Histopathological alterations in the gills of Nile tilapia exposed to carbofuran and multiwalled carbon nanotubes

Potential toxicity of carbonaceous nanomaterials on aquatic organisms and their alleviation strategies: A review

Carbonaceous nanomaterials (CNMs) are widely used in electronics, biomedicine, agriculture, environmental remediation, and catalysis due to their excellent biocompatibility, high reactivity, and high specific surface area. However, the extensive applications of CNMs cause their inevitable release into water, which may result in toxic effects on the aquatic ecological environment and organisms. CNMs can cause lipid peroxidation damage and neurotoxicity in aquatic organisms, affecting embryo hatching and larval morphology. The effects of CNMs on aquatic organisms vary depending on their structures and physicochemical properties, as well as the species, age, and tolerance of the tested organisms. The above uncertainties have increased the difficulty of exploring the impact of carbonaceous nanomaterials on the toxicity of aquatic organisms to a certain extent. Solving these issues is of great significance and reference value for promoting the research and safe utilization of carbon nanomaterials. Therefore, a systematic review of the effects of potential toxicity of carbonaceous nanomaterials on aquatic organisms and their alleviation strategies is needed. This paper firstly summarizes the toxic effects of commonly used CNMs (i.e., carbon nanotubes, graphene, and fullerene) on different aquatic organisms, which include developmental toxicity, behavioral and metabolic toxicity, reproductive toxicity, and organ toxicity. Then the main mechanisms of CNMs to aquatic organisms are further explored, and the methods to reduce the toxicity of CNMs are also summarized. Finally, the current challenges and future perspectives for studying CNM toxicity to aquatic organisms are proposed.

Mixture effect of parental exposure to triazophos and fenvalerate on the early development of zebrafish offspring

Triazophos (TRI) and fenvalerate (FEN) have been extensively used in the world and frequently coexist in the water environments, might pose health risk to aquatic species. However, investigations of their mixture toxic effects on offspring after parental exposure have been neglected, especially for aquatic vertebrates such fish. To address this knowledge gap, parental zebrafish (F0 generation) were exposed to TRI, FEN and their mixture for 60 days, as well as the embryos (F1 generation) were hatched without or with continued corresponding exposures at the same concentrations until 7 days post fertilization. The results exhibited that exposure to TRI and FEN altered the expression levels of biomarkers associated with several biological processes, such as apoptosis and inflammatory response. Compared to individual exposure in the F1 generation, the co-exposure to TRI and FEN resulted in increased the expression of T4 and cc-chem mRNA and decreased the expression of ROS, trα, il-8, and gpx mRNA when the F0 generation was similarly exposed. These results revealed that the co-exposure to TRI and FEN has detrimental effects on fish progeny following parental exposure, even if the progeny are not directly exposed to the pesticides, and such negative effects may be intensified if the offspring continue to be exposed. This study enhances the understanding of the harmful impacts of parental exposure to the pesticide mixture on descendants and holds implications for the ecological risk assessment of pesticide mixtures in aquatic vertebrates. Further mechanistic studies are necessary to gain a deeper insight into the mixture effects of pesticides and other kinds of pollutants on subsequent offspring following parental exposure.

Evaluation of behavioral and neurochemical changes induced by carbofuran in zebrafish (Danio rerio)

Carbofuran (CF) is a carbamate class pesticide, widely used in agriculture for pest control in crops. This pesticide has high toxicity in non-target organisms, and its presence in the environment poses a threat to the ecosystem. Research has revealed that this pesticide acts as an inhibitor of acetylcholinesterase (AChE), inducing an accumulation of acetylcholine in the brain. Nonetheless, our understanding of CF impact on the central nervous system remains elusive. Therefore, this study explored how CF influences behavioral and neurochemical outcomes in adult zebrafish. The animals underwent a 96-hour exposure protocol to different concentrations of CF (5, 50, and 500 μg/L) and were subjected to the novel tank (NTT) and social preference tests (SPT). Subsequently, they were euthanized, and their brains were extracted to evaluate neurochemical markers associated with oxidative stress and AChE levels. In the NTT and SPT, CF did not alter the evaluated behavioral parameters. Furthermore, CF did not affect the levels of AChE, non-protein sulfhydryl groups, and thiobarbituric acid reactive species in the zebrafish brain. Nevertheless, further investigation is required to explore the effects of environmental exposure to this compound on non-target organisms.

Co-exposure to cadmium and triazophos induces variations at enzymatic and transcriptional levels in Opsariichthys bidens

Heavy metals and pesticides are significant pollutants in aquatic environments, often leading to combined pollution and exerting toxic effects on aquatic organisms. With the rapid growth of modern industry and agriculture, heavy metal cadmium (Cd) and pesticide triazophos (TRI) are frequently detected together in various water bodies, particularly in agricultural watersheds. However, the combined toxic mechanisms of these pollutants on fish remain poorly understood. This experiment involved a 21-day co-exposure of Cd and TRI to the hook snout carp Opsariichthys bidens to investigate the toxic effects on liver tissues at both enzymatic and transcriptional levels. Biochemical analysis revealed that both individual and combined exposures significantly increased the content or activity of caspase-3 (CASP-3) and malondialdehyde (MDA). Moreover, the impact on these parameters was greater in the combined exposure groups compared to the corresponding individual exposure groups. These findings suggested that both individual and combined exposures could induce mitochondrial dysfunction and lipid peroxidation damage, with combined exposure exacerbating the toxicological effects of each individual pollutant. Furthermore, at the molecular level, both individual and combined exposures upregulated the expression levels of cu-sod, cat, and erβ, while downregulating the expression of il-1. Similar to the patterns observed in the biochemical parameters, the combined exposure group exhibited a greater impact on the expression of these genes compared to the individual exposure groups. These results indicated that exposure to Cd, TRI, and their combination induced oxidative stress, endocrine disruption, and immunosuppression in fish livers, with more severe effects observed in the combined exposure group. Overall, the interaction between Cd and TRI appeared to be synergistic, shedding light on the toxic mechanisms by which fish livers responded to these pollutants. These findings contributed to the understanding of mixture risk assessment of pollutants and were valuable for the conservation of aquatic resources.

