Long-term exposure to polycyclic musk tonalide - A potential threat to juvenile zebrafish (Danio rerio)?

Polycyclic musk compounds are commonly used in personal care products to replace expensive natural fragrances. Due to their huge consumption, they have become a part of the aquatic environment. In the present study, a two-month exposure effect of tonalide on juvenile zebrafish (Danio rerio) was investigated. We determined the vitellogenin concentration to define the potential endocrine-disrupting effect of tonalide and also analysed selected indices to evaluate the induction of oxidative stress. The environmentally relevant concentration of tonalide (i.e., 500 ng/l) caused a significant decrease in the catalase activity (P < 0.05) and a significant increase (P < 0.05) in the lipid peroxidation. An increasing lipid peroxidation was also recorded for the highest concentration group tested (i.e., 50 000 ng/l). On the other hand, no significant changes were recorded in vitellogenin in all the exposed groups. Thus, based on these results, we have not demonstrated the endocrine-disrupting activity of tonalide in zebrafish. The results of the oxidative stress indices showed a significant impairment of the antioxidant defence after the two-month tonalide exposure, which could indicate part of the adaptive response to the tonalide toxicity.

Effect of Gold Nanoparticles and Ions Exposure on the Aquatic Organisms.

An increase in the production and usage of gold nanoparticles (AuNPs) triggers the necessity to focus on their impact on ecosystems. Therefore, the purpose of this study was to investigate the acute toxicity of AuNPs and ionic gold (Au (III)) to organisms representing all trophic levels of the aquatic ecosystem, namely producers (duckweed Lemna minor), consumers (crustacean Daphnia magna, embryos of Danio rerio) and decomposers (bacteria Vibrio fischeri). The organisms were exposed according to a standardized protocol for each species and endpoints. The AuNPs (1.16 and 11.6 d.nm) were synthesized using citrate (CIT) and polyvinylpyrrolidone (PVP) as capping agents, respectively. It was found, that Au (III) was significantly more toxic than AuNPs PVP and AuNPs CIT. AuNPs showed significant toxicity only at high concentrations (mg/L), which are not environmentally relevant in the present time, but a cautious approach is advised, due to the possibility of interactions with other contaminants.

Multibiomarker Responses of Juvenile Stages of Zebrafish (Danio rerio) to Subchronic Exposure to Polycyclic Musk Tonalide.

Synthetic polycyclic musks, widely used as additives in personal care products, are present in both biotic and abiotic matrices of the aquatic environment at concentrations of ng/l to µg/l. Although they are determined at comparatively low concentrations, these levels are biologically relevant and pose a significant growing risk as stressors to aquatic organisms. The purpose of our study was to evaluate the effects of 28-day-long exposure to polycyclic musk tonalide in zebrafish juvenile stages (Danio rerio) using selected biomarkers. Environmentally relevant concentrations of tonalide caused significant changes in selected enzyme activities in the experimental groups exposed to the highest concentrations. The activity of glutathione S-transferase and lipid peroxidation increased significantly (p < 0.05) after exposure to the highest concentration (50,000 ng/l) compared with the control. A similar trend was observed in catalase activity; there was a significant increase (p < 0.05) after exposure to two highest concentrations of tonalide (5000 and 50,000 ng/l). In addition, a statistically significant decrease (p < 0.05) in glutathione reductase activity was found in the lowest test concentration of tonalide (50 ng/l). None of the tested concentrations resulted in histopathological changes in liver, kidney, skin, or gill. Furthermore, no effects on body weight, body length, specific growth rate, and behavior were observed. Our results showed that tonalide exposure induced profound changes in the activities of antioxidant and detoxifying enzymes, such changes representing an adaptive response of the fish organism to tonalide toxicity.

Effects of therapeutic formalin bath on selected indices in fish.

