Dinitroaniline herbicide pendimethalin affects development and induces biochemical and histological alterations in zebrafish early-life stages

Dinitroaniline herbicide exposure, mitochondrial DNA copy number, and 10-year risk of atherosclerotic cardiovascular disease: A community-based cohort study

Dinitroaniline herbicides are widely used to control weed resistance, but their effects on atherosclerotic cardiovascular disease (ASCVD) are unknown. Serum trifluralin and pendimethalin, mitochondrial DNA copy number (mtDNAcn), and predictors of 10-year ASCVD risk were measured in participants from the Wuhan-Zhuhai cohort. Linear mixed model, restricted cubic spline (RCS) model, Bayesian kernel machine regression (BKMR) model, and weighted quantile sum (WQS) regression model were used for association analyses. Mediation models were used to estimate the potential role of mtDNAcn in the above associations. Cross-sectionally, each 1-unit increase in ln-transformed serum trifluralin and pendimethalin levels were associated with an increase in 10-year ASCVD risk of 0.272 % and 0.178 %, respectively (all P < 0.05). The BKMR and WQS models showed that trifluralin and pendimethalin co-exposure was associated with the increased 10-year ASCVD risk, with trifluralin being the primary contributor. Longitudinally, each 1-unit increase in ln-transformed serum trifluralin and pendimethalin levels were associated with the annual increase in 10-year ASCVD risk of 0.192 % and 0.156 %, respectively (all P < 0.05). Mediation analysis showed that mtDNAcn mediated 3.8 % of the trifluralin-associated increase in 10-year ASCVD risk. In conclusion, trifluralin and pendimethalin were cross-sectionally and longitudinally associated with the increased 10-year ASCVD risk, and mtDNAcn partially mediated the association.

Genotoxic, biochemical, cytotoxic and biomolecular alterations in the early-life stage of zebrafish exposed to diphenyl ether

Diphenyl ether (DE) is a chemical compound being used in a number of industries such as soap, detergents, perfumes, adhesive, dyes, herbicides and as a flame retardant in plastics, rubbers and textiles, etc. DE is the final debromination product of polybrominated diphenyl ethers (PBDEs) under anaerobic conditions. The present investigation evaluated the genotoxic, biochemical, histopathological, ultrastructural (SEM) and biomolecular (ATR-FTIR) changes in the zebrafish larvae after DE exposure. After the determination of 96 h LC50 value zebrafish embryos were exposed to sublethal concentrations (¼ LC50 and ½ LC50) of DE. Significantly increased DNA damage in terms of tail length (TL), tail intensity (TI), olive tail moment (OTM) and tail moment (TM) was observed after the DE exposure to zebrafish larvae. Also, increased lipid peroxidation (MDA) and decreased FRAP activity were reported after DE exposure. The catalase (CAT), Glutathione-S-transferase (GST), and Acetylcholinesterase (AChE) activity were reported to be significantly increased and a decreased superoxide dismutase (SOD) activity was observed in DE-exposed groups. After DE exposure, Decreased cell viability and increased apoptosis were reported in zebrafish larvae. The histological and ultrastructural (SEM) analysis revealed the alterations in the zebrafish larvae exposed to DE. The ATR-FTIR study revealed the changes in the biomolecules such as DNA and protein after the DE exposure. The present study will help to understand the destructive aspects of DE in the early life stages of aquatic organisms and could be utilized to assess environmental risk.

Developmental effects of fenpropathrin on zebrafish (Danio rerio) embryo-larvae: Toxic endpoints and potential mechanism