Carbon nanotubes and nanofibers seen as emerging threat to fish: Historical review and trends

Since the discovery of the third allotropic carbon form, carbon-based one-dimensional nanomaterials (1D-CNMs) became an attractive and new technology with different applications that range from electronics to biomedical and environmental technologies. Despite their broad application, data on environmental risks remain limited. Fish are widely used in ecotoxicological studies and biomonitoring programs. Thus, the aim of the current study was to summarize and critically analyze the literature focused on investigating the bioaccumulation and ecotoxicological impacts of 1D-CNMs (carbon nanotubes and nanofibers) on different fish species. In total, 93 articles were summarized and analyzed by taking into consideration the following aspects: bioaccumulation, trophic transfer, genotoxicity, mutagenicity, organ-specific toxicity, oxidative stress, neurotoxicity and behavioral changes. Results have evidenced that the analyzed studies were mainly carried out with multi-walled carbon nanotubes, which were followed by single-walled nanotubes and nanofibers. Zebrafish (Danio rerio) was the main fish species used as model system. CNMs' ecotoxicity in fish depends on their physicochemical features, functionalization, experimental design (e.g. exposure time, concentration, exposure type), as well as on fish species and developmental stage. CNMs' action mechanism and toxicity in fish are associated with oxidative stress, genotoxicity, hepatotoxicity and cardiotoxicity. Overall, fish are a suitable model system to assess the ecotoxicity of, and the environmental risk posed by, CNMs.

The adsorption effects of biochar on carbofuran in water and the mixture toxicity of biochar-carbofuran in rats

Carbofuran, a widely used carbamate insecticide, is frequently detected in water. In this study, a high-performance adsorbent (WAB4) for carbofuran was obtained from laboratory-synthesized biochars. The maximum adsorption of carbofuran by WAB4 reaches 113.7 mg/g approximately. The adsorption of carbofuran by biochar was a multi-molecular layer and the adsorption process conforms to the pseudo-second-order kinetic model (R2 = 0.9984) and Freundlich isotherm model (R2 = 0.99). Importantly, an in vivo rat model was used to assess the combined toxicological effects of biochar-carbofuran complexes. The toxicity of the complexes (LD50 > 12 mg/kg) is lower than that of carbofuran (LD50 = 7.9 mg/kg) alone. The damage of biochar-carbofuran complex on rat liver and lung is significantly less than that of carbofuran. The Cmax and bioavailability of carbofuran were found to be reduced by 64% and 68%, respectively, when biochar was present, by UPLC-MS/MS analysis of carbofuran in rat plasma. Furthermore, it was confirmed that the biochar-carbofuran complex is relatively stable in the gastrointestinal tract, by performing a carbofuran release assay in artificial gastrointestinal fluids in vitro. Collectively, biochar is a bio-friendly material for the removal of carbofuran from water.

Effects of hyperoxia during oxygen nanobubble treatment on innate immunity, growth performance, gill histology, and gut microbiome in Nile tilapia, Oreochromis niloticus

Oxygen nanobubble (NB-O2) technology has been introduced to the aquaculture industry in recent years. This treatment usually results in a tremendously high level of dissolved oxygen (DO) in the water. However, little is known about the possible negative effects of hyperoxia due to NB-O2 treatment (hyper-NB-O2) on farmed fish. Here, we investigated i) the effect of short-term hyper-NB-O2 exposure (single treatment) on the innate immunity in Nile tilapia, Oreochromis niloticus, and ii) the effect of long-term hyper-NB-O2 exposure (26-day treatments) on survival, growth performance, gill histology, and gut microbiome in Nile tilapia. A single treatment with NB-O2 for 10 min in 50 L of water resulted in 24.2 ± 0.04 mg/L DO (approximately 2-3 × 107 nanoscale oxygen bubbles/mL). This treatment did not result in differences in expression of several immune-related genes (e.g., TNF-α, LYZ and HPS70) in various tissues (e.g., gill, head kidney, and spleen) compared to the non-treated control. Over a 26-day period of exposure, no significant differences were observed in survival and growth performance of the fish, but minor histological changes were occasionally noted on the gills. Analysis of the gut microbiome revealed a significant increase in the genera Bosea, Exiguobacterium, Hyphomicrobium, and Singulisphaera in the group receiving NB-O2. Moreover, no signs of "gas bubble disease" were observed in the fish throughout the duration of the experiment. Overall, these results suggest that both short- and long-term hyper-NB-O2 exposure appears to be benign and has no obvious adverse effects on fish.

Multi-walled carbon nanotubes enhance the toxicity effects of dibutyl phthalate on early life stages of zebrafish (Danio rerio): Research in physiological, biochemical and molecular aspects

Phthalate esters (PAEs) are widely used as plasticizers. PAEs are ubiquitous in natural water bodies, with dibutyl phthalate (DBP) being one of the most common PAEs. DBP is prone to leaching or migration into the environment, posing serious health and environmental risks. Carbon nanotubes (CNTs) have been widely used in various fields with the rapid development of nanotechnology. CNTs could alter the environmental behavior and toxicity of co-existing pollutants. CNTs have been shown to rapidly adsorb PEAs. However, current knowledge about the effects of CNTs on DBP toxicity is limited. Here we show that the toxic effects of single and combined exposure to DBP (0.1, 0.5, 1.0 mg/L) and different CNTs (MWCNTs/MWCNTs-COOH, 0.5 mg/L) on the early growth stage of zebrafish. The results suggested that a significant increase in heart rate and heart malformation rate was observed after co-exposure of DBP and MWCNTs/MWCNTs-COOH (p < 0.05). Furthermore, combined exposure increased antioxidant enzyme activity during early developmental stages in zebrafish (p < 0.05). The qRT-PCR results revealed that DBP and MWCNTs/MWCNTs-COOH co-exposure significantly interfered with the expression of genes related to oxidative stress, energy metabolism, development of cardiac function, and apoptosis (p < 0.05). In addition, for oxidative stress and cardiotoxicity, MWCNTs/MWCNTs-COOH aggravated the toxic effects of 0.5 mg/L DBP on embryos/larvae. The metabolomics results showed that co-exposure mitigated the disturbance of amino acid metabolism mediated by single DBP exposure. In general, MWCNTs/MWCNTs-COOH increased the impact of DBP in the early developmental stages of zebrafish. This study provides new insights into the toxicology of early developmental stages of aquatic organisms exposed to co-exist pollutants of DBP and CNTs.