OBJECTIVES: The aim of this study is to assess the effects of a treatment bath in a formalin solution on fish, focusing on haematological, biochemical and histopathological profiles. METHODS: A total of 96 common carps (Cyprinus carpio) were randomly assigned to eight groups. Four experimental groups were placed in the test solution for 60 minutes. The concentration of the formalin bath was 0.17 ml/l (38% formaldehyde), with the water temperature of 20°C. The effects of the bath were monitored immediately (E0) and 24 hours (E24h), 48 hours (E48h) and 10 days (E10d) after the bath. There was a control group (C0, C24h, C48h, C10d) for each of the experimental groups. RESULTS: Histopathological indices were strongly affected. Extensive changes were found on gill and skin immediately and also after 24 h, 48 h and 10 d of the formalin treatment bath. A plurality of mucinous elements was observed on the skin. Moreover, structural devastation of lamellas and numerous mucinous cells were observed on the gill. Changes were also found in haematological and biochemical indices. CONCLUSIONS: It can be concluded that after applying the treatment bath in the formalin solution, the monitored profiles were affected immediately after the bath and also after 10 days (histopathological changes of skin and gill). Such significant impact of therapeutic formalin bath should be considered in treatment of fish.

The Effects of Salicylic Acid on Juvenile Zebrafish Danio rerio Under Flow-Through Conditions.

The aquatic environment is becoming increasingly contaminated with pharmaceuticals. Salicylic acid (SA), which can be used individually or appear as a degradation product of the widely used acetylsalicylic acid was chosen for testing. Juvenile zebrafish Danio rerio were subjected to OECD test No. 215 (fish, juvenile growth test) with salicylic acid concentrations of 0.004; 0.04; 0.4; 4 and 40 mg/L. Specific growth rate (SGR), histological changes, and parameters of oxidative stress were evaluated. SA had no effects on histological changes, SGR, glutathione reductase, and lipid peroxidation. Increased catalytic activity of GPx was found at 0.04 mg/L compared to control, increased catalytic activity of catalase was found at 0.04 and 4 mg/L compared to control, and increased catalytic activity of glutathione-S-transferase was found at 0.004 and 0.04 mg/L compared to control (P < 0.05). Juvenile zebrafish turned out to be relatively insensitive to both environmentally relevant (0.004 mg/L) and higher concentrations of salicylic acid.

Oxidative stress indices and histopathological effects of the nonsteroidal antiinflammatory drug naproxen in adult zebrafish (Danio rerio).

OBJECTIVES: The aim of this study was to investigate the effects of the nonsteroidal antiinflammatory drug naproxen on adult zebrafish (Danio rerio). METHODS: Three months old zebrafish (Danio rerio) were exposed to naproxen at concentrations of 0.001, 0.1 and 5 mg.L(-1). We focused on the changes in oxidative stress indices during and at the end of the experiment and histopathological examination of tissues after a two week long exposure period. RESULTS: We found that a 3 day long exposure to naproxen causes mild oxidative stress and affects detoxification in zebrafish, which is demonstrated by the increased activity of glutathione peroxidase and glutathione S-transferase at 0.001 and 0.1 mg.L(-1) of naproxen, respectively. After a 7 day long exposure to 0.1 and 5 mg.L(-1), more potent effects on enzymes occur. However, these effects are only short lasting. At the end of the experiment, the activities of the target enzymes recover back to homeostatic baseline levels. Except catalase, which is induced only after a two week long exposure to the environmental concentration of naproxen. Despite the fact that naproxen causes mild oxidative stress in zebrafish, exposure to this drug does not result in lipid peroxidation. Histopathological examination revealed obvious changes to the gills and liver even at exposure to the environmental concentration of naproxen. CONCLUSION: This study demonstrates that the environmental concentration of naproxen can slightly influence both the antioxidant defense system and histopathology of non-target fish.

The effect of the fluoroquinolone norfloxacin on somatic indices and oxidative stress parameters in early stages of common carp (Cyprinus carpio L.).

