Influence of sublethal doses of acetamiprid and halosulfuron-methyl on metabolites of zebra fish (Brachydanio rerio)

Insight of neonicotinoid insecticides: Exploring exposure, mechanisms in non-target organisms, and removal technologies

Neonicotinoid insecticides (NEOs) have garnered global attention due to their selective toxicity to insects and minimal impact on mammals. However, growing concerns about their extensive use and potential adverse effects on the ecological environment and non-target organisms necessitate further investigation. This study utilized bibliometric tools to analyze Web of Science data from 2003 to 2024, elucidating the current research landscape, identifying key research areas, and forecasting future trends related to NEOs. This paper provides an in-depth analysis of NEO exposure in non-target organisms, including risk assessments for various samples and maximum residue limits established by different countries. Additionally, it examines the impacts and mechanisms of NEOs on non-target organisms. Finally, it reviews the current methods for NEO removal and degradation. This comprehensive analysis provides valuable insights for regulating NEO usage and addressing associated exposure challenges.

Conjoint transcriptomics and metabolomics analyses provide insights into the toxicity of acetamiprid to Lethenteron reissneri larvae

The neonicotinoid pesticide acetamiprid has been widely used in agricultural pest control and was frequently detected in the water environment. There have been some studies of the toxic effects of acetamiprid on fish, but studies on aquatic lower vertebrates are still very limited. As a primitive jawless vertebrate, Lethenteron reissneri has a special position in evolution and is now listed as a national second level protected animal in China. The present study aimed to investigate the toxic effect of acetamiprid on the liver of L. reissneri larvae. A conjoint analysis of the transcriptomics and metabolomics was performed to determine the responses of L. reissneri larvae liver to acetamiprid at different concentrations (L for low concentration 25 mg/L and H for high concentration 100 mg/L). Even low concentrations of acetamiprid can cause significant liver damage to L. reissneri larvae in a short period. In omics analyses, 2141 differentially expressed genes (DEGs) and 183 differentially abundant metabolites (DAMs) were identified in the H/Control group, and 229 DEGs and 144 DAMs were identified in the L/C group. Correlation analyses revealed acetamiprid affected the metabolic pathways of L. reissneri larvae liver such as the glycerophospholipid metabolism and arachidonic acid metabolism. This study not only enriches the basis for understanding the toxic effect of acetamiprid exposure to L. reissneri larvae liver and provides more information on the breeding and conservation of L. reissneri, but also further causes attention on toxicity risk from acetamiprid to aquatic lower vertebrate species.

Characterization of near-field temporal and spatial variations of pesticide residues using honeybee specimens as bio-sensing matrices

This study was prompted by recent reports of the ubiquity of neonicotinoids (neonics) in environment and the likelihood of exposures and health hazards to non-target organisms. We aimed to quantify neonics levels in time- and location-match pollen and nectar samples foraged by honeybees (Apis mellifera) and characterized the temporal and spatial variations using a relative potency factor method to determine the total neonic levels, expressed as the imidacloprid-adjusted total neonics, IMIRPF (ng/g). Six pairs of pollen and nectar samples, a total of twelve samples, were collected from each of the thirty-two experimental hives during the active foraging months of March, April, and June and analyzed for eight neonics. We found 59% and 64% of pollen and nectar contained at least one neonic, respectively. Among those neonic-detected pollen and nectar samples, 45% and 77% of them contained more than one neonic, respectively. Imidacloprid and acetamiprid in pollen and clothianidin and thiamethoxam in nectar accounted for 60% and 83% detection, respectively. The highest 3-month average of IMIRPF in pollen (6.56 ng/g) and nectar (11.19 ng/g) were detected in a location with the predominant production of citrus fruit. The temporal and spatial variations of IMIRPF levels demonstrated the robustness of using paired pollen and nectar data as the bio-sensing matrices to facilitate the assessment of near-field exposure to total neonics and the delineation of risks.

Neonicotinoids as emerging contaminants in China's environment: a review of current data

Neonicotinoids (NEOs), the most widely used class of insecticides, are pervasive in the environment, eliciting concerns due to their hydrophilicity, persistence, and potential ecological risks. As the leading pesticide consumer, China shows significant regional disparities in NEO contamination. This review explores NEO distribution, sources, and toxic risks across China. The primary NEO pollutants identified in environmental samples include imidacloprid, thiamethoxam, and acetamiprid. In the north, corn cultivation represents the principal source of NEOs during wet seasons, while rice dominates in the south year-round. The high concentration levels of NEOs have been detected in the aquatic environment in the southern regions (130.25 ng/L), the urban river Sects. (157.66 ng/L), and the downstream sections of the Yangtze River (58.9 ng/L), indicating that climate conditions and urban pollution emissions are important drivers of water pollution. Neonicotinoids were detected at higher levels in agricultural soils compared to other soil types, with southern agricultural areas showing higher concentrations (average 27.21 ng/g) than northern regions (average 12.77 ng/g). Atmospheric NEO levels were lower, with the highest concentration at 1560 pg/m3. The levels of total neonicotinoid pesticides in aquatic environments across China predominantly exceed the chronic toxicity ecological threshold of 35 ng/L, particularly in the regions of Beijing and the Qilu Lake Basin, where they likely exceed the acute toxicity ecological threshold of 200 ng/L. In the future, efforts should focus on neonicotinoid distribution in agriculturally developed regions of Southwest China, while also emphasizing their usage in urban greening and household settings.

Bioconcentration, oxidative stress and molecular mechanism of the toxic effect of acetamiprid exposure on Xenopus laevis tadpoles

Acetamiprid is a neonicotinoid commonly detected in aquatic ecosystems, with residual concentrations of up to 0.41 mg/L in surface water, posing a threat to the health of nontarget aquatic organisms. However, studies on the potential toxicity and underlying mechanisms of action of acetamiprid on nontarget aquatic organisms are limited. This study investigated the acute and short-term toxicity of acetamiprid to Xenopus laevis tadpoles. A 96-h acute toxicity test determined the LC50 of acetamiprid to be 32.1 mg/L. After 28 days of exposure to 1/10 and 1/100 LC50 concentrations, tadpole samples were collected for bioconcentration elimination analysis, biochemical analyses, transcriptomics, and metabolomics studies to comprehensively evaluate the toxic effects of acetamiprid and its underlying mechanisms. The results, indicating bioconcentration factors (BCFs) < 1, suggest that acetamiprid has a low bioconcentration in tadpoles. Additionally, oxidative stress was observed in treated Xenopus laevis tadpoles. Transcriptomic and nontargeted metabolomic analyses identified 979 differentially expressed genes (DEGs) and 95 differentially metabolites in the 0.321 mg/L group. The integrated analysis revealed that disruption of purine and amino acid metabolic pathways potentially accounts for acetamiprid-induced toxic effects in tadpoles. The disruptive effects of acetamiprid on valine, leucine and isoleucine biosynthesis; and aminoacyl-tRNA biosynthesis metabolic pathways in tadpoles were validated through targeted metabolomics analysis. These findings are crucial for assessing the risk of acetamiprid to nontarget aquatic organisms.

