibited a 96 h LC50 of 24.78 mg a.e./L and a 96 h EC50 of 7.8 mg a.e./L. A Teratogenic Index of 3.4 was derived, pointing out the high teratogenic potential of the Roundup® Power 2.0. Specific concentration-dependent abnormal phenotypes, such as craniofacial alterations, microphthalmia, narrow eyes and forebrain regionalization defects were evidenced by gross malformation screening and histopathological analysis. These phenotypes are coherent with those evidenced in Xenopus laevis embryos injected with glyphosate, allowing us to hypothesize that the teratogenicity observed for Roundup® Power 2.0 may be related to the improved efficacy in delivering glyphosate to cells, guaranteed by the specific surfactant formulation. In conclusion, the differences in GBH formulations should be carefully considered by the authorities, since sub-lethal and/or long-term effects (e.g. teratogenicity) can be significantly modulated by the active ingredient salt type and concentration of the adjuvants. Finally, the mechanistic toxicity of glyphosate and GBHs are worthy of further research.
Microplastics cause neurotoxicity, oxidative damage and energy-related changes and interact with the bioaccumulation of mercury in the European seabass, Dicentrarchus labrax (Linnaeus, 1758) Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-20 Luís Gabriel Antão Barboza, Luís Russo Vieira, Vasco Branco, Neusa Figueiredo, Felix Carvalho, Cristina Carvalho, Lúcia Guilhermino
Microplastics pollution is a global paradigm that raises concern in relation to environmental and human health. This study investigated toxic effects of microplastics and mercury in the European seabass (Dicentrarchus labrax), a marine fish widely used as food for humans. A short-term (96 h) laboratory bioassay was done by exposing juvenile fish to microplastics (0.26 and 0.69 mg/L), mercury (0.010 and 0.016 mg/L) and binary mixtures of the two substances using the same concentrations, through test media. Microplastics alone and mercury alone caused neurotoxicity through acetylcholinesterase (AChE) inhibition, increased lipid oxidation (LPO) in brain and muscle, and changed the activities of the energy-related enzymes lactate dehydrogenase (LDH) and isocitrate dehydrogenase (IDH). All the mixtures caused significant inhibition of brain AChE activity (64–76%), and significant increase of LPO levels in brain (2.9–3.4 fold) and muscle (2.2–2.9 fold) but not in a concentration-dependent manner; mixtures containing low and high concentrations of microplastics caused different effects on IDH and LDH activity. Mercury was found to accumulate in the brain and muscle, with bioaccumulation factors of 4–7 and 25–40, respectively. Moreover, in the analysis of mercury concentrations in both tissues, a significant interaction between mercury and microplastics was found. The decay of mercury in the water increased with microplastics concentration, and was higher in the presence of fish than in their absence. Overall, these results indicate that: microplastics influence the bioaccumulation of mercury by D. labrax juveniles; microplastics, mercury and their mixtures (ppb range concentrations) cause neurotoxicity, oxidative stress and damage, and changes in the activities of energy-related enzymes in juveniles of this species; mixtures with the lowest and highest concentrations of their components induced different effects on some biomarkers. These findings and other published in the literature raise concern regarding high level predators and humans consuming fish being exposed to microplastics and heavy metals, and highlight the need of more research on the topic.
The effects of high environmental ammonia on the structure of rainbow trout hierarchies and the physiology of the individuals therein Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-19 Josias M.B. Grobler, Chris M. Wood
Our goals were: (i) to determine whether sublethal concentrations of water-borne ammonia would prevent the formation of a dominance hierarchy, or alter its structure, in groups of 4 juvenile trout; (ii) to investigate the behavioral and physiological responses of individuals of different social rank exposed to a concentration of ammonia that still allowed hierarchy formation. Social hierarchies were created by using a technique in which a food delivery system that created competition also served to isolate individual fish for respirometry. Groups of 4 fish were exposed to elevated ammonia (NH4HCO3) 12 h before first feeding; aggression was recorded by video camera during morning feedings. Experimental ammonia concentrations were 700, 1200 and 1500 μmol L−1 at pH 7.3, 12 °C (9.8, 16.8, and 21.0 mg L−1 as total ammonia-N, or 0.0515, 0.0884, and 0.1105 mg L−1 as NH3<img border="0" alt="single bond" src="https://cdn.els-cdn.com/sd/entities/sbnd">N). Aggression was severely reduced by 1200 and abolished by 1500 μmol L−1 total ammonia, such that hierarchies did not form. However, groups exposed to 700 μmol L−1 total ammonia still formed stable hierarchies but displayed lower levels of aggression in comparison to control hierarchies. Exposure continued for 11 days. Physiological parameters were recorded on day 5 (end of period 1) and day 10 (end of period 2), while feeding and plasma cortisol were measured on day 11. In control hierarchies, dominant (rank 1) trout generally exhibited higher growth rates, greater increases in condition factor, higher food consumption, and lower cortisol levels than did fish of ranks 2, 3, and 4. In comparison to controls, the 700 μmol L−1 total ammonia hierarchies generally displayed lower growth, lower condition factor increases, lower O2 consumption, lower cortisol levels, but similar feeding patterns, with smaller physiological differences amongst ranks during period 1. Effects attenuated during period 2, as aggression and physiological measures returned towards control levels, indicating both behavioral and physiological acclimation to ammonia. These disturbances in social behavior and associated physiology occurred at an ammonia concentration in the range of regulatory significance and relevance to aquaculture.
Transcriptomic analysis reveals transgenerational effect of hypoxia on the neural control of testicular functions Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-16 Keng Po Lai, Jing Woei Li, Simon Yuan Wang, Miles Teng Wan, Ting Fung Chan, Wing Yee Lui, Doris Wai-Ting Au, Rudolf Shiu-Sun Wu, Richard Yuen-Chong Kong
There are over 400 hypoxic zones in the ocean worldwide. Both laboratory and field studies have shown that hypoxia causes endocrine disruption and reproductive impairments in vertebrates. More importantly, our recent study discovered that parental (F0) hypoxia exposure resulted in the transgenerational impairment of sperm quality in the F2 generation through the epigenetic regulation of germ cells. In the present study, we aim to test the hypothesis that the brain, as the major regulator of the brain-pituitary-gonad (BPG) axis, is also involved in the observed transgenerational effect. Using comparative transcriptomic analysis on brain tissues of marine medaka Oryzias melastigma, 45 common differentially expressed genes caused by parental hypoxia exposure were found in the hypoxic group of the F0 and F2 generations, and the transgenerational groups of the F2 generation. The bioinformatic analysis on this deregulated gene cluster further highlighted the possible involvement of the brain in the transgenerational effect of hypoxia on testicular structure, including abnormal morphologies of the epididymis and the seminal vesicle, and degeneration of the seminiferous tubule. This finding is concordant to the result of hematoxylin and eosin staining, which showed the reduction of testicular lobular diameter in the F0 and F2 generations. Our study demonstrated for the first time the involvement of the brain in the transgenerational effect of hypoxia.
Induction of oxidative stress by chlorothalonil in the estuarine polychaete Laeonereis acuta Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-15 Juliano da Silva Barreto, Fabio de Melo Tarouco, Filipe Guilherme Andrade de Godoi, Márcio Alberto Geihs, Fiamma Eugenia Lemos Abreu, Gilberto Fillmann, Juliana Zomer Sandrini, Carlos Eduardo da Rosa
Chlorothalonil is an active biocide applied in antifouling paints, and also used as fungicide in agricultural activities with the purpose to protect plants from foliar and seed diseases. Thus, the aim of this study was to evaluate the effects of chlorothalonil exposure on biochemical biomarkers of oxidative metabolism as well as on cholinesterases in the estuarine polychaete Laeonereis acuta. Animals were exposed for 24 and 96 h to the following nominal concentrations of chlorothalonil: 0.1, 10.0 and 100.0 μg/L. The antioxidant capacity against peroxyl radicals (ACAP) and the activity of the enzymes catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), glutamate cysteine ligase (GCL), acetylcholinesterase (AChE) and propionylcholinesterase (PChE) were evaluated in whole-body tissue. In addition, the levels of reduced glutathione (GSH), lipid peroxidation (LPO), glycogen and lactate levels were also analyzed. A reduction in ACAP levels was observed in animals exposed to the higher chlorothalonil concentration, concomitantly with an induction of GST activity as well as diminution in GSH content in these animals. This disturbance in the redox state of animal tissues leads to an oxidative stress situation, resulting in an induction in LPO levels. It was also demonstrated that chlorothalonil exposure causes alteration in AChE activity, possibly related to damage to membrane lipids. These results demonstrated that chlorothalonil possesses harmful effects to estuarine animals and its use as antifouling biocide has to be carefully reconsidered in risk analysis studies.