OBJECTIVES: The aim of this study was to assess the effect of the subchronic exposure of early stages of common carp (Cyprinus carpio L.) to norfloxacin using morphometric data and oxidative stress parameters. METHODS: A subchronic toxicity test was performed on fertilized embryos of common carp according to the OECD Guidelines No. 210. Embryos were exposed to norfloxacin concentrations of 0.0001 (environmental), 0.1, 1.0, 5.0, and 10.0 mg.L(-1) for 34 days. RESULTS: At the end of the test (day 34), significant (p<0.05) stimulation of development was observed in all experimental groups, in contrast to the control. Significantly greater (p<0.01) total body length was also observed in the group exposed to 10.0 mg.L(-1) of norfloxacin compared to the control. A significant increase in the activity of glutathione S-transferase in all carp exposed to norfloxacin concentrations of 0.1 and 1.0 mg.L(-1) (p<0.01), and 5.0 mg.L(-1) (p<0.05) compared to control group was revealed. The activity of glutathione peroxidase was significantly lower (p<0.01) in experimental carp exposed to a norfloxacin concentration of 10.0 mg.L(-1). In experimental carp exposed to a norfloxacin concentration of 0.0001 mg.L(-1), a significant increase (p<0.05) in glutathione reductase activity was found. Significant (p<0.01) decreases in the content of thiobarbituric acid reactive substances in the groups exposed to norfloxacin concentrations of 1.0, 5.0, and 10.0 mg.L(-1) were revealed. CONCLUSION: From the results, we can conclude that norfloxacin has a negative impact on selected biochemical processes related to the production of reactive oxygen species in early-life stages of common carp.

Effects of the exposure of fish to triazine herbicides.

Triazines are an important group of herbicides, which have been used extensively or selectively both in agricultural and non-agricultural areas worldwide for more than fifty years to control broadleaf and some grassy weeds. As a consequence of their massive application, they have become and remain significant environmental pollutants, especially in aquatic ecosystems. Fish are an integral part of the aquatic environment and are, therefore, suitable models for the study of the behavioral, biological, and biochemical effects of triazine exposure. We have summarized and evaluated the effects of triazine herbicides on fish in order to provide an overview of current information on triazines. The overall effects of triazine herbicide exposure on the physiology of fish were evaluated by considering a variety of parameters in a number of reports. Haematological and biochemical profiles of blood provide important information about the internal environment of the organism and the general physiology and health status of triazine exposed fish. According to studies using biotransformation and bioaccumulation indices to estimate the effects of triazines on fish, changes in fish metabolism reflect the pollution of the environment by these herbicides. The responses of antioxidant defence systems in fish to triazine exposure could be an adaptive mechanism to protect the fish from triazine-induced oxidative stress. Acute exposure to triazines affects reproduction or reproductive development in fish; however, some triazines did not affect fish behavior during long-term exposure to low concentrations. Nevertheless, an impact on the overall behavioral response of fish cannot be excluded.

The effects of subchronic exposure to ciprofloxacin on zebrafish (Danio rerio).

OBJECTIVES: The aim of this study was to assess the impact of ciprofloxacin in Danio rerio on growth, on the development of histopathological changes in selected organs (gills, kidney, liver), and on the activity of some oxidative stress markers during a 28-day toxicity test. METHODS: Juvenile growth tests were performed on D. rerio according to OECD guideline No. 215. Fish at the age of 30 days were exposed for 28 days to a range of concentrations of ciprofloxacin (0.7 µg x L(-1)--environmental concentration, 100, 650, 1100 and 3 000 µg x L(-1)). RESULTS: There were no significant differences between the specific growth rates of fish from the test groups and from the control group. Histopathological examination revealed no pathological changes in organs of fish exposed to any ciprofloxacin concentration. The activity of glutathione S-transferase increased at the ciprofloxacin concentrations of 0.7 and 100 µg x L(-1) compared to the control. A significant decrease in glutathione reductase activity was obtained in fish exposed to ciprofloxacin at 1100 and 3000 µg x L(-1); a significant decrease in glutathione peroxidase activity was also found, but at all tested concentrations except for 100 µg x L(-1). A decrease in the concentration of thiobarbituric acid reactive substances was noted only at 100 µg x L(-1) compared to the control. CONCLUSIONS: According to our results, all tested concentrations of ciprofloxacin, including the environmental concentration, had an influence on oxidative stress markers and detoxifying enzymes in exposed fish, but did not affect fish growth or cause the development of histopathological changes in the fish organism.