Toxicological approaches as tool to assess the effects of a mixture of photocatalytic degradation products originated from the unregulated neonicotinoid acetamiprid employing a terrestrial organism (Eisenia andrei)

Acetamiprid (ACT) has been detected in several water sources in Latin America. The presence of its degradation products in the environment is not negligible and transformation products (TPs) significantly contribute to environmental health risks. Although advanced oxidative processes are promising for the treatment of this neocotinoid, effects of these are still unknown. In this context, the effects of a mixture of photocatalytic degradation products resulting from an ACT treatment for 90 min employing TiO2/UV on cytotoxicity and oxidative stress parameters in Eisenia andrei earthworms in acute and chronic experiments using typical Latin American soil were assessed. Acute contact tests were performed (72 h) using a filter paper moistened with an ACT solution and a chronic test was performed using Oxisoil (200 g) moistened with an ACT solution for 45 days. Catalase (CAT) and glutathione-S-transferase (GST) activities, reduced glutathione (GSH) levels and cytotoxicity (cellular eleocyte and amoebocyte assessments) were investigated. Over 75 % of ACT was degraded within the first 15 min of treatment, with levels below the limit of detection after 60 min. The acute test revealed greater cytotoxic effects associated with the effluents treated for T0 and T15 min, with decreased cell density noted after 48 h of exposure, in addition to CAT induction (in all treatments) and GST induction following T0, T15 and T90 min exposures. Concerning the chronic assay, decreases in cell density (T0, T15, T60 and T90 min) and viability (T0, T60 and T90 min) were observed after 45 days, in addition to induced CAT activity following T0, T15 and T60 exposures and GST induction following the T60 min exposure. Reduced glutathione levels were unaltered, comprising the least sensitive biomarker among the investigated parameters to the treated effluent exposures. The mixture of ACT degradation products can cause toxic effects to non-target organisms, despite parent compound degradation, alerting for the need for ecotoxicological tests to prove decreased effluent toxicity, in addition to the improvement of degradation techniques.

Combined toxicity of acetamiprid and cadmium to larval zebrafish (Danio rerio) based on metabolomic analysis

Emerging contaminants, such as neonicotinoid pesticide acetamiprid (Ace), are frequently detected in the water environment, which can interact with existing heavy metal cadmium (Cd) to produce unpredicted influence. Limited studies have evaluated the effects of multiple pollutant exposures on aquatic animals. Here, we characterized the joint toxicity of Ace and Cd exposure to zebrafish (Danio rerio). The results revealed that Cd and its combined exposure with Ace had an inhibitory effect on the growth of larval zebrafish and induced morphological defects. Combined exposure to high doses of Ace and Cd could significantly reduce the levels of TG, glucose, and pyruvate in larval zebrafish. Untargeted metabolomics revealed that Cd treatment (285) produced more differentially expressed metabolites (DEMs) than Ace treatment (115), and combined treatment produced the most DEMs (294). The KEGG pathway enrichment analysis showed that they could disrupt riboflavin metabolism, amino acid metabolism, and glycolipid metabolism in the larvae of D. rerio. ELISA showed that VB2, FMN, and FAD levels were significantly increased. In addition, gene expression analysis exhibited that the mRNA levels of essential genes related to glycolipid metabolism were substantially affected, such as PK, PEPckc, PPAR-α, and FABP6. Furthermore, targeted amino acid metabolomics confirmed that both single exposure to Cd and combined exposure to Ace and Cd altered the levels of amino acids in larvae, including ALA, ARG, MET, PRO, TYR, VAL, GLY, ORN, and PHE. Taken together, exposure to Ace and Cd, alone or in combination, exerted harmful effects on the individual development, riboflavin metabolism, glycolipid metabolism, and amino acid metabolism disorder of D. rerio. These findings highlighted that more attention should be paid to the compound toxicity of chemical mixtures to aquatic organisms.

Novel Pilot-Scale Photocatalytic Nanofiltration Reactor for Agricultural Wastewater Treatment

Nowadays, the increased agro-industrial activities and the inability of traditional wastewater treatment plants (WWTPs) to eliminate recalcitrant organic contaminants are raising a potential worldwide risk for the environment. Among the various advanced water treatment technologies that are lately proposed for addressing this challenge, the development and optimization of an innovative hybrid photocatalytic nanofiltration reactor (PNFR) prototype emerges as a prominent solution that achieves synergistic beneficial effects between the photocatalytic degradation activity and size exclusion capacity for micropollutant molecules. Both these features can be contemporarily endued to a multitude of membrane monoliths. The physicochemical and the photoinduced decontamination properties of the titania materials were firstly determined in the powder form, and subsequently, the structural and morphological characterization of the obtained titania-modified membrane monoliths were accomplished. The PNFR unit can operate at high water recovery and low pressures, exhibiting promising removal efficiencies against Acetamiprid (ACT) and Thiabendazole (TBZ) pesticides and achieving the recycling of 15 m³/day of real agro-wastewater. The obtained results are very encouraging, demonstrating the integration of titania photocatalysts in a photocatalytic membrane reactor as a feasible technological solution for the purification of agricultural wastewater.