Ultrastructural characteristics of the accumulation of iron nanoparticles in the intestine of Cyprinus carpio (Linnaeus, 1758) under aquaculture

During the development of nanotechnology, the production of many substances containing nanoparticles leads to the release of various nanoparticles into the environment, including the water ecosystem. The main goal of the current research was to study the ultrastructural characteristics of the entry and bioaccumulation of Fe3O4 nanoparticles in the small intestine of Cyprinus carpio (Linnaeus, 1758), as well as the pathomorphological changes in the fish organism. Two different doses (10 and 100 mg) of Fe3O4 nanoparticles were fed to fingerlings for 7 days and then intestinal samples were taken and studied. It was found that the extent of damages was boosted within the increment of nanoparticle concentration. The sequence and bioaccumulation of Fe3O4 nanoparticles in the small intestine of fish occurred as below: firstly, the nanoparticles passed into microvilli located in the apical part of enterocytes in the mucosa layer, from there into the cytoplasm of the epithelial cells, including cytoplasmatic organelles (nucleus, mitochondria, lysosomes, fat granules), and then into a lamina propria of the mucosa of the small intestine and passed into the endothelium of the blood vessels and to the erythrocytes of the vessels which located in the lumen. It was determined that although the nanoparticles were up to 30 nm in size, only particles with a maximum size of 20 nm could penetrate the intestinal wall. Thus, the release of Fe3O4 nanoparticles into the environment in high doses has a negative effect on the living ecosystem, including the body of fish living in the water.

In vitro toxicity assessment of polyethylene terephthalate and polyvinyl chloride microplastics using three cell lines from rainbow trout (Oncorhynchus mykiss)

The RTgill-W1 (gill), RTG-2 (gonad), and RTL-W1 (liver) cell lines derived from a freshwater fish rainbow trout (Oncorhynchus mykiss), were used to assess the toxicity of polyethylene terephthalate (PET) and two forms of polyvinyl chloride (PVC). Two size fractions (25-μm and 90-μm particles) were tested for all materials. The highest tested concentration was 1 mg/ml, corresponding to from 70 000 ± 9000 to 620 000 ± 57 000 particles/ml for 25-μm particles and from 2300 ± 100 to 11 000 ± 1000 particles/ml for 90-μm particles (depending on the material). Toxicity differences between commercial PVC dry blend powder and secondary microplastics created from a processed PVC were newly described. After a 24-h exposure, the cells were analyzed for changes in viability, 7-ethoxyresorufin-O-deethylase (EROD) activity, and reactive oxygen species (ROS) generation. In addition to the microplastic suspensions, leachates and particles remaining after leaching resuspended in fresh exposure medium were tested. The particles were subjected to leaching for 1, 8, and 15 days. The PVC dry blend (25 μm and 90 μm) and processed PVC (25 μm) increased ROS generation, to which leached chemicals appeared to be the major contributor. PVC dry blend caused substantially higher ROS induction than processed PVC, showing that the former is not suitable for toxicity testing, as it can produce different results from those of secondary PVC. The 90-μm PVC dry blend increased ROS generation only after prolonged leaching. PET did not induce any changes in ROS generation, and none of the tested polymers had any effect on viability or EROD activity. The importance of choosing realistic extraction procedures for microplastic toxicity experiments was emphasized. Conducting long-term experiments is crucial to detect possible environmentally relevant effects. In conclusion, the tested materials showed no acute toxicity to the cell lines.

Co-exposure of zinc oxide nanoparticles and multi-layer graphenes in blackfish (Capoeta fusca): evaluation of lethal, behavioural, and histopathological effects

Zinc oxide nanoparticles (ZnO NPs) and multi-layer graphenes (MLGs) are widely used, and due to the lack of appropriate wastewater treatment may end up in the aquatic environment, with unknown consequences to biota. The main purpose of this study was to assess the acute toxicity, histopathological and behavioural changes caused by the exposure of ZnO NPs and MLGs, alone and combined, to the blackfish Capoeta fusca. The estimated mean 96 h-LC₅₀ for ZnO NPs was 4.9 mg L^-1 and 68.4 mg L^-1 for MLGs. In combination, MLGs increased the acute toxicity of the ZnO NPs. The effects of the different NPs on the gills included hyperplasia, aneurisms, and fusion of the lamellae. In the intestine, exposure to the NPs resulted in an increase in the number and swelling of goblet cells and tissue degeneration. Loss of balance, restlessness, erratic and abnormal swimming patterns were the most common behavioural changes seen in the ZnO NPs' exposed blackfish. In contrast with the acute toxicity findings, MLGs decreased the histopathological and behavioural effects of the ZnO NPs on both gills and intestinal tissues as well as fish behaviour. Our experimental results illustrated insights into the simultaneous exposure assessment of metal-based NPs and carbon nanomaterials, although further research is needed on the interactions exposure of these substances to interpreting the toxicological effects of metal-based nanomaterials seen in exposed organisms.

