Behavioural and physiological impacts of low salinity on the sea urchin Echinus esculentus.

Reduced seawater salinity as a result of freshwater input can exert a major influence on the ecophysiology of benthic marine invertebrates, such as echinoderms. While numerous experimental studies have explored the physiological and behavioural effects of short-term, acute exposure to low salinity in echinoids, surprisingly few have investigated the consequences of chronic exposure, or compared the two. In this study, the European sea urchin, Echinus esculentus, was exposed to low salinity over the short term (11‰, 16‰, 21‰, 26‰ and 31‰ for 24 h) and longer term (21, 26 and 31‰ for 25 days). Over the short term, oxygen consumption, activity coefficient and coelomic fluid osmolality were directly correlated with reduced salinity, with 100% survival at ≥21‰ and 0% at ≤16‰. Over the longer term at 21‰ (25 days), oxygen consumption was significantly higher, feeding was significantly reduced and activity coefficient values were significantly lower than at control salinity (31‰). At 26‰, all metrics were comparable to the control by the end of the experiment, suggesting acclimation. Furthermore, beneficial functional resistance (righting ability and metabolic capacity) to acute low salinity was observed at 26‰. Osmolality values were slightly hyperosmotic to the external seawater at all acclimation salinities, while coelomocyte composition and concentration were unaffected by chronic low salinity. Overall, E. esculentus demonstrate phenotypic plasticity that enables acclimation to reduced salinity around 26‰; however, 21‰ represents a lower acclimation threshold, potentially limiting its distribution in coastal areas prone to high freshwater input.

Interspecific differences in oxidative DNA damage after hydrogen peroxide exposure of sea urchin coelomocytes.

Interspecific comparison of DNA damage can provide information on the relative vulnerability of marine organisms to toxicants that induce oxidative genotoxicity. Hydrogen peroxide (H2O2) is an oxidative toxicant that causes DNA strand breaks and nucleotide oxidation and is used in multiple industries including Atlantic salmon aquaculture to treat infestations of ectoparasitic sea lice. H2O2 (up to 100 mM) can be released into the water after sea lice treatment, with potential consequences of exposure in nontarget marine organisms. The objective of the current study was to measure and compare differences in levels of H2O2-induced oxidative DNA damage in coelomocytes from Scottish sea urchins Echinus esculentus, Paracentrotus lividus, and Psammechinus miliaris. Coelomocytes were exposed to H2O2 (0-50 mM) for 10 min, cell concentration and viability were quantified, and DNA damage was measured by the fast micromethod, an alkaline unwinding DNA method, and the modified fast micromethod with nucleotide-specific enzymes. Cell viability was >92% in all exposures and did not differ from controls. Psammechinus miliaris coelomocytes had the highest oxidative DNA damage with 0.07 ± 0.01, 0.08 ± 0.01, and 0.07 ± 0.01 strand scission factors (mean ± SD) after incubation with phosphate-buffered saline, formamidopyrimidine-DNA glycosylase, and endonuclease-III, respectively, at 50 mM H2O2. Exposures to 0.5 mM H2O2 (100-fold dilution from recommended lice treatment concentration) induced oxidative DNA damage in all three species of sea urchins, suggesting interspecific differences in vulnerabilities to DNA damage and/or DNA repair mechanisms. Understanding impacts of environmental genotoxicants requires understanding species-specific susceptibilities to DNA damage, which can impact long-term stability in sea urchin populations in proximity to aquaculture farms.

The influence of Magnafloc10 on the acidic, alkaline, and electrodialytic desorption of metals from mine tailings.

