Arsenate and perchlorate toxicity, growth effects, and thyroid histopathology in hypothyroid zebrafish Danio rerio

Exposure to perchlorate or other thyrotoxic compounds can cause hypothyroidism in most vertebrates, and this may affect levels of endogenous antioxidants and cause oxidative stress. Arsenic also induces oxidative stress in animals by modifying the antioxidant capacity and may alter the thyroid homeostasis. Therefore, hypothyroidism may affect the toxicity of arsenate. In order to test this hypothesis, zebrafish (Danio rerio) were made hypothyroid by exposure to perchlorate, and toxicity of arsenate in hypothyroid and euthyroid fish was compared. The endpoints were LC50 and thyroid histopathology. Additionally, the recovery of thyroid histopathological indices after cessation of perchlorate exposure was determined. The current study showed that 96 h LC50 of perchlorate anion and arsenate ion to juveniles fish (37 day post-fertilization) were 2532 and 56 mg l(-1), respectively. In addition, hypothyroid fish were more sensitive to arsenate, with a 96 h LC50 of 43 mg l(-1). Growth rates were also significantly retarded by perchlorate exposure. After cessation of perchlorate exposure, there was recovery of thyroid histopathology in terms of epithelial cell height, but not colloid area or growth rate. In conclusion, perchlorate enhances arsenate toxicity to juvenile zebrafish, and the rate of thyroid recovery after cessation of perchlorate exposure depends on the endpoints examined.     

Study on acute toxicity and structure-activity relationship of zebrafish (Danio rerio) exposed to naphthoquinones

In this paper, we evaluated the acute toxicity of five naphthoquinone compounds, expressed as median lethal concentration at 96 h (LC₅₀) using zebrafish as a model. The five compounds were classified as harmful or very toxic. The Gaussian method was used to calculate the quantitative-chemical parameters of each compound. Based on the structure-activity relationship analysis, the interaction between the naphthoquinones and the target is likely mediated by 1-carbonyl and the hydrophobic fraction substituted in α -position of naphthoquinone via hydrogen bonding and hydrophobic interactions. Our results provide a foundation for evaluating the aquatic ecological risk and the mode of action of naphthoquinones in the environment.     

Embryo/larval toxicity and transcriptional effects in zebrafish (Danio rerio) exposed to endocrine active riverbed sediments

Environmental Science and Pollution Research - Sediment toxicity plays a fundamental role in the health of inland fish communities; however, the assessment of the hazard potential of contaminated...     

Effects of triclosan on zebrafish early-life stages and adults

Background, aim and scope  

The biocide triclosan (TCS) is commonly used in personal care, acrylic, plastic, and textiles products. TCS has been detected in surface water in several countries, and its ecological impact is largely unknown. In this work, the toxicity of TCS in zebrafish (Danio rerio), embryos and adults was studied. Several lethal and sub-lethal endpoints were analysed in organisms exposed to TCS such as mortality, embryo development and behaviour, hatching, micronuclei and biochemical markers (cholinesterase (ChE), glutathione S-transferase (GST) and lactate dehydrogenase (LDH)).     

磺胺甲恶唑对斑马鱼胚胎/仔鱼的毒性效应

为研究磺胺甲恶唑对斑马鱼胚胎/仔鱼的早期发育及抗氧化系统的影响,将受精2h的斑马鱼胚胎暴露在不同浓度的磺胺甲恶唑水溶液中,观察斑马鱼胚胎死亡率、孵化率、仔鱼心包囊肿率、心跳数、体长以及仔鱼内抗氧化酶活性、丙二醛(MDA)含量的变化。结果表明,磺胺甲恶唑对斑马鱼胚胎/仔鱼120h的急性毒性半数致死质量浓度(LC50)为1 250.5mg/L;斑马鱼胚胎孵化率随着暴露浓度的增加呈现明显的下降趋势,96h胚胎孵化率抑制的半数有效质量浓度(EC50)为1 299.7mg/L;当暴露质量浓度≥1 500mg/L时,斑马鱼胚胎患心包囊肿率明显升高,呈现剂量—效应关系;经磺胺甲恶唑暴露96h的斑马鱼仔鱼30s心跳数及120h斑马鱼仔鱼体长总体降低;10~(-2)mg/L磺胺甲恶唑染毒96h后,即观察到斑马鱼仔鱼细胞出现明显的氧化损伤,过氧化氢酶的酶活性受到显著抑制,超氧化物歧化酶和谷胱甘肽S-转移酶被显著诱导,MDA含量显著增加。研究表明,磺胺甲恶唑暴露对斑马鱼胚胎细胞产生了明显的损伤,进而可能影响斑马鱼仔鱼的发育。     

