Genotoxicity evaluation of metronidazole using the piscine micronucleus test by acridine orange fluorescent staining

Evidence of genotoxicity, neurotoxicity, and antioxidant imbalance in silver catfish Rhamdia quelen after subchronic exposure to diisopentyl phthalate

Diisopentyl phthalate (DiPeP) is a plasticizer with significant offer and application in Brazilian industries. This is attributed to its origin, which is closely linked to the refining process of sugarcane for ethanol production in the country. In this work, we developed a model for trophic exposure to environmentally relevant doses (5, 25, and 125 ng/g of DiPeP) to identify possible target tissues and toxic effects promoted by subchronic exposure to DiPeP in a Neotropical catfish species (Rhamdia quelen). After thirty days of exposure, blood, liver, kidney, brain, and muscle were collected and studied regarding DNA damage in blood cells and biochemical analyses. The kidney was the most affected organ, as in the head kidney, genotoxicity was evidenced in all groups exposed to DiPeP. Besides, the caudal kidney showed a reduction in the superoxide dismutase and glutathione peroxidase activities as well as a reduced glutathione concentration. In the liver, exposure to 125 ng/g of DiPeP increased glutathione S-transferase activity and reduced glutathione levels. In muscle, acetylcholinesterase (AChE) was reduced. However, in the brain, an increase in AChE activity was observed after the exposure to lowest doses. In contrast, a significant reduction of brain AChE activity after exposure to the highest dose was detected. The pronounced genotoxicity observed in head kidney cells is of concern, as it may compromise different functions performed by this organ (e.g., hematopoiesis, immune and endocrine functions). In our study, DiPeP proved to be a compound of environmental concern since we have evidenced its nephrotoxic and neurotoxic potential even in low doses.

Assessment of toxicity potential of neglected Mithi River water from Mumbai megacity, India, in zebrafish using embryotoxicity, teratogenicity, and genotoxicity biomarkers

The Mithi River begins at Vihar Lake and flows through the industrial hub of the city of Mumbai, India, and merges with the Arabian Sea at Mahim Creek. The current study was carried out to assess the ecotoxicological effects of the Mithi River surface water in zebrafish (Danio rerio) embryos. Water samples were collected from ten sampling sites (S1 to S10) located along the course of the Mithi River. The toxicity of water samples was assessed using a zebrafish embryo toxicity test (ZFET). Water samples were diluted from all sites at 1:0, 1:2, 1:4, 1:8, 1:16, 1:32, 1:64, and 1:128 times. The lowest and highest LDil 20 values for 96 h were estimated as 9.16 and 74.18 respectively for the S2 and S5 sites. The results of embryotoxicity and teratogenicity assays indicated a significant difference (p < 0.0001) between embryos exposed to control and sampling sites (except S1) for various endpoints such as mortality, egg coagulation, pericardial edema, yolk sac edema, tail bend, and skeletal deformities. The histopathological analysis revealed various lesions, ascertaining the toxic effects of water samples. The comet assay revealed significantly higher DNA damage (except S1) in embryos exposed to sites S5 and S6 with OTM values of 4.46 and 2.48 respectively. The results indicated that the Mithi River is polluted with maximum pollution load at the middle stretches. The study further indicated that the pollutants in the Mithi River (except S1) could potentially be hazardous to the aquatic organisms; therefore, continuous biomonitoring of the river is needed for its revival.

Assesment of hematotoxic, oxidative and genotoxic damage potentials of fipronil in rainbow trout Oncorhynchus mykiss, Walbaum

In this study, changes in the blood tissue of rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) caused by Fipronil (FP) insecticide were investigated using different biomarkers (Hematology parameters, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), malondialdehyde (MDA), paraoxonase (PON), arylesterase (ARE), myeleperoxidase (MPO), micronucleus (MN), 8-hydroxy-2-deoxyguanosine (8-OHdG)) level and caspase-3 activity. Statistically significant alterations in hematology parameters occurred with FP effect. In blood tissue, dose-dependent inhibition was determined in SOD-CAT-GPX-PON and ARE enzyme activities, but MDA and MPO were induced statistically significant. The results of MN assay were compared with the control group and it was obtained that genotoxicity of different dose groups was similar. The level of 8-OHdG and the activity and caspase-3 examined in blood tissue was increased depending on the dose. It was determined with different biomarkers that this insecticide caused physiological stress changes in the tissues examined.