Repparfjorden in northern Norway has been partly designated for submarine mine tailings disposal when the adjacent Cu mine re-opens in 2019. In order to increase sedimentation, the flocculant, Magnafloc10 is planned to be added to the mine tailings prior to discharge into the fjord. This study investigated the feasibility of reducing the Cu concentrations (375 mg/kg) in the mine tailings by applying electrodialytic extraction, including potential optimisation by adding Magnafloc10. In the acidic electrodialytic treatment (pH < 2), Magnafloc10 increased the extraction of Cu from the mine tailings particles from 76 to 86%, and the flocs with adsorbed metals were separated from the tailings solids by the electric field (1 mA/cm2). The electric energy consumption increased with the use of Magnafloc10 (from 17 to 30 kWh/g Cu extracted), due to lower conductivity in the liquid phase and clogging of the membrane by the flocs. In the alkaline electrodialytic treatment (pH > 12), Magnafloc10 reduced the extraction of Cu from 17% to 0.7%, due to the flocs remaining in the tailing slurries. The electric energy consumption per extracted Cu was similar in the acidic and alkaline electrodialytic treatments without the addition of Magnafloc10. In the alkaline electrodialytic treatment, the extraction of other metals was low (<2%), however longer treatment time is necessary to achieve similar Cu extraction as in the acidic electrodialysis. Depending on the target and timescale for treatment, acidic and alkaline electrodialysis can be employed to reduce the Cu concentration in the mine tailings thereby reducing the metal toxicity potential.

Response of gene expression in zebrafish exposed to pharmaceutical mixtures: Implications for environmental risk.

Complex mixtures of pharmaceutical chemicals in surface waters indicate potential for mixture effects in aquatic organisms. The objective of the present study was to evaluate whether effects on target gene expression and enzymatic activity of individual substances at environmentally relevant concentrations were additive when mixed. Expression of zebrafish cytochrome P4501A (cyp1a) and vitellogenin (vtg) genes as well as activity of ethoxyresorufin-O-deethylase (EROD) were analyzed after exposure (96h) to caffeine-Caf, ibuprofen-Ibu, and carbamazepine-Cbz (0.05 and 5µM), tamoxifen-Tmx (0.003 and 0.3µM), and after exposure to pharmaceutical mixtures (low mix: 0.05µM of Caf, Ibu, Cbz and 0.003µM of Tmx, and high mix: 5µM of Caf, Ibu, Cbz and 0.3µM of Tmx). Pharmaceuticals tested individually caused significant down regulation of both cyp1a and vtg, but EROD activity was not affected. Exposure to low mix did not cause a significant change in gene expression; however, the high mix caused significant up-regulation of cyp1a but did not affect vtg expression. Up-regulation of cyp1a was consistent with induction of EROD activity in larvae exposed to high mix. The complex mixture induced different responses than those observed by the individual substances. Additive toxicity was not supported, and results indicate the need to evaluate complex mixtures rather than models based on individual effects, since in environment drugs are not found in isolation and the effects of their mixtures is poorly understood.

Profiling DNA damage and repair capacity in sea urchin larvae and coelomocytes exposed to genotoxicants.

The ability to protect the genome from harmful DNA damage is critical for maintaining genome stability and protecting against disease, including cancer. Many echinoderms, including sea urchins, are noted for the lack of neoplastic disease, but there are few studies investigating susceptibility to DNA damage and capacity for DNA repair in these animals. In this study, DNA damage was induced in adult sea urchin coelomocytes and larvae by exposure to a variety of genotoxicants [UV-C (0-3000 J/m(2)), hydrogen peroxide (0-10mM), bleomycin (0-300 µM) and methylmethanesulfonate (MMS, 0-30 mM)] and the capacity for repair was measured over a 24-h period of recovery. Larvae were more sensitive than coelomocytes, with higher levels of initial DNA damage (fast micromethod) for all genotoxicants except MMS and increased levels of mortality 24h following treatment for all genotoxicants. The larvae that survived were able to efficiently repair damage within 24-h recovery. The ability to repair DNA damage differed depending on treatments, but both larvae and coelomocytes were able to most efficiently repair H2O2-induced damage. Time profiles of expression of a panel of DNA repair genes (ddb1, ercc1, xpc, xrcc1, pcna, ogg1, parp1, parp2, ape, brca1, rad51, xrcc2, xrcc3, xrcc4, xrcc5, xrcc6 and gadd45), throughout the period of recovery, showed greater gene induction in coelomocytes compared with larvae, with particularly high expression of xrcc1, ercc1, parp2 and pcna. The heterogeneous response of larvae to DNA damage may reflect a strategy whereby a subset of the population is equipped to withstand acute genotoxic stress, while the ability of coelomocytes to resist and repair DNA damage confirm their significant role in protection against disease. Consideration of DNA repair capacity is critical for understanding effects of genotoxicants on organisms, in addition to shedding light on life strategies and disease susceptibility.

