Battling pollution in coastal areas / Lutter contre la pollution dans les zones côtières
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Item Acute toxicity, accumulation and tissue distribution of copper in the blue crab Callinectes sapidus acclimated to different salinities: in vivo and in vitro studies(2010) Martins, C M; Barcarolli, I F; de Menezes, E J; Giacomin, M M; Wood, C MIn vivo and in vitro studies were performed to evaluate acute toxicity, organ-specific distribution, and tissue accumulation of copper in Callinectes sapidus acclimated to two different experimental salinities (2 and 30 ppt). Blue crabs were quite tolerant to copper. Acute dissolved copper toxicity (96-h LC50 and its corresponding 95% confident interval) was higher at salinity 2 ppt (5.3 (3.50–8.05) μM Cu) than at 30 ppt (53.0 (27.39–102.52) μM Cu). The difference between salinities can be completely explained based on the water chemistry because it disappeared when 96-h LC50 values were expressed as the free Cu2+ ion (3.1 (1.93–4.95) μM free Cu at 2 ppt versus 5.6 (2.33–13.37) μM free Cu at 30 ppt) or the Cu2+ activity (1.4 (0.88–2.26) μM Cu activity at 2 ppt versus 1.7 (0.71–4.07) μM Cu activity at 30 ppt). The relationships between gill Cu burden and % mortality were very similar at 2 and 30 ppt, in accord with the Biotic Ligand Model. In vivo experiments showed that copper concentration in the hemolymph is not dependent on metal concentration in the surrounding medium at either experimental salinity. They also showed that copper flux into the gills is higher than into other tissues analyzed, and that anterior and posterior gills are similarly important sites of copper accumulation at both experimental salinities. In vitro experiments with isolated-perfused gills showed that there is a positive relationship between copper accumulation in this tissue and the metal concentration in the incubation media for both anterior and posterior gills. A similar result was observed at both low and high salinities. Furthermore, in vitro experiments showed that copper accumulation in posterior gills is also positively and strongly dependent on the incubation time with copper. Gill copper accumulation occurred at a lower rate in the first 2 h of metal exposure, increasing markedly after this “steady-state” period. This finding was corroborated by a significant increase in copper influx to the gill perfusate (corresponding to crab hemolymph) after this time, measured using 64Cu. In vivo, after uptake from solution, 64Cu was primarily accumulated in the gills and the rest of the body rather than in the hemolymph, hepatopancreas, or other internal tissues. Overall, the present findings indicate that gills are a key target organ for copper accumulation, as well as an important biological barrier against the excessive uptake of copper into the hemolymph and the subsequent distribution of this metal to internal organs of the blue crab.Item Integrated biological responses of zebrafish (Danio rerio) to analyze water quality in regions under anthropogenic influence(2010) Amado, L L; Rosa, C E; Castro, M R; Votto, A P; Cougo Santos, LThis study analyzed water quality in regions around Patos lagoon (Southern Brazil) that are under anthropogenic pressure. Water samples were collected from five different sites, including one used as a source for human consumption (COR) and others known to be influenced by human activities (IP). Danio rerio (Teleostei, Cyprinidae) organisms were exposed for 24 h to these water samples, plus a control group. It was observed that: (1) reactive oxygen species levels were lower in COR and IP than in the control group; (2) glutamate-cysteine ligase (catalytic subunit) expression was higher in COR than in other sites; (3) exposure to all water samples affected long-term memory (LTM) when compared to control group. Thus, some water samples possess the ability to modulate the antioxidant system and to induce a decline in cognitive functions, as measured by LTM. The obtained results indicate that a combination of variables of different organization level (molecular, biochemical and behavioral) can be employed to analyze water quality in impacted regions.Item mRNA Expression and activity of ion-transporting proteins in gills of the blue crab Callinectes sapidus: Effects of waterborne copper(2010) Martins, C M G; Almeida, D V; Marins, L F F; Bianchini, AItem Utility of Tissue Residues for Predicting Effects of Metals on Aquatic Organisms(SETAC, Pensacola, FL, 2010-07) Adams, William J; Blust, Ronny; Borgmann, Uwe; Brix, Kevin V; DeForest, David