Removal of antibiotic from the water environment by the adsorption technologies: a review

Antibiotics are known as emergent pollutants because of their toxicological properties. Due to continuous discharge and persistence in the aquatic environment, antibiotics are detected almost in every environmental matrix. Therefore antibiotics that are polluting the aquatic environment have gained significant research interest for their removal. Several techniques have been used to remove pollutants, but appropriate technology is still to be found. This review addresses the use of modified and cheap materials for antibiotic removal from the environment.

The redox-active drug metronidazole and thiol-depleting garlic compounds act synergistically in the protist parasite Spironucleus vortens

Spironucleus vortens is a protozoan parasite associated with significant mortalities in the freshwater angelfish, Pterophyllum scalare. Control of this parasite is especially problematic due to restrictions on the use of the drug of choice, metronidazole (MTZ), on fish farms. Use of garlic (Allium sativum) is undergoing a renaissance following experimental validations of its antimicrobial efficiency. Ajoene ((E,Z)-4,5,9-trithiadodeca-1,6,11-triene 9-oxide), is a stable transformation product of allicin, the primary biologically active component of garlic. In the current study, an ajoene oil crude extract had a minimum inhibitory concentration (MIC) of 40μg/ml against S. vortens. GC-MS and NMR spectroscopy revealed this ajoene extract contained a mixture of the (E) and (Z)-ajoene isomers along with diallyl disulphide (DADS) and diallyl trisulphide (DATS). The only component of the ajoene crude oil found to substantially inhibit S. vortens growth by optical density monitoring (Bioscreen C Reader) was (Z)-ajoene (MIC 16μg/ml). Ajoene oil acted in synergy with MTZ in vitro, reducing the individual MIC of this drug (4μg/ml) by 16-fold, and that of ajoene oil by 200-fold with a fractional inhibitory concentration (FIC) index of 0.263. This synergistic interaction was confirmed in vivo. S. vortens-infected Pterophyllum scalare angelfish dosed orally with 0.5% (v/w) MTZ combined with 0.05% (v/w) ajoene displayed a significant reduction in faecal trophozoite count, whilst those fed on 0.5% MTZ flakes (half the recommended oral dose) alone did not. This study demonstrates for the first time the synergistic interaction between the synthetic drug MTZ and natural ajoene oil both in vitro and in vivo. Future work should evaluate the potential synergy of ajoene and MTZ against MTZ-resistant bacteria and protists.

Matrix changes due to the toxic effects of metronidazole in intestinal tissue of fish (Onchorhynchus mykiss)

Metranidazole (MTZ) is an antibiotic used for parasitic infections in a number of species. Accumulation of this drug in the environment and its interaction with fish of economic value makes this drug particularly important. In the present study, we examined the histopathological effects of MTZ on the intestinal tissue of Oncorhynchus mykiss. The fish in aquarium were exposed to MTZ at doses of 5, 10, 20 mg/L for 2, 4 and 8 days. At the end of the experiments, macroscopic pathology or death were not observed at these doses. Histochemical staining with Haematoxylene-Eosin, Periodic Acid Schiff and Gomori Trichrome showed, depending on increased dose and prolonged duration, areas of necrosis, edema, inflammation, small tears at the tips of the villi and excretion with heterogenic distribution of the Goblet cells. Moreover, changes in the connective tissue of the intestines due to toxicity of MTZ and decreases in immunostaining of matrix proteins such as laminin and collagen IV, especially in the epithelium were observed. Findings of the present study would be useful to demonstrate the adverse effects of MTZ use, emphasizing the importance of the effect on fish which could be very important public health.