Changes in expression profiles of genes associated with DNA repair following induction of DNA damage in larval zebrafish Danio rerio.

DNA repair is initiated by transcription of genes in response to specific types of damage. Breaks in DNA strands (single and double) are repaired predominantly through non-homologous end-joining (NHEJ) or homologous recombination (HR), but progression of repair and changes in expression profiles of genes involved are unknown. DNA damage was induced in zebrafish larvae by brief exposure (10min) to hydrogen peroxide (H2O2; 100mM), and induction of DNA strand breaks was assessed by single-cell gel electrophoresis (comet) assay over 24h. H2O2 was selected because it is eliminated rapidly after induction of DNA damage. DNA damage [mean ± standard error of the mean (SEM), % tail DNA] increased significantly immediately after 10-min H2O2 exposure (35.4±3.8; control 17.2±2.0), but damage did not differ from control levels 24h after exposure (9.2±0.4; control 9.9±0.9). At 0-, 1-, 3-, 6-, 12- and 24-h post-exposure, quantitative reverse transcriptase-PCR was conducted to assess expression of selected genes involved in DNA repair including xrcc5, xrcc6 (NHEJ), rad51 (HR) and gadd45a (DNA damage detection). Expression (maximum fold-change ± SEM, triplicate samples of 40 larvae) of each gene increased rapidly (within 6h) after exposure to 100mM of H2O2: 1.8±0.2, rad51; 1.7±0.2, xrcc5 and 1.5±0.1, xrcc6. Acute exposure (200mM of H2O2) caused 10% larval mortality within 2h, upregulated gadd45a (5.0±0.8), but did not change expression of rad51, xrcc5 or xrcc6. Expression profiles (critical exponential model) were similar among genes but differed relative to time and among independent experiments. Results indicate that repair mechanisms are initiated rapidly after DNA damage, that gene expression profiles vary according to potency of H2O2 exposure and that examination of the time course of gene expression changes is necessary to understand the complete gene response over time.

Aromatic naphthenic acids in oil sands process-affected water, resolved by GCxGC-MS, only weakly induce the gene for vitellogenin production in zebrafish (Danio rerio) larvae.

Process waters from oil sands industries (OSPW) have been reported to exhibit estrogenic effects. Although the compounds responsible are unknown, some aromatic naphthenic acids (NA) have been implicated. The present study was designed to investigate whether aromatic NA might cause such effects. Here we demonstrate induction of vitellogenin genes (vtg) in fish, which is a common bioassay used to indicate effects consistent with exposure to exogenous estrogens. Solutions in water of 20-2000 µg L(-1) of an extract of a total OSPW NA concentrate did not induce expression of vtg in larval zebrafish, consistent with earlier studies which showed that much higher NA concentrations of undiluted OSPW were needed. Although 20-2000 µg L(-1) of an esterifiable NA subfraction of the OSPW NA concentrate did induce expression, this was of much lower magnitude to that induced by much lower concentrations of 17α-ethynyl estradiol, indicating that the effect of the total NAs was only weak. However, given the high NA concentrations and large volumes of OSPW extant in Canada, it is important to ascertain which of these esterifiable NA in the OSPW produce the effect. Up to 1000 µg L(-1) of an OSPW subfraction containing only alicyclic NA, and considered by most authors to be NA sensu stricto, did not produce induction; but, as predicted, 10-1000 µg L(-1) of an aromatic NA fraction did. Such effects by the aromatic acids are again consistent with those of only a weak estrogenic substance. These findings may help to focus studies of the most environmentally significant OSPW-related pollutants, if reproduced in a greater range of OSPW.