Effects of subchronic exposure of diclofenac on growth, histopathological changes, and oxidative stress in zebrafish (Danio rerio).

The aim of this study was to investigate effects of subchronic exposure to sublethal levels of diclofenac on growth, oxidative stress, and histopathological changes in Danio rerio. The juvenile growth tests were performed on Danio rerio according to OECD method number 215. Fish at the age of 20 days were exposed to the diclofenac environmental concentration commonly detected in the Czech rivers (0.02 mg L(-1)) and the range of sublethal concentrations of diclofenac (5, 15, 30, and 60 mg L(-1)) for 28 days. A significant decrease (P < 0.01) in the fish growth caused by diclofenac was observed in the concentrations of 30 and 60 mg L(-1). The identified value of LOEC (lowest observed effect concentration) was 15 mg L(-1) of diclofenac and NOEC (no observed effect concentration) value was 5 mg L(-1) of diclofenac. We did not find histopathological changes and changes of selected parameters of oxidative stress (glutathione S-transferase, glutathione reductase) in tested fish. The environmental concentration of diclofenac in Czech rivers did not have any effect on growth, selected oxidative stress parameters (glutathione S-transferase, glutathione reductase), or histopathological changes in Danio rerio but it could have an influence on lipid peroxidation.

The effects of atrazine exposure on early life stages of common carp (Cyprinus carpio).

OBJECTIVES: Atrazine and its chloro-s-triazine metabolites are found in surface water and groundwater of the Czech Republic, although their use has been banned since 2005. The objective of the study was to determine the toxic effects of atrazine at an environmentally relevant concentration of atrazine, 0.3 µg.L-1 and at concentrations of 30, 100, and 300 µg.L-1 on morphometric and condition characteristics, development of early life stages, and antioxidant defense enzymes of common carp. METHODS: The embryo-larval toxicity test was performed according to the OECD Guidelines 210 (Fish, Early-life Stage Toxicity Test). RESULTS: Atrazine exposure showed no effect on morphometric and condition characteristics or histology. Exposure at 0.3 µg.L-1 was associated with significantly increased activity of glutathione peroxidase, glutathione S-transferase, superoxide dismutase, and catalase compared to control. Activity of glutathione reductase was slightly higher at a concentration of 0.3 µg.L-1, with significantly lower (p<0.05) activity observed in groups exposed to 30, 100, and 300 µg.L-1 compared to the group exposed to 0.3 µg.L-1. The level of oxidized lipids was slightly higher in groups exposed to atrazine at 100 and 300 µg.L-1 compared to controls. CONCLUSIONS: Atrazine has a significant influence on the biotransformation enzyme and oxidative defense enzymes of early life stages of common carp. The lowest observed effect concentration (LOEC) was 0.3 µg.L-1.

Biochemical markers for the assessment of pollution of selected small streams in the Czech Republic.

OBJECTIVES: The objective of the presented study was to investigate levels of the most important biochemical markers in fish which were caught upstream and downstream from sites near waste water treatment plants situated at 3 selected small streams of the Czech Republic. Organic pollutants and mercury were determined in muscle tissue of fish for complex assessment. DESIGN: Levels of biochemical markers (cytochrome P450 (CYP450), ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), vitellogenin (VTG)) were measured in selected tissues (liver, plasma, brain, gill and kidney) samples of brown trout. The concentrations of persistent organic pollutants (POPs) and mercury were determined in muscle samples. RESULTS: Significantly higher levels of biochemical markers (EROD, GST, VTG) were measured downstream from waste water treatment plant (WWTP) in Vlachovo Brezí (the small Libotýnský brook). Values of biochemical markers at the other localities Cerný brook and Moravice River were measured downstream from WWTP consistently or slightly lower with values of upstream. The values of POPs and mercury were in all monitored sites higher upstream compared with downstream from WWTP. The highest values of POPs and mercury were found on Cerný brook in Bruntál (more industrial and agricultural activity). CONCLUSION: The highest occurrence of selected POPs and mercury was generally upstream suggesting that small WWTP are able to partially remove these substances in those locations. But finding higher values of biochemical markers in downstream shows that there are many other substances endocrine disrupting chemicals (EDCs) that WWTP are unable to remove.