KAs part of a SETAC Pellston Workshop, we evaluated the potential use of metal tissue residues for predicting effects in aquatic organisms. This evaluation included consideration of different conceptual models and then development of several case studies on how tissue residues might be applied for metals, assessing the strengths and weaknesses of these different approaches.We further developed a new conceptual model in which metal tissue concentrations from metal-accumulating organisms (principally invertebrates) that are relatively insensitive to metal toxicity could be used as predictors of effects in metal-sensitive taxa that typically do not accumulate metals to a significant degree. Overall, we conclude that the use of tissue residue assessment for metals other than organometals has not led to the development of a generalized approach as in the case of organic substances. Species-specific and site-specific approaches have been developed for one or more metals (e.g., Ni). The use of gill tissue residues within the biotic ligand model is another successful application. Aquatic organisms contain a diverse array of homeostatic mechanisms that are both metal- and species-specific. As a result, use of whole-body measurements (and often specific organs) for metals does not lead to a defensible position regarding risk to the organism. Rather, we suggest that in the short term, with sufficient validation, species- and site-specific approaches for metals can be developed. In the longer term it may be possible to use metal-accumulating species to predict toxicity to metal-sensitive species with appropriate field validation.Item Effects of salinity on acute and chronic nickel toxicity and bioaccumulation in two euryhaline crustaceans: Litopenaeus vannamei and Excirolana armata(2011) Leonard, E M; Barcarolli, I; Silva, K R; Wasielesky, W; Wood, C MWe investigated the influence of salinity (5 ppt versus 25 ppt) on acute (96-h LC50) and chronic toxicity (15–30 day LC50) of Ni in two euryhaline crustaceans, the shrimp (Litopenaeus vannamei) and the isopod (Excirolana armata). 96-h LC50 values were 41 μmol L−1 and 362 μmol L−1 for L. vannamei and 278 μmol L−1 and > 1000 μmol L−1 for E. armata at 5 ppt and 25 ppt, respectively. Speciation analysis demonstrated that complexation with anions such as SO42−, HCO3− and Cl− at 25 ppt had a negligible effect on reducing the free Ni2+ ion component in comparison to 5 ppt. The salinity-dependent differences in acute Ni toxicity could not be explained by differences in Ni bioaccumulation. Therefore, differences in physiology of the organisms at the two salinities may be the most likely factor contributing to differences in acute Ni toxicity. Chronic LC50 values (2.7–23.2 μmol L−1) were similar in the two species, but salinity had no significant effect, indicating that water chemistry and osmoregulatory strategy do not influence chronic toxicity. However chronic (15-day) mortality in both species could be predicted by acute (96-h) Ni bioaccumulation patterns.Item Multibiomarker approach at different organization levels in the estuarine Perinereis gualpensis (Polychaeta; Nereididae) under chronic and acute pollution conditions(2011) Díaz-Jaramillo, M; Martins da Rocha, A; Gomes, V; Bianchini, A; Monserrat, J MThis work aimed to study biochemical biomarkers and population responses in the polychaete Perinereis gualpensis (Nereididae) from two Chilean estuaries, Lenga (36°45′S; 73°10′W) and Tubul–Raqui (37°14′S,73°26′W). Lenga estuary is characterized by high mercury and PAH levels as consequence of several historic incidental spills while Tubul is mainly impacted by intensive fish activity. Raqui estuary, with low anthropogenic impact was considered the reference site. Worms were collected in winter and summer periods and tissues were differentiated between anterior (first 40 segments) and posterior region (the rest of the body). Levels of the antioxidant glutathione (GSH), glutathione-S-transferase (GST) activity, total antioxidant capacity against peroxyl radicals (ACAP), lipid peroxidation (TBARS) levels, Na+, K+–ATPase activity (NKA) and metalothioneins (MTs) content were determined in each region. L3 (combined length of prostomiun + peristomiun + first segment) length, size, frequency, histograms and density of individuals were studied in all sites and seasons. Significant differences (p < 0.05) were observed among sites for most of the biochemical responses (GSH, GCL, GST, ACAP and TBARS), showing variation between seasons and body regions. Population responses in the most polluted estuary (Lenga) showed differences in size, frequency, lengths and low densities compared with lower impacted sites, indicating the costs associated with tolerance in organisms chronically exposed to estuarine pollution.Item An introduction to metals in fish physiology and toxicology: basic principles(2011) Wood, C MA brief history of metals, their early investigation in fish by physiologists and toxicologists, and current terminology are presented. The conceptual basis for the topics explored in each of the metal-specific chapters of these two volumes is then described. These include sources of metals, their economic importance, environmental situations of concern, essentiality or non-essentiality, bioconcentration or lack thereof, and the overarching importance of chemical speciation in understanding their effects on fish. The techniques used to derive ambient water quality criteria for metals are explained. Key mechanisms of acute and chronic toxicity are reviewed, as well as recent findings on the mechanisms and sites of uptake, internal handling, biotransformation, subcellular partitioning, detoxification, storage, and excretion. Important new research fronts focus on behavioral effects, molecular and omic analyses of cellular responses, and the effects of interacting metals in fish. Similarities and differences among the metals dealt with in these volumes are highlighted.Item Mechanisms of sodium extrusion in isolated mitochondria-rich cells of the freshwater mussel Lasmigona costata after copper exposure(2011) Nogueira, L S; Wood, C M; Bianchini, A; Gillis, P LGill tissues in aquatic animals are composed of various cell types, each with specific functions such as respiration, excretion, acid-base balance and ionic regulation. In the bivalves, the gill is the main route of contaminant uptake and metals can be absorbed through specific transporters in cell membranes. Among the gill cells, mitochondria-rich cells (MRCs) are considered to be the primary sites responsible for iron transport. In order to determine the mechanisms of sodium extrusion in MRCs after copper exposure, gill cells from Lasmigona costata were isolated and layered on a discontinuous Percoll gradient. The pavement cells (PCVs) and MRCs populations were confirmed by a specific mitochondrial dye (DASPEI) and Na, K-ATPase activity. It is the first time at literature that isolated fill cells from freshwater mussels are identified in two different populations and used in toxicological experiments. MRCs were then exposed to a range of copper concentrations environmentally relevant (5, 10 and 20 ug/L) for 3 hours. Copper accumulation increased in all copper exposures. In contrast, the sodium content did not change in low exposures and decreased significantly when cells were exposed to high copper concentrations. To further explore this result, both sodium and copper were measured after specific pharmacological blockade of Na, K-ATPase and carbonic anhydrase enzymes. Carbonic anhydrase inhibition suggest that sodium and copper uptake mechanisms are not dependent on a supply of protons and intracellular increase of both ions might be associated to blocked of Na extrusion via Na/HCO3-. The inhibition of Na, K-ATPase by ouabain also resulted in an increase in sodium and copper content in the MRCs. This enzyme is responsible for sodium extrusion from the cell, and the results suggest that it is also a route for copper extrusion.Item Avaliação da lipoperoxidação em peixe como potencial biomarcador de contaminação aquática(2011) Gomes, E G; Machado, A A S; Hoff, M L M; Bianchini, AA contaminação aquática por pesticidas, metais e hidrocarbonetos pode ser monitorada usando-se biomarcadores. A lipoperoxidação (LPO) é um biomarcador que pode ser induzido pela exposição a contaminantes como atrazina (pesticida), cobre (metal) e fenantreno (hidrocarboneto). Avaliar LPO em músculo, brânquia e fígado do peixe Poecilia viviparaapós exposição a cobre, atrazina e fenantreno. Machos de P. vivípara foram coletados no Arroio do Gelo (Rio Grande, RS), aclimatados à salinidade 24, fotoperíodo 12:12 h C:E e 20°C, e expostos (96 h) aatrazina(controle, controle metanol, 2, 10, 100µg/L), Cu (controle, 5, 9 e 20µg Cu/L) e fenantreno (controle, controle DMSO, 10, 20, 200µg/L) em água do mar filtrada (0,5 µm). Após expostos, os peixes foram anestesiados e retirados brânquias, fígado e músculo. A LPO foi avaliada nestes tecidos através do método TBARS. ANOVA, Kruskal Wallis e coeficiente de correlação linear de Spearman foram utilizados. Os peixes expostos ao cobre apresentaram um aumento da LPO