The influence of temperature in sea urchin embryo toxicity of crude and bunker oils alone and mixed with dispersant.

This investigation deals with how temperature influences oil toxicity, alone or combined with dispersant (D). Larval lengthening, abnormalities, developmental disruption, and genotoxicity were determined in sea urchin embryos for assessing toxicity of low-energy water accommodated fractions (LEWAF) of three oils (NNA crude oil, marine gas oil -MGO-, and IFO 180 fuel oil) produced at 5-25 °C. PAH levels were similar amongst LEWAFs but PAH profiles varied with oil and production temperature. The sum of PAHs was higher in oil-dispersant LEWAFs than in oil LEWAFs, most remarkably at low production temperatures in the cases of NNA and MGO. Genotoxicity, enhanced after dispersant application, varied depending on the LEWAF production temperature in a different way for each oil. Impaired lengthening, abnormalities and developmental disruption were recorded, the severity of the effects varying with oil, dispersant application and LEWAF production temperature. Toxicity, only partially attributed to individual PAHs, was higher at lower LEWAF production temperatures.

Toxicity to sea urchin embryos of crude and bunker oils weathered under ice alone and mixed with dispersant.

A multi-index approach (larval lenghthening and malformations, developmental disruption, and genotoxicity) was applied using sea-urchin embryos as test-organisms. PAH levels measured in the under-ice weathered aqueous fraction (UIWAF) were lower than in the low-energy water accommodated fraction (LEWAF) and similar amongst UIWAFs of different oils. UIWAFs and LEWAFs caused toxic effects, more markedly in UIWAFs, that could not be attributed to measured individual PAHs or to their mixture. Conversely, UIWAF was less genotoxic than LEWAF, most likely because naphthalene concentrations were also lower. In agreement, NAN LEWAF, the most genotoxic, exhibited the highest naphthalene levels. Dispersant addition produced less consistent changes in PAH levels and embryo toxicity in UIWAFs than in LEWAFs, and did not modify LEWAF genotoxicity. Overall, under ice weathering resulted in lowered waterborne PAHs and genotoxicity but augmented embryo toxicity, not modified by dispersant application.

Reduced pH increases mortality and genotoxicity in an Arctic coastal copepod, Acartia longiremis.

This study investigates DNA damage and mortality in an Arctic marine copepod after long-term exposure to lowered pH. Acartia longiremis were collected from northern Norway and incubated in ambient pH 8.1, and reduced pH 7.6 and 7.2 over 3-4 weeks. Cumulative mortality was significantly elevated in the lowered pH treatments in all exposures. The fluorescence-based fast micromethod for analysis of DNA strand breaks and alkali-labile sites was modified for use on crustaceous zooplankton. DNA damage initially increased in the lowered pH treatments, decreasing after >14 days, and DNA damage was significantly higher in lowered pH conditions. This method is ideal for investigating oxidative stress and genotoxicity response to low pH in Arctic marine copepods exposed to future ocean acidification conditions.

Combined effects of crude oil exposure and warming on eggs and larvae of an arctic forage fish.

Climate change, along with environmental pollution, can act synergistically on an organism to amplify adverse effects of exposure. The Arctic is undergoing profound climatic change and an increase in human activity, resulting in a heightened risk of accidental oil spills. Embryos and larvae of polar cod (Boreogadus saida), a key Arctic forage fish species, were exposed to low levels of crude oil concurrently with a 2.3 °C increase in water temperature. Here we show synergistic adverse effects of increased temperature and crude oil exposure on early life stages documented by an increased prevalence of malformations and mortality in exposed larvae. The combined effects of these stressors were most prevalent in the first feeding larval stages despite embryonic exposure, highlighting potential long-term consequences of exposure for survival, growth, and reproduction. Our findings suggest that a warmer Arctic with greater human activity will adversely impact early life stages of this circumpolar forage fish.

Effects of the sea lice bath treatment pharmaceuticals hydrogen peroxide, azamethiphos and deltamethrin on egg-carrying shrimp (Pandalus borealis).