Fenpropathrin (FEN), a highly efficient and broad-spectrum synthetic pyrethroid insecticide. Although sufficient concern has been given to the negative impacts of FEN on non-target organisms, limited knowledge exists regarding the developmental effects of FEN. In this study, effects of FEN (0.45, 1.35, 4.05, and 12.15 μg/L) on various early life-stage endpoints of zebrafish were investigated from 3 to 144 h post-fertilization (hpf) in order to disclose the developmental effects and underlying mechanisms caused by FEN. The results indicate that exposure to FEN induced developmental toxicity in zebrafish, including decreased heart rate, reduced blood flow, shorter body length, smaller eye size, non-inflated swim bladder, and disrupted craniofacial chondrogenesis, which were possibly due to a significant decrease in the levels of thyroxine (T4), triiodothyronine (T3), insulin-like growth factor-1 (IGF-1), and growth hormone (GH), increase in lipid accumulation, and alteration in the contents of total cholesterol (T-CHO) and triglyceride (TG) in larvae exposed to FEN. Besides, FEN exposure also resulted in the inhibition of spontaneous movement of embryo at 24 hpf, a decline in touch evoke response (TER) at 72 hpf, and a reduction in free-swimming activity at 144 hpf, as well as the larval activity at 144 hpf during the dark-light transition stimulus. Mechanistic examinations have shown that FEN treatment inhibits the activities of AChE and elevates the ACh levels. In addition, FEN exposure increased ROS levels and altered the levels of malondialdehyde (MDA), and induced apoptosis as determined by acridine orange staining and elevated caspase-3 levels, suggesting that the involvement of oxidative stress and apoptosis in FEN-induced developmental toxicity of embryos. Transcriptome sequencing of larvae showed that FEN altered the expressions of multiple metabolic and nervous system pathways, including PPAR signaling pathway, lipid metabolism pathway, carbohydrate metabolism pathway, retinol metabolism pathway, and neuroactive ligand-receptor interaction pathway, demonstrating that FEN alters the normal development of zebrafish embryos, and multiple pathways mediating the FEN-induced developmental toxicity. Overall, these findings enhance our understanding of the developmental toxic effects of FEN and provide fundamental data for assessing the risk of FEN on non-target organisms.

Effects of praziquantel on early life stages of Grass carp, Ctenopharyngodon idella

This study aimed to assess the toxicity of the anthelmintic drug praziquantel in the early life stages of grass carp (Ctenopharyngodon idella). The toxicity was evaluated based on mortality, early ontogeny development, growth, oxidative stress biomarkers, antioxidant enzymes and histopathology. Praziquantel at all tested concentrations (1, 2, 4 and 6 mg/l) showed no significant adverse effects on the hatching of grass carp. Concentrations of 2, 4 and 6 mg/l praziquantel caused significantly (P < 0.01) higher mortality and slower growth compared with controls. Praziquantel at concentrations (4 and 6 mg/l) showed a significant (P < 0.01) delay of early ontogeny of grass carp. Concentration of 2 mg/l praziquantel caused significantly (P < 0.01) higher GST activity than controls. Among the groups, no histological changes were detected in tissues. For the early life of grass carp, praziquantel is safe at concentrations ≤1 mg/l.

Effects of Silver Nanoparticles on Ctenopharyngodon idella: Synthesis, Characterization, Antibacterial Activity, and Toxicological Assessment

Currently, nanotechnology (NT) and nanoparticles (NPs) have gained significant attention in the scientific field due to their diverse application history. Particularly, in environmental applications, their antibacterial efficiency in fisheries due to antibacterial resistance. However, the NPs have been found toxic in the environment. Therefore, the current study aimed to fabricate less toxic NPs using environmentally dried leaves to check their antibacterial efficacy and possible toxicity against grass carp. The findings confirmed the good dispersity of obtained AgNPs, which further showed promising antibacterial activity against several bacterial isolates including Staphylococcus with a zone of inhibition (23.73 ± 0.57 nm). Also, the AgNPs were exposed to the grass carp (Ctenopharyngodon idella) for possible toxicity and toxic effects. First, the bioaccumulation of AgNPs was significantly observed in gills followed by intestines and muscles (p < 0.05). Finally, the AgNPs mainly accumulate in the liver, followed by the intestine, gills, and muscles. Additionally, the deposition of AgNPs in various organs resulted in histological alteration such as necrosis and infiltration of red blood cells in the intestine and the fusion of gill lamella. Hence, the synthesized NPs using dried leaf extract could be a promising approach in applied science. The significant features of the nanoparticles in the present work using green synthesis can help in synthesizing less toxic materials.