Oxidative stress parameters in fish after subchronic exposure to acetylsalicylic acid.

OBJECTIVES: The aim of this study was to investigate the effects of subchronic exposure of juvenile development stages of zebrafish (Danio rerio) to acetylsalicylic acid using selected oxidative stress biomarkers. DESIGN: Toxicity test with acetylsalicylic acid was performed according to the OECD Guideline No. 215, fish D. rerio aged 30 days were used. The tested concentrations were 0.004, 0.4, 40, 120 and 250 mg.L-1, duration of the test was 28 days. Products of lipid peroxidation and antioxidant enzymes were determined as the markers of oxidative stress. RESULTS: Significantly increased glutathione S-transferase activity was found in fish exposed to acetylsalicylic acid concentrations 40, 120 and 250 mg.L-1. The highest values of glutathione reductase activity were found in the groups exposed to acetylsalicylic acid concentrations 0.4, 40 and 120 mg.L-1. In the group exposed to acetylsalicylic acid concentrations 40 mg.L-1, catalase activity was significantly higher compared to the control group. Significantly higher glutathione peroxidase activity was found in the groups exposed to acetylsalicylic acid concentrations 0.004 and 120 mg.L-1. The concentrations of TBARS were lower in fish exposed to acetylsalicylic acid at all tested concentrations compared to control. CONCLUSION: The subchronic exposure of zebrafish to acetylsalicylic acid causes an increase in activity of antioxidant and biotransformation enzymes and a decrease in lipid peroxidation.

Effect of four selected carrier solvents on embryonal stages of Danio rerio.

OBJECTIVES: The aim of this study was to determine the effects of 96 hour exposure to selected solvents on the embryonic stages of zebrafish (Danio rerio). We investigated mortality and various types of changes which appeared (oedema, tail and eye defects, weak pigmentation, and deformation of the body). Based on the results, values of NOEC and LOEC for embryos of D. rerio were determined. METHODS: Embryonal toxicity tests were conducted according to OECD guideline 212. Ethanol and methanol were tested at concentrations of 0.1, 0.5, 1, 1.5, 2%; acetone at concentrations of 0.1, 0.5, 1, 1.25, 1.5%; and dimethylsulfoxide at concentrations of 1, 1.5, 2, 2.5, 3%. RESULTS: The LOEC values of ethanol and methanol were detected in the 1% concentration. Statistically significant changes (oedema) were reported in 1% ethanol, and oedema, weak pigmentation and deformation of the body were observed in 1% methanol. After exposure to acetone, the most common occurrence of oedema was in the 0.5% concentration (LOEC = 0.5%). The solvent dimethylsulfoxide caused oedema and body deformation at the 2% concentration (LOEC = 2%). CONCLUSIONS: The NOEC concentrations of the individual solvents were as follows: ethanol and methanol, 0.5%; acetone, 0.1%; and dimethylsulfoxide, 1.5%. These concentrations of individual solvents were higher than the maximum recommended concentration for toxicity tests on fish. For this reason, it can be assumed that the concentration of solvent allowed by the norm does not affect the procedure or results of such tests.

Oxidative stress parameters in early developmental stages of common carp (Cyprinus carpio L.) after subchronic exposure to terbuthylazine and metribuzin.