branquial e hepática em função da concentração do metal (brânquia r = 0,83; fígado r = 0,90). A exposição a 100 µg/L de atrazina induziu aumento da LPO branquial. Por sua vez, a exposição a 10 µg/L causou uma diminuição da LPO muscular. No fígado, observou-se uma tendência de diminuição da LPO com o aumento da concentração de atrazina (r = -0,88). A exposição a 10 µg/L de fenantreno causou um aumento da LPO branquial. No músculo, este contaminante causou um aumento da LPO em função da concentração (r = 0,94). Por sua vez, não foi observada variação significativa na LPO hepática. Os resultados obtidos indicam que o cobre, a atrazina e o fenantreno afetam a LPO em tecidos de P. vivipara, porém o efeito é dependente do tecido analisado e da concentração testada. Assim, um aumento da LPO muscular remete à exposição ao fenantreno, enquanto uma diminuição da LPO hepática em paralelo a um aumento da LPO branquial remete à exposição à atrazina e um aumento da LPO hepática conjuntamente a um aumento da LPO branquial remete à exposição ao cobre. Estes resultados indicam que a LPO se constitui em um potencial biomarcador para identificar a exposição de peixes à contaminação por fenantreno, atrazina e cobre em ambientes estuarinos.Item Effects of salinity on growth of juvenile mullet Mugil platanus(2011) Lisboa da Cunha, Viviana; Barcarolli, Indianara Fernanda; Sampaio, Luis André; Bianchini, AdaltoAssuming the energetic cost of osmoregulation is minimized in an isosmotic medium, the energy spared could support a higher growth rate of fish. The isosmotic point of juvenile mullet Mugil platanus was estimated at 414 mOsmol/Kg H2O, which corresponds to salinity 12‰.The aim of this study was to investigate the effect of salinity on the performance of juvenile mullet reared at different salinities. Four hundred and eighty fish (0.48±0.01g and 3.27±0.01cm) were randomly distributed into 16 tanks (50L). These tanks were connected to four recirculating aquaculture systems (RAS) equipped with UV sterilization, mechanical and biological filtration and temperature controllers. Each RAS was maintained at salinities 0, 6, 12, and 24, equivalent to 0, 50, 100 and 200% of the isosmotic point of M. platanus. During the experimental period (40 days), fish were maintained at 28.2 ± 0.1°C and oxygen saturation was always above 90%. Fish were fed 4 times per day on NRD INVE (50% protein) until apparent satiation. Results were analyzed by analysis of variance (One-Way) followed by Test of Tukey. All analyses were performed with significance level of p<0.05 and were conducted using the software Statistic 6.0. Salinity did not influence survival of juvenile mullet (p>0.05), nor influenced feed efficiency. However, final weight and specific growth rate were significantly affected at different salinities (p<0.05). Overall survival was above 90% and feed efficiency was y. Fish reared at salinities 12 and 24 grew faster than those reared at lower salinities (Figure 1 and 2) Results indicated that salinity plays an important role in juvenile mullet growth and that final weight and SGR were maximized when they were reared at salinity equivalent to, or higher, than the isosmotic point.Item Toxicity tests aiming to protect Brazilian aquatic systems: current status and implications for management(2011) Martins, S E; Bianchini, AThe current status of toxicological tests performed with Brazilian native species was evaluated through a survey of the scientific data available in the literature. The information gathered was processed and an electronic toxicology database (http://www.inct-ta.furg.br/bd_toxicologico.php) was generated. This database provides valuable information for researchers to select sensitive and tolerant aquatic species to a large variety of aquatic pollutants. Furthermore, the toxicology database allows researchers to select species representative of an ecosystem of interest. Analysis of the toxicology database showed that ecotoxicological assays have significantly improved in Brazil over the last decade, in spite of the still relatively low number of tests performed and the restricted number of native species tested. This is because most of the research is developed in a few laboratories concentrated in certain regions of Brazil, especially in Southern and Southeast regions. Considering the extremely rich biodiversity and the large variety of aquatic ecosystems in Brazil, this finding points to the urgent need for the development of ecotoxicological studies with other groups of aquatic animals, such as insects, foraminifera, cnidarians, worms, amphibians, among