This study investigated effects of sea lice pharmaceuticals on egg-bearing deep-water shrimp (Pandalus borealis). Both mortality and sub-lethal effects (behavior, embryo development, and reproductive output) were studied for each of three pharmaceuticals alone and in different sequential combinations. The most severe effect was observed for deltamethrin where 2 h exposure to 330 times diluted treatment dose (alone and in sequential application with hydrogen peroxide and azamethiphos) induced almost 100% mortality within a few days after exposure. Similar effects were not observed for hydrogen peroxide or azamethiphos. However, sequential treatment of hydrogen peroxide and azamethiphos (2 h exposure to each pharmaceutical; 500 times dilution) resulted in >40% mortality during the first week following treatment. No sub-lethal effects or loss of eggs in female shrimp could be related to exposure to the bath treatments. Future studies should investigate potential sub-lethal effects at exposure concentrations close to the no-effect concentration.

Effects of mine tailings exposure on early life stages of atlantic cod.

In Norway, mine tailings waste can be deposited by coastal submarine dispersal. Mine tailings slurry includes fine particles <10 µm with elevated levels of metals (e.g., copper, iron) from residual mineral ore. Prolonged suspension of small particles in the water column may bring them into contact with locally spawned pelagic fish eggs, including Atlantic cod, Gadus morhua. Newly fertilized cod embryos were exposed to suspended mine tailings particles up to 3.2 mg/L in flow-through aquaria for a total of 21 d. Significantly more particles adhered to the surface of the chorion from the high treatment after 11-d exposure, and dissolved Cu concentrations increased in the water (up to 0.36 ± 0.06 µg/L). There was no adverse effect on embryo mortality but an 8% elevation in larval mortality. There were no differences with treatment on timing of hatching, embryo and larva morphometrics, abnormalities, or cardiac activity. There was a treatment-dependent up-regulation of stress marker genes (hspa8, cyp1c1) but no indication of metal-induced activation of metallothionien (mt gene transcription). Transcription markers for DNA and histone methyltransferases did show treatment-related up-regulation, indicative of altered methylation in larvae when developmental methylation patterns are determined, indicating some level of chronic toxicity that may have longer-term effects. Environ Toxicol Chem 2019;38:1446-1454. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Ocean acidification impacts spine integrity but not regenerative capacity of spines and tube feet in adult sea urchins.

Increasing atmospheric carbon dioxide (CO2) has resulted in a change in seawater chemistry and lowering of pH, referred to as ocean acidification. Understanding how different organisms and processes respond to ocean acidification is vital to predict how marine ecosystems will be altered under future scenarios of continued environmental change. Regenerative processes involving biomineralization in marine calcifiers such as sea urchins are predicted to be especially vulnerable. In this study, the effect of ocean acidification on regeneration of external appendages (spines and tube feet) was investigated in the sea urchin Lytechinus variegatus exposed to ambient (546 µatm), intermediate (1027 µatm) and high (1841 µatm) partial pressure of CO2 (pCO2) for eight weeks. The rate of regeneration was maintained in spines and tube feet throughout two periods of amputation and regrowth under conditions of elevated pCO2. Increased expression of several biomineralization-related genes indicated molecular compensatory mechanisms; however, the structural integrity of both regenerating and homeostatic spines was compromised in high pCO2 conditions. Indicators of physiological fitness (righting response, growth rate, coelomocyte concentration and composition) were not affected by increasing pCO2, but compromised spine integrity is likely to have negative consequences for defence capabilities and therefore survival of these ecologically and economically important organisms.

Tissue regeneration and biomineralization in sea urchins: role of Notch signaling and presence of stem cell markers.