Environmental occurrence, toxicity concerns, and biodegradation of neonicotinoid insecticides

Neonicotinoids (NEOs) are fourth generation pesticides, which emerged after organophosphates, pyrethroids, and carbamates and they are widely used in vegetables, fruits, cotton, rice, and other industrial crops to control insect pests. NEOs are considered ideal substitutes for highly toxic pesticides. Multiple studies have reported NEOs have harmful impacts on non-target biological targets, such as bees, aquatic animals, birds, and mammals. Thus, the remediation of neonicotinoid-sullied environments has gradually become a concern. Microbial degradation is a key natural method for eliminating neonicotinoid insecticides, as biodegradation is an effective, practical, and environmentally friendly strategy for the removal of pesticide residues. To date, several neonicotinoid-degrading strains have been isolated from the environment, including Stenotrophomonas maltophilia, Bacillus thuringiensis, Ensifer meliloti, Pseudomonas stutzeri, Variovorax boronicumulans, and Fusarium sp., and their degradation properties have been investigated. Furthermore, the metabolism and degradation pathways of neonicotinoids have been broadly detailed. Imidacloprid can form 6-chloronicotinic acid via the oxidative cleavage of guanidine residues, and it is then finally converted to non-toxic carbon dioxide. Acetamiprid can also be demethylated to remove cyanoimine (=N-CN) to form a less toxic intermediate metabolite. A few studies have discussed the neonicotinoid toxicity and microbial degradation in contaminated environments. This review is focused on providing an in-depth understanding of neonicotinoid toxicity, microbial degradation, catabolic pathways, and information related to the remediation process of NEOs. Future research directions are also proposed to provide a scientific basis for the risk assessment and removal of these pesticides.

Insight into the toxic effects, bioconcentration and oxidative stress of acetamiprid on Rana nigromaculata tadpoles

Pesticide pollution has been identified as a factor in the amphibian population decrease. Acetamiprid is a common neonicotinoid pesticide that poses a risk to amphibians due to its high water solubility and inability to be digested. However, there is little research on acetamiprid's toxicity in amphibians, particularly on its biochemical toxic effects. In this study, we investigated the acute toxicity, bioenrichment-elimination, biochemical parameters and metabolism of acetamiprid in Rana nigromaculata tadpoles. The results indicated that acetamiprid is harmful to Rana nigromaculata tadpoles, with an LC₅₀ = 18.49 mg L^-1 of 96 h for acute toxicity. Acetamiprid showed rapid accumulation and low bioconcentration levels in tadpoles, with bioconcentration factors (BCFs) < 1. In the elimination process, the concentration of acetamiprid decreased rapidly, with the elimination half-life t_1/2 values < 1 d. Additionally, oxidative stress was observed in tadpoles, with biochemical parameters such as superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) being significantly altered. Nontargeted metabolomics revealed significant changes in biomolecules such as lipids, organic acids and nucleotides in tadpoles, and these metabolites influence pathways including serine and threonine metabolism, histidine metabolism, linoleic acid metabolism and sphingolipid metabolism. These results indicate that acetamiprid caused toxic effects on Rana nigromaculata tadpoles. Our study provides a better understanding of the fate and risk of acetamiprid in amphibians, as well as guidelines for its rational use.

Metabolomics analysis of the potential toxicological mechanisms of diquat dibromide herbicide in adult zebrafish (Danio rerio) liver

Although diquat is a widely used water-soluble herbicide in the world, its sublethal adverse effects to fish have not been well characterised. In this study, histopathological examination and biochemical assays were applied to assess hepatotoxicity and combined with gas chromatography-mass spectrometry (GC-MS)-based metabolomics analysis to reveal overall metabolic mechanisms in the liver of zebrafish (Danio rerio) after diquat exposure at concentrations of 0.34 and 1.69 mg·L^-1 for 21 days. Results indicated that 1.69 mg·L^-1 diquat exposure caused cellular vacuolisation and degeneration with nuclear abnormality and led to the disturbance of antioxidative system and dysfunction in the liver. No evident pathological injury was detected, and changes in liver biochemistry were not obvious in the fish exposed to 0.34 mg·L^-1 diquat. Multivariate statistical analysis revealed differences between profiles obtained by GC-MS spectrometry from control and two treatment groups. A total of 17 and 22 metabolites belonging to different classes were identified following exposure to 0.34 and 1.69 mg·L^-1 diquat, respectively. The metabolic changes in the liver of zebrafish are mainly manifested as inhibition of energy metabolism, disorders of amino acid metabolism and reduction of antioxidant capacity caused by 1.69 mg·L^-1 diquat exposure. The energy metabolism of zebrafish exposed to 0.34 mg·L^-1 diquat was more inclined to rely on anaerobic glycolysis than that of normal zebrafish, and interference effects on lipid metabolism were observed. The metabolomics approach provided an innovative perspective to explore possible hepatic damages on fish induced by diquat as a basis for further research.

Neuro-hepatopathological changes in juvenile Oreochromis niloticus exposed to sublethal concentrations of commercial herbicides

The current study estimates the impact of different common herbicides on antioxidant defenses and histological structure of liver and spinal cord of juvenile tilapia. Eighty-four fish were divided into seven groups: group 1 fish acted as controls and the remaining fish were exposed to sublethal concentrations of acetochlor, bispyribac-sodium, bentazon, bensulfuron-methyl, halosulfuron-methyl, or quinclorac at sublethal concentrations 2.625, 0.800, 36.00, 2.50, 1.275, and 11.250 mg/l, respectively, for 96 h. Antioxidant parameters changed in response to some test herbicides and the greatest effects were caused by exposure to acetochlor and quinelorac for all antioxidant measurements. Prominent histological changes in liver tissue included loss of liver architecture and the appearance of fatty liver cells, necrotic areas, foci of leukocytic infiltration and many apoptotic cells. The most obvious changes in the spinal cord in all treated fish were degradation of myelinated white matter fibers with the emergence of empty spaces, large aggregation of pyknotic neuroglial nuclei, and damaged areas in the dorsal horn of gray matter. Collectively, the harmful effect of tested herbicides on antioxidant capacity and significant alterations in histological structures of liver and spinal cord of Oreochromis niloticus.