Effect of cadmium exposure on hepatopancreas and gills of the estuary mud crab (Scylla paramamosain): Histopathological changes and expression characterization of stress response genes Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-01 Qi-Hui Zhu, Zhong-Kai Zhou, Dan-Dan Tu, Yi-Lian Zhou, Cong Wang, Ze-Peng Liu, Wen-Bin Gu, Yu-Yin Chen, Miao-An Shu
Cadmium (Cd) is a heavy metal that accumulates easily in organisms and causes several detrimental effects, including tissue damage. Cd contamination from anthropogenic terrestrial sources flows into rivers, and through estuaries to the ocean. To evaluate the toxic effects of Cd on estuary crustaceans, we exposed the mud crab Scylla paramamosain to various Cd concentrations (0, 10.0, 20.0, and 40.0 mg/L) for 24 h. We also exposed mud crabs to a fixed Cd concentration (20.0 mg/L) for various periods of time (0, 6, 12, 24, 48, and 72 h). We observed that after exposure to Cd, the surfaces of the gill lamellae were wrinkled, and the morphologies of the nuclei and mitochondria in the hepatopancreas were altered. We analyzed the expression profiles of 36 stress-related genes after Cd exposure, including those encoding metallothioneins, heat shock proteins, apoptosis-related proteins, and antioxidant proteins, with quantitative reverse transcription PCR. We found that exposure to Cd altered gene expression, and that some genes might be suitable bioindicators of Cd stress. Gene expression profiles were organ-, duration-, and concentration-dependent, suggesting that stress-response genes might be involved in an innate defense system for handling heavy metal exposure. To the best of our knowledge, this study is the first one of histopathology and stress-response gene expression pattern of Scylla paramamosain after Cd exposure. Our work could increase our understanding of the effect of environmental toxins on estuary crustaceans.
Bioaccumulation of oil compounds in the high-Arctic copepod Calanus hyperboreus Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-05 Mette Dalgaard Agersted, Eva Friis Møller, Kim Gustavson
Oil and gas exploration in the Arctic will increase the risk for accidental oil spills and thereby have a potential impact on the ecosystem and the organisms inhabiting these areas. Lipid rich copepods are an important food source for higher trophic levels in Arctic marine ecosystems. However, high lipid content and a slower metabolism increase the risk for bioaccumulation in Arctic species. Here we exposed three late development stages of the lipid rich high-Arctic copepod species Calanus hyperboreus to two different 14C-marked crude oil model compounds, the alkane dodecane (log Kow 6.10) and the polycyclic aromatic hydrocarbon (PAH) phenanthrene (log Kow 4.46) on a short-term scale of 4 days. Exposure was followed by a depuration phase of 3 days. We observed a difference in estimated bioaccumulation of the two model compounds between stages and found a slower depuration of dodecane than of phenanthrene in the two largest and most lipid rich stages. However, depuration of dodecane and phenanthrene was non-significant for all three stages. The results indicate that even short-term exposure may result in long-term bioaccumulation and internal exposure of oil compounds in the lipid rich high-Arctic copepods C. hyperboreus. Slow elimination and depuration of oil components indicate a risk for transfer of oil component up the food web to pelagic fish, seabirds and baleen whales.
Impacts on the seagrass, Zostera nigricaulis, from the herbicide Fusilade Forte® used in the management of Spartina anglica infestations Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-01 Megan Carve, Timothy L. Coggan, Jackie H. Myers, Bradley Clarke, Dayanthi Nugegoda, Jeff Shimeta
The herbicide Fusilade Forte® (FF) is widely applied in agricultural weed management and in the management of the invasive saltmarsh grass, Spartina anglica (ricegrass or cordgrass). FF (active ingredient fluazifop-P acid, FPA) is selective for poaceous grasses. Its primary mode of action is inhibition of the acetyl coenzyme-A carboxylase (ACCase) specific to this taxonomic group, and its secondary mode is by promotion of oxidative stress. FF is applied to S. anglica infestations in the intertidal zone, in proximity to seagrass meadows. Despite the potential for vital seagrass ecosystems to be exposed to FF, there is limited knowledge of any potential impacts. We investigated impacts of FPA on the endemic Australian seagrass, Zostera nigricaulis, measuring ACCase activity and parameters that reflect oxidative stress: photosynthetic performance, lipid peroxidation and photosynthetic pigment content. Seagrass was exposed to FF (0.01–10 mg L−1 FPA and a control) for 7 d, followed by a 7-d recovery in uncontaminated seawater. An enzyme assay demonstrated that FPA ≤10 mg L−1 did not inhibit the activity of ACCase isolated from Z. nigricaulis, demonstrating that this seagrass is resistant to FF's primary mode of action. However, physiological impacts occurred following 7 days exposure to ≥0.1 mg L−1 FPA, including up to a 72% reduction in photosynthetic pigment concentration. After 7-d recovery, photosynthetic pigment content improved in treatment plants; however, treated plants exhibited higher levels of lipid peroxidation. This study demonstrates that while Z. nigricaulis is resistant to FF's primary mode of action, significant physiological impacts occur following 7 days exposure to ≥0.1 mg L−1 FPA. This study provides valuable information on the effects of FF on a non-target species that can better inform approaches to Spartina management in coastal seagrass ecosystems.
6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB), a novel perfluorooctane sulfonate alternative, induced developmental toxicity in zebrafish embryos Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-07 Guohui Shi, Yu Xie, Yong Guo, Jiayin Dai
6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) is a major component of Forafac®1157, a novel perfluorooctane sulfonate (PFOS) alternative used globally in aqueous film forming foams (AFFFs). Although 6:2 FTAB has been recently detected in the aquatic environment, its toxic effects on aquatic organisms remain unclear. Here, zebrafish embryos were exposed to various concentrations of 6:2 FTAB (0, 5, 10, 20, 40, 60, 80, and 100 mg/L) from 6 to 120 h post-fertilization (hpf) to investigate its developmental toxicity and possible mechanism of action. Results showed that exposure to 40 mg/L or higher concentrations of 6:2 FTAB significantly decreased the survival percentage and increased the malformation percentage. The median lethal concentration (LC50) at 120 hpf was 43.73 ± 3.24 mg/L, and the corresponding benchmark dose lower limit (BMDL) of lethal effect was 33.79 mg/L. These values were both higher than those for PFOS, supporting the notion that 6:2 FTAB is less toxic than PFOS to zebrafish embryos. The most common developmental defect in 6:2 FTAB-treated embryos was rough-edged skin/fins. TUNEL assay showed that 6:2 FTAB exposure induced cell apoptosis in the tail region compared with that of the control, which might explain the rough-edged skin/fins. The increased transcriptional levels of p53, bax, and apaf1 and the increased activities of caspase-3, -8, and -9 provided further evidence of 6:2 FTAB-induced apoptosis. We also analyzed the effects of 6:2 FTAB on oxidative stress and the immune system. Results showed that reactive oxygen species and malondialdehyde accumulated in concentration-dependent manners after exposure to 6:2 FTAB, and antioxidant enzyme activities (catalase and glutathione peroxidase) also changed. Exposure to 6:2 FTAB also altered the transcriptional levels of ccl1, il-1β, il-8, tnfα, ifn, and cxcl-c1c, which play important roles in the innate immune system. Collectively, our data suggest that 6:2 FTAB exposure can induce cell apoptosis, oxidative stress, and immunotoxicity, thus highlighting the developmental toxicity of 6:2 FTAB in zebrafish embryos.
Fish as a model to assess chemical toxicity in bone Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-26 Ignacio Fernández, Paulo J. Gavaia, Vincent Laizé, M. Leonor Cancela
Environmental toxicology has been expanding as growing concerns on the impact of produced and released chemical compounds over the environment and human health are being demonstrated. Among the toxic effects observed in organisms exposed to pollutants, those affecting skeletal tissues (osteotoxicity) have been somehow overlooked in comparison to hepato-, immune-, neuro- and/or reproductive toxicities. Nevertheless, sub-lethal effects of toxicants on skeletal development and/or bone maintenance may result in impaired growth, reduced survival rate, increased disease susceptibility and diminished welfare. Osteotoxicity may occur by acute or chronic exposure to different environmental insults. Because of biologically and technically advantagous features – easy to breed and inexpensive to maintain, external and rapid rate of development, translucent larvae and the availability of molecular and genetic tools – the zebrafish (Danio rerio) has emerged in the last decade as a vertebrate model system of choice to evaluate osteotoxicity. Different experimental approaches in fish species and analytical tools have been applied, from in vitro to in vivo systems, from specific to high throughput methodologies. Current knowledge on osteotoxicity and underlying mechanisms gained using fish, with a special emphasis on zebrafish systems, is reviewed here. Osteotoxicants have been classified into four categories according to the pathway involved in the transduction of the osteotoxic effects: activation/inhibition of membrane and/or nuclear receptors, alteration of redox condition, mimicking of bone constituents and unknown pathways. Knowledge on these pathways is also reported here as it may provide critical insights into the development, production and release of future chemical compounds with none or low osteotoxicity, thus promoting the green/environmental friendly chemistry.