Echinoderms represent a phylum with exceptional regenerative capabilities that can reconstruct both external appendages and internal organs. Mechanistic understanding of the cellular pathways involved in regeneration in these animals has been hampered by the limited genomic tools and limited ability to manipulate regenerative processes. We present a functional assay to investigate mechanisms of tissue regeneration and biomineralization by measuring the regrowth of amputated tube feet (sensory and motor appendages) and spines in the sea urchin, Lytechinus variegatus. The ability to manipulate regeneration was demonstrated by concentration-dependent inhibition of regrowth of spines and tube feet by treatment with the mitotic inhibitor, vincristine. Treatment with the gamma-secretase inhibitor DAPT resulted in a concentration-dependent inhibition of regrowth, indicating that both tube feet and spine regeneration require functional Notch signaling. Stem cell markers (Piwi and Vasa) were expressed in tube feet and spine tissue, and Vasa-positive cells were localized throughout the epidermis of tube feet by immunohistochemistry, suggesting the existence of multipotent progenitor cells in these highly regenerative appendages. The presence of Vasa protein in other somatic tissues (e.g. esophagus, radial nerve, and a sub-population of coelomocytes) suggests that multipotent cells are present throughout adult sea urchins and may contribute to normal homeostasis in addition to regeneration. Mechanistic insight into the cellular pathways governing the tremendous regenerative capacity of echinoderms may reveal processes that can be modulated for regenerative therapies, shed light on the evolution of regeneration, and enable the ability to predict how these processes will respond to changing environmental conditions.

Comparative DNA damage and repair in echinoderm coelomocytes exposed to genotoxicants.

The capacity to withstand and repair DNA damage differs among species and plays a role in determining an organism's resistance to genotoxicity, life history, and susceptibility to disease. Environmental stressors that affect organisms at the genetic level are of particular concern in ecotoxicology due to the potential for chronic effects and trans-generational impacts on populations. Echinoderms are valuable organisms to study the relationship between DNA repair and resistance to genotoxic stress due to their history and use as ecotoxicological models, little evidence of senescence, and few reported cases of neoplasia. Coelomocytes (immune cells) have been proposed to serve as sensitive bioindicators of environmental stress and are often used to assess genotoxicity; however, little is known about how coelomocytes from different echinoderm species respond to genotoxic stress. In this study, DNA damage was assessed (by Fast Micromethod) in coelomocytes of four echinoderm species (sea urchins Lytechinus variegatus, Echinometra lucunter lucunter, and Tripneustes ventricosus, and a sea cucumber Isostichopus badionotus) after acute exposure to H2O2 (0-100 mM) and UV-C (0-9999 J/m2), and DNA repair was analyzed over a 24-hour period of recovery. Results show that coelomocytes from all four echinoderm species have the capacity to repair both UV-C and H2O2-induced DNA damage; however, there were differences in repair capacity between species. At 24 hours following exposure to the highest concentration of H2O2 (100 mM) and highest dose of UV-C (9999 J/m2) cell viability remained high (>94.6 ± 1.2%) but DNA repair ranged from 18.2 ± 9.2% to 70.8 ± 16.0% for H2O2 and 8.4 ± 3.2% to 79.8 ± 9.0% for UV-C exposure. Species-specific differences in genotoxic susceptibility and capacity for DNA repair are important to consider when evaluating ecogenotoxicological model organisms and assessing overall impacts of genotoxicants in the environment.

Cobalt-induced genotoxicity in male zebrafish (Danio rerio), with implications for reproduction and expression of DNA repair genes.

Although cobalt (Co) is an environmental contaminant of surface waters in both radioactive (e.g. (60)Co) and non-radioactive forms, there is relatively little information about Co toxicity in fishes. The objective of this study was to investigate acute and chronic toxicity of Co in zebrafish, with emphasis on male genotoxicity and implications for reproductive success. The lethal concentration for 50% mortality (LC(50)) in larval zebrafish exposed (96 h) to 0-50 mg l(-1) Co was 35.3 ± 1.1 (95%C.I.) mg l(-1) Co. Adult zebrafish were exposed (13 d) to sub-lethal (0-25 mg l(-1)) Co and allowed to spawn every 4 d and embryos were collected. After 12-d exposure, fertilisation rate was reduced (6% total eggs fertilised, 25 mg l(-1)) and embryo survival to hatching decreased (60% fertilised eggs survived, 25 mg l(-1)). A concentration-dependent increase in DNA strand breaks was detected in sperm from males exposed (13 d) to Co, and DNA damage in sperm returned to control levels after males recovered for 6 d in clean water. Induction of DNA repair genes (rad51, xrcc5, and xrcc6) in testes was complex and not directly related to Co concentration, although there was significant induction in fish exposed to 15 and 25 mg l(-1) Co relative to controls. Induction of 4.0 ± 0.9, 2.5 ± 0.7, and 3.1 ± 0.7-fold change (mean ± S.E.M. for rad51, xrcc5, and xrcc6, respectively) was observed in testes at the highest Co concentration (25 mg l(-1)). Expression of these genes was not altered in offspring (larvae) spawned after 12-d exposure. Chronic exposure to Co resulted in DNA damage in sperm, induction of DNA repair genes in testes, and indications of reduced reproductive success.