Different cellular mechanism of imidacloprid and acetamiprid by a combined targeted lipidomics and metabolomics approach in Neuro-2a cells

As commonly used neonicotinoid insecticides for pest control, imidacloprid (IMI) and acetamiprid (ACE) posed neurotoxicity effects on living organisms. However, researches of the differences in toxicity mechanism between these two neonicotinoid insecticides are still limited. In this study, different cellular metabolism perturbations and redox homeostasis damages induced by IMI and ACE exposure in Neuro-2a cells were investigated. Distinct elevation of lactate dehydrogenase (LDH) activity and caspase 7 level demonstrated the influences on necrosis and apoptosis. There were 21 and 12 metabolites screened out as potential biomarkers after IMI and ACE exposure, including lipids and amino acids. Remarkable decrease of lipid hydroperoxides (LOOH) and increase of reactive oxygen species (ROS) generation were found only in the ACE20 group. Interference with glutathione metabolism pathway was further validated by detecting GPx (glutathion peroxidase), GSH (reduced glutathione) and GSSG (oxidized glutathione) levels. Taken together, the metabolic interferences and oxidative damages in ACE20 group were significantly different from the other three exposure groups. These results help to explore the toxicity mechanism of neonicotinoid insecticides from multiple perspectives. This study provides scientific basis for evaluating toxicity of different neonicotinoid insecticides.

Oxidative stress and metal homeostasis alterations in Danio rerio (zebrafish) under single and combined carbamazepine, acetamiprid and cadmium exposures

Contaminants of emerging concern (CEC) are routinely detected in aquatic environments, especially pharmaceuticals, such as carbamazepine (CBZ), and neonicotinoid pesticides, like acetamiprid (ACT). CECs can interact with each other and with other legislated contaminants like Cd, resulting in unknown effects. Most studies evaluate only the effects of single contaminant exposures on aquatic biota. Therefore, the aim of the present study was to assess the effects of both single and combined CBZ, ACT and Cd exposures on zebrafish brain and liver oxidative stress parameters and metal homeostasis. The biomarkers catalase (CAT), glutathione-S-transferase (GST), total thiols (TOT), metallothionein (MT) and malondialdehyde (MDA) and the essential elements Ca, Cu, K, Na, Mg, Mn and Zn were evaluated after 96-hour static exposures. CBZ, ACT and Cd single (brain and liver) and combined (liver) treatments resulted in oxidative effects in both fish organs, also leading to metal (Ca, Mg, K, Mn, Zn and Cu) homeostasis alterations. ACT exposure resulted in the greatest adverse effects in the brain, while CBZ was the cause of major element homeostasis and oxidative stress alterations in the liver. Lower LPO levels were observed in the combined treatments compared to single treatments, suggesting interactions and contaminant effect attenuation. This study is the first to evaluate the initial effects of combined CBZ, ACT and Cd exposures in zebrafish, paving the way for further investigations concerning other biomarkers during longer exposure times.

Using metabolomic profiling to inform use of surrogate species in ecological risk assessment practices

The U.S. EPA frequently uses avian or fish toxicity data to set protective standards for amphibians in ecological risk assessments. However, this approach does not always adequately represent aquatic-dwelling and terrestrial-phase amphibian exposure data. For instance, it is accepted that early life stage tests for fish are typically sensitive enough to protect larval amphibians, however, metamorphosis from tadpole to a terrestrial-phase adult relies on endocrine cues that are less prevalent in fish but essential for amphibian life stage transitions. These differences suggest that more robust approaches are needed to adequately elucidate the impacts of pesticide exposure in amphibians across critical life stages. Therefore, in the current study, methodology is presented that can be applied to link the perturbations in the metabolomic response of larval zebrafish (Danio rerio), a surrogate species frequently used in ecotoxicological studies, to those of African clawed frog (Xenopus laevis) tadpoles following exposure to three high-use pesticides, bifenthrin, chlorothalonil, or trifluralin. Generally, D. rerio exhibited greater metabolic perturbations in both number and magnitude across the pesticide exposures as opposed to X. laevis. This suggests that screening ecological risk assessment surrogate toxicity data would sufficiently protect amphibians at the single life stage studied but care needs to be taken to understand the suite of metabolic requirements of each developing species. Ultimately, methodology presented, and data gathered herein will help inform the applicability of metabolomic profiling in establishing the risk pesticide exposure poses to amphibians and potentially other non-target species.

The Role of the Ecotoxicology Applied to Seafood as a Tool for Human Health Risk Assessments Concerning Polycyclic Aromatic Hydrocarbons

Background: Polycyclic aromatic hydrocarbons (PAHs) are persistent pollutants routinely detected in aquatic ecosystems. It is, therefore, necessary to assess the link between deleterious marine biota PAH effects, especially in commercialized and consumed animals, environmental health status, and potential human health risks originating from the consumption of contaminated seafood products. Thus, this review seeks to verify the relationships of ecotoxicological studies in determining effect and safety concentrations on animals routinely consumed by humans. Methods: A total of 52 published studies between 2011 and 2021, indexed in three databases, were selected following the PICO methodology, and information on test animals, evaluated PAH, and endpoints were extracted. Results: Benzo(a)pyrene and phenanthrene were the most investigated PAHs in terms of biomarkers and test organisms, and mussels were the most evaluated bioindicator species, with an emphasis on reproductive responses. Furthermore, despite the apparent correlation between environmental PAH dynamics and effects on aquatic biota and human health, few assessments have been performed in a multidisciplinary manner to evaluate these three variables together. Conclusions: The links between human and environmental sciences must be strengthened to enable complete and realistic toxicity assessments as despite the application of seafood assessments, especially to mussels, in bioassays, the connection between toxicological animal responses and risks associated with their consumption is still understudied.

Multi-omic approach to evaluate the response of gilt-head sea bream (Sparus aurata) exposed to the UV filter sulisobenzone

Sulisobenzone (BP-4) is one of the benzophenone type UV filters most frequently detected in aquatic ecosystems. As a suspected endocrine disrupting compound, scarce information is available yet about other molecular effects and its mechanism of action. Here, we used an integrated transcriptomic and metabolomic approach to improve the current understanding on the toxicity of BP-4 towards aquatic species. Gilt-head sea bream individuals were exposed at environmentally relevant concentrations (10 μg L^-1) for 22 days. Transcriptomic analysis revealed 371 differentially expressed genes in liver while metabolomic analysis identified 123 differentially modulated features in plasma and 118 in liver. Integration of transcriptomic and metabolomic data showed disruption of the energy metabolism (>10 pathways related to the metabolism of amino acids and carbohydrates were impacted) and lipid metabolism (5 glycerophospholipids and the expression of 3 enzymes were affected), suggesting oxidative stress. We also observed, for the first time in vivo and at environmental relevant concentrations, the disruption of several enzymes involved in the steroid and thyroid hormones biosynthesis. DNA and RNA synthesis was also impacted by changes in the purine and pyrimidine metabolisms. Overall, the multiomic workflow presented here increases the evidence on suspected effects of BP-4 exposure and identifies additional modes of action of the compounds that could have been overlooked by using single omic approaches.