Combined toxicity of imidacloprid,acetochlor, and tebuconazole to zebrafish ( Danio rerio ): acute toxicity and hepatotoxicity assessment

Compound pollution refers to two or more kinds of pollutants with different properties, a pollutant from different sources, or the simultaneous existence of two or more different types of pollutants in the same environment. In this study, we aimed to investigate the individual and combined toxicity of the insecticide imidacloprid (IMI), the herbicide acetochlor (ACT), and the fungicide tebuconazole (TBZ) to zebrafish. The acute toxicity test results showed that the 96-h LC50 values of IMI, ACT, and TBZ were 276.84 (259.62–294.35) mg active ingredient (a.i.) L−1, 1.52 (1.34–1.74) mg a.i. L−1, and 8.16 (7.7–8.6) mg a.i. L−1, respectively. The combinations of IMI, ACT, and TBZ with toxicity ratios of 1:2:2, 1:4:4, 2:4:1, and 4:1:4 displayed synergistic toxic effects on zebrafish, while the toxicity ratios of 1:1:1, 1:1:2, 2:1:2, 2:2:1, and 4:2:1 of IMI, ACT, and TBZ, respectively, exhibited antagonistic toxic effects on zebrafish. The following experiments were performed with a toxicity ratio of 1:4:4 (IMI:ACT:TBZ). The activities of four enzyme biomarkers related to oxidative stress in the liver, catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and malondialdehyde (MDA) content were evaluated in each exposure group on days 7, 14, 21, and 28. Compared with those of the control group, the activities of CAT, SOD, and GST and the MDA content were significantly altered at different time points in the individual and combined exposure groups. Additionally, the activities of CAT, SOD, and GST and the MDA content were significantly altered in the combined group compared with those of the individual group after 14 days or 21 days of exposure. Therefore, it was confirmed that combined toxicity studies are indispensable in risk assessment.     

Suborganismic and organismic effects of aldicarb and its metabolite aldicarb-sulfoxide to the zebrafish embryo (Danio rerio)

The new European chemical regulation (REACH) requires a short-term fish test for chemicals where the level of production exceeds 10tons per year. For ethical reasons (3R-concept), an alternative to the acute fish test should be introduced to decrease the number of animal testing with fish. The zebrafish embryo (Danio rerio) test became a valuable tool in ecotoxicology and already replaces the acute fish test for the evaluation of wastewater in Germany. Recent efforts are targeted to use this and other fish embryo tests for the effect assessment of chemicals. The toxic effects of the carbamate insecticide aldicarb and its metabolite aldicarb-sulfoxide to zebrafish embryos were analysed using two approaches with different endpoints. Organismic tests were conducted with zebrafish embryos exposed to the pesticides for 48h. In addition, suborganismic effects were examined analysing the enzyme inhibition of cholinesterases and carboxylesterases. On the organismic level, the only sublethal effect seen was the increase of heart rate at low and decrease at higher concentration with the use of aldicarb-sulfoxide but not with aldicarb (concentration range 0.2-300microM). In contrast, analysis of enzyme inhibitions showed high to very high effects caused by the two carbamates. The enzyme inhibition analysis of whole homogenates of exposed embryos may be advantageous for toxicant screening (biomarker of exposure) and might be used to bridge the gap of sensitivity of the (48h old) zebrafish embryos to adult fish when exposed to anti-cholinesterase substances (biomarker of prospective effect).     