Co-exposure of carbon nanotubes with carbofuran pesticide affects metabolic rate in Palaemon pandaliformis (shrimp)

Palaemon pandalirformis (shrimp) is a species widely distributed in the Brazilian coastal region and with an important economic role. In addition, this organism is considered an indicator of environmental pollution in estuaries; however, its physiological responses to toxic environmental pollutants, including pesticides and nanomaterials, are not well known, mainly, the effects of co-exposure. Thus, the purpose of this study was to evaluate the ecotoxicological effects of co-exposure between oxidized multiwalled carbon nanotubes (HNO₃-MWCNT) and carbofuran pesticide on the routine metabolism of P. pandalirformis. The shrimps were exposed to different concentrations of HNO₃-MWCNT (0; 10; 100; 500; 1000 μg L^-1), carbofuran (0; 0.1; 1.0; 5.0; 10 μg L^-1) and to co-exposure with 100 μg L^-1 of HNO₃-MWCNT + carbofuran (0; 0.1; 1.0; 5.0; 10 μg L^-1), to evaluate the effects on metabolic rate (O₂ consumption) and excretion of ammonia (NH₄+NH₃). Our results showed that the shrimps exposed to HNO₃-MWCNT (10 μg L^-1) increased the metabolic rate by 292% and the excretion of ammonia by 275%; those exposed to carbofuran (10 μg L^-1) increased their metabolic rate by 162% and the excretion of ammonia by 425%; and with the co-exposure of HNO₃-MWCNT + carbofuran there was also an increase in the metabolic rate by 317% and an excretion of ammonia by 433% when compared to control. These findings provides useful information toward better understanding the physiological responses of shrimps after combined exposure to nanomaterials and pesticides in aquatic environments.

Carbofuran affects behavior and metabolism of the Atlantic Forest lambari Deuterodon iguape, a native species from Brazil

One of the major causes of aquatic biodiversity loss is the contamination of the environment by pesticides. Even though there is a considerable amount of studies on the subject, there are still few that deal with the effects of carbofuran on native species in Brazil. Although carbofuran is widely used in Brazil, its action on native organisms, such as the Atlantic Forest lambari Deuterodon iguape, has not yet been studied. This work aimed to evaluate the effects of exposure to carbofuran on the fish D. iguape, considering the behavior and specific oxygen consumption as end points. Opercular movements, dorsal fin movements, and swimming speed were analyzed as behavioral parameters. To assess specific oxygen consumption, fish were subjected to concentrations of 0.0, 0.05, 0.1, 0.25, and 0.5 mg/L, for 24 h. For behavior analysis, fish remained exposed to carbofuran at concentrations of 0.0, 0.01, 0.05, 0.1, and 0.5 mg/L, in periods of 0, 2, 24, and 48 h. The behavior was studied through filming, analyzed with the free software, Tracker 4.92 (Open Source Physics). The results demonstrate an increase in opercular movements (18% ± 2.65) and a decrease in dorsal fin movements (- 21.2% ± 2.97), as well as in swimming speed (- 58.3% ± 1.83) of the experimental groups compared to the control group. There was an increase in oxygen consumption of 58.4% in fish exposed to the highest concentration of carbofuran. Thus, it is concluded that carbofuran altered D. iguape's behavior and oxygen consumption. The species was sensitive to carbofuran concentrations and can be used as a bioindicator.

Sublethal effects of propiconazole on the metabolism of lambari Deuterodon iguape (Eigenmann 1907), a native species from Brazil

The objective of this study was to analyze the sublethal effects of propiconazole on Deuterodon iguape, a native fish common in Brazil, which has potential for aquaculture and use as a bioindicator. The hypothesis was to test whether D. iguape has a metabolism similar to Danio rerio so that its use in bioassays may be validated. Lethal concentration (LC50) and metabolic rates were studied in fish exposed to propiconazole. Specific oxygen consumption and ammonia excretion for D. iguape and D. rerio increased by 0.01 µg L^-1 and then decreased as the propiconazole concentration increased. The decrease in the averages of specific oxygen consumption at the concentration of 0.1 µg L^-1 represented a reduction in the metabolic rate compared to the control of 71% for D. iguape and 40% D. rerio. For the ammonia excretion, at the same concentration, there was a reduction of 68.7% and 45.4% for D. iguape and D. rerio, respectively. When comparing ammonia excretion of the two species for each concentration of propiconazole, there was a significant difference (p < 0.05) in relation to the control and for the highest concentration (0.1 µg L^-1). As for specific oxygen consumption, there was a statistically significant difference only for the concentration of 0.1 µg L^-1. D. iguape proved to be a good and useful bioindicator for ichthyologists or ecologists in studies of moderate pesticide contamination in freshwater aquatic environments, as its metabolic response was similar to D. rerio.

Ameliorating effect of ascorbic acid on fenvalerate induced ultrastructural changes in scales, erythrocytes and gills of Ctenopharyngodon idella (Valenciennes, 1844)

Fenvalerate (type II synthetic pyrethroid), widely used in agricultural practices, find its way into aquatic ecosystem through air, by runoff, or by percolation to groundwater. It is an extremely toxic insecticide for aquatic organisms especially fish. In the present study, the fenvalerate (FEN) induced toxicity and the protective efficacy of ascorbic acid (AA) against FEN in Ctenopharyngodon idella was evaluated by studying the structural alterations in scales, erythrocytes and gills. The fishes were exposed to 1.2 μg/L and 2 μg/L of FEN and orally administered with 1000 mg/kg diet of AA. The fishes were scrutinized on 15^th, 30^th and 60^th day of experiment. Scanning electron microscopic studies (SEM) of FEN-treated fish revealed extensive morphological alterations on the microstructure of scales including deformed focus, uprooted lepidonts and tubercles, hole formation and worn out calcareous material from the surface. FEN intoxication induced severe damage on erythrocytes including formation of dacrocytes, serrated spherocytes, echinocytes with oozed out cytoplasmic content, contracted plasma membrane and appearance of lobopodial projections. Ultrastructural studies in gills declared profound lesions in the form of aneurysm, loss of secondary lamellae and destructed microstructures of pavement cells. On the other hand, supplementation of AA in diet mitigated the impairment provoked by FEN on the scales, erythrocytes and gills due to its antioxidant properties.