The enantioselective toxicity and oxidative stress of dinotefuran on zebrafish (Danio rerio)

Dinotefuran is a widely used neonicotinoid pesticides in agriculture and it has certain ecological toxicity to aquatic organisms. Studies on the potential toxicological effects of dinotefuran on fish are limited. In the present study, 96 h acute toxicity test indicated that enantiomers of R-(-)-dinotefuran had a greater toxic effect than Rac-dinotefuran on zebrafish, and S-(+)-dinotefuran was the least. In chronic assay, R-(-)-dinotefuran exerted more effects on the development of zebrafish than S-(+)-dinotefuran, and dinotefuran also had enantioselective effect on oxidative stress. Significant changes were observed in the superoxide dismutase (SOD), glutathione S-transferase (GST) and acetylcholinesterase (AChE) activities and malondialdehyde (MDA) contents, which demonstrated dinotefuran induced oxidative stress in zebrafish. Besides, through an ultra-performance liquid chromatography quadrupole-TOF mass spectrometry (UPLC-Q-TOF-MS)-based metabolomics method was used to evaluate the enantioselectivity of dinotefuran enantiomers in zebrafish. The results indicated that R-(-)-dinotefuran caused greater disturbances of endogenous metabolites. Phenylalanine metabolic pathways, glycine, serine and threonine metabolic pathways are only involved in zebrafish exposed to R-(-)-dinotefuran; whereas phenylalanine, tyrosine and tryptophan biosynthesis was only involved in zebrafish exposed to S-(+)-dinotefuran. This study provides a certain reference value for assessing the environmental risks of dinotefuran enantiomers to aquatic organisms, and has practical significance for guiding the ecologically and environmentally safety use of dinotefuran.

Ameliorative role of ascorbic acid on the oxidative stress and genotoxicity induced by acetamiprid in Nile tilapia (Oreochromis niloticus)

On juveniles of Oreochromis niloticus, the protective potential of ascorbic acid (Asc) against oxidative stress and genotoxicity induced by acetamiprid (Aceta) sub-lethal concentrations was investigated in this study. Fishes were divided into six groups and exposed to either Asc (50 ppm), 10 and 20 ppm Aceta, 10 ppm (Aceta)+Asc, 20 ppm (Aceta)+Asc, or the unexposed control group. Superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities and their transcripts were assessed. DNA damage in erythrocytes, hepatocytes, and gill cells, in addition to the mitotic index (MI), and the existence of erythrocytic nuclear abnormalities (ENAs) were performed. The results showed that concentrations of Aceta (10 and 20 ppm) induced oxidative stress by altering the antioxidant enzyme activities and transcripts. There were genotoxic effects of Aceta exposure showed by the significant (P < 0.05) increase in DNA-damaged cells and ENA, meanwhile a decrease in MI. Co-exposure with Asc showed significant alleviations of oxidative status and genotoxicity. Thus, results suggest that Asc-combined exposure could be the effective treatment against Aceta-induced oxidative stress accompanied with genotoxicity in O. niloticus.

Integrated non-targeted lipidomics and metabolomics analyses for fluctuations of neonicotinoids imidacloprid and acetamiprid on Neuro-2a cells

Neonicotinoid insecticides are widely used for pest control. However, they are highly water-soluble and easily ingested by organisms, posing potential health risks. In this study, cytotoxicity evaluations of imidacloprid and acetamiprid were conducted in Neuro-2a cells by obtaining their half maximal inhibitory concentration (IC₅₀ values) (1152.1 and 936.5 μM, respectively). The toxic effects at the IC₁₀ and IC₂₀ on cell metabolism were determined by integrated non-targeted lipidomics and metabolomics analyses. Changes in the concentration of acetamiprid caused the most drastic perturbations of metabolism in Neuro-2a cells. Altogether, the detected lipids were mainly attributed to triglyceride, phosphatidylcholine (PC), and diglyceride. These three categories of lipids accounted for more than 67% of the sum in Neuro-2a cells. A total of 14 lipids and other 40 metabolites were screened as differential metabolites based on multivariate data analysis, and PCs were most frequently observed with a proportion of 25.9%. The results demonstrated that lipid metabolism should be paid considerable attention after imidacloprid and acetamiprid exposure. Pathway analysis showed that the metabolisms of glycerophospholipid, sphingolipid, and glutathione were the dominant pathways that were interfered. The present study is the first to investigate the cellular toxic mechanisms after separate imidacloprid and acetamiprid exposure by using lipidomics and metabolomics simultaneously. This research also provides novel insights into the evaluation of the ecological risk of imidacloprid and acetamiprid and contribute to the study of toxicity mechanism of these neonicotinoid insecticides to animals and humans in the future.

Chronic effects of a binary insecticide Acer 35 EC on Nile tilapia Oreochromis niloticus through a multi-biomarker approach

Acer 35 EC is a widely used insecticide (a binary mixture of lambda-cyhalothrin and acetamiprid) in pest control in many West African countries, particularly in the cotton culture in north Benin. The aim of this study was to investigate the chronic effects of Acer 35 EC on Nile tilapia Oreochromis niloticus juveniles using a multi-biomarker approach under laboratory conditions. For this purpose, fish were exposed to sublethal concentrations of Acer 35 EC (0, 1 and 10% of LC₅₀- 96 h value). After 28 and 56 days of exposure, several biomarkers were measured in males and females including enzymatic activities related to detoxification and oxidative stress, neurotoxicity and immune responses, sex steroid hormones (testosterone, 17β-estradiol and 11-keto-testosterone) and histological alterations of liver, kidney and gonads. An Integrated Biomarker Response (IBR) was then calculated. The results showed a reduction of cholinesterase activity in muscles, and intercellular superoxide anion production in both sexes. Female steroidogenesis and gametogenesis were affected, especially testosterone levels and oocyte growth. More alterations were observed in liver after exposure to Acer 35 EC. In both sexes, IBR values were higher after 56 days than after 28 days of exposure. In conclusion, based on a large set of biomarkers and IBR values, the chronic exposure to low doses of insecticide Acer 35 EC seems to impair different physiological functions in Nile tilapia juveniles on a time-dependent manner, with a stronger impact on females than on males.