The effects of henna (hair dye) on the embryonic development of zebrafish (Danio rerio)

The powder of henna is extensively used as decorative skin paint for nail coloring and as a popular hair dye in Asian countries. Its human health risk is extensive, and it is frequently released as waste into the aquatic environment raising the concerns. Zebrafish (Danio rerio) embryos were employed to study the developmental effects of henna. Normal fertilized zebrafish embryos under standard water were selected for the control and test chambers. Three predetermined sublethal concentrations (100, 200, and 275 μM) of henna in 24-well cell culture plates were tested on 1-h postfertilized embryo (pfe) for 96 h. Observation for rates of survival and mortality was recorded; digital camera was used to image morphological anomalies of embryos with a stereomicroscope; and functional abnormalities at 24, 48, 72, and 96 h were performed. The hatching rates of embryos were reduced significantly when treated with 200 and 275 μM or higher concentrations of henna. Slow blood circulation in the whole body was observed with a median effect on hatching exposed to 200 and 275 μM of henna at 48-h pfe. At 72- and 96-h pfe, blood circulation was ceased in the whole body but still had a heartbeat. At 96-h pfe, pericardial sac edema, yolk sac edema, head deformation, spine crooked malformation, and tail malformation (bent tails or hook-like tails) were observed in the surviving larvae at 100 μM. In summary, exposure to henna at 100, 200, and 275 μM causes some altered morphological and physiological abnormalities including increased mortality, hatching delay, slow blood circulation, pericardial sac edema, yolk sac edema, abnormal body axes, twisted notochord, tail deformation, weak heartbeat, and growth retardation and was also detected in some treated embryos and groups having adverse effects on embryonic development of zebrafish provoking potential human developmental risk studies.     

Assessment of Jatropha curcas L. biodiesel seed cake toxicity using the zebrafish (Danio rerio) embryo toxicity (ZFET) test

Consequent to the growing demand for alternative sources of energy, the seeds from Jatropha curcas remain to be the favorite for biodiesel production. However, a significant volume of the residual organic mass (seed cake) is produced during the extraction process, which raises concerns on safe waste disposal. In the present study, we assessed the toxicity of J. curcas seed cake using the zebrafish (Danio rerio) embryotoxicity test. Within 1-h post-fertilization (hpf), the fertilized eggs were exposed to five mass concentrations of J. curcas seed cake and were followed through 24, 48, and 72 hpf. Toxicity was evaluated based on lethal endpoints induced on zebrafish embryos namely egg coagulation, non-formation of somites, and non-detachment of tail. The lowest concentration tested, 1 g/L, was not able to elicit toxicity on embryos whereas 100 % mortality (based also on lethal endpoints) was recorded at the highest concentration at 2.15 g/L. The computed LC50 for the J. curcas seed cake was 1.61 g/L. No further increase in mortality was observed in the succeeding time points (48 and 72 hpf) indicating that J. curcas seed cake exerted acute toxicity on zebrafish embryos. Sublethal endpoints (yolk sac and pericardial edema) were noted at 72 hpf in zebrafish embryos exposed to higher concentrations. The observed lethal endpoints induced on zebrafish embryos were discussed in relation to the active principles, notably, phorbol esters that have remained in the seed cake even after extraction.     