Hazardous Effects of SiO2 Nanoparticles on Liver and Kidney Functions, Histopathology Characteristics, and Transcriptomic Responses in Nile Tilapia (Oreochromis niloticus) Juveniles

Simple Summary

Waterborne exposure of Nile tilapia (Oreochromis niloticus) juveniles to sub-lethal concentrations of silicon dioxide nanoparticles (SiO₂NPs) induced hepato-renal damage through elevation of aspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphatase (ALP) activities as well as creatinine and blood urea levels. SiO₂NPs induced irreversible dose-dependent histopathological changes in the hepatopancreas, gills, and posterior kidneys, alongside modulation of the pro-inflammatory cytokines, apoptosis-related genes, and oxidative stress genes in gills and liver of exposed fish.

Abstract

The current investigation assessed the impacts of sub-lethal concentrations of silicon dioxide nanoparticles (SiO₂NPs) on hepato-renal functions, histopathological characteristics, and gene transcription in gills and liver of Nile tilapia juveniles. Fish were exposed to 20, 40, and 100 mg/L of SiO₂NPs for 3 weeks. Pairwise comparisons with the control group showed a significant dose-dependent elevation in serum ALP, ALT, and AST enzyme activities as well as blood urea and creatinine levels in SiO₂NP-intoxicated groups. Exposure to 100 mg/L SiO₂NPs significantly upregulated expression of HSP70, TNF-α, IL-1β, and IL-8 genes in the gills as compared to the control group. Moreover, exposure to 100 mg/L SiO₂NPs significantly upregulated the expression SOD, HSP70, IL-1β, IL-8, and TNF-α genes in the hepatic tissues as compared to the control group. Exposure of fish to 20 mg SiO₂NPs/L significantly increased the mRNA expression levels of IL-12 in both the gills and liver tissues. Notably, all tested SiO₂NP concentrations significantly upregulated the transcription of CASP3 gene in gills and liver of Nile tilapia as compared to the control group. Interestingly, varying histopathological alterations in renal, hepatopancreatic, and branchial tissues were observed to be correlated to the tested SiO₂NP concentrations. In conclusion, our results provide additional information on the toxic impacts of SiO₂NPs in Nile tilapia at the hematological, tissue, and molecular levels.

Effects of multi-walled carbon nanotubes on the enantioselective toxicity of the chiral insecticide indoxacarb toward zebrafish (Danio rerio)

The mass production and usage of carbon nanotubes (CNTs) have led to the inevitable release into the environment, and the effects of CNTs on the toxicity of co-existing pollutants have been well documented. However, knowledge of the effects of CNTs on the enantioselective toxicity of chiral compounds is limited. Using zebrafish as an experimental model, the enantioselective expression of the apoptosis, CYP3C and EAAT-related genes were analyzed following exposure to multi-walled carbon nanotubes (MWCNTs) (0.05 and 0.5 mg/L), rac-/R-/S-indoxacarb (0.01 mg/L), or the combination of rac-/R-/S-indoxacarb mixed with MWCNTs for 28d. Sex-specific differences were observed in both the liver and brain of zebrafish. The expression of apoptosis and CYP3C-related genes was 16.55-44.29 times higher in the livers of males treated with R-indoxacarb than in S-indoxacarb treated groups. The EAAT-related genes were expressed at 1.38-2.56 times higher levels in the brain of females treated with R-indoxacarb than in S-indoxacarb-treated groups. In the presence of MWCNTs, the expression of caspase-3, cyp3c3, cyp3c4, eaat1a, eaat1b and eaat2 in the livers of males and brains of females treated with S-indoxacarb were 1.65-15.33 times higher than in fish treated with R-indoxacarb. Based on these results, MWCNTs affected the enantioselective toxicity of indoxacarb toward zebrafish.

Accumulation and toxicity of multi-walled carbon nanotubes in Xenopus tropicalis tadpoles

Multi-walled carbon nanotubes (MWCNTs), a common nanomaterial widely used and discharged in environment, might exert toxic effects on aquatic animals. In this paper, filter-feeding tadpole of Xenopus tropicalis was selected as bioindicator to study the exposure effects of MWCNTs suspensions of 0.5, 1, 2, 4 and 8 mg/L for 72 h. The results showed that the tadpoles could remain high survival rate of over 96.7% after 24 h's exposure to MWCNTs, but then decrease considerably, showing a significant time-dependent relationship. The LC₅₀ was 2.53 mg/L for tadpoles exposed to MWCNTs for 72 h, when MWCNTs accumulated in their gills and digestive tracts. Moreover, the enrichment degree of MWCNTs in tadpole was related to exposure density than time. When MWCNTs suspension concentration was not over 1 mg/L, the heart rates increased significantly and then decreased continuously. The survivors from the toxicity test were transferred to fresh filtered water for recovery, but MWCNTs accumulated in the tadpoles' body didn't decrease obviously after 4 days. Although the maximum tadpoles survival rate of 80% was recorded in the exposure group of 0.5 mg/L MWCNTs, only 43.3% of the survivors could recover. Therefore, the final survival rate was negative related to the exposure densities of MWCNTs but positive related to the accumulating degree in tadpoles' body. The results demonstrated that MWCNTs exposure posed potential health risks to filter-feeding organisms by intake and accumulation in organs, which could provide useful information for the reasonable evaluation and scientific management of nanomaterials.

Exposure of rainbow trout (Oncorhynchus mykiss) to magnetite (Fe3O4) nanoparticles in simplified food chain: Study on ultrastructural characterization

The widespread exposure of metallic nanoparticles to the aquatic ecosystem and its adverse impact on human life is the colossal concern worldwide. In view of this, this context was investigated to analyze microscopically the bioaccumulation and localization of magnetite (Fe₃O₄) nanoparticles in the cellular organelles of rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) in aquatic conditions. Initially, Fe₃O₄ nanoparticles were absorbed on to Elodea (Elodea canadensis) and fed to molluscs (Melanopsis praemorsa). Fish were fed with the same molluscs, and then the intestines and liver were examined using light and transmission electron microscopy. Results showed that nanoparticles were present in the cytoplasm and other organelles of cells (mitochondrion and lysosome) by absorbing through microvilli of the epithelial cells of the tunica mucosa in the intestine. Further, nanoparticles passed through the vessels of the lamina propria of the tunica mucosa and reached to the sinusoids of the liver via blood circulation. It was then accumulated from the endothelium of the sinusoid to the cytoplasm of liver hepatocytes and to mitochondria and lysosome. The accumulation of nanoparticles in the epithelial cells, cytoplasm, mitochondria, and lysosome revealed the degree of transparency of the pattern with slight hesitation. In summary, this investigation contributed towards the understanding of the physiological effects of Fe₃O₄ nanoparticles on O. mykiss, which ascertains essentiality for sustainable development of nanobiotechnology in the aquatic ecosystem.