Dietary toxicity of single-walled carbon nanotubes and fullerenes (C60) in rainbow trout (Oncorhynchus mykiss).

The objective of this investigation was to compare the toxicity of two manufactured carbon nanomaterials (CNs) to determine if shape influenced toxicity. Juvenile rainbow trout Oncorhynchus mykiss were fed a control diet (no CN addition), or a diet supplemented with 500 mg single-walled carbon nanotubes (SWCNT) kg(-1) or 500 mg C(60) kg(-1) for six weeks. Fish growth, haematology, tissue ion concentrations, histopathology, osmoregulation, and biochemistry were evaluated. At week 4, but not on weeks 2 and 6, significant elevation in brain TBARS (an indication of lipid peroxidation) was observed in fish exposed to SWCNTs (16.2 ± 1.38 nmol mg(-1) protein) compared to the control (9.11 ± 0.81 nmol mg(-1) protein) and fish exposed to C(60) (8.28 ± 0.56 nmol mg(-1) protein). No other significant treatment-related differences were observed. Results indicate that dietary exposure to SWCNTs and C(60) in rainbow trout did not result in overt toxicity.

Uptake, depuration, and radiation dose estimation in zebrafish exposed to radionuclides via aqueous or dietary routes.

Understanding uptake and depuration of radionuclides in organisms is necessary to relate exposure to radiation dose and ultimately to biological effects. We investigated uptake and depuration of a mixture of radionuclides to link bioaccumulation with radiation dose in zebrafish, Danio rerio. Adult zebrafish were exposed to radionuclides ((54)Mn, (60)Co, (65)Zn, (75)Se, (109)Cd, (110m)Ag, (134)Cs and (241)Am) at tracer levels (<200 Bq g(-1)) for 14 d, either via water or diet. Radioactivity concentrations were measured in whole body and excised gonads of exposed fish during uptake (14 d) and depuration phases (47 d and 42 d for aqueous and dietary exposures respectively), and dose rates were modelled from activity concentrations in whole body and exposure medium (water or diet). After 14-day aqueous exposure, radionuclides were detected in decreasing activity concentrations: (75)Se>(65)Zn>(109)Cd>(110m)Ag>(54)Mn>(60)Co>(241)Am>(134)Cs (range: 175-8 Bq g(1)). After dietary exposure the order of radionuclide activity concentration in tissues (Bq g(-1)) was: (65)Zn>(60)Co>(75)Se>(109)Cd>(110m)Ag>(241)Am>(54)Mn>(134)Cs (range: 91-1 Bq g(-1)). Aqueous exposure resulted in higher whole body activity concentrations for all radionuclides except (60)Co. Route of exposure did not appear to influence activity concentrations in gonads, except for (54)Mn, (65)Zn, and (75)Se, which had higher activity concentrations in gonads following aqueous exposure. Highest gonad activity concentrations (Bq g(-1)) were for (75)Se (211), (109)Cd (142), and (65)Zn (117), and highest dose rates (µGy h(-1)) were from (241)Am (aqueous, 1050; diet 242). This study links radionuclide bioaccumulation data obtained in laboratory experiments with radiation dose determined by application of a dosimetry modelling tool, an approach that will enable better linkages to be made between exposure, dose, and effects of radionuclides in organisms.