others. This would help to derive more realistic water quality criteria (WQC) values, which would better protect the different aquatic ecosystems in Brazil. Finally, the toxicology database generated presents solid and science based information, which can encourage and drive the Environmental Regulatory Agencies in Brazil to derive WQC based on native species. In this context, the present paper discusses the historical evolution of ecotoxicological studies in Brazil, and how they have contributed to the improvement of the Brazilian Federal and Regional regulations for environment.Item Effect of copper on ion content in isolated mantle cells of the marine clam Mesodesma mactroides(2011) Lopes, T M; Barcarolli, I F; de Oliveira, C B; Souza, M MItem Chitobiase of planktonic crustaceans from South Atlantic coast (Southern Brazil): Characterization and influence of abiotic parameters on enzyme activity(2011) Avila, T R; Machado, A A S; Bianchini, AChitobiase is one of the enzymes involved in chitin degradation in nature. It is produced and released by a variety of organisms from bacteria to fish. In crustaceans, it is associated with digestive function and acts on the epidermis during the molting process. In the present study, the influence of water pH, temperature and salinity on maximum chitobiase activity (MCA), as well as the enzyme affinity (Km) for a substrate, the methylumbelliferyl N-acetyl-ß-d-glucosaminide (MUFNAG) was evaluated in the copepod Acartia tonsa. Km values for chitobiases of other crustaceans from the Patos Lagoon estuary and Cassino Beach (Southern Brazil) were also determined. For A. tonsa, MCA was observed at pH 5–6 and 30–35 °C. The range of pH was quite similar to that reported for other aquatic organisms. However, the range of temperature was lower than that previously reported. For salinity, no previous studies have considered the influence of this parameter on MCA. For A. tonsa, MCA was observed in freshwater, showing a significant linear decrease with increasing salinity. Considering that maximum copepod survival and growth rates are observed between 15 and 25 ppt, these findings suggest that the observed enzyme activity in this range of salinity (68 to 47% of that measured in freshwater) is not a limiting factor for A. tonsa growth. However, the extremely decreased enzyme activity observed in salinity 30 ppt (33% of that measured in freshwater) suggests that chitobiase activity might be one of the limiting factor for copepod growth at 30 ppt salinity or higher. Km values (μM) determined for organisms evaluated in the present study (copepod A. tonsa = 20.77; mysid Metamysidopsis elongata atlantica = 14.67; nauplii barnacle Balanus improvisus = 18.19; decapod zoea = 14.30; decapod megalopa = 24.77) were lower than those reported for other crustaceans from Northern Hemisphere. Also, they were much lower than those of organisms from different taxonomic groups like bacteria and fungi, but much higher than in protozoans and dinoflagelates. These findings suggest that chitobiase might be differentially evolved in each specific group of organism, and even within different ontogenetic stages of the same species, for a better adaptation to cope with its respective environmental needs.Item Produção secundária baseada no crescimento de crustáceos: aspectos metodológicos(2011) Ramos Avila, Tatiana; Bianchini, Adalto; Oceanografia Biológica da Universidade Federal do Rio GrandeItem New insights into gill epithelial transport: Linking ammonia excretion and sodium uptake(2011) Wright, P A; Wood, C M; Cooper, C AModels of gill epithelial transport are rapidly changing as researchers discover more complex and specialized cell types and use genomic data to uncover completely new protein transporters. Maetz and Garcia Romeu (1964) first suggested a linkage between ammonia excretion and active Na+ uptake at the gills of freshwater animals. Although many studies have provided supporting evidence for such a linkage, only in the last 4 years with the discovery of ammonia-transporting Rhesus (Rh) glycoproteins in gill tissue have we been able to more fully understand the model of gill ammonia transport in freshwater animals. Recent evidence supports an apical “Na+/NH4 + exchange complex” consisting of several membrane transporters (Rhcg, V type H+ATPase, Na+/H+ exchanger (NHE 2/3, Na+ channel) working together as a metabolon providing an acid-trapping mechanism for apical excretion in freshwater fish. The model for gill ammonia transport in seawater is more controversial, although Rhcg also appears to be associated