Mechanisms of halosulfuron methyl pesticide biosorption onto neem seeds powder

The current investigation was designed to remove halosulfuron methyl from aqueous media by means of neem seed powder (NSP) in batch modes. Characterizations of NSP were carried out by using EDX, SEM, FTIR, point of zero charge and surface analysis. Optimum operation conditions were scrutinized by studying the influence of different factors like solution pH, dose of NSP, contact time, initial halosulfuron methyl concentration and temperature. Result indicates the dependency of the removal of halosulfuron methyl on solution pH and maximal removal (54%) was achieved in acidic medium (i.e. pH 3.0). To identify the chemical surface of NSP, point of zero charge of NSP was determined and was found to be 6.5 which imply that the surface of NSP is positively charged below pH 6.6 and favored the anionic sorption. Kinetics of halosulfuron methyl were demonstrated well by pseudo second order due to highest R2 (0.99) owing to the nearness between experimental and calculated sorption capacities. Isotherm results imply that Langmuir was found to the principal model to explain the removal of halosulfuron methyl and maximum monolayer sorption capacity was determined to be 200 mg g-1. Thermodynamic parameters like ΔH°, ΔG° and ΔS° were calculated from van't Hoff plot and were found negative which suggest that removal of halosulfuron methyl is exothermic and spontaneous at low temperature. These outcomes insinuate that neem seed power may be a valuable, inexpensive and ecofriendly biosorbent for the removal of pesticides.

Low concentration acetamiprid-induced oxidative stress hinders the growth and development of silkworm posterior silk glands

Acetamiprid is a new type of nicotinic insecticide that is widely used in pest control. Its environmental residues may cause silkworm cocooning disorder. In this study, silkworms that received continuous feeding of low concentration acetamiprid (0.15 mg/L) showed significantly decreased silk gland index and cocooning rate. Gene expression profiling of posterior silk glands (PSGs) revealed that the differentially expressed genes were significantly enriched in oxidative stress-related signal pathways with significant up-regulation. The contents of both H₂O₂ and MDA were increased, along with significantly elevated SOD and CAT activities, all of which reached maximal values at 48 h when H₂O₂ and MDA's contents were 10.46 and 7.98 nmol/mgprot, respectively, and SOD and CAT activities were 5.51 U/mgprot and 33.48 U/gprot, respectively. The transcription levels of antioxidant enzyme-related genes SOD, Mn-SOD, CuZn-SOD, CAT, TPX and GPX were all up-regulated, indicating that exposure to low concentration acetamiprid led to antioxidant response in silkworm PSG. The key genes in the FoxO/CncC/Keap1 signaling pathway that regulates antioxidant enzyme activity, FoxO, CncC, Keap1, NQO1, HO-1 and sMaf were all up-regulated during the whole process of treatment, with maximal values being reached at 72 h with 2.91, 1.46, 1.82, 2.52, 2.32 and 4.01 times of increases, respectively. These results demonstrate that exposure to low concentration acetamiprid causes oxidative stress in silkworm PSG, which may be the cause of cocooning disorder in silkworm. Our study provides a reference for the safety evaluation of environmental residues of acetamiprid on non-target insects.

Blood Will Tell: What Hematological Analyses Can Reveal About Fish Welfare

Blood analyses provide substantial information about the physiological aspects of animal welfare assessment, including the activation status of the neuroendocrine and immune system, acute and long-term impacts due to adverse husbandry conditions, potential diseases, and genetic predispositions. However, fish blood is still not routinely analyzed in research or aquaculture for the assessment of health and/or welfare. Over the years, the investigative techniques have evolved from antibody-based or PCR-based single-parameter analyses to now include transcriptomic, metabolomic, and proteomic approaches and from hematological observations to fluorescence-activated blood cell sorting in high-throughput modes. The range of testing techniques established for blood is now broader than for any other biogenic test material. Evaluation of the particular characteristics of fish blood, such as its cell composition, the nucleation of distinct blood cells, or the multiple isoforms of certain immune factors, requires adapted protocols and careful attention to the experimental designs and interpretation of the data. Analyses of fish blood can provide an integrated picture of the endocrine, immunological, reproductive, and genetic functions under defined environmental conditions and treatments. Therefore, the scarcity of high-throughput approaches using fish blood as a test material for fish physiology studies is surprising. This review summarizes the wide range of techniques that allow monitoring of informative fish blood parameters that are modulated by different stressors, conditions, and/or treatments. We provide a compact overview of several simple plasma tests and of multiparametric analyses of fish blood, and we discuss their potential use in the assessment of fish welfare and pathologies.

Ecological and toxicological assessments of anthropogenic contaminants based on environmental metabolomics

There has long been a great concern with growing anthropogenic contaminants and their ecological and toxicological effects on living organisms and the surrounding environment for decades. Metabolomics, a functional readout of cellular activity, can capture organismal responses to various contaminant-related stressors, acquiring direct signatures to illustrate the environmental behaviours of anthropogenic contaminants better. This review entails the application of metabolomics to profile metabolic responses of environmental organisms, e.g. animals (rodents, fish, crustacean and earthworms) and microorganisms (bacteria, yeast and microalgae) to different anthropogenic contaminants, including heavy metals, nanomaterials, pesticides, pharmaceutical and personal products, persistent organic pollutants, and assesses their ecotoxicological impacts with regard to literature published in the recent five years. Contaminant-induced metabolism alteration and up/down-regulation of metabolic pathways are revealed in typical organisms. The obtained insights of variations in global metabolism provide a distinct understanding of how anthropogenic contaminants exert influences on specific metabolic pathways on living organisms. Thus with a novel ecotechnique of environmental metabolomics, risk assessments of anthropogenic contaminants are profoundly demonstrated.