OBJECTIVES: This work assessed the subchronic effects of the triazine compounds terbuthylazine and metribuzin on embryo-larval stages of common carp (Cyprinus carpio L.) using biotransformation enzyme and selected oxidative stress parameters. DESIGN: Early developmental stages of fish, from embryo to larvae, were exposed to terbuthylazine at concentrations of 0.9, 160, 520, and 820 µg/L, and metribuzin at concentrations of 0.9, 4, 14, and 32 mg/L for 30 days and compared to the non-treated control group. For assessment of free radical defence the activities of glutathione S-transferase (GST) and glutathione reductase (GR) were measured; the lipid peroxidation (TBARS) level was determined as a marker of free radical damage. RESULTS: Terbuthylazine had no significant effect (p>0.05) at any tested concentrations on GST activity. Terbuthylazine caused an increase (p<0.05) in GR activity at the concentration of 520 µg/L. We found a non-significant (p>0.05) effect of terbuthylazine exposure on TBARS level. In metribuzin treated groups, the activity of GST was increased (p<0.05) in all experimental groups, with the highest at the concentration of 32 mg/L. GR activity was increased in the 0.9, 4, and 14 mg/L groups and the TBARS levels were the highest in the 0.9 mg/L group. CONCLUSION: Our results suggest that terbuthylazine and metribuzin induced oxidative stress in embryo-larval stages of common carp. Increased activities of biotransformation enzymes or antioxidant defence enzymes were markers of free radical attack. There was low lipid peroxidation in early developed fish after triazine exposure.

The effects of subchronic exposure to terbuthylazine on zebrafish.

OBJECTIVES: Terbuthylazine belongs to the group of symmetrical triazine herbicides used extensively in agriculture and non-agricultural sites, primarily to control broadleaf and some grassy weeds that have become ubiquitous contaminants of the environment. The aim of this study was to assess the impact of terbuthylazine in surface waters on fish under experimental conditions. The effects of subchronic exposure to terbuthylazine on fish growth and the development of histopathological changes in selected organs (gill, kidney, liver), and on the activity of some biochemical parameters - glutathione S-transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx) and on the concentration of thiobarbituric acid reactive substances (TBARS) in Danio rerio were investigated during a 28 day toxicity test. METHODS: Juvenile growth tests were performed on Danio rerio according to OECD guideline No. 215. Fish at the age of 30 days were exposed for 28 days to a range of sublethal concentrations of terbuthylazine (0.55 - environmental concentration, 150, 400, 700 and 1000 µg/L). RESULTS: There were no significant differences (p<0.05) between the specific growth rates (r) of the test groups and control group. Histopathological examination revealed pathological changes only in the liver in fish exposed to terbuthylazine at concentrations of 700 and 1000 µg/L. Significant differences (p<0.05) in activities of biochemical markers were found in GST (400, 700 and 1000 µg/L), GR (700 and 1000 µg/L), significant differences (p<0.05) of TBARS concentration were found at 1000 µg/L. CONCLUSIONS: Based on the results of growth rate, the histopathological examination of selected organs, and the results of biochemical parameters, it was found that the environmental concentration of terbuthylazine did not have any effects on juvenile D. rerio. The values of NOEC and LOEC for terbuthylazine for juvenile D. rerio were 150 µg/L and 400 µg/L.

The effects of subchronic exposure to terbuthylazine on early developmental stages of common carp.

The aim of this study was to assess the impact of terbuthylazine in surface waters on fish under experimental conditions. Subchronic toxic effects on embryos and larvae of common carp (Cyprinus carpio) were investigated during a 30-day toxicity test. The exposure to terbuthylazin showed no effect on mortality, but significant differences (P < 0.0001) were revealed on weight and growth parameters at concentrations of 520 and 820 µg/L. The inhibition of specific growth rate at concentrations of 520 and 820 µg/L was 14% compared to the control group. No significant negative effects on total body length and body weight were observed at lower concentrations (0.9 and 160 µg/L). The concentrations 520 and 820 µg/L were associated with a delay in development compared to other experimental groups and controls. On the basis of weight and growth rate evaluation and determination of developmental stages, the No Observed Effect Concentration (NOEC) of terbuthylazine was estimated at 160 µg/L and the Lowest Observed Effect Concentration (LOEC) was 520 µg/L. According to these results, the reported environmental concentration of terbuthylazine in Czech rivers does not impact growth, development, morphology, or histology of carp embryos and larvae.