with Na+ transport.Item Two faces of DOC(2011) Wood, C M; Al-Reasi, Hassan Ali; Smith, SDissolved organic carbon (DOC), through its ability to complex metals and thereby reduce their bioavailability, plays a major role in ameliorating metal toxicity in natural waters. Indeed DOC is a key variable in the Biotic Ligand Model (BLM) for predicting metal toxicity on a site-specific basis. However, recent evidence indicates that all DOCs are not alike, but rather heterogeneous in their ability to protect organisms against metal toxicity, at least in fresh water. The degree of protection appears to correlate with optical properties, such that dark, aromatic-rich compounds of allochthonous origin, with greater humic acid content, are more effective in this regard, particularly against Cu, Ag, and Pb toxicity. The specific absorption coefficient of the DOC in the 300–350 nm range (SAC300–350) has proven to be a simple and effective index of this protective ability. PARAFAC, a multivariate statistical technique for analysis of excitation-emission fluorescence spectroscopy data, also holds promise for quantifying the humic-like and fulvic-like fluorophores, which tend to be positively and negatively correlated with protective ability, respectively. However, what has been largely missing in the toxicological realm is any appreciation that DOC may also affect the physiology of target organisms, such that part of the protection may occur by a mechanism other than metal complexation. Recently published evidence demonstrates that DOC has effects on Na+ transport, diffusive permeability, and electrical properties of the gills in fish and crustaceans in a manner which will promote Na+ homeostasis. These actions could thereby protect against metal toxicity by physiological mechanisms. Future research should investigate potential direct interactions of DOC molecules with the branchial epithelium. Incorporation of optical properties of DOC could be used to improve the predictive capabilities of the BLM.Item Biomarkers response to zinc exposure in the symbiont-bearing foraminifer Amphistegina lessonii (Amphisteginidae, Foraminifera)(2011) Prazeres, M F; Martins, S E; Bianchini, AThe aim of the study is to evaluate populations of the symbiont-bearing foraminifer Amphistegina lessonii both by using established visual assessment methods and by adapting cellular diagnostic methods for use on these protists. Findings suggest that an activation of some components of the antioxidant system occurred in A. lessonii to counteract the oxidative stress induced by Zn exposure, and consequently avoid a possible complete loss of the symbiont.See also http://hdl.handle.net/10625/49042Item Dietary salt supplementation for juvenile mullet Mugil platanus reared in freshwater(2011) Lisboa da Cunha, Viviana; Barcarolli, Indianara Fernanda; Sampaio, Luis André; Bianchini, AdaltoDietary salt supplementation for seawater/euryhaline fish reared in low salinities and/or freshwater might spare energy expenditure for osmoregulation allowing more energy for growth. Growth of mullet Mugil platanus is hampered in hypoosmotic environments, thus the objective of this study was to evaluated the effect of dietary salt supplementation on their performance when reared in freshwater. Two hundred and forty fish (4.50 ± 0.07g e 7.41 ± 0.03cm) were randomly distributed into 16 tanks (50L). These tanks were connected to a recirculating aquaculture system (RAS) equipped with UV sterilization, mechanical and biological filtration and temperature controller. A commercial diet (32%CP and 1.5% NaCl) was grinded to powder, supplemental salt was added, and cellulose was used to compensate for the extra salt. Fish were fed 3 times per day on diets supplemented with 0, 3, 6, and 9% NaCl. During the experiment, fish were maintained at temperature of 27 ± 0.1°C, oxygen saturation above 89%, 78.56 ± 1.09, 7.92 ± 0.02 and photoperiod 14C:10E. Fish were fed three times per day until apparent satiation. Biometry was made every 15 days. The data (average ± SE) were analyzed by analysis of variance (One-Way) (ANOVA) followed by Test of Tukey. All analyses were performed with significance level of p<0.05 and were conducted using the software statistic 6.0. Dietary salt supplementation did not affect survival of juvenile mullet, survival was above 90% in all tanks. Feed efficiency was not influenced by the experimental diets either, it averaged 0.31 ± 0.01 (p>0.05). However, final weight of juvenile mullet fed NaCl-enriched diets (6 and 9%) was significantly smaller than fish fed control or NaCl-enriched (3%) diets (p<0.05) (Figure 1). Considering the specific growth rate, juvenile mullet fed NaCl-enriched diet (9%) showed the poorest performance when compared to fish fed any other diet (Figure 2). Results indicated that diets supplemented with NaCl are not beneficial to juvenile mullet. Furthermore, excess salt (6% and 9% NaCl) are harmfull and compromise their growthItem Silver(2011) Wood, C MIn pristine natural waters, silver (Ag) occurs at low ng L−1 levels, rising to 1000-fold at highly contaminated sites. The free ion Ag+ appears to be the sole cause of acute toxicity in freshwater, being among the most toxic of the metals in this regard, but probably does not occur to any significant extent in natural waters, where speciation is dominated by complexation to sulfide, dissolved organic carbon, chloride, and particles. Nevertheless, Ag+ is the form used in regulatory tests, and on which environmental water quality criteria are based. Such criteria are often related to water hardness, but this probably reflects a misinterpretation of original test data, since other water quality parameters are far more protective than calcium and magnesium. The biotic ligand model approach holds promise for improving water quality criteria for Ag. In freshwater fish, waterborne Ag+ poisons two key enzymes of ion transport in the gills (Na+/K+-ATPase and carbonic anhydrase), and death results from ionoregulatory failure. Dietborne toxicity is negligible. Silver appears to be taken up by sodium and copper transport pathways in the gills, as well as by diffusion of neutral complexes. Chronic toxicity occurs at much lower Ag concentrations, and may again involve ionoregulatory disturbance as well as other mechanisms. Acclimation may occur. In saltwater, Ag speciation is dominated by salinity-dependent chloride complexation, and Ag is far less toxic on an acute basis than in freshwater. Since seawater fish drink the medium, both gills and gut are targets of acute toxicity and potential routes of Ag uptake, but mechanisms remain unclear. Marine elasmobranchs are far more sensitive, and take up much more Ag, than marine teleosts. Bioconcentration of Ag clearly occurs in both freshwater and saltwater fish, but the bioconcentration factor approach is not a useful regulatory tool for Ag. Silver accumulates preferentially in the liver, which serves as a scavenging organ. Silver is a powerful inducer of metallothionein synthesis for detoxification. Biological half-lives are long and excretory mechanisms remain poorly characterized. Trophic transfer efficiency is low and biomagnification of Ag does not occur.Item Mechanisms of copper accumulation in isolated mantle cells of the marine clam Mesodesma mactroides(2011) Lopes, T M; Barcarolli, I F; de Oliveira, C B; de Souza, M M; Bianchini, AIn vivo copper accumulation was determined in tissues (mantle, gills, digestive gland, and hemolymph) following exposure to Cu (5 µM) for up to 96 h. Mantle was the tissue that accumulated the most Cu, followed by gill, digestive gland, and hemolymph. Therefore, in vitro Cu accumulation was evaluated in isolated mantle cells exposed to 0.5, 1.0, 2.5, and 5.0 µM Cu for 1 and 3 h. After both exposure times, no change in cell viability was observed. However, a significant Cu accumulation was observed in cells exposed to 2.5 and 5.0 µM Cu. Cell exposure to 2.5 µM Cu for 1 h did not affect the ionic (Na(+), K(+), Ca(2+), and Cl(-)) content of isolated mantle cells, characterizing an "ideal" noneffect concentration for the study of the involvement of different ion-transporting proteins (Na(+), K(+), and Cl(-) channels; Na(+)/K(+) 2Cl(-) and Na(+)/Cl(-) cotransporters; Na(+)/Ca(2+), Cl(-)/HCO3-, and Na(+)/H(+) exchangers; Na(+)/K(+) -ATPase; V-ATPase; and carbonic anhydrase) in Cu accumulation. Isolated cells were pre-exposed (30 min) to specific blockers or inhibitors of the ion-transporting proteins and then exposed (1 h) to Cu (2.5 µM) in the presence of the drug. A significant increase of 29.1 and 24.3% in Cu accumulation was observed after cell incubation with acetozalamide (carbonic anhydrase inhibitor) and NPPB (Cl(-) channels blocker), respectively. On the other hand, a significant decrease (48.2%) in Cu accumulation was observed after incubation with furosemide (Na(+) /K(+)/2Cl(-) blocker). Taken together, these findings indicate the mantle as an important route of Cu entry in M. mactroides, pointing to the cotransporter Na(+)/K(+)/2Cl(-) as a major mechanism of Cu accumulation in mantle cells of the clam.
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