Toxicity of hexahydro-1,3,5-trinitro-1,3,5-triazine to larval zebrafish (Danio rerio)

Hexahydro-1,3,5-trinitro-1,3,5-triazine, a cyclonitramine commonly known as RDX, is used in the production of military munitions. Contamination of soil, sediment, and ground and surface waters with RDX has been reported in different places around the world. Acute and subacute toxicities of RDX have been relatively well documented in terrestrial vertebrates, but among aquatic vertebrates the information available is limited. The objective of this study was to characterize the acute toxicity of RDX to larval zebrafish. Mortality (LC50) and incidence of vertebral column deformities (EC50) were two of the end points measured in this study. The 96-h LC50 was estimated at 22.98 and 25.64 mgl(-1) in two different tests. The estimated no-observed-effective-concentration (NOEC) values of RDX on lethality were 13.27+/-0.05 and 15.32+/-0.30 mgl(-1); and the lowest-observed-effective-concentration (LOEC) values were 16.52+/-0.05 and 19.09+/-0.23 mgl(-1) in these two tests, respectively. The 96-h EC50 for vertebral deformities on survivors from one of the acute lethality tests was estimated at 20.84 mgl(-1), with NOEC and LOEC of 9.75+/-0.34 and 12.84+/-0.34 mgl(-1), respectively. Behavioral aberrations were also noted in this acute toxicity study, including the occurrence of whirling movement and lethargic behavior. The acute effects of RDX on survival, incidence of deformities, and behavior of larval zebrafish occurred at the high end of the most frequently reported concentrations of RDX in aquatic environments. The chronic effects of RDX in aquatic vertebrates need to be determined for an adequate assessment of the ecological risk of environmental RDX.     

Influence of sediment composition on PAH toxicity using zebrafish (Danio rerio) and Japanese medaka (Oryzias latipes) embryo-larval assays

Due to hydrophobic and persistent properties, polycyclic aromatic hydrocarbons (PAHs) have a high capacity to accumulate in sediment. Sediment quality criteria, for the assessment of habitat quality and risk for aquatic life, include understanding the fate and effects of PAHs. In the context of European regulation (REACH and Water Framework Directive), the first objective was to assess the influence of sediment composition on the toxicity of two model PAHs, benzo[a]pyrene and fluoranthene using 10-day zebrafish embryo-larval assay. This procedure was undertaken with an artificial sediment in order to limit natural sediment variability. A suitable sediment composition might be then validated for zebrafish and proposed in a new OECD guideline for chemicals testing. Second, a comparative study of toxicity responses from this exposure protocol was then performed using another OECD species, the Japanese medaka. The potential toxicity of both PAHs was assessed through lethal (e.g., survival, hatching success) and sublethal endpoints (e.g., abnormalities, PMR, and EROD) measured at different developmental stages, adapted to the embryonic development time of both species. Regarding effects observed for both species, a suitable artificial sediment composition for PAH toxicity testing was set at 92.5 % dry weight (dw) silica of 0.2–0.5-mm grain size, 5 % dw kaolin clay without organic matter for zebrafish, and 2.5 % dw blond peat in more only for Japanese medaka. PAH bioavailability and toxicity were highly dependent on the fraction of organic matter in sediment and of the K _ow coefficients of the tested compounds. The biological responses observed were also dependent of the species under consideration. Japanese medaka embryos appeared more robust than zebrafish embryos for understanding the toxicity of PAHs following a sediment contact test, due to the longer exposure duration and lower sensitivity of sediment physical properties.     

Evaluation of HODE-15, FDE-15, CDE-15, and BDE-15 toxicity on adult and embryonic zebrafish (Danio rerio)