Effects of waterborne cadmium on metabolic rate, oxidative stress, and ion regulation in the freshwater fish, inanga (Galaxias maculatus) Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-31 Nicole K. McRae, Sally Gaw, Chris N. Glover
The freshwater fish Galaxias maculatus (inanga) is a widespread Southern hemisphere species, but despite its habitation of lowland near-coastal waters with a high potential for cadmium contamination, nothing is known regarding its sensitivity to this toxic trace metal. Acute (96 h) exposures were therefore performed to determine sublethal responses of inanga to waterborne cadmium at a regulatory trigger value (nominally 0.2 μg L−1; measured 1 μg L−1), an environmental level (measured at 2.5 μg L−1), and an effect level (measured at 10 μg L−1). Whole body (tissue remaining following excision of kidney and liver) cadmium burden remained constant up until an exposure concentration of 10 μg L−1, at which point cadmium concentration increased significantly. A transient effect of cadmium on metabolic rate was observed, with an impaired oxygen consumption noted at 2.5, but not 1 or 10, μg L−1. Cadmium did not impair influx rates of either sodium or calcium, and no effects of cadmium on oxidative stress parameters (catalase activity, lipid peroxidation) were noted in the kidney. However, at cadmium concentrations of 2.5 and 10 μg L−1, lipid peroxidation in the liver increased, concomitant with a decline in hepatic catalase activity. These data indicate that there are significant differences in the mechanisms of cadmium toxicity in inanga, relative to better-studied Northern hemisphere species, especially with respect to ionoregulatory impacts. However, effects were induced at cadmium concentrations unlikely to be encountered in any but the most highly contaminated waterways, and thus our data suggest that current trigger values for cadmium concentrations in Australian and New Zealand waters are likely to be protective of inanga.
Antioxidant responses and oxidative stress in sheepshead minnow larvae exposed to Corexit 9500® or its component surfactant, DOSS Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-28 Subham Dasgupta, Sarah Choyke, P. Lee Ferguson, Anne E. McElroy
Large-scale use of dispersants to remediate oil spills has raised concerns about their toxicity to marine organisms. Of particular concern is oxidative stress and resulting membrane damage due to exposure to surfactants in dispersant mixtures. We investigated the potential of the dispersant Corexit 9500® and one of its major components, the anionic surfactant dioctyl sodium sulfosuccinate (DOSS), to induce oxidative stress in larval sheepshead minnows after 24 and 96 h exposures, at two sublethal concentrations, the lesser being environmentally realistic for each compound. Corexit exposures elicited only minimal antioxidant responses for most antioxidant components tested, with increased glutathione peroxidase (GPx) and glutathione S-transferase (GST) activities observed only after 96 h and at the higher exposure concentration. In contrast, DOSS induced statistically significant increases in the levels of reactive oxygen species (ROS), GPx, and lipid peroxidation, as well as depleted reduced glutathione (GSH) levels at both time points and concentrations. These data indicate that short-term and environmentally realistic exposures to DOSS can impact antioxidant response capabilities, raising concern about its use in oil dispersants and other high volume use products where environmental releases are likely.
Effects of Microcystis on development of early life stage Japanese medaka (Oryzias latipes): Comparative toxicity of natural blooms, cultured Microcystis and microcystin-LR Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-01 Spencer R. Saraf, Amy Frenkel, Matthew J. Harke, Jennifer G. Jankowiak, Christopher J. Gobler, Anne E. McElroy
Freshwater cyanobacterial harmful algal blooms (CyanoHABs) caused by algae in the genus Microcystis have been increasing in frequency and severity in recent decades. Microcystis blooms threaten aquatic organisms through effects associated with the rapid increase of biomass and the production of the hepatotoxin microcystin (MC) by toxic strains. Among fish, effects of blooms are likely to be more severe for early life stages, and physiological impacts on this life stage could significantly impact recruitment and fish populations. This study explores the effects of Microcystis blooms on the development of fish using the model organism, the Japanese medaka (Oryzias latipes), under realistic exposure conditions. Medaka embryos were exposed to natural blooms collected from New York City (USA) lakes, lab cultures of Microcystis, and MC-LR solutions. Field collected samples were more toxic than lab cultures (even when compared at the same algal density or MC concentration), causing decreased survival, premature time to hatch, reduced body length, yolk sac edema, and decreased heart rate, while lab culture exposures only resulted in bradycardia. Heart rate was the most sensitive endpoint measured, being depressed in embryos exposed to both lab cultures and field collected blooms. Generalized linear model analysis indicated bradycardia was statistically associated with both cell densities of blooms and MC concentrations, while single factor analysis indicated that MC concentrations had a stronger correlation compared to cell densities. However, MC exposure could not fully explain the effects observed, as exposures to MC-LR solutions alone were not able to reduce heart rate as severely as algal exposures. Collectively, these experiments indicate that factors beyond exposure to MC or even isolated Microcystis strains influence heart rate of fish exposed to Microcystis blooms. Enhanced mortality, depressed heart rate, and abnormal development observed in response to environmentally realistic exposures of Microcystis blooms could affect success of fish at both individual or population levels.
Influence of body size, metabolic rate and life history stage on the uptake and excretion of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) by invasive sea lampreys (Petromyzon marinus) Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-28 Laura R. Tessier, Tristan A.F. Long, Michael P. Wilkie
Invasive sea lamprey (Petromyzon marinus) are controlled in the Great Lakes using the lampricide 3-trifluoromethyl-4-nitrophenol (TFM), which is applied to streams infested with larval lamprey. However, lamprey that survive treatments (residuals) remain a challenge because they may subsequently undergo metamorphosis into parasitic juvenile animals that migrate downstream to the Great Lakes, where they feed on important sport and commercial fishes. The goal of this study was to determine if body size and life stage could potentially influence sea lamprey tolerance to TFM by influencing patterns of TFM uptake and elimination. Because mass specific rates of oxygen consumption ( M ˙ O 2 ) are lower in larger compared to smaller lamprey, we predicted that TFM uptake would be negatively correlated to body size, suggesting that large larvae would be more tolerant to TFM exposure. Accordingly, TFM uptake and M ˙ O 2 were measured in larvae ranging in size from 0.2–4.2 g using radio-labelled TFM (14C-TFM) and static respirometry. Both were inversely proportional to wet mass (M), and could be described usingthe allometric power relationship: Y = aMb, in which M ˙ O 2 = 1.86 M0.53 and TFM Uptake = 7.24 M0.34. We also predicted that body size would extend to rates of TFM elimination, which was measured following the administration of 14C-TFM (via intraperitoneal injection). However, there were no differences in the half-lives of elimination of TFM (T 1/2-TFM). There were also no differences in M ˙ O 2 or TFM uptake amongst size-matched larval, metamorphosing (stages 6–7), or post-metamorphic (juvenile) sea lamprey. However, the T1/2-TFM was significantly lower in larval than post-metamorphic lamprey (juvenile), indicating the larval lamprey cleared TFM more efficiently than juvenile lamprey. We conclude that larger larval sea lamprey are more likely to survive TFM treatments suggesting that body size might be an important variable to consider when treating streams with TFM to control these invasive species.
Oxidative stress, cell cycle arrest, DNA damage and apoptosis in adult zebrafish (Danio rerio) induced by tris(1,3-dichloro-2-propyl) phosphate Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-10 Hanyan Chen, Pingping Wang, Zhongkun Du, Guowei Wang, Shixiang Gao
Tris(1,3-dichloro-2-propyl)phosphate (TDCPP) is an additive flame retardant of high production volume, and frequently detected in biota and environment. However, knowledge on its potential risk and toxicological mechanism still remains limited. In this study, DNA damage, transcriptomic responses and biochemical changes in the liver of zebrafish (Danio rerio) induced by TDCPP were investigated. Zebrafish was exposed to 45.81 μg/L (1/100 (96h-LC50)) and 229.05 μg/L (1/20 (96h-LC50)) TDCPP for 7 d. The reactive oxygen species (ROS) and GSH contents, in addition to antioxidant enzyme activities in the liver changed significantly, and the mRNA levels of genes related to oxidative stress were alerted in a dose-dependent and/or sex-dependent manner after exposure to TDCPP. Significant DNA damage in zebrafish liver was found, and olive tail moment increased in a concentration-dependent manner. Moreover, exposure of TDCPP at 45.81 μg/L level activated the cell cycle arrest, DNA repair system and apoptosis pathway in male zebrafish, and 229.05 μg/L TDCPP exposure inhibited those pathways in both male and female zebrafish. The cell apoptosis was confirmed in TUNEL assay as higher incidence of TUNEL-positive cells were observed in zebrafish exposed to 229.05 μg/L TDCPP. Our results also indicated that males were more sensitive to TDCPP exposure compared with females. Taken together, our results showed that TDCPP could induce oxidative stress, cell cycle arrest, DNA damage and apoptosis in adult zebrafish liver in sex- and concentration-dependent manners.