Cross-Taxa Distinctions in Mechanisms of Developmental Effects for Aquatic Species Exposed to Trifluralin

Standard ecological risk assessment practices often rely on larval and juvenile fish toxicity data as representative of the amphibian aquatic phase. Empirical evidence suggests that endpoints measured in fish early life stage tests are often sufficient to protect larval amphibians. However, the process of amphibian metamorphosis relies on endocrine cues that affect development and morphological restructuring and are not represented by these test endpoints. The present study compares developmental endpoints for zebrafish (Danio rerio) and the African clawed frog (Xenopus laevis), 2 standard test species, exposed to the herbicide trifluralin throughout the larval period. Danio rerio were more sensitive and demonstrated a reduction in growth measurements with increasing trifluralin exposure. Size of X. laevis at metamorphosis was not correlated with exposure concentration; however, time to metamorphosis was delayed relative to trifluralin concentration. Gene expression patterns indicate discrepancies in response by D. rerio and X. laevis, and dose-dependent metabolic activity suggests that trifluralin exposure perturbed biological pathways differently within the 2 species. Although many metabolites were correlated with exposure concentration in D. rerio, nontargeted hepatic metabolomics identified a subset of metabolites that exhibited a nonmonotonic response to trifluralin exposure in X. laevis. Linking taxonomic distinctions in cellular-level response with ecologically relevant endpoints will refine assumptions used in interspecies extrapolation of standard test effects and improve assessment of sublethal impacts on amphibian populations. Environ Toxicol Chem 2020;39:1797-1812. Published 2020. This article is a US government work and is in the public domain in the USA.

Toxicity of the herbicides used on herbicide-tolerant crops, and societal consequences of their use in France

In France, the implementation of mutant herbicide-tolerant crops and the use of the related herbicides - sulfonylureas and imidazolinones - have triggered a strong societal reaction illustrated by the intervening actions of environmentalist groups illegally mowing such crops. Trials are in progress, and therefore should be addressed the questions of the environmental risks and the toxicity of these herbicides for the animals and humans consuming the products derived from these plants. Regulatory authorities have allowed these mutant and herbicide-tolerant plants arguing that the herbicides against which they resist only target an enzyme found in 'weeds' (the acetolactate synthase, ALS), and that therefore all organisms lacking this enzyme would be endowed with immunity to these herbicides. The toxicological literature does not match with this argument: 1) Even in organisms displaying the enzyme ALS, these herbicides impact other molecular targets than ALS; 2) These herbicides are toxic for animals, organisms that do not possess the enzyme ALS, and especially invertebrates, amphibians and fish. In humans, epidemiological studies have shown that the use and handling of these toxins are associated with a significantly increased risk of colon and bladder cancers, and miscarriages. In agricultural soils, these herbicides have a persistence of up to several months, and water samples have concentrations of some of these herbicides above the limit value in drinking water.

Targeted toxicometabolomics of endosulfan sulfate in adult zebrafish (Danio rerio) using GC-MS/MS in multiple reaction monitoring mode

Endosulfan sulfate is a major oxidative metabolite of the chlorinated insecticide endosulfan. In this study, a targeted metabolomics approach was used to investigate the toxic mechanisms of endosulfan sulfate in adult zebrafish using the multiple reaction monitoring mode of a GC-MS/MS. The LC₅₀ of endosulfan sulfate in adult zebrafish was determined and then zebrafish were exposed to endosulfan sulfate at one-tenth the LC₅₀ (0.1LC₅₀) or the LC₅₀ for 24 and 48 h. After exposure, the fish were extracted, derivatized and analyzed by GC-MS/MS for 379 metabolites to identify 170 metabolites. Three experimental groups (control, 0.1LC₅₀ and LC₅₀) were clearly separated in PLS-DA score plots. Based on the VIP, ANOVA, and fold change results, 40 metabolites were selected as biomarkers. Metabolic pathways associated with those metabolites were identified using MetaboAnalyst 4.0 as follows: aminoacyl-tRNA biosynthesis, valine/leucine/isoleucine biosynthesis, citrate cycle, glycerolipid metabolism, and arginine/proline metabolism. Gene expression studies confirmed the activation of citrate cycle and glycerolipids metabolism. MDA levels of the exposed group significantly increased in oxidative toxicity assay tests. Such significant perturbations of important metabolites within key biochemical pathways must result in biologically hazardous effects in zebrafish.

Novel electrochemical aptasensor with dual signal amplification strategy for detection of acetamiprid

In this work, a novel dual signal amplification strategy for aptasensor employing reduced graphene with silver nanoparticles and prussian blue-gold nanocomposites was developed for detection of acetamiprid. To improve the sensitivity of aptasensors, reduced graphene oxide-silver nanoparticles (rGo-AgNPs) were modified on a bare glassy carbon electrode surface, which provided a large specific surface area for subsequent material immobilization and amplified current signal. The electrical signal output and sensitivity of the aptasensor was significantly improved after the immobilization of prussian blue-gold nanoparticles (PB-AuNPs) as a catalyst for the redox reaction. The analysis experiment exhibited that it had super-high sensitivity with a detection limit of 0.30 pM (S/N = 3), which met the requirements of the vast majority of daily leaf vegetable testing. Under optimized conditions, the proposed aptasensor showed a wide linear detection range from 1 pM to 1 μM. This aptasensor also had good stability and high selectivity for acetamiprid detection without an interfering effect of some other pesticides. The proposed aptasensor displayed good recovery rates in real samples, which proposed a new method for constructing electrochemical sensors and provided a novel tool for rapid, sensitive analysis of pesticides with low cost.

Hemotoxic effects of some herbicides on juvenile of Nile tilapia Oreochromis niloticus

Recently, the residues of some common and widely used herbicides (acetochlor, bispyribac-sodium, bentazon, bensulfuron-methyl, halosulfuron-methyl, and quinclorac) were detected in the surface water, soil, sediments, and fish tissues as the agricultural drainage problems. In this study, juveniles of Nile tilapia Oreochromis niloticus were exposed to sub-lethal concentrations of these herbicides as 2.625, 0.800, 36.00, 2.50, 1.275, and 11.250 mg/l for acetochlor, bispyribac-sodium, bentazon, bensulfuron-methyl, halosulfuron-methyl, and quinclorac respectively for 96 h. Some hemato-biochemical parameters were evaluated. In comparison with the control group, sub-lethal concentrations of all tested herbicides induced alterations in the shape of erythrocytes. Also, in all tested herbicides, hematological parameters of exposed fish exhibited a significant decrease in red blood cell count except bentazon. However, all tested herbicides showed an insignificant reduction in mean corpuscular hemoglobin concentration and total white blood cells except bensulfuron-methyl. For biochemical parameters, most tested herbicides induced a significant increase in levels of cholesterol, albumin, globulin, albumin/globulin ratio, activity of alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and total plasma protein (only with acetochlor), urea, and creatinine (except bentazon and halosulfuron-methyl that exhibited non-significant decrease in creatinine level) compared with the control. In conclusion, the fish blood profiles can be used as good biomarkers for laboratory study to assess the toxicity of the tested rice herbicides at a sub-acute level especially acetochlor on O. niloticus. Graphical Abstract.