Diphenyl ether and its derivatives are widely used in the industry of spices, dyes, agrochemicals, and pharmaceuticals. Following the previous study, we selected 4,4′-dihydroxydiphenyl ether, 4,4′-difluorodiphenyl ether, 4,4′-dichlorodiphenyl ether, and 4,4′-dibromodiphenyl ether as research objects. The LC₅₀ (96 h) values for these compounds in adult zebrafish were determined with the acute test. Also, developmental toxicities of the four substances to zebrafish embryos were observed at 24, 48, 72, and 96 hpf. All the LC₅₀ (96 h) values of these compounds were between 1 and 10 mg/L, suggesting that they all had moderate toxicity to adult zebrafish. The embryonic test demonstrated that with increasing doses, 4,4′-dihydroxydiphenyl ether decreased the hatching rate, while 4,4′-difluorodiphenyl ether, 4,4′-dichlorodiphenyl ether, and 4,4′-dibromodiphenyl ether delayed the hatching time but had little effect on final hatchability at 96 hpf. All of these compounds inhibited larval growth, especially 4,4′-dihydroxydiphenyl ether. Exposure to these chemicals induced embryo yolk sac and pericardial edema. Spine deformation was visible in hatched larvae after 96 hpf 4,4′-dihydroxydiphenyl ether exposure, while tail curvature was observed for the halogenated compounds. The overall results indicated that 4,4′-dihydroxydiphenyl ether, 4,4′-difluorodiphenyl ether, 4,4′-dichlorodiphenyl ether, and 4,4′-dibromodiphenyl ether all had significant toxicity on adult and embryonic zebrafish.     

Comparison of metabolome profiles in zebrafish (Danio rerio) intestine induced by polystyrene microplastics with different sizes

Environmental Science and Pollution Research - Microplastics (MPs) are widespread in aquatic environments. They could induce intestinal toxicity in the fish. However, research on the metabolic...     

Integrated biological responses of zebrafish (Danio rerio) to analyze water quality in regions under anthropogenic influence

This 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.     

Effects of penconazole enantiomers exposure on hormonal disruption in zebrafish Danio rerio (Hamilton, 1822)

Environmental Science and Pollution Research - PEN is a widely used triazole fungicide, usually used to control grape white rot. In the process of agricultural use, PEN will be scattered to the...     

Uptake, accumulation and depuration of sodium perchlorate and sodium arsenate in zebrafish (Danio rerio)

In toxicokinetics studies, interactions between chemicals in mixtures has been largely neglected. This study examines a mixture of perchlorate and arsenate because (1) they have the potential to co-occur in contaminated aquatic habitats, and (2) a previous study by the authors found possible toxicological interactive effects. In the present study, zebrafish (Danio rerio) were exposed to two concentrations of sodium perchlorate (10 and 100 mg l(-1)), sodium arsenate (1 and 10 mg l(-1)), and the mixture-sodium perchlorate+sodium arsenate (10+1 mg l(-1) and 100+10 mg l(-1) Na(2)HAsO(4)-high mixture) for 90 d. Their uptake and accumulation by zebrafish was evaluated at 10, 30, 60, and 90 d. In addition, depuration was examined at 1, 3, and 5d after cessation of the exposure. The uptake of either chemical was concentration-dependent, with significantly higher uptake at high concentrations at either exposure interval. In contrast, there was no significant difference in whole body residue between single chemicals and the corresponding mixture except for 100 mg l(-1) sodium arsenate at 90 d. However, there was increasing accumulation over time at the high concentration of either chemical alone and their mixture, and this increasing trend was more pronounced in the single chemical exposures than in the mixture. At the concentrations tested in the current study, both chemicals reduced the uptake but enhanced the depuration of the other chemical from the zebrafish. This study represents the first examination of the interaction of two anions-perchlorate and arsenate with respect to toxicokinetics.     

Cypermethrin has the potential to induce hepatic oxidative stress, DNA damage and apoptosis in adult zebrafish (Danio rerio)