The role of the p38-activated protein kinase signaling pathway-mediated autophagy in cadmium-exposed monogonont rotifer Brachious koreanus Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-10 Hye-Min Kang, Chang-Bum Jeong, Min-Sub Kim, Jin-Sol Lee, Jiaying Zhou, Young Hwan Lee, Duck-Hyun Kim, Eunyoung Moon, Hee-Seok Kweon, Su-Jae Lee, Jae-Seong Lee
Autophagy is a ‘self-eating’ system that regulates the degradation of cellular components and is involved in various biological processes including survival and development. However, despite its crucial role in organisms, the regulatory mechanism of autophagy remains largely unclear, particularly in invertebrates. In this study, conserved autophagy in the rotifer Brachionus koreanus in response to cadmium (Cd) exposure was verified by measuring acidic vesicle organelles using acridine orange (AO) and neutral red (NR) staining, and by detecting LC3 I/II on Western blot and immunofluorescence. We also demonstrated activation of p38 mitogen-activated protein kinase (MAPK) in response to Cd-induced oxidative stress, leading to the induction of autophagy in B. koreanus. This was further verified by analysis of MAPK protein levels and immunofluorescence of LC3 I/II after treatment with reactive oxygen species (ROS) scavengers and inhibitors specific to MAPKs. We propose a p38 MAPK-mediated regulatory mechanism of autophagy in B. koreanus in response to Cd-induced oxidative stress. This study will contribute to a better understanding of autophagic processes in invertebrates and its modulation by environmental stressors.
Gadolinium perturbs expression of skeletogenic genes, calcium uptake and larval development in phylogenetically distant sea urchin species Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-11 Chiara Martino, Caterina Costa, Maria Carmela Roccheri, Demian Koop, Rosaria Scudiero, Maria Byrne
Chelates of Gadolinium (Gd), a lanthanide metal, are employed as contrast agents for magnetic resonance imaging and are released into the aquatic environment where they are an emerging contaminant. We studied the effects of environmentally relevant Gd concentrations on the development of two phylogenetically and geographically distant sea urchin species: the Mediterranean Paracentrotus lividus and the Australian Heliocidaris tuberculata. We found a general delay of embryo development at 24 h post-fertilization, and a strong inhibition of skeleton growth at 48 h. Total Gd and Ca content in the larvae showed a time- and concentration-dependent increase in Gd, in parallel with a reduction in Ca. To investigate the impact of Gd on the expression of genes involved in the regulation of skeletogenesis, we performed comparative RT-PCR analysis and found a misregulation of several genes involved in the skeletogenic and left-right axis specification gene regulatory networks. Species-specific differences in the biomineralization response were evident, likely due to differences in the skeletal framework of the larvae and the amount of biomineral produced. Our results highlight the hazard of Gd for marine organisms.
Evaluating features of periphytic diatom communities as biomonitoring tools in fresh, brackish and marine waters Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-10 Lalit K. Pandey, Yogesh Chandra Sharma, Jihae Park, Soyeon Choi, Hojun Lee, Jie Lyu, Taejun Han
Cyanobacteria blooms induce embryonic heart failure in an endangered fish species Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-16 Jinmei Zi, Xiaofu Pan, Hugh J. MacIsaac, Junxing Yang, Runbing Xu, Shanyuan Chen, Xuexiu Chang
Estrogenic and anti-androgenic effects of the herbicide tebuthiuron in male Nile tilapia (Oreochromis niloticus) Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-14 Milena Devechi de Almeida, Thiago Scremin Boscolo Pereira, Sergio Ricardo Batlouni, Camila Nomura Pereira Boscolo, Eduardo Alves de Almeida
Tebuthiuron is a phenylurea herbicide widely used in agriculture that can reach the aquatic environments, possibly posing negative effects to the aquatic biota. Phenylurea herbicides, such as diuron, are known to cause estrogenic and anti-androgenic effects in fish, but no such effects were yet reported for tebuthiuron exposure. Thus, the aim of this study was to evaluate if tebuthiuron, at environmentally relevant concentrations (100 and 200 ng/L) and after 25 days of exposure have estrogenic and/or anti-androgenic effects on male of Nile tilapia (Oreochromis niloticus), through the evaluation of plasmatic testosterone (T) and estradiol (E2) levels, brain aromatase (CYP19) levels (western-blot), and by evaluating the histology of the testicles. When compared to the control group, plasmatic T levels decreased about 76% in the animals exposed to 200 ng/L of tebuthiuron, while E2 levels increased about 94%, which could be related to a significant increase (77%) in CYP19A1 levels, an enzyme that catalyzes the conversion of androgens into estrogens. Histological analyses of the testicles also demonstrated that tebuthiuron at both tested concentrations caused a decrease in the diameter of the seminiferous tubules and in the diameter of the lumen. Therefore, the gonadosomatic index (GSI) was reduced by 36% % in the animals exposed 200 ng/L to tebuthiuron. Indeed, the relative frequency of spermatocytes and spermatids increased respectively 73% (200 ng/L) and 61% (100 ng/L) in the tebuthiuron exposed animals, possibly due to the impairment of sperm release into the lumen, that was decreased 93% (200 ng/L) in the treated animals compared to the control. These results confirm that tebuthiuron causes estrogenic and anti-androgenic effects in Nile tilapias at environmentally relevant concentrations.
Multigenerational effects of 4-methylbenzylidene camphor (4-MBC) on the survival, development and reproduction of the marine copepod Tigriopus japonicus Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-16 Leyun Chen, Xiaolin Li, Haizheng Hong, Dalin Shi
One of the most widely used organic UV filters, 4-methylbenzylidene camphor (4-MBC), is present at high concentrations in offshore waters. The marine copepod Tigriopus japonicus was exposed to different concentrations of 4-MBC (i.e., 0, 0.5, 1, 5 and 10 μg L−1) for 4 consecutive generations (F0-F3) to evaluate the impact of 4-MBC on marine ecosystems. The results showed that in the F0 generation, 4-MBC caused significant lethal toxicity in T. japonicas at concentrations of 5 and 10 μg L−1 and the nauplii were more sensitive to 4-MBC toxicity than the adults. However in the F1-F3 generations, 4-MBC exposure did not affect the survival rate. The hatching rate and the developmental duration from the nauplii to the copepodite (N-C) and from the nauplii to adult (N-A) decreased significantly in the F1-F2 generations and in the F2-F3 generations, respectively, even at the lowest exposure concentration (0.5 μg L−1). In the subsequent two generations (i.e., the F4-F5 generations) of recovery exposure in clean seawater, the growth rates of the original 4-MBC exposure groups were still faster than the control in both the N-C and N-A stages, suggesting possible transgenerational genetic and/or epigenetic changes upon chronic 4-MBC exposure. The expression of the ecdysone receptor gene was up-regulated by 4-MBC, which was consistent with the decrease of the N-C/N-A duration. In addition, 4-MBC may induce oxidative stress and trigger apoptosis in T. japonicas, resulting in developmental, reproductive and even lethal toxicity. A preliminary risk assessment suggested that under environmentally realistic concentrations, 4-MBC had significant potential to pose a threat to marine crustaceans and marine ecosystems.
Effects of two-hour exposure to environmental and high concentrations of methylmercury on the transcriptome of the macrophyte Elodea nuttallii Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-17 Rebecca Beauvais-Flück, Vera I. Slaveykova, Claudia Cosio
Metabolomics and transcriptomics reveal the toxicity of difenoconazole to the early life stages of zebrafish (Danio rerio) Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-21 Miaomiao Teng, Wentao Zhu, Dezhen Wang, Suzhen Qi, Yao Wang, Jin Yan, Kai Dong, Mingqi Zheng, Chengju Wang
Difenoconazole is widely used to inhibit the growth of fungi, but its residue in the water environment may threaten ecosystem and human health. Here, 1H nuclear magnetic resonance (NMR) and LC–MS/MS based metabolomics and transcriptomics approaches were used to assess the response of zebrafish to difenoconazole exposure. Early life stages of zebrafish were exposed to difenoconazole at environmentally relevant concentrations for 168 h. Their comparison with the control group suggested an adverse development and disturbance of steroid hormones and VTG. KEGG pathway analysis identified five biological processes on the basis of differentially expressed genes (DEGs), as well as altered metabolites and amino acids in zebrafish following difenoconazole exposure. These affected processes included energy metabolism, amino acids metabolism, lipid metabolism, nucleotide metabolism, and an immune-related pathway. Collectively, these results bring us closer to an incremental understanding of the toxic effects of difenoconazole on zebrafish in its early development, and lend support to the continued use of the early life stages of zebrafish as a classical model to evaluate underlying environmental risks of xenobiotics in aquatic organisms.
Digital gene expression analysis in the gills of Ruditapes philippinarum exposed to short- and long-term exposures of ammonia nitrogen Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-23 Ming Cong, Huifeng Wu, Tengfei Cao, Jiasen Lv, Qing Wang, Chenglong Ji, Chenghua Li, Jianmin Zhao
Previous study revealed severe toxic effects of ammonia nitrogen on Ruditapes philippinarum including lysosomal instability, disturbed metabolic profiles, gill tissues with damaged structure, and variation of neurotransmitter concentrations. However, the underlying molecular mechanism was not fully understood yet. In the present study, digital gene expression technology (DGE) was applied to globally screen the key genes and pathways involved in the responses to short- and long-term exposures of ammonia nitrogen. Results of DGE analysis indicated that short-term duration of ammonia exposure affected pathways in Dorso-ventral axis formation, Notch signaling, thyroid hormone signaling and protein processing in endoplasmic reticulum. The long-term exposure led to DEGs significantly enriched in gap junction, immunity, signal and hormone transduction, as well as key substance metabolism pathways. Functional research of significantly changed DEGs suggested that the immunity of R. philippinarum was weakened heavily by toxic effects of ammonia nitrogen, as well as neuro-transduction and metabolism of important substances. Taken together, the present study provides a molecular support for the previous results of the detrimental toxicity of ammonia exposure in R. philippinarum, further work will be performed to investigate the specific genes and their certain functions involved in ammonia toxicity to molluscs.