Toxic Effects of 4-Bromodiphenyl Ether (BDE-3) on Antioxidant Enzymes, Cell Viability, Histology and Biomolecules in Zebrafish Embryo-Larvae

Polybrominated diphenyl ethers (PBDEs) are a class of flame retardants that are being used widely in industrial and consumers products such as plastics, electronics, furniture, textiles and so forth. They can undergo debromination process to form less brominated diphenyl ethers, which are bioaccumulative, more volatile and more toxic in nature. The current study was conducted to reveal the biochemical, apoptotic, histopathological, ultrastructural and biomolecular (ATR-FTIR) toxicity of 4-bromodiphenyl ether (BDE-3) in zebrafish larvae. After the 96-h LC50 determination, the zebrafish embryos were exposed to sublethal concentrations of BDE-3, that is, 0.79 and 1.59 mg/L. The MDA content was found to be significantly increased in BDE-3 exposed larvae whereas the FRAP activity was found to be decreased. The catalase (CAT), glutathione-S-transferase (GST) and acetylcholinesterase (AChE) activity were observed to be significantly increased, and a decreased superoxide dismutase (SOD) activity was reported after the BDE-3 exposure in zebrafish larvae. The cell viability was reported to be decreased in zebrafish larvae after BDE-3 exposure. Histopathological and ultrastructural alterations were also observed in the BDE-3 exposed zebrafish larvae. The changes in the biomolecules such as DNA and protein were also revealed via ATR-FTIR analysis. The present investigation will help to understand the toxic nature of less brominated diphenyl ethers and could be utilised to assess environmental risk.

Evaluating the impact of neonicotinoids on aquatic non-target species: A comprehensive review

Neonicotinoid insecticides (NNIs) are the fastest-growing class in agricultural protection. They target nicotinic acetylcholine receptors (nAChR) in pests, stimulating the nervous system at low doses and causing paralysis and death at higher concentrations. NNIs are used in crop protection, seed treatment, forestry, agriculture, and flea control in domestic cattle. Effective at lower concentrations and offering long-term control, NNIs are favoured for their systemic activity. However, due to their water solubility, mobility, and moderate persistence, NNIs easily contaminate adjacent aquatic environments via runoff, leaching, or spray drift. While less toxic to vertebrates, their widespread use poses threats to aquatic and terrestrial organisms, causing neurotoxicity, nephrotoxicity, cytotoxicity, genotoxicity, immunotoxicity, hepatotoxicity, endocrine disruption, and reproductive malformations. This review synthesizes research to address knowledge gaps on the environmental impact of NNIs and proposes policies to mitigate their harmful effects on aquatic non-target species.

Testing the detoxification power of black cumin oil (Nigella sativa) over cypermethrin insecticide effects in rainbow trout (Oncorhynchus mykiss) at multiple scales

This study investigated the curative effect of black cumin oil (Nigella sativa, NS), which is a phytotherapeutic agent against to cypermethrin (CYP), which is known to have adverse effects on rainbow trout (Oncorhynchus mykiss)'s behavioral changes, oxidative stress-mediated neurotoxicity, hematotoxicity and hepatotoxicity parameters.At the end of the trial period; (i) evaluation of critical swimming speed (Ucrit) (ii) hematology indices [white blood cell (WBC), red blood cell (RBC), hemoglobin (Hgb), hematocrit (Hct), mean cell volume (MCV), mean cell hemoglobin) (MCH), mean cell hemoglobin concentration (MCHC)] (iii) Elucidation of the mechanism of functional damage in brain tissue of O. mykiss by neurological parameter [acetylcholinesterase (AChE)] (iv) Evaluation of oxidative damage in oxidative stress-mediated neurotoxicity and hepatotoxicity in liver, gill and brain tissue of O. mykiss with antioxidant enzymes [(Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), Glutathione (GSH)] and [(detection by means of malondialdehyde (MDA)] (v) Obtaining applicable data in the toxicological field using a multi-biomarker approach to investigate the modulation of NS administration via target markers in the physiological pathway of O. mykiss were aimed.As a result of CYP application, it was determined that the Ucrit value of O. mykiss decreased significantly. It was determined that the changes in the values of RBC, Hgb and Hct, which are among the hematology parameters examined in the blood tissue, were statistically significant (p < 0.05). It was determined that WBC value was inhibited by CYP application and NS tried to make a positive contribution to WBC. It was determined that the AChE activity of O. mykiss in the brain tissue had a statistically significant inhibition in the CYP-treated group (p < 0.05). SOD, CAT, GPx, enzyme activities were found to be inhibited by CYP application and were statistically significant (p < 0.05). Acute toxicity of CYP was determined by antioxidant enzyme biomarkers in gill tissue. In the results obtained; While inhibitions were determined in SOD, CAT, GPx activities compared to the control group, an induction occurred in MDA value.NS administration was noted to be an important modulator of the SOD-CAT system against CYP exposure at both concentrations. Thus, it can be said that it indirectly functions as an effective antioxidant through the NS receptor protein and structurally stimulates the synthesis and activity of antioxidative enzymes under oxidative stress.