Radiolabeling of amide functionalized multi-walled carbon nanotubes for bioaccumulation study in fish bone using whole-body autoradiography

Commercial and medicinal applications of functionalized carbon nanotubes (f-CNTs) such as amidated f-CNTs are expanding rapidly with a potential risk exposure to living organisms. The effects of amidated f-CNTs on aquatic species have received a limited attention. In this work, an easy wet method to prepare [¹⁴C]-label amide multi-walled carbon nanotubes (MWNTs) is reported. Labeled carbon nanotubes were prepared by successive reactions of carboxylation, chloroacylation, and final amidation using [¹⁴C]-labeled ethanolamine. The f-CNTs were characterized using elemental analysis, electron dispersive X-ray, transmission electron microscopy, thermogravimetric analysis, and Raman and FTIR spectroscopy. An uptake experiment was carried out with juvenile Arctic char (Salvelinus alpinus) using water dispersed amidated [¹⁴C]-f-CNTs to assess their biodistribution in fish tissues using whole body autoradiography. The radioactivity pattern observed in fish head suggests that f-CNTs were accumulated in head bone canals, possibly involving an interaction with mineral or organic phases of bones such as calcium and collagen. This f-CNTs distribution illustrates how important is to consider the surface charges of functionalized carbon nanotubes in ecotoxicological studies.

Environmental impact of biogenic silver nanoparticles in soil and aquatic organisms

Synthetic silver nanoparticles (AgNPs) are being extensively used in our daily lives; however, they may also pose a risk to public health and environment. Nowadays, biological AgNPs are considered an excellent alternative, since their synthesis occurs by a green technology of low cost and easy scaling. However, studies with these biological nanomaterials (NM) are still limited. Thus, a more careful assessment of their industrial application, economic feasibility and ecotoxicological impacts is crucial. The aim of this study was to investigate the effects of different concentrations of mangrove fungus Aspergillus tubingensis AgNPs on the aerobic heterotrophs soil microorganisms, rice seeds (Oryza sativa) and zebrafish (Danio rerio). Biogenic AgNPs were less harmful for soil microbiota compared to AgNO₃. On rice seeds, the AgNPs displayed a dose-dependent inhibitory effect on germination and their subsequent growth and development. The percentage of inhibition of rice seed germination was 30, 69 and 80% for 0.01, 0.1 and 0.5 mM AgNPs, respectively. After 24 h of AgNPs exposition at a limit concentration of 0.2 mM, it did not induce mortality of the zebrafish D. rerio. Overall, A. tubingensis AgNPs can be considered as a suitable alternative to synthetic nanoparticles.

Bioaccumulation and Metabolism of Carbosulfan in Zebrafish (Danio rerio) and the Toxic Effects of Its Metabolites

Carbosulfan is a carbamate insecticide that has been widely used in agriculture. However, studies showed that carbosulfan could be highly toxic to aquatic organisms. The metabolism of carbosulfan in adult zebrafish is still largely unexplored, and the metabolites in individual or in combination may pose a potential threat to zebrafish. In the present study, the bioaccumulation and metabolism of carbosulfan in zebrafish (Danio rerio) were assessed, and the main metabolites, including carbofuran and 3-hydroxycarbofuran, were determined. The toxicity of carbosulfan and its metabolites individually or in combination to zebrafish was also investigated. The bioaccumulation and metabolism experiment indicated that carbosulfan was not highly accumulated in zebrafish, with a bioaccumulation factor of 18 after being exposed to carbosulfan for 15 days, and the metabolism was fast, with a half-life of 1.63 d. The two main metabolites were relatively persistent, with half-lives of 3.33 and 5.68 d for carbofuran and 3-hydroxycarbofuran, respectively. The acute toxicity assay showed that carbofuran and 3-hydroxycarbofuran had 96-h LC₅₀ values of 0.15 and 0.36 mg/L, showing them to be more toxic than carbosulfan (96-h LC₅₀ = 0.53 mg/L). Combinations of binary or ternary mixtures of carbosulfan and its metabolites displayed coincident synergistic effects on acute toxicity, with additive index (AI) values of 1.9-14.3. In the livers and gills of zebrafish exposed to carbosulfan, carbofuran, and 3-hydroxycarbofuran, activities of catalase, superoxide dismutase, and glutathione-S-transferase were significantly changed in most cases, and the content of malondialdehyde was greatly increased, indicating that carbosulfan and its metabolites induced varying degrees of oxidative stress. The metabolites were more persistent and toxic to zebrafish and exhibit coincident synergistic effects in combination. These results can provide evidence for the potential risk of pesticides and highlight the importance of a systematic assessment for the combination of the precursor and its metabolites.

Co-exposure of graphene oxide with trace elements: Effects on acute ecotoxicity and routine metabolism in Palaemon pandaliformis (shrimp)

Graphene oxide (GO) has been evaluated for application in environmental remediation and pollution control strategies. However, the side effects caused by the interactions of GO with classical pollutants in aquatic environments are still largely unknown. In this work, the ecotoxicological effects of GO, cadmium, zinc and the interactions between GO and these trace elements (co-exposure) were evaluated through acute toxicity tests and routine metabolism (i.e., oxygen consumption and ammonia excretion) in Palaemon pandaliformis (shrimp). After 96 h of exposure, GO did not present acute ecotoxicity at concentrations up to 5.0 mg L^-1. However, the association of GO with Cd or Zn increased the toxicity of these trace elements as demonstrated by the decrease in LC₅₀ values. The 96 h LC₅₀ of Cd associated with GO was 1.7 times less than the 96 h LC₅₀ of Cd alone. Similarly, the 96 h LC₅₀ of Zn associated with GO was 1.8 times less than the 96 h LC₅₀ of Zn alone. Additionally, the co-exposure of GO with trace elements impaired the routine metabolism of P. pandaliformis. Finally, the GO potentiated the ecotoxicological effects of Cd and Zn in the shrimp model. Future research on this emerging nanomaterial should focus on its use and disposal in aquatic ecosystems.