Systemic response of the stony coral Pocillopora damicornis against acute cadmium stress Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-23 Zhi Zhou, Xiaopeng Yu, Jia Tang, Yibo Wu, Lingui Wang, Bo Huang
Heavy metals have become one of the main pollutants in the marine environment and a major threat to the growth and reproduction of stony corals. In the present study, the density of symbiotic zooxanthellae, levels of crucial physiological activities and the transcriptome were investigated in the stony coral Pocillopora damicornis after the acute exposure to elevated cadmium concentration. The density of symbiotic zooxanthellae decreased significantly during 12–24 h period, and reached lowest at 24 h after acute cadmium stress. No significant changes were observed in the activity of glutathione S-transferase during the entire stress exposure. The activities of superoxide dismutase and catalase, and the concentration of glutathione decreased significantly, but the activation level of caspase3 increased significantly after cadmium exposure. Furthermore, transcriptome sequencing and bioinformatics analysis revealed 3538 significantly upregulated genes and 8048 significantly downregulated genes at 12 h after the treatment. There were 12 overrepresented GO terms for significantly upregulated genes, mostly related to unfolded protein response, endoplasmic reticulum stress and apoptosis. In addition, a total of 32 GO terms were overrepresented for significantly downregulated genes, and mainly correlated with macromolecular metabolic processes. These results collectively suggest that acute cadmium stress could induce apoptosis by repressing the production of the antioxidants, elevating oxidative stress and activating the unfolded protein response. This cascade of reactions would result to the collapse of the coral-zooxanthella symbiosis and the expulsion of symbiotic zooxanthellae in the stony coral P. damicornis, ultimately leading to coral bleaching.
Differential response between histological and biochemical biomarkers in the apple snail Pomacea canaliculata (Gasteropoda: Amullariidae) exposed to cypermethrin Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-23 F. Arrighetti, E. Ambrosio, M. Astiz, A. Rodrigues Capítulo, S. Lavarías
To develop effective programs to monitor water quality is necessary to identify sensitive biomarkers in indicator species. The aim of this study was to evaluate different biomarkers in the apple snail Pomacea canaliculata exposed to the insecticide Cypermethrin (CYP). Adult male and female snails were exposed to sublethal CYP concentrations (10, 25 and 100 μg l−1) for 1, 4, 7 and 14 days. The recovery of the exposed snails was also studied by a post-exposure assay. The activities of the enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST), the levels of lipid peroxidation (LPO) and protein oxidation (PC) in digestive gland and gills were studied as biomarkers of exposure. Histopathological changes in target tissues were also evaluated. In digestive gland, CYP caused a significant increase in SOD, CAT and GST activities compared to control (p < 0.05) as well as in LPO and PC levels (p < 0.05). However, such biochemical effects were neither concentration nor time dependent. Histopatological changes were observed in the exposed groups, such as an increase in the number of basophilic cells, hemocytic infiltration and epithelia atrophy. Additionally, a positive correlation between the surface occupied by pigmented corpuscles and CYP concentrations was observed at all exposure periods. Gills showed greater sensitivity to oxidative damage than digestive gland. CYP caused an acute toxic effect in LPO levels in this respiratory organ. The gill filament of exposed snails, exhibited a reduction or loss of cilia, vacuolization of the columnar cells and an increase in haemocyte content irrespective of the concentration. High concentrations of CYP caused disruptions in the columnar muscle fibers. In general, snails did not show an improvement in their basal state during post-exposure treatment. Apparently, males and females do not have differential sensitivity to the pesticide. The results of this study suggest that histopathological changes are the most sensitive time- and dose-dependent biomarkers of toxicity induced by CYP in P. canaliculata.
Effect of imidacloprid on the survival of Xenopus tadpoles challenged with wild type frog virus 3 Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-12 Morgan A. Hrynyk, Craig Brunetti, Leslie Kerr, Chris D. Metcalfe
The sensitivity of amphibians to Ranavirus may be increased by exposure to other environmental stressors, including chemical contaminants. Neonicotinoid insecticides comprise 27% of the global insecticide market and have been detected in wetlands and other aquatic habitats. The present study focused on the effects of exposure of pre-metamorphic Xenopus laevis to the neonicotinoid, imidacloprid (IMI) on sensitivity to frog virus 3 (FV3) infection. It was hypothesized that exposure of tadpoles to IMI at sublethal concentrations of 1 and 500 μg L−1 would increase FV3 related mortalities relative to tadpole mortalities in a control treatment with only the virus. However, contrary to the predicted outcome, IMI reduced the rates of mortality following viral challenge, although the total mortalities by the 25th day after infection did not differ among the treatments. These results should not be interpreted as an indication that neonicotinoid insecticides are beneficial to aquatic ecosystems, since these insecticides cause toxic responses at low concentrations to other non-target aquatic organisms.
Uniquely high turnover of nickel in contaminated oysters Crassostrea hongkongensis: Biokinetics and subcellular distribution Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-28 Qijun Yin, Wen-Xiong Wang
Despite the environmental concerns regarding nickel (Ni) especially in China, it has received little attention in aquatic animals due to its comparatively weak toxicity. In the present study, we explored the bioaccumulation, biokinetics, and subcellular distribution of Ni in an estuarine oyster Crassostrea hongkongensis. We demonstrated that Ni represented a new pattern of bioaccumulation in oysters characterized by rapid elimination and low dissolved uptake. The waterborne uptake rate constant and dietary assimilation efficiency were 0.036 L/g/h and 28%, respectively, and dissolved uptake was the predominant exposure route. The efflux rate constant was positively related to tissue Ni concentration, with the highest efflux of 0.155 d−1. Such high elimination resulted in a high Ni turnover and steady-state condition reached rapidly, as shown with a 4-week waterborne exposure experiment at different Ni concentrations. Ni in oysters was mainly sequestered in metallothionein-like protein (MTLP), metal-rich granule, and cellular debris. MTLP was the most important binding fraction during accumulation and depuration, and played a dynamic role leading to rapid Ni elimination. Pre-exposure to Ni significantly reduced the dissolved uptake, probably accompanied by depressed filtration activity. Overall, the high turnover and regulation of Ni in oysters were achieved by enhanced efflux, suppressed uptake, and sequestration of most Ni into the detoxified pool.
Role of neurexin2a in lead-induced locomotor defect in developing zebrafish Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-22 Hongwei Tu, Tao Peng, Jiaxian Liu, Xiaohui Chen, Chengji Fan, Zhibin Huang, Yiyue Zhang, Fei Zou, Xiaojing Meng
Low-dose chronic lead (Pb) exposure interferes with the development of the nervous system, which may lead to learning disabilities, behavioral abnormalities, and mental retardation. Neurexins (Nrxns) are synaptic cell-adhesion molecules associated with neurological disorders. We hypothesized that Pb can affect the expression of nrxns during synapse formation and alter the phenotype behavior. Here, apoptosis, nrxns mRNA expression, and alterations of locomotion were examined after exposure to Pb in zebrafish embryos/larvae. To confirm the function of nrxn2a, rescue experiments were performed using β-nrxn2a mRNA microinjection. Pb exposure increased apoptosis and altered locomotor behavior in zebrafish larvae. Quantitative PCR showed that among several synaptic adhesion molecules, only nrxn2a were affected by Pb exposure. Moreover, exposure to Pb at 10 μmol/L upregulated mRNA expression of nrxn1a and nrxn3a at 24 h post fertilization (hpf) and downregulated expression at 48 hpf, whereas the expression remained unchanged at 72 hpf. Only the two isoforms of nrxn2a were downregulated by Pb at 10 μmol/L at all three time points. Rescue experiments showed that β-nrxn2a mRNA injection recovered the decreased locomotor activity and the increased apoptosis induced by Pb. In addition, overexpression of β-nrxn2a mRNA upregulated α-nrxn2a. These data indicated that Pb inhibited the expression of nrxn2a genes, which play a critical role in neural development, and further altered the behavior of zebrafish embryos/larvae.