Cypermethrin (CYP), a widely used Type II pyrethroid pesticide, is one of the most common contaminants in the freshwater aquatic system. We studied the effects of CYP exposure on the induction of hepatic oxidative stress, DNA damage and the alteration of gene expression related to apoptosis in adult zebrafish. Hepatic mRNA levels for the genes encoding antioxidant proteins, such as Cu/Zn-Sod, Mn-Sod, Cat, and Gpx, were significantly upregulated when zebrafish were exposed to various concentrations of CYP for 4 or 8 days. In addition, the main genes related to fatty acid β-oxidation and the mitochondrial genes related to respiration and ATP synthesis were also significantly upregulated after exposure to high concentrations (1 and 3 μg L⁻¹) of CYP for 4 or 8 days. Moreover, in a comet assay of zebrafish hepatocytes, tail DNA, tail length, tail moment and Olive tail moment increased in a concentration-dependent manner. The significant induction (p < 0.01) of all four parameters observed with CYP concentrations of 0.3 μg L⁻¹ or higher suggests that heavy DNA damage was induced even at low levels. Furthermore, several apoptosis- related genes, such as p53, Apaf1 and Cas3, were significantly upregulated after CYP exposure, and Bcl2/Bax expression ratio decreased, especially in groups treated with 1 and 3 μg L⁻¹ CYP for 8 days. Taken together, our results suggested that CYP has the potential to induce hepatic oxidative stress, DNA damage and apoptosis in zebrafish. This information will be helpful in fully understanding the mechanism of aquatic toxicology induced by CYP in fish.     

Effects of cyanobacterium Fischerella ambigua isolates and cell free culture media on zebrafish (Danio rerio) embryo development

The toxic effects of several species of fresh water cyanobacteria, notably Microcystis species and associated toxins, the microcystins, Anabaena species (anatoxin), Nodularia sp. (nodularin), and Cylindrospermopsis raciborskii (cylindrospermopsin), are well known. Little, however, is known about the effects of secondary metabolites other than alkaloids. Early life stage tests with zebrafish (Danio rerio) were used to detect bioactive properties of compounds released by healthy cyanobacteria (Fischerella ambigua), particularly on the early developmental stages of fish. This approach, using F. ambigua is probably most valuable as it shows the toxicity of healthy growing cyanobacteria. The effects of cyanobacterial secondary metabolites on the embryonic stages of fish are of considerable interest as many aquatic creatures, particularly fish, are unable to avoid the potential toxins that may be released by undesirable algal blooms or as a result of allelopathic effects. In the current study, the zebrafish (D. rerio) was used as a model experimental system to investigate the effects of ambigols A and C, tjipanazole D and C, 2,4-dichlorobenzoic acid, cell free culture media, and media extracts of a terrestrial/fresh water strain of the cyanobacterium F. ambigua on embryo development. Fish embryo tests performed with the cell free culture medium showed that after 3h of exposure to undiluted culture medium all fish embryos died. At a tenfold dilution the process of epiboly (formation of the gastrula) was retarded in all embryos, lesions were observed, and their general development was significantly arrested, finally followed by death. The same tests performed with extracts (dichloromethane, n-butanol, and residual cell free culture medium) of the cell free culture medium, ambigol A, ambigol C, 2,4-dichlorobenzoic acid and tjipanazole D showed only ambigol A to have an influence on zebrafish development at concentrations>or=1 mg/l (2.06 microM). After 55 h all embryos showed pectoral oedema, irregularly shaped fin folds, bent tails, and unusual circular neoplasms in the dorsal tail fin fold. Due to the high concentration of ambigol A used in this assay these effects were considered to be of minor importance when compared to those of the culture medium.     

Lethal effects of abamectin on the aquatic organisms Daphnia similis, Chironomus xanthus and Danio rerio

Abamectin is used as an acaricide and insecticide for fruits, vegetables and ornamental plants, as well as a parasiticide for animals. One of the major problems of applying pesticides to crops is the likelihood of contaminating aquatic ecosystems by drift or runoff. Therefore, toxicity tests in the laboratory are important tools to predict the effects of chemical substances in aquatic ecosystems. The aim of this study was to assess the potential hazards of abamectin to the freshwater biota and consequently the possible losses of ecological services in contaminated water bodies. For this purpose, we identified the toxicity of abamectin on daphnids, insects and fish. Abamectin was highly toxic, with an EC₅₀ 48 h for Daphnia similis of 5.1 ng L⁻¹, LC₅₀ 96 h for Chironomus xanthus of 2.67 μg L⁻¹ and LC₅₀ 48 h for Danio rerio of 33 μg L⁻¹.