Effects of multiwalled carbon nanotubes and carbofuran on metabolism in Astyanax ribeirae, a native species

The study of the toxic effect of carbofuran and multiwalled carbon nanotubes (MWCNTs) on Astyanax ribeirae metabolism is of paramount importance due to the increasing use of this pesticide in agriculture and in the production of nanotubes within the material industry. This study aimed to evaluate the effects of carbofuran, MWCNT, and the combination of these compounds on specific oxygen consumption and excretion of ammonia in A. ribeirae. Therefore, 65 fish were divided into three groups of treatments at varying concentrations: carbofuran (0.01, 0.05, 0.1, and 0.5 mg/L), MWCNT (0.1, 0.25, 0.5, and 1.0 mg/L), and 0.5 mg/L of MWCNT added to carbofuran concentrations (0.01, 0.05, 0.1, and 0.5 mg/L). The average specific oxygen consumption in the groups exposed to carbofuran, compared to the control, increased 73.49% at the 0.01 mg/L concentration and decreased 63.86% and 91.57% with treatments of 0.1 and 0.5 mg/L, respectively. For groups exposed to the MWCNT, there was an 83.91% drop with the 1.0 mg/L treatment, and the carbofuran + MWCNT groups recorded a decrease of 71.09%, 92.77%, and 93.98% at concentrations of 0.05, 0.1, and 0.5 mg/L, respectively. In relation to specific ammonia excretion, in groups exposed to carbofuran compared to the control, there was an increase of 134.37% and 200% with the 0.1 and 0.5 mg/L treatments, respectively. The group exposed to carbofuran + MWCNT experienced a decrease of 60% and 80% with treatments of 0.1 mg/L carbofuran + 0.5 mg/L MWCNT and 0.5 mg/L carbofuran + 0.5 mg/L MWCNT, respectively. Therefore, it was concluded that carbofuran + MWCNT interact, increasing the effects in Astyanax sp.

Innate Immunity Provides Biomarkers of Health for Teleosts Exposed to Nanoparticles

In recent years, the unique properties of nanoparticles have fostered novel applications in various fields such as biology, pharmaceuticals, agriculture, and others. Unfortunately, their rapid integration into daily life has also led to environmental concerns due to uncontrolled release of nanoparticles into the aquatic environment. Despite increasing awareness of nanoparticle bioaccumulation in the aquatic environment, much remains to be learned about their impact on aquatic organisms and how to best monitor these effects. Herein, we provide the first review of innate immunity as an emerging tool to assess the health of fish following nanoparticle exposure. Fish are widely used as sentinels for aquatic ecosystem pollution and innate immune parameters offer sensitive and reliable tools that can be harnessed for evaluation of contamination events. The most frequent biomarkers highlighted in literature to date include, but are not limited to, parameters associated with leukocyte dynamics, oxidative stress, and cytokine production. Taken together, innate immunity offers finite and sensitive biomarkers for assessment of the impact of nanoparticles on fish health.

Toxicological effects of transition metal-doped titanium dioxide nanoparticles on goldfish (Carassius auratus) and common carp (Cyprinus carpio)

The aim of present study was to assess the toxicological effects of transition metal-doped titanium dioxide nanoparticles (TiO₂ NPs) on histopathological changes, behavioral patterns, and antioxidant responses of goldfish (Carassius auratus) and common carp (Cyprinus carpio). The synthesized nanoparticles were confirmed by Transmission Electron Microscopy, Field Emission Scanning Electron Microscopy, X-ray diffraction, UV-visible, and Vibration Sample Magnetometer. Fish in four experimental groups exposed to sub-lethal concentrations of pure TiO₂ NPs (10 mg L^-1), chromium (Cr), iron (Fe), and nickel (Ni) doped TiO₂ NPs for seven days. Statistical analysis of oxidative stress responses in gills showed significant differences in superoxide dismutase, total antioxidant capacity, and malondialdehyde parameters between two species and in all parameters than glutathione peroxidase between experimental groups and control group. In intestine, no significant difference was observed among groups, but oxidative responses were markedly different in all parameters among fish species. The histopathological analysis showed hyperplasia, fusion, and aneurism in the gills as well as degeneration, integration of villi, necrosis and erosion of the intestine. Our findings indicated that compare to pure TiO₂ NPs, exposure to transition metals-doped TiO₂ NPs induced oxidative stress and histopathological changes in both fish species.

Enantioselective bioaccumulation and metabolism of lactofen in zebrafish Danio rerio and combined effects with its metabolites

Pesticide residue in agricultural land might led to contamination of fresh waters, creating potential risks to organisms. The environmental behavior of herbicide lactofen may be enantioselective and the metabolites may have high toxic effects in individual or in combination. In this work, the enantioselective bioaccumulation, metabolism and toxic effects of lactofen and three metabolites (desethyl lactofen, acifluorfene, and amino acifluorfene) in zebrafish were investigated. The antioxidase activity (superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase), lipid peroxidation content were measured after exposure, and genetic toxicity was evaluated by a micronucleus test. The integrated biomarker response (IBR) method was used to determine the effects of the lactofen and its metabolites as well as their combinations. The metabolites were found to have higher toxic effects, and enantioselective toxic effects of lactofen and desethyl lactofen were observed, with the S-enantiomer more toxic. Based on IBR values, synergistic effects existed in combination of lactofen and desethyl lactofen, while antagonistic effects of lactofen with acifluorfene or amino acifluorfene were observed. Zebrafish were exposed to 0.5 mg L^-1 lactofen and the bioaccumulation were measured during a 15 d period followed by a 7 d elimination. The half-lives of the metabolites varied between 0.66 and 5.21 d, with bioconcentration factors (BCFs) in the range of 39-120. The metabolic pathways of R- and S-lactofen were found to be significantly different. The results supported our hypothesis. Therefore, the assessment of enantiomers and metabolites in individual or in combination should be taken into consideration in evaluating chiral pesticide risks.