Uptake and effects of 2, 4, 6 - trinitrotoluene (TNT) in juvenile Atlantic salmon (Salmo salar) Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-24 Espen Mariussen, Siv Marie Stornes, Kari Oline Bøifot, Bjørn Olav Rosseland, Brit Salbu, Lene Sørlie Heier
Organ specific uptake and depuration, and biological effects in Atlantic salmon (Salmo salar) exposed to 2, 4, 6-trinitrotoluene (TNT) were studied. Two experiments were conducted, the first using radiolabeled TNT (14C-TNT, 0.16 mg/L) to study uptake (48 h) and depuration (48 h), while the second experiment focused on physiological effects in fish exposed to increasing concentrations of unlabeled TNT (1 μg–1 mg/L) for 48 h. The uptake of 14C-TNT in the gills and most of the organs increased rapidly during the first 6 h of exposure (12 h in the brain) followed by a rapid decrease even though the fish were still exposed to TNT in the water. The radioactivity in the gall bladder reached a maximum after 55 h, 7 h after the transfer to the clean water. A high concentration of 14C-TNT in the gall bladder indicates that TNT is excreted through the gall bladder. Mortality (2 out of 14) was observed at a concentration of 1 mg/L, and the surviving fish had hemorrhages in the dorsal muscle tissue near the spine. Analysis of the physiological parameters in blood from the high exposure group revealed severe effects, with an increase in the levels of glucose, urea and HCO3, and a decrease in hematocrit and the levels of Cl and hemoglobin. No effects on blood physiology were observed in fish exposed to the lower concentrations of TNT (1–100 μg/L). TNT and the metabolites 2-amino-4,6-dinitrotoluene (2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT) were found in the muscle tissue, whereas only 2-ADNT and 4-ADNT were found in the bile. The rapid excretion and estimated bioconcentration factors (range of 2–18 after 48 h in gills, blood, liver, kidney, muscle and brain) indicated a low potential for bioaccumulation of TNT.
Uptake, tissue distribution, and toxicity of polystyrene nanoparticles in developing zebrafish (Danio rerio) Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-24 Jordan A. Pitt, Jordan S. Kozal, Nishad Jayasundara, Andrey Massarsky, Rafael Trevisan, Nick Geitner, Mark Wiesner, Edward D. Levin, Richard T. Di Giulio
Plastic pollution is a critical environmental concern and comprises the majority of anthropogenic debris in the ocean, including macro, micro, and likely nanoscale (less than 100 nm in at least one dimension) plastic particles. While the toxicity of macroplastics and microplastics is relatively well studied, the toxicity of nanoplastics is largely uncharacterized. Here, fluorescent polystyrene nanoparticles (PS NPs) were used to investigate the potential toxicity of nanoplastics in developing zebrafish (Danio rerio), as well as to characterize the uptake and distribution of the particles within embryos and larvae. Zebrafish embryos at 6 h post-fertilization (hpf) were exposed to PS NPs (0.1, 1, or 10 ppm) until 120 hpf. Our results demonstrate that PS NPs accumulated in the yolk sac as early as 24 hpf and migrated to the gastrointestinal tract, gallbladder, liver, pancreas, heart, and brain throughout development (48–120 hpf). Accumulation of PS NPs decreased during the depuration phase (120–168 hpf) in all organs, but at a slower rate in the pancreas and gastrointestinal tract. Notably, exposure to PS NPs did not induce significant mortality, deformities, or changes to mitochondrial bioenergetics, but did decrease the heart rate. Lastly, exposure to PS NPs altered larval behavior as evidenced by swimming hypoactivity in exposed larvae. Taken together, these data suggest that at least some nanoplastics can penetrate the chorion of developing zebrafish, accumulate in the tissues, and affect physiology and behavior, potentially affecting organismal fitness in contaminated aquatic ecosystems.
Microbiota and environmental stress: how pollution affects microbial communities in Manila clams Aquat. Toxicol. (IF 4.129) Pub Date : 2017-11-27 M. Milan, L. Carraro, P. Fariselli, M.E. Martino, D. Cavalieri, F. Vitali, L. Boffo, T. Patarnello, L. Bargelloni, B. Cardazzo
Given the crucial role of microbiota in host development, health, and environmental interactions, genomic analyses focusing on host-microbiota interactions should certainly be considered in the investigation of the adaptive mechanisms to environmental stress. Recently, several studies suggested that microbiota associated to digestive tract is a key, although still not fully understood, player that must be considered to assess the toxicity of environmental contaminants. Bacteria-dependent metabolism of xenobiotics may indeed modulate the host toxicity. Conversely, environmental variables (including pollution) may alter the microbial community and/or its metabolic activity leading to host physiological alterations that may contribute to their toxicity. Here, 16s rRNA gene amplicon sequencing has been applied to characterize the hepatopancreas microbiota composition of the Manila clam, Ruditapes philippinarum. The animals were collected in the Venice lagoon area, which is subject to different anthropogenic pressures, mainly represented by the industrial activities of Porto Marghera (PM). Seasonal and geographic differences in clam microbiotas were explored and linked to host response to chemical stress identified in a previous study at the transcriptome level, establishing potential interactions among hosts, microbes, and environmental parameters. The obtained results showed the recurrent presence of putatively detoxifying bacterial taxa in PM clams during winter and over-representation of several metabolic pathways involved in xenobiotic degradation, which suggested the potential for host-microbial synergistic detoxifying actions. Strong interaction between seasonal and chemically-induced responses was also observed, which partially obscured such potentially synergistic actions. Seasonal variables and exposure to toxicants were therefore shown to interact and substantially affect clam microbiota, which appeared to mirror host response to environmental variation. It is clear that understanding how animals respond to chemical stress cannot ignore a key component of such response, the microbiota.
Low-dose metformin exposure causes changes in expression of endocrine disruption-associated genes Aquat. Toxicol. (IF 4.129) Pub Date : 2017-12-08 Nicholas J. Niemuth, Rebecca D. Klaper
The presence of intersex fish in watersheds around the world is a warning of the presence of anthropogenic endocrine-disrupting compounds (EDCs) being deposited into the aquatic environment. The anti-diabetic drug metformin is among the most prevalent and ubiquitous of the myriad pharmaceuticals found in wastewater effluent and watersheds worldwide. In addition to its prescription for type-2 diabetes, metformin is indicated as a treatment in cancers and the endocrine disorder polycystic ovarian syndrome (PCOS). Our previous research found evidence of endocrine-disruption following Pimephales promelas (fathead minnow) exposure to metformin at an environmentally relevant concentration. However, the mechanism of action leading to these impacts is unknown. Although metformin does not structurally resemble classical EDCs, there’s an increasing recognition that endocrine disruption may occur by mechanisms other than classical endocrine receptor binding, and metformin’s off-label use for treating endocrine-related disorders such as PCOS indicates its potential interaction with the endocrine system. To further explore metformin’s mechanism of action as an EDC, we measured expression of numerous endocrine-related genes in male fathead minnows exposed to metformin at a low-dose similar to that found in wastewater effluent and the environment (40 μg L−1) for a full year (early development to adulthood) and discovered significant upregulation of the AR (3.6 ± 0.9-fold), 3β-HSD (3.9 ± 0.8-fold), 17β-HSD (17 ± 4-fold), CYP19A1 (40 ± 20-fold), and SULT2A1 (2.3 ± 0.4-fold) genes in exposed male gonad. We also found a significant correlation between expression of 3β-HSD, 17β-HSD, and CYP19A1 in testis of metformin-treated male fish and the degree of intersex occurring in their gonads. These results provide additional evidence of the endocrine disrupting impact of the drug metformin and insight into the potential mechanisms by which metformin may influence the endocrine system in aquatic organisms.
Omics tools: New challenges in aquatic nanotoxicology? Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-12 Messika Revel, Amélie Châtel, Catherine Mouneyrac
In recent years, the implication of genomics into ecotoxicological studies has been studied closely to allow a better understanding of organism’s responses to environmental contaminants including engineering nanomaterials (ENMs). ENMs are increasingly produced for various applications including cosmetics, electronics, sports equipment, biomedicine and agriculture. Because of their small size, ENMs possess chemical or physical characteristics improved compared to the corresponding macro-sized material. As their application expend, the release of manufactured ENMs into the environment is likely to increase and concern over impacts for the aquatic ecosystem is growing. Several studies reported deleterious effect of ENMs to aquatic organisms, but there is little information about the molecular mechanisms of toxicity. The development of ecotoxicogenomic approaches will improve the characterization of cellular and molecular modes of action of ENMs to aquatic organisms and allow a better prediction of contaminants toxicity. This paper presents an overview of transciptomic/proteomic studies in freshwater and marine organisms exposed to ENMs. Overall, induction of gene expression in relations to defense mechanisms, immune responses, growth and reproduction were measured after ENMs exposures of organisms, but with different patterns depending on exposure duration and concentrations used. In addition, some studies reported a positive correlation between gene expression and cellular modifications, but not at the individual level.