The effects of subchronic exposure to metribuzin on Danio rerio.

The aim of this study was to assess the impact of metribuzin in surface waters on fish under experimental conditions. The effects of subchronic exposure to metribuzin on fish growth and the development of histopathological changes in selected organs (gill, kidney, liver) and on activity of some biochemical markers (CYP450, EROD) in Danio rerio were investigated during a 28-day toxicity test. Juvenile growth tests were performed on D. rerio according to OECD method number 215. Fish at an initial age of 30 days were exposed to a range of metribuzin concentrations (1.5, 5, 16, 33, and 53 mg L⁻¹). Exposure to metribuzin at 53 mg L⁻¹ was associated with increased mortality. Negative effects with regard to total body weight, length, and the inhibition of specific growth rate were induced at concentrations of 33 and 53 mg L⁻¹. Histopathological examination revealed pathological lesions in the liver in pesticide-exposed fish only at the highest concentration of 53 mg L⁻¹ of metribuzin. Based on the results of growth rate, biochemical markers (CYP450, EROD), and histopathological examination, the lowest observed effect concentration (LOEC) value was 33 mg L⁻¹ and the no observed effect concentration (NOEC) value was 16 mg L⁻¹.

Comparison of acute toxicity of ketoprofen to juvenile and embryonic stages of Danio rerio.

OBJECTIVES: Ketoprofen is a common human medicine from a class of non-steroidal anti-inflammatory drugs (NSAIDs), which is provably detected in surface waters in concentrations ordinarily in µg.L-1. The aim of this study was to compare the acute toxicity of ketoprofen to embryonic and juvenile stages of aquarium fish - zebrafish (Danio rerio). METHODS: Tests were performed according to the methods of the Organisation for Economic Co-operation and Development (OECD) No. 203 (Fish, acute toxicity test) and OECD No. 212 (Fish, short-term toxicity test on embryo and sac-fry stages). RESULTS: The results showed (mean ± SD) LC50 value of ketoprofen to be 632.30 ± 10.10 mg.L-1 in juvenile zebrafish and 6.44 ± 2.22 mg.L-1 in embryonic stages of zebrafish. The results revealed statistically significantly higher sensitivity (p<0.01) of the embryonic stages of zebrafish to ketoprofen compared to its juveniles. The susceptibility of embryos depends on many factors, especially yet improperly developed enzymatic system in embryos, different ways of the absorption of the substance into the organism or differences in metabolism pathways. CONCLUSIONS: The acute toxicity of ketoprofen for juvenile stages of zebrafish is low, but the substance seems to be toxic for embryonic stages.

Effects of subchronic exposure to simazine on zebrafish (Danio rerio).

OBJECTIVES: Simazine is a triazine herbicide which has been used for a long period in agriculture and in the aquatic environment for control of weeds and algae. The aim of this study was to investigate the effects of subchronic exposure to simazine on growth and the development of histopathological changes in selected organs (gills, kidney, liver) in Danio rerio. METHODS: Juvenile growth tests were performed on D. rerio according to the OECD method No. 215. Fish at the age of 20 days were exposed to the environmental simazine concentration commonly detected in Czech rivers (0.06 µg.L-1) and a range of sublethal concentrations of simazine (0.6, 6.0 and 60.0 µg.L-1) for 28 days. RESULTS: There were no significant differences (p<0.05) between the specific growth rates (r) of the test groups and those of both control groups. Histopathological examination revealed pathological changes in fish exposed to a simazine concentration of 60.0 µg.L-1. The values of NOEC and LOEC of simazine were 6.0 µg.L-1 and 60.0 µg.L-1. CONCLUSIONS: The environmental concentration of simazine in Czech rivers did not have any effects on the growth and development of histopathological changes in D. rerio.