Long-term exposure to environmentally relevant Bisphenol-A levels affects growth, swimming, condition factor, sex ratio and histology of juvenile zebrafish

Bisphenol A (BPA) is an environmental estrogen which perturbs hormone signaling pathways adversely affecting aquatic organisms. To evaluate the impact of developmental exposure to long term yet environmentally relevant low doses of BPA, wild-type juvenile zebrafish of 35 days post fertilization were treated with BPA (1 and 10 µg/L), treatment control (0.5% v/v methanol) and control for 60 days. Both BPA treatments led to significantly increased morality overtime. Length increment and specific growth rates became significantly high in BPA exposed zebrafish overtime. Obesogenic property of BPA was not evident with longexposure to low BPA doses. A significantly high and BPA dose-dependent female-biased sex ratios were observed following the juvenile exposure. Significantly low swimming speed was recorded in the fish of both BPA-treated tanks than that of control. Condition factor was significantly low in BPA exposed fish indicating the poor-wellness. There were numerous histopathological alterations of gonads, liver and kidney indicating impacts of juvenile exposure in zebrafish. Altered growth, swimming, mortality, feminization and histopathological changes in zebrafish induced by BPA indicate the risks associated with developmental exposures. The findings call for more comprehensive studies to comprehend the ecological risks imposed by low concentrations of environmental estrogens in urban aquatic ecosystems.

Subchronic oral toxic effects of 2,4-dinitroaniline in wistar rats: A comprehensive toxicity evaluation

2,4-dinitroaniline (2,4-D), a widely used dye intermediate, is one of the typical pollutants, and its potential health risks and toxicity are still largely unknown. To explore its subchronic oral toxicity, Wistar rats (equal numbers of males and females) were used as test animals, and a 90-day oral dosing experiment was conducted, divided into control group, low-dose group (0.055 mg/kg), medium-dose group (0.22 mg/kg), medium-high dose group (0.89 mg/kg), and high-dose group (3.56 mg/kg). The body weight data, clinical appearance, and drug reactions of each test rat within 90 days of dosing were recorded; morning urine samples were collected four times to test for eight urinary indicators; blood samples were collected to test for nineteen hematological indicators and sixteen biochemical indicators; tissue samples were collected for pathological analysis; moreover, the no-observed-adverse-effect level (NOAEL) was determined, and the benchmark dose method was used to support this determination and provide a statistical estimate of the dose corresponding. The results indicated that the chronic toxicity of 2,4-dinitroaniline showed certain gender differences, with the eyes, liver, and kidneys being the main potential target organs of toxicity. Moreover, the subchronic oral NOAEL for 2,4-dinitroaniline was determined to be 0.22 mg/kg body weight (0.22 mg/kg for males and 0.89 mg/kg for females), and a preliminary calculation of the safe exposure limit for human was 0.136 mg/kg. The research results greatly enriched the safety evaluation data of 2,4-dinitroaniline, contributing to a robust scientific foundation for the development of informed safety regulations and public health precautions.

The Determination of the Prohibited Herbicide 4,6-Dinitro-Ortho-Cresol (DNOC) in Poisoned Domestic and Wild Animals in Italy

This study reports the determination of DNOC in the baits and gastric contents of poisoned dogs and wild canids collected in the Abruzzo region between 2014 and 2022. A total of 663 samples of the baits and carcasses of domestic and wild animals were analyzed for the determination of DNOC through GC-MS. DNOC was found to be present in 58 cases from 663 analyzed samples, with 49 poison baits and nine gastric content samples from dogs and red foxes. This study confirms for the first time that the banned pesticide DNOC still poisons both domestic and wild animals in the Abruzzo region. It should be considered that this study was carried out on a population of animals from a regional geographical area, and more detailed country-wide studies need to be carried out to obtain the incidence of poisoning from this herbicide in Italy. Furthermore, these findings emphasize the importance of considering this chemical in differential diagnosis during toxicological investigations of animal poisoning.