Effects of benzophenone-3 on the green alga Chlamydomonas reinhardtii and the cyanobacterium Microcystis aeruginosa Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-02 Feijian Mao, Yiliang He, Ariel Kushmaro, Karina Yew-Hoong Gin
Effects of benzophenone-3 (BP-3) on the green alga, Chlamydomonas reinhardtii, and the cyanobacterium, Microcystis aeruginosa, were investigated. The tested organisms were exposed to environmental levels of BP-3 for 10 days, at nominal concentrations from 0.01 to 5000 μg L−1. Specific growth rate and photosynthetic pigments were employed to evaluate the toxic responses. The two tested algae had distinct toxic responses towards BP-3 stress, with the green alga C. reinhardtii being more sensitive than the cyanobacterium M. aeriginosa, based on EC20 and EC50 values. Uptake of BP-3 from the medium occurred in both species, with M. aeruginosa showing greater overall uptake (27.2–77.4%) compared to C. reinhardtii (1.1–58.4%). The effects of BP-3 on C. reinhardtii were variable at concentrations lower than 100 μg L−1. At higher concentrations, the specific growth rate of C. reinhardtii decreased following a reduction in chlorophyll a (chl-a) content. Further experiments showed that BP-3 regulated the growth of C. reinhardtii by affecting the production of chl-a, chlorophyll b and carotenoids. In M. aeruginosa, specific growth rate was only moderately affected by BP-3. Additionally, the production of chl-a was significantly inhibited over the different exposure concentrations, while the production of carotenoids was stimulated. These results indicate a potential detrimental effect on prokaryotes and eukaryotes and that the mechanism of action varies with species.
Combinatory effects of low concentrations of 17α-etinylestradiol and citalopram on non-reproductive behavior in adult zebrafish (Danio rerio) Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-04 Tove Porseryd, Martin Kellner, Nasim Reyhanian Caspillo, Kristina Volkova, Lubna Elabbas, Shahid Ullah, Håkan Olsén, Patrik Dinnétz, Inger Porsch Hällström
Sewage effluents contain pharmaceuticals, personal care products and industrial chemicals, exposing aquatic organisms to complex mixtures. The consequences of exposure to combinations of different classes of drugs in fish are largely unknown. In this study, we exposed adult zebrafish (Danio rerio) males and females for two weeks to low, environmentally relevant concentrations of the endocrine disrupting chemical 17α-etinylestradiol (EE2) and the selective serotonin re-uptake inhibitor (SSRI) citalopram, alone and in combination, and analyzed behaviors of importance for population fitness, scototaxis (light/dark preference), the novel tank test and shoal cohesion. Control water contained 0.4 ng/L EE2 and the measured exposure concentrations were 0.9 ng/L EE2 (nominal 0.1) and 1 ng/L EE2 (nominal 0.5). The measured concentrations of citalopram were 0.1 (nominal 0.1) and 0.4 μg/L (nominal 0.5). Both EE2 exposures increased anxiety in males in the scototaxis test, with significantly longer latency periods before entering and fewer visits to the white zone of the tank. The combined exposures (0.9 ng/L EE2 + 0.1 μg/L citalopram and 1 ng/L EE2 + 0.4 μg/L citalopram) resulted in abolishment of effects of EE2, with shorter latency period and more transitions to white than for fish exposed to EE2 alone. In the novel tank test, the results surprisingly indicated lower anxiety after both EE2 and citalopram exposure. Significantly more transitions to the upper half of the tank observed in males exposed to 0.1 μg/L citalopram alone compared to control males. Males exposed to EE2 (0.9 ng/L) had shorter latency period to the upper half. Combination exposure resulted in a longer latency and fewer transitions to the upper half compared to both control, EE2- and citalopram-exposed males. Males exposed to the combination spent significantly less time in the upper half than males EE2 or citalopram-exposed males. Females exposed to 1 ng/L EE2 had fewer transitions to the upper half than the control group and females exposed to 0.4 μg/L citalopram. In the shoaling test, males exposed to 0.1 μg/L citalopram + 0.9 ng/L EE2 showed more transitions away from peers than males exposed to 0.1 μg/L citalopram alone. In conclusion, low concentrations of EE2, closely above the predicted no effect concentration (NOEC) of 0.1 ng/L, created anxiety-like behavior in zebrafish males. Citalopram showed marginal effects at these low concentrations but in the combination exposure the behavioral effects of EE2 were abolished. This is an initial effort to understand the effects of cocktails of anthropogenic substances contaminating aquatic environments.
Paternal exposure to environmental 17-alpha-ethinylestradiol concentrations modifies testicular transcription, affecting the sperm transcript content and the offspring performance in zebrafish Aquat. Toxicol. (IF 4.129) Pub Date : 2017-09-28 David G. Valcarce, Elena Vuelta, Vanesa Robles, Maria Paz Herráez
The synthetic estrogen 17-α-ethinylestradiol (EE2), a major constituent in contraceptive pills, is an endocrine disrupting chemical (EDC) present in the aquatic environment at concentrations of ng/L. Developmental exposure to these low concentrations in fish can induce several disorders. Zebrafish (Danio rerio) is a perfect organism for monitoring the effects of environmental contaminants. Our hypothesis is that changes promoted by EE2 in the germ line of male adults could be transmitted to the unexposed progeny. We exposed male zebrafish to 2.5, 5 and 10 ng/L of EE2 during spermatogenesis and mated them with untreated females. Detailed progeny development was studied concentrating to survival, hatching and malformations. Due to the high incidence of lymphedemas within larvae, we performed qPCR analysis of genes involved in lymphatic development (vegfc and vegfr3) and endothelial cell migration guidance (cxcr4a and cxcl12b). Estrogen receptor (ER) transcript presence was also evaluated in sperm, testis and embryos. Progenies showed a range of disorders although at a low incidence: skeletal distortions, uninflated swimbladder, lymphedema formation, cartilage deformities and otolith tethering. Swimming evaluation revealed less active locomotion. All these processes are related to pathways involving ERs (esr1, esr2a and esr2b). mRNA analysis revealed that environmental EE2 causes the up-regulation of esr1 an esr2b in testis and the increase of esr2b transcripts in sperm pointing to a link between lymphedema in embryos and ER expression impairment. We demonstrate that the effects induced by environmental toxicants can be paternally inherited and point to the changes on the sperm transcriptome as the responsible mechanism.
Testosterone-induced modulation of peroxisomal morphology and peroxisome-related gene expression in brown trout (Salmo trutta f. fario) primary hepatocytes Aquat. Toxicol. (IF 4.129) Pub Date : 2017-09-28 Célia Lopes, Fernanda Malhão, Cláudia Guimarães, Ivone Pinheiro, José F. Gonçalves, L. Filipe C. Castro, Eduardo Rocha, Tânia V. Madureira
Disruption of androgenic signaling has been linked to possible cross-modulation with other hormone-mediated pathways. Therefore, our objective was to explore effects caused by testosterone – T (1, 10 and 50 μM) in peroxisomal signaling of brown trout hepatocytes. To study the underlying paths involved, several co-exposure conditions were tested, with flutamide – F (anti-androgen) and ICI 182,780 – ICI (anti-estrogen). Molecular and morphological approaches were both evaluated. Peroxisome proliferator-activated receptor alpha (PPARα), catalase and urate oxidase were the selected targets for gene expression analysis. The vitellogenin A gene was also included as a biomarker of estrogenicity. Peroxisome relative volumes were estimated by immunofluorescence, and transmission electron microscopy was used for qualitative morphological control. The single exposures of T caused a significant down-regulation of urate oxidase (10 and 50 μM) and a general up-regulation of vitellogenin. A significant reduction of peroxisome relative volumes and smaller peroxisome profiles were observed at 50 μM. Co-administration of T and ICI reversed the morphological modifications and vitellogenin levels. The simultaneous exposure of T and F caused a significant and concentration-dependent diminishing in vitellogenin expression. Together, the findings suggest that in the tested model, T acted via both androgen and estrogen receptors to shape the peroxisomal related targets.
Physiological impacts of acute Cu exposure on deep-sea vent mussel Bathymodiolus azoricus under a deep-sea mining activity scenario Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-09 Inês Martins, Joana Goulart, Eva Martins, Rosa Morales-Román, Sergio Marín, Virginie Riou, Ana Colaço, Raul Bettencourt
Over the past years, several studies have been dedicated to understanding the physiological ability of the vent mussel Bathymodiolus azoricus to overcome the high metal concentrations present in their surrounding hydrothermal environment. Potential deep-sea mining activities at Azores Triple junction hydrothermal vent deposits would inevitably lead to the emergence of new fluid sources close to mussel beds, with consequent emission of high metal concentrations and potential resolubilization of Cu from minerals formed during the active phase of the vent field. Copper is an essential metal playing a key role in the activation of metalloenzymes and metalloproteins responsible for important cellular metabolic processes and tissue homeostasis. However, excessive intracellular amounts of reactive Cu ions may cause irreversible damages triggering possible cell apoptosis. In the present study, B. azoricus was exposed to increasing concentrations of Cu for 96 h in conditions of temperature and hydrostatic pressure similar to those experienced at the Lucky Strike hydrothermal vent field. Specimens were kept in 1L flasks, exposed to four Cu concentrations: 0 μg/L (control), 300, 800 and 1600 μg/L and pressurized to 1750 bar. We addressed the question of how increased Cu concentration would affect the function of antioxidant defense proteins and expression of antioxidant and immune-related genes in B. azoricus. Both antioxidant enzymatic activities and gene expression were examined in gills, mantle and digestive gland tissues of exposed vent mussels. Our study reveals that stressful short-term Cu exposure has a strong effect on molecular metabolism of the hydrothermal vent mussel, especially in gill tissue. Initially, both the stress caused by unpressurization or by Cu exposure was associated with high antioxidant enzyme activities and tissue-specific transcriptional up-regulation. However, mussels exposed to increased Cu concentrations showed both antioxidant and immune-related gene suppression. Under a mining activity scenario, the release of an excess of dissolved Cu to the vent environment may cause serious changes in cellular defense mechanisms of B. azoricus. This outcome, while adding to our knowledge of Cu toxicity, highlights the potentially deleterious impacts of mining activities on the physiology of deep-sea organisms.