Earthworm biomarker responses on exposure to commercial cypermethrin

Cypermethrin is a synthetic pyrethroid insecticide used worldwide in agriculture, home pest control, disease vector control, and food safety. It accumulates in soil. Therefore, traces of cypermethrin may frequently appear in vegetables grown in contaminated soil. There is a push now to develop biomarkers as early warning indicators of environmental pollution. In this study, DNA damage (tail DNA%, tail length, and olive tail moment), the micronucleus, neutral red retention (NRR) time, and pinocytic adherence ability of coelomocytes were investigated in Pheretima peguana earthworms exposed to cypermethrin in filter paper tests. The NRR time of earthworm coelomocytes decreased significantly at a concentration of 3.5 × 10(-3) µg · cm(-2) (1/100 LC50 ) after 48 h exposure, with a highly negative correlation with cypermethrin concentration. Pinocytic adherence ability of coelomocytes also declined significantly at a cypermethrin concentration of 3.5 × 10(-2) µg · cm(-2) (1/10 LC50 ). The DNA damage to earthworm coelomocytes (tail DNA%, tail length, and olive tail moment) increased considerably at the highest concentration (3.5 × 10(-1) µg · cm(-2) ) although the correlation between tail DNA% and cypermethrin concentration was low. Thus, physiological biomarkers were more sensitive than the genotoxic effects in earthworms exposed to commercial cypermethrin. Although a suite of earthworm biomarkers could be used to evaluate cypermethrin terrestrial pollution, the NRR test is easier to conduct and a more sensitive indicator.

Do cancer cells in human and meristematic cells in plant exhibit similar responses toward plant extracts with cytotoxic activities?

We examined the effect of water extracts of Persea americana fruit, and of the leaves of Tabernamontana divericata, Nerium oleander and Annona cherimolia (positive control) on Vicia faba root cells. We had confirmed in our previously published data the cytotoxicity of these plant extracts on four human cancer cell lines: liver (HepG-2), lung (A549), colon (HT-29) and breast (MCF-7). Vicia faba roots were soaked in plant extracts at dilutions of 100, 1,250, 2,500, 5,000, 10,000, 20,000 ppm for 4 and 24 h. All treatments resulted in a significant reduction in the mitotic index in a dose dependant manner. Root cells treated with T. divericata, N. oleander and A. cherimolia exhibited a decrease in prophase cell percentage, increase in micronuclei and chromosomal abnormalities as concentration increased. The P. americana treatment showed the highest cytotoxic effect on cancer cells, prophase cell percentage increased linearly with the applied concentration and no micronuclei were detected. This study shows that root tip assay of beans can be used in initial screening for new plant extracts to validate their use as candidates for containing active cytotoxic agents against malignant cells. This will greatly help in exploring new plant extracts as drugs for cancer treatment.

Hexamitiasis leads to lower metabolic rates in rainbow trout Oncorhynchus mykiss (Walbaum) juveniles

This study assessed the effects of Hexamita salmonis (Moore) on metabolism of rainbow trout Oncorhynchus mykiss (Walbaum) and its effect on the host's susceptibility to infectious pancreatic necrosis virus (IPNV) after antiparasitic treatment. Rainbow trout naturally infected with H. salmonis were treated with 10 mg metronidazole kg fish(-1) per day, and their physiological recovery was assessed through measuring resting metabolism on the 7th, 14th, 21st and 28th day after treatment. In addition, we exposed the naïve fish to H. salmonis and measured the resting metabolism (oxygen consumption as mg O2 kg(-1) per hour) on the 10th, 20th and 30th day after the exposure to assess the variation in metabolic rates after infection. Significantly lower rates of metabolic activity (P < 0.05) were anticipated 20 days after infection with H. salmonis compared with the fish infected with H. salmonis for 10 days or with the parasite-free fish. Similarly, the treated fish needed about 20 days to fully recover from hexamitiasis. The susceptibility of rainbow trout to IPNV remained unchanged in the presence of H. salmonis. Weight loss was significantly higher (P < 0.05) in infected than that in the parasite-free fish. Fish should be examined regularly for H. salmonis and treated immediately whether found to prevent economic losses and excessive size variation.

Detrimental effects of metronidazole on the liver of freshwater common carp (Cyprinus carpio L.)

The widely used antibiotic metronidazole (MTZ) was investigated for its toxic effects on the liver of the common carp (Cyprinus carpio L.). The fish were exposed to 0.1, 0.5, and 2.5 mg/L MTZ in water for 30 days, and parameters that are indicative of liver damage and oxidative stress were measured. MTZ increased liver ethoxyresorufin-O-deethylase, malondialdehyde, and glutathione levels, and elevated the activities of superoxide dismutase, catalase, aspartate aminotransferase, and alanine aminotransferase. These parameters usually showed significant differences in the 0.5 and 2.5 mg/L MTZ groups compared to the control group (p < 0.05). These findings indicated that MTZ induced oxidative stress and caused liver damage in common carp, suggesting that measures should be taken to avoid contamination of surface waters with MTZ.

Pirimicarb-based formulation-induced genotoxicity and cytotoxicity in the freshwater fish Cnesterodon decemmaculatus (Jenyns, 1842) (Pisces, Poeciliidae)

We analyzed the aspects of lethality, genotoxicity, and cytotoxicity in the ten spotted live-bearer exposed under laboratory conditions to the pirimicarb-based formulation Patton Flow® (50% active ingredient (a.i.)). Acute effects were evaluated using different end points for lethality, genotoxicity, and cytotoxicity. Median lethal concentration (LC50) estimation was employed as a bioassay for lethality, whereas micronucleus (MN) induction and alterations in erythrocyte/erythroblast frequency were used as end points for genotoxicity and cytotoxicity, respectively. Results demonstrated an LC5096h value of 88 mg/L. Patton Flow® increased the MN frequency in fish erythrocytes after 48 h of exposure at a concentration of 66 mg/L, whereas a concentration range of 22–66 mg/L was able to exert the same genotoxic effect at 96 h of treatment. Furthermore, cytotoxicity was also observed by alterations in erythrocyte/erythroblast frequencies within the concentration range of 22–66 mg/L, regardless of the exposure time. Our current observations provide evidence that Patton Flow® (50% a.i.) should be considered a clear lethal, cytotoxic, and genotoxic agent on Cnesterodon decemmaculatus. Thus, repeated applications of this carbamic insecticide can enter the aquatic environment and exert deleterious effects on aquatic organisms other than the evaluated species C. decemmaculatus.

Nitroimidazolyl hydrazones are better amoebicides than their cyclized 1,3,4-oxadiazoline analogues: In vitro studies and Lipophilic efficiency analysis

Two series of compounds with hydrazone derivatives (HZ1-HZl2, series 1) and oxadiazoline derivatives (OZ1-OZ12, series 2) of the 2-methyl-5-nitro-1H-imidazole scaffold were designed and synthesized. Physicochemical properties and Lipophilic efficiency (LipE) analysis predicted higher intrinsic quality of the acylhydrazone derivatives (series 1) than their corresponding oxadiazoline analogues (series 2). In vitro antiamoebic results supported the above findings and validated that the acylhydrazone derivatives (HZ1-HZl2) show better activity than the oxadiazoline derivatives (OZ1-OZ12). MTT assay, using HepG2 cell line, revealed noncytotoxic nature of the compounds. The most promising results were observed for compounds HZ5 (IC50 = 0.96 μM) and HZ9 (IC50 = 0.81 μM) both in silico and in vitro. Analysis of the Lipophilic efficiency (LipE) of the compounds provided new insight for the design of potent and selective amoebicides.

Genotoxic evaluation of different doses of methylmercury (CH₃Hg⁺) in Hoplias malabaricus

The survey of the effects of toxic metals and its organic compounds are of critical importance because these compounds tend to accumulate in aquatic environments. In the present work, the genotoxic potential of methylmercury, an organomercurial compound with high toxicity and present in large amounts in fish of the Amazon due to the mining process, was evaluated using the piscine micronucleus test and comet assay in fish. Specimens of Hoplias malabaricus (popularly known as traira), a neotropical specie, was exposed to methylmercury via food web, over 70 days, in two different concentrations: two groups of fifteen fish were tested with 0.075 μg CH(3)Hg(+)/g and 0.75 μg CH(3)Hg(+)/g of methylmercury per gram of fish, at 5-day intervals and over 14 successive intervals whereas control group, composed by nine fish, was fed by uncontaminated prey fish (Astyanax sp). One of the aims of this study was to reproduce the contamination found in nature in an attempt to increase our biological knowledge on the neotropical species. Hoplias malabaricus specimens were then anesthetized for removal of blood samples and dissected, for cephalic kidney removal. As a result, it was observed that the piscine micronucleus test showed no significant differences between exposed groups and control group. The comet assay performed on erythrocyte system cells, showed a significant difference between controls and contaminated, but there was no difference between doses. In contrast, the kidney cells comet assay showed no significant difference between groups, probably due to the type of damage caused by xenobiotics to be related to the tissues of most contact with it, as well as its mode of action and the chain of bioaccumulation within bodies.

Mutagenic impact on fish of runoff events in agricultural areas in south-west France

When heavy rainfall follows herbicide application, the intense surface runoff causes stream water contamination. Aquatic organisms are then briefly exposed to a complex mixture of contaminants. The aim of the present study is to investigate the genotoxic impact of such events on fish. A model fish, the Crucian carp (Carassius carassius) was exposed in controlled conditions, for 4 days, to water sampled daily in the Save River (France). The watershed of this stream is representative of agricultural areas in south-west France. Three hydrological conditions were compared: basal flow, winter flood, and spring flood. Chemical analysis of the water samples confirmed the higher contamination of the spring flood water, mainly explained by a peak of metolachlor. Genotoxicity was evaluated by micronucleus (MN) test and comet assay in peripheral erythrocytes. A significant increase in DNA breakdowns compared to controls was detected by the comet assay for all conditions. Exposure to spring flood water resulted in the highest damage induction. Moreover, induced chromosomal damage was only detected in this condition. In addition, fish were exposed, for 4 days, to an experimental mixture of 5 herbicides representative of the spring flood water contamination. Fish exhibited moderate DNA damage induction and no significant chromosomal damage. The mutagenicity induced by field-collected water is then suspected to be the result of numerous interactions between contaminants themselves and environmental factors, stressing the use of realistic exposure conditions. The results revealed a mutagenic impact of water contamination during the spring flood, emphasizing the need to consider these transient events in water quality monitoring programs.

Giemsa versus acridine orange staining in the fish micronucleus assay and validation for use in water quality monitoring

This study concerns a comparative analysis of the acridine orange and Giemsa staining procedures for the fish erythrocyte micronucleus assay. The goal was to optimize the assay in the context of field water monitoring. Fish (Carassius carassius) were exposed to a reference genotoxic agent, cyclophosphamide monohydrate 5 mg l(-1) for 2, 4, and 6 days before testing. Slides from each individual were scored using the two procedures. The results show that the assay was more sensitive when acridine orange was used. When slides were Giemsa stained, the presence of ambiguous artefacts, leading to false positives and increasing random variance, reduced the contrast between exposed and control samples. Acridine Orange staining was then applied in the context of water quality monitoring. Fish were exposed for 4 days to water sampled in two hydrological contexts: basal flow and spring flood. The results show that exposure to spring flood water in an agricultural stream can induce mutagenicity.

Use of native species Crenicichla menezesi (Ariidae) as a model for in situ evaluation of genotoxicity in surface water

The aim of this work was to analyze the genotoxicity in surface water from the Pitimbú River (Natal, Brazil) using a neotropical species Crenicichla menezesi as bioindicator for in situ evaluation. The genotoxicity was analyzed using the micronucleus (MN) and comet assays in erythrocytes. The animals were collected from five sites of the river. A significant increase of MN frequency and comet class L1 to L4 were observed only in specimens collected from three sampling sites (SS3, SS4 and SS5) located into urban areas. These same sites also presented high metals concentration. Correlation of DNA damage and concentrations of Cu (Spearman r=0.8080), Cr (Spearman r=0.9772), and Ni (Spearman r=0.9909) were observed. These data indicate the presence of genotoxic agents. Moreover the C. menezesi species showed to be a good indicator for prompt analyses since this species presents sedentary and carnivore habits.

In vivo genotoxicity of mercury chloride and lead acetate: Micronucleus test on acridine orange stained fish cells

The genotoxic effects of mercury chloride and lead acetate were evaluated in vivo using the micronucleus (MN) assay on acridine-orange (AO) stained peripheral blood erythrocytes, gill and fin epithelial cells of Carassius auratus auratus. Fish were exposed to three different concentrations of mercury chloride (MC) (1 microg/, 5 microg/L and 10 microg/L) and lead acetate (LA) (10 microg/L, 50 microg/L and 100 microg/L) for 2, 4 and 6 days. A single dose of 5 mg/L cyclophosphamide was used as a positive control. In addition to micronuclei, nuclear buds (NBs) were assessed in the erythrocytes. The ratio of polychromatic and normochromatic erythrocytes (PCE/NCE) in peripheral blood was also evaluated to assess cytotoxicity. MN frequencies in all three tissues were elevated in fish exposed to both LA and MC. However, NBs showed different sensitivity to metal treatments. MN frequencies in both control and treated fish were highest in gill cells and generally lower in erythrocytes and fin cells. PCE/NCE rations decreased in relation to MC and LA treatments. The results of this study indicate that LA and MC have genotoxic and cytotoxic damage in fish and confirmed that AO staining is a suitable technique for in vivo MN test in fish.

A sub-acute study of metronidazole toxicity assessed in Egyptian Tilapia zillii

Metronidazole (MTZ), an antiparasitic and antibacterial compound, is one of the world's most widely used drugs. Despite being considered as a rodent mutagen and a carcinogen, it is still widely used in humans for the treatment of infections with anaerobic organisms. Therefore, the main objective of the current study was to evaluate the in vivo toxicity of MTZ using the micronucleus (MN) assay and random amplified polymorphism DNA (RAPD-PCR) analysis as well as histopathological examination in Tilapia zillii. Moreover, the protective effect of vitamin C (VitC) against toxicity of MTZ was investigated in the present study. Fish were treated with three doses of MTZ (5, 10 and 20 mg l(-1)) alone or in combination with VitC (200 mg kg(-1) food) at several time intervals (2 days, 7 days and 14 days). The results of the present study showed a significant effect of MTZ on micronucleus formation and changes in polymorphic band patterns as well as induction of different histopathological alterations in Tilapia zillii. The effects of the drug were reduced when fish were exposed to a combination of MTZ and VitC.

The micronucleus test in piscine erythrocytes

Cytogenetic assays on aquatic organisms are essential, as humans are exposed throughout their lifetime to several xenobiotics present in both the water and aquatic food. The micronucleus test showed to be a useful in vivo assay for genotoxicity testing. However, many aspects of its protocol need to be refined, knowledge of confounding factors should be improved and inter-species differences need further investigation. This review summarizes the protocols developed until now, provides knowledge from hematology and physiology that might be useful to researchers dealing with the micronucleus test and indicates the drawbacks of this assay.

Induction of micronuclei and nuclear abnormalities in Oreochromis niloticus following exposure to petroleum refinery and chromium processing plant effluents

The genotoxic effects of effluents from a petroleum refinery and a chromium processing plant were evaluated in Oreochromis niloticus (Pisces: Perciformes) using the micronucleus test. Fish were exposed to different concentrations (5, 10 and 20%, v/v) of the effluents for 3, 6 and 9 days. Micronucleus analyses were carried out on gill epithelial cells and peripheral blood erythrocytes. Nuclear abnormalities other than micronuclei, considered as genetic damage indicators, were also evaluated on erythrocytes. Cyclophosphamide at a single dose of 4 mg/L was used as a positive control. The results of this study showed that both effluents had genotoxic potential. On the other hand, the level of genetic damage induced by petroleum refinery effluent was considerably higher than that of chromium processing plant effluent. Our results further indicate that nuclear abnormalities other than micronuclei, such as blebbed and lobed nuclei, may also be used as indicators of genotoxic damage.

Micronucleus test in fish cells: a bioassay for in situ monitoring of genotoxic pollution in the marine environment

To evaluate the use of native fish species for assessing genotoxic pollution in the marine environment, micronucleus (MN) analysis was performed in peripheral blood erythrocytes and gill cells of the grey mullet (Mugil cephalus) from three sampling stations off the southeastern Mediterranean coast of Turkey. The frequencies of blebbed, notched, and lobed nuclei and binucleated cells also were evaluated in peripheral erythrocytes. The sampling sites were chosen on the basis of pollution levels; Karaduvar harbor, contaminated by different types of industrial effluents, and Mersin harbor, mainly contaminated by aromatic hydrocarbons, were selected as polluted areas. Erdemli harbor, a relatively unpolluted site, was used as the control area. Sampling was carried out at four different seasons. The frequencies of both micronuclei and other nuclear abnormalities (NAs) in mullets captured from polluted areas were significantly higher than those in mullets from the reference area. In general, gill cells had considerably higher MN frequencies than did erythrocytes, and genotoxic responses were higher in summer than in winter. The results of this study indicate that the MN test in fish is a suitable biomarker for in situ monitoring of genotoxic pollution in the marine environment. As demonstrated in this study, NAs other than micronuclei are also useful indices of chemical exposure and toxic responses. Therefore, measuring both micronuclei and NAs may increase the sensitivity of the test system.