Decrypting the skeletal toxicity of vertebrates caused by environmental pollutants from an evolutionary perspective: From fish to mammals

The rapid development of modern society has led to an increasing severity in the generation of new pollutants and the significant emission of old pollutants, exerting considerable pressure on the ecological environment and posing a serious threat to both biological survival and human health. The skeletal system, as a vital supportive structure and functional unit in organisms, is pivotal in maintaining body shape, safeguarding internal organs, storing minerals, and facilitating blood cell production. Although previous studies have uncovered the toxic effects of pollutants on vertebrate skeletal systems, there is a lack of comprehensive literature reviews in this field. Hence, this paper systematically summarizes the toxic effects and mechanisms of environmental pollutants on the skeletons of vertebrates based on the evolutionary context from fish to mammals. Our findings reveal that current research mainly focuses on fish and mammals, and the identified impact mechanisms mainly involve the regulation of bone signaling pathways, oxidative stress response, endocrine system disorders, and immune system dysfunction. This study aims to provide a comprehensive and systematic understanding of research on skeletal toxicity, while also promoting further research and development in related fields.

Environmental presence and toxicological outcomes of the herbicide pendimethalin in teleost fish

Herbicides are often detected in aquatic ecosystems due to residential and agricultural applications and can harm aquatic organisms once deposited into water systems. Pendimethalin is part of the dinitroaniline chemical family and is applied to crops like corn, legumes, potatoes, and soybeans. The potential toxicity of pendimethalin to aquatic species is understudied compared to other widely studied herbicides, like atrazine and glyphosate. The objectives of this review were to (1) collate information on sub-lethal responses to pendimethalin exposure in fish, (2) evaluate how exposure studies relate to environmental concentrations, and (3) identify putative bioindicators for exposure studies. Overall, studies reporting pendimethalin in water systems worldwide indicate a range of 100-300 ng/L, but levels have been reported as high as ~15 µg/g in sediment. In teleost fish, studies demonstrate developmental toxicity, immunotoxicity, and behavioral disruptions. The strongest evidence for pendimethalin-induced toxicity involves oxidative stress, although studies often test toxicity at higher concentrations than environmentally relevant levels. Using the Comparative Toxicogenomics Database, pathway analysis reveals linkages to neurotoxicity and mechanisms of neurodegeneration like "Ubiquitin Dependent Protein Degradation", "Microtubule Cytoskeleton", "Protein Oxidation and Aggregation in Aging", and "Parkinson's Disease". Other prominent pathways included those related to mTOR signaling and reproduction. Thus, two potential mechanisms underlying pendimethalin-induced toxicity in fish include the neural and reproductive systems. This review synthesizes current data regarding environmental fate and ecotoxicology of pendimethalin in teleost fish and points to some putative physiological and molecular responses that may be beneficial for assessing toxicity of the herbicide in future investigations.

Frontier of toxicology studies in zebrafish model

Based on the 87 original publications only from quartiles 1 and 2 of Journal Citation Report (JCR) collected by the major academic databases (Science Direct, Web of Science, PubMed, and Wiley) in 2022, the frontier of toxicology studies in zebrafish model is summarized. Herewith, a total of six aspects is covered such as developmental, neurological, cardiovascular, hepatic, reproductive, and immunizing toxicities. The tested samples involve chemicals, drugs, new environmental pollutants, nanomaterials, and its derivatives, along with those related mechanisms. This report may provide a frontier focus benefit to researchers engaging in a zebrafish model for environment, medicine, food, and other fields.

Ecotoxicological insights: Effects of pesticides on ionic metabolism regulation in freshwater catfish, Mystus keletius

Fish maintain their body fluid ionic and osmotic homeostasis using sophisticated iono-/osmoregulation mechanisms through gills ionocytes. Pesticide-induced ionic imbalance in fish has been recognized as a valuable tool to determine its toxic effects. Acute exposure to synthetic and organo-chemical pesticides on the regulation of ionic (Na+, Ca2+, P) metabolism in freshwater catfish Mystus keletius was evaluated. Fish were exposed to sub-lethal concentrations (mg/l) of selected pesticide for a period of 7, 14, 21 and 28 days. Results indicated that chemical pesticides - Impala and Ekalux - evoked adverse toxic effects on selected tissues compared to organo-chemical pesticide tested. Statistical analysis of the summative data using two-way ANOVA was significant (p-value<