Alterations to Juvenile Zebrafish (Danio rerio) Swim Performance after Acute Embryonic Exposure to Sub-lethal Exposures of Hydraulic Fracturing Flowback and Produced Water Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-07 Erik J. Folkerts, Tamzin A. Blewett, Yuhe He, Greg G. Goss
Hydraulic fracturing flowback and produced water (FPW) is a wastewater produced during fracturing activities in an operating well which is hyper saline and chemically heterogeneous in nature, containing both anthropogenic and petrogenic chemicals. Determination of FPW associated toxicity to embryonic fish is limited, while investigation into how embryonic exposures may affect later life stages is not yet studied. Zebrafish embryos (24 hrs post fertilization) were acutely exposed to 2.5% and 5% FPW fractions for either 24 or 48 hrs and returned to freshwater. After either 24 or 48 h exposures, embryos were examined for expression of 3 hypoxia related genes. Erythropoietin (epoa) but not hypoxia inducible factor (hif1aa) nor hemoglobin −ß chain (hbbe1.1) was up-regulated after either 24 or 48 h FPW exposure. Surviving embryos were placed in freshwater and grown to a juvenile stage (60 days post fertilization). Previously exposed zebrafish were analyzed for both swim performance (Ucrit and Umax) and aerobic capacity. Fish exposed to both sediment containing (FPW-S) or sediment free (FPW-SF) FPW displayed significantly reduced aerobic scope and Ucrit/Umax values compared to control conditions. Our results collectively suggest that organics present in our FPW sample may be responsible for sub-lethal fitness and metabolic responses. We provide evidence supporting the theory that the cardio-respiratory system is impacted by FPW exposure. This is the first known research associating embryonic FPW exposures to sub-lethal performance related responses in later life fish stages.
Combined toxicity of prevalent mycotoxins studied in fish cell line and zebrafish larvae revealed that type of interactions is dose-dependent Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-03 Hongyuan Zhou, Saji George, Caixia Li, Subramaniam Gurusamy, Xiulan Sun, Zhiyuan Gong, He Qian
While, Aflatoxin B1 (AFB1), deoxynivalenol (DON) and zearalenone (ZEN) are the most prevalent mycotoxins co-existing in grain products and animal feeds, little is known about their combinatorial toxicities on aquatic life-forms. We studied the individual and combined effects of these mycotoxins in a fish cell line (BF-2) and zebrafish larvae (wild-type and transgenic). The types of interactions in mycotoxins combinations on cell viability were determined by using Chou-Talalay model. Induction of oxidative stress pathway in mycotoxins-exposed BF-2 cells was assessed using high content screening (HCS). Mycotoxin-exposed wild-type zebrafish larvae were examined for mortality and morphological abnormalities and transgenic zebrafish larvae (expressing DsRed in the liver) were imaged using HCS and examined for liver abnormalities. Results showed that the cytotoxicity of mycotoxins in a decreasing order was AFB1 > DON > ZEN, however, the highest mortality rate and liver damage in zebrafish were observed for AFB1 followed by ZEN. AFB1 + DON and AFB1 + ZEN synergistically enhanced the toxic effects on BF-2 cells and zebrafish while DON + ZEN showed antagonism. Interestingly, in the tertiary combination, the synergism seen at lower individual concentrations of mycotoxins progressively turned to an overall antagonism at higher doses. The results provide a scientific basis for the necessity to consider co-exposure when formulating risk-management strategies.
Identification of up-regulated genes from the metal-hyperaccumulator aquatic fern Salvinia minima Baker, in response to lead exposure Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-16 Daniel A. Leal-Alvarado, A. Martínez-Hernández, C.L. Calderón-Vázquez, D. Uh-Ramos, G. Fuentes, J.H. Ramírez-Prado, L. Sáenz-Carbonell, J.M. Santamaría
Lead (Pb) is one of the most serious environmental pollutants. The aquatic fern Salvinia minima Baker is capable to hyper-accumulate Pb in their tissues. However, the molecular mechanisms involved in its Pb accumulation and tolerance capacity are not fully understood. In order to investigate the molecular mechanisms that are activated by S. minima in response to Pb, we constructed a suppression subtractive hybridization library (SSH) in response to an exposure to 40 μM of Pb(NO3)2 for 12 h. 365 lead-related differentially expressed sequences tags (ESTs) were isolated and sequenced. Among these ESTs, 143 unique cDNA (97 were registered at the GenBank and 46 ESTs were not registered, because they did not meet the GenBank conditions). Those ESTs were identified and classified into 3 groups according to Blast2GO. In terms of metabolic pathways, they were grouped into 29 KEGG pathways. Among the ESTs, we identified some that might be part of the mechanism that this fern may have to deal with this metal, including abiotic-stress-related transcription factors, some that might be involved in tolerance mechanisms such as ROS scavenging, membrane protection, and those of cell homeostasis recovery. To validate the SSH library, 4 genes were randomly selected from the library and analyzed by qRT-PCR. These 4 genes were transcriptionally up-regulated in response to lead in at least one of the two tested tissues (roots and leaves). The present library is one of the few genomics approaches to study the response to metal stress in an aquatic fern, representing novel molecular information and tools to understand the molecular physiology of its Pb tolerance and hyperaccumulation capacity. Further research is required to elucidate the functions of the lead-induced genes that remain classified as unknown, to perhaps reveal novel molecular mechanisms of Pb tolerance and accumulation capacity in aquatic plants.
Hydrilla verticillata employs two different ways to affect DNA methylation under excess copper stress Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-14 Danlu Shi, Kai Zhuang, Yan Xia, Changhua Zhu, Chen Chen, Zhubing Hu, Zhenguo Shen
Because of the accumulation of heavy metals, Hydrilla verticillata (L.f.) Royle, a rooted submerged perennial aquatic herb, is being developed as a potential tool to clean the aquatic ecosystem polluted by heavy metals. However, its physiological responses for heavy metal remain to be elucidated. Here, through employing proteomics approach, we found that excess Cu significantly induced the expressions of four DNA methylation related proteins in H. verticillata, which were the homologues of two domains rearranged methyltransferases (DRM), a methyltransferases chromomethylase (CMT) and a histone H3 lysine-9 specific SUVH6-like (SUVH6). Consistently, a dramatic change in DNA methylation patterns was detected in excess Cu-exposed H. verticillata. Surprisingly, administration of the NADPH oxidase inhibitors, diphenylene iodonium (DPI) and imidazole (IMZ) that block production of reactive oxygen species (ROS) could trigger the remethylation of genomic sites that were demethylated by excess Cu, indicating that Cu-induced ROS might be another way to affect DNA methylation. Further analysis suggested this changed DNA methylation may be owing to the ROS-induced DNA damage. Taken together, our findings demonstrate that two different ways to influence DNA methylation in excess Cu-treated H. verticillata.
Maturation of Xenopus laevis oocytes under cadmium and lead exposures: Cell biology investigations Aquat. Toxicol. (IF 4.129) Pub Date : 2017-10-16 Sylvain Slaby, Julie Hanotel, Guillaume Marchand, Arlette Lescuyer, Jean-François Bodart, Alain Leprêtre, Sébastien Lemière, Matthieu Marin
Since amphibians are recognised as good models to assess the quality of environments, only few studies have dealt with the impacts of chemical contaminants on their gametes, while toxic effects at this stage will alter all the next steps of their life cycle. Therefore, we propose to investigate the oocyte maturation of Xenopus laevis in cadmium- and lead-contaminated conditions. The impacts of cadmium and lead ions were explored on events involved in the hormone‐dependent process of maturation. In time-course experiments, cadmium, at the highest concentration, delayed and prevented the germinal vesicle breakdown. Even in the absence of progesterone this ion could also induce it. No such spontaneous maturation was observed after lead exposures. An acceleration of the process at the highest tested concentration of lead (90 μM), in presence of progesterone, was recorded. Cytological observations highlighted that cadmium exposures drove severe disturbances of meiotic spindle morphogenesis. At last, cadmium exposures altered the MAPK pathway, regarding the activation of ERK2 and RSK, but also the activation and the activity of the MPF, by disturbing the state of phosphorylation of Cdc2 and histone H3. Xenopus laevis oocytes were affected by these metal ion exposures, notably by Cd2+. Signatures of these metal exposures on the oocyte maturation were detected. This germ cell appeared to be a relevant model to assess the effects of environmental contaminants such as metals.
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