The mechanism of damage by trace amounts of acetamiprid to the midgut of the silkworm, Bombyx mori

Acetamiprid is widely used for agricultural pest control. However, it remains poorly understood whether the environmental residues of acetamiprid have the potential effects on economic insect. In this study, we evaluated the effects of acetamiprid on silkworm growth and development. The exposure to trace amounts of acetamiprid significantly decreased body weight, viability, and spinning ability. In addition, the activity of trypsin in the midgut was decreased after exposure. DGE and KEGG pathway enrichment analysis revealed that the significantly differentially expressed genes were mainly involved in nutrient metabolism, stress responses, and inflammation pathways. These results, in combination with hematoxylin-eosin staining and transmission electron microscopy, indicated that acetamiprid could cause oxidative damage to midgut, lead to inflammatory responses, and affect the activities of midgut digestive enzymes, thus resulting in abnormal growth and development. Our findings greatly contributed to the evaluation of the effects of acetamiprid residues on other nontarget beneficial insect.

Developmental Toxicity of a Neonicotinoid Insecticide, Acetamiprid to Zebrafish Embryos

Agricultural use of neonicotinoid insecticides is increasing worldwide, posing a risk to nontarget organisms. The present study investigated developmental toxicity of a widely used neonicotinoid, acetamiprid, to zebrafish embryos. Sublethal (malformations, hatchability, heart rate, body length, alteration of spontaneous movement and touch responses) and lethal effects were monitored during exposure period from 6 h post fertilization (hpf) to 120 hpf. Zebrafish embryos exhibited significant mortality and teratogenic effects at acetamiprid concentration greater than 263 mg/L, with bent spine being the main malformation. Toxicity spectra were constructed to rank the sensitivity of individual end points to acetamiprid exposure and impaired spontaneous movement was the most sensitive end point of those tested. The present study provides the basis for understanding developmental toxicity of acetamiprid exposure to zebrafish embryos. This information is critical for future studies evaluating aquatic risk from neonicotinoids as little is known regarding adverse effects of neonicotinoids to aquatic vertebrate species.

Non-targeted metabolomics reveals alterations in liver and plasma of gilt-head bream exposed to oxybenzone

The extensive use of the organic UV filter oxybenzone has led to its ubiquitous occurrence in the aquatic environment, causing an ecotoxicological risk to biota. Although some studies reported adverse effects, such as reproductive toxicity, further research needs to be done in order to assess its molecular effects and mechanism of action. Therefore, in the present work, we investigated metabolic perturbations in juvenile gilt-head bream (Sparus aurata) exposed over 14 days via the water to oxybenzone (50 mg/L). The non-targeted analysis of brain, liver and plasma extracts was performed by means of UHPLC-qOrbitrap MS in positive and negative modes with both C18 and HILIC separation. Although there was no mortality or alterations in general physiological parameters during the experiment, and the metabolic profile of brain was not affected, the results of this study showed that oxybenzone could perturb both liver and plasma metabolome. The pathway enrichment suggested that different pathways in lipid metabolism (fatty acid elongation, α-linolenic acid metabolism, biosynthesis of unsaturated fatty acids and fatty acid metabolism) were significantly altered, as well as metabolites involved in phenylalanine and tyrosine metabolism. Overall, these changes are signs of possible oxidative stress and energy metabolism modification. Therefore, this research indicates that oxybenzone has adverse effects beyond the commonly studied hormonal activity, and demonstrates the sensitivity of metabolomics to assess molecular-level effects of emerging contaminants.

A label-free triplex-to-G-qadruplex molecular switch for sensitive fluorescent detection of acetamiprid

The detection and monitoring of acetamiprid has drawn extensive attentions, due to their potential threat to human health. Herein, a simple, sensitive and label-free fluorescent assay based on triplex-to-G-qadruplex (TTGQ) molecular switch, was developed for the assay of acetamiprid in aqueous solution. In this detection, the proposed TTGQ molecule contained the acetamiprid aptamer sequence at its loop part and the triple-helix structure at its stem part. One single-stranded DNA grafted by two split G-rich DNA sequences at its two ends, participated in the assembly of the triplex part in TTGQ. In the presence of acetamiprid, TTGQ was dissociated, and the split G-rich DNA was released out to result in the fluorescent signal enhancement of a G-quadruplex's probe. By virtue of this TTGQ molecular switch, the proposed assay can sense acetamiprid at the concentration as low as 2.38 nM with excellent selectivity. Furthermore, the detection of acetamiprid in three kinds of foods extract demonstrated the high application potential of the detection platform in the field of food safety. Compared with the other reported strategies for acetamiprid assay, this triplex-to-G-qadruplex-based fluorescent molecular switch was just composed of two DNA probes without the labeling procedure, presenting a really simple and low-cost fluorescent detection for acetamiprid assay.

Metabolomic analysis of short-term sulfamethazine exposure on marine medaka (Oryzias melastigma) by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry

Toxicological effects of sulfamethazine (SM₂) have garnered increasing concern due to its wide applications in aquaculture and persistence in the aquatic environment. Most studies have main focused on freshwater fish (i.e. zebrafish), while information regarding effects of SM₂ on marine species is still scarce. Here, the hepatotoxicities in marine medaka (Oryzias melastigma) with an increasing SM2 concentration exposures (0.01 mg/L, 0.1 mg/L and 1 mg/L) were assessed by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOF/MS) based metabolomics. Significant metabolites belonging to different metabolites classes were identified by multivariate statistical analysis. The increases levels of amino acids including alanine, asparagine, ornithine, proline, threonine, glutamic acid, lysine, tyrosine and phenylalanine were found in at least two exposure levels. Pathway analysis revealed that amino acids played important biological roles during SM₂ exposure: up-regulation of high energy-related amino acids for energy alteration; immune function disorder, oxidative stress and corresponding toxicities defenses. The down regulations of sugar and fatty acid metabolism were observed with an increasing level of SM2 exposure, suggesting that extra energy for cellular defense and detoxification was demanded in terms of different stress request. This study provided an innovative perspective to explore possible SM2 induced hepatic damages at three exposure levels on a nontarget aquatic specie.