Fipronil (Phenylpyrazole) induces hemato-biochemical, histological and genetic damage at low doses in common carp, Cyprinus carpio (Linnaeus, 1758)

This study was conducted to investigate the toxic effects of fipronil on common carp (Cyprinus carpio). The trial was performed in laboratory of Department of Life Sciences at the Islamia University of Bahawalpur, Punjab, Pakistan. Total of 72 fishes, with apparently no clinical signs were purchased from local fish hatchery near Bahawalpur, Punjab, Pakistan. After 2 weeks of acclimatization fish were divided into six groups in glass aquaria (each having 100 liters of water capacity) and treated with different concentrations of fipronil for 12 days: 0 mg/L-control group (A),0.02 mg/L (B),0.04 mg/L (C),0.06 mg/L (D),0.08 mg/L (E) and 0.10 mg/L (F). Blood samples were taken every 4 days for evaluation of hemato-biochemical parameters. Fish in high doses treated groups show severe abnormalities in clinical-hematological and biochemical parameters. At high dose in group E and F fish show clinical ailments such as convulsions, jerking, faintness, increase in operculum movement, body curvature and breathing difficulty. Erythrocyte count, hemoglobin, hematocrit were decreased significantly (P < 0.05) and mean corpuscular volume, total leukocyte count, neutrophils, monocytes, and lymphocytes were significantly increased. Biochemical parameters including urea, creatinine, cholesterol, triglyceride, glucose were significantly increased but albumin was significantly decreased. Nuclear and cellular abnormalities were also increased in high dose treated groups. Hence fipronil induces clinico-hematological and serum biochemical changes in common carp C. carpio.

Agrotóxicos e seus impactos na saúde humana e ambiental: uma revisão sistemática

RESUMO Atualmente, o Brasil é o maior consumidor de agrotóxicos do mundo. Diversos estudos comprovam os malefícios para a saúde humana e ambiental da exposição aos agrotóxicos. Realizou-se uma revisão sistemática no período de 2011 a 2017 acerca desse tema em bases de dados científicos. Foram incluídos 116 estudos que demonstraram o impacto negativo para a saúde humana e ambiental. É essencial a realização de estudos sobre os efeitos da exposição crônica e simultânea a diversos agrotóxicos, além de estudos sobre os nexos de determinação estrutural do uso dos venenos e suas consequências.

Modulatory effect of lycopene against carbofuran toxicity in African catfish, Clarias gariepinus

In the current study, African catfish, Clarias gariepinus, was exposed to a sublethal concentration of carbofuran (CF) to investigate its negative effects on biochemical and oxidative stress biomarkers. Also, the putative role of lycopene (LYC) administration in alleviating these negative effects was evaluated. Fish were divided into six groups in triplicates as follows: group I was without treatment, group II was orally administered corn oil, group III was orally administered 18 mg LYC/kg body weight, group IV was exposed to 0.121 mg CF/L, group V was orally administered 9 mg LYC/kg body weight and exposed to 0.121 mg CF/L, and group VI was orally administered 18 mg LYC/kg body weight and exposed to 0.121 mg CF/L for 4 weeks. At the end of this period, blood and tissue (liver and kidney) samples were collected and biochemical and oxidative stress biomarkers were analysed. Also, histopathological changes were determined. Carbofuran caused significant increments of glucose, cortisol, aspartic amino transferase, alanine amino transferase, cholesterol, urea, and creatinine; meanwhile, serum acetylcholinesterase, total protein, albumin, and total lipids were significantly reduced. Significant increments in hepatic and renal malondialdehyde (MDA) and superoxide dismutase (SOD) levels and marked reduction in hepatic and renal catalase (CAT), glutathione (GSH), and total antioxidant capacity (TAC) levels were observed in CF-exposed fish comparing to the control group. Treatment with LYC attenuated the CF-induced oxidative stress, and this improvement was more pronounced in fish received the high LYC dose (18 mg/kg body weight). Further, congestion of the central vein with infiltration of mononuclear inflammatory cells, vacuolar necrosis, and haemorrhage was observed in the livers of CF-exposed fish. Oral administration of LYC reduced behavioural changes and histopathological alterations. All the altered biochemical parameters and antioxidant biomarkers were also restored to be near the normal levels. The obtained results evoked that LYC administration alleviated the destructive effects of carbofuran and reduced its toxicity effect on African catfish.

Histopathological Effects on Gills of Nile Tilapia (Oreochromis niloticus, Linnaeus, 1758) Exposed to Pb and Carbon Nanotubes

The effect of heavy metal in fish has been the focus of extensive research for many years. However, the combined effect of heavy metals and nanomaterials is still a new subject that needs to be studied. The aim of this study was to examine histopathologic alterations in the gills of Nile tilapia (Oreochromis niloticus) to determine possible effects of lead (Pb), carbon nanotubes, and Pb+carbon nanotubes on their histological integrity, and if this biological system can be used as a tool for evaluating water quality in monitoring programs. For this, tilapia were exposed to Pb, carbon nanotubes and Pb+carbon nanotubes for 4 days. The main alterations observed were epithelial structure, hyperplasia and displacement of epithelial cells, and alterations of the structure and occurrence of aneurysms in the secondary lamella. The most severe alterations were related to the Pb+carbon nanotubes. We conclude that the oxidized multi-walled carbon nanotubes enhanced the acute lead toxicity in Nile tilapias. This work draws attention to the implications of carbon nanomaterials released in the aquatic environment and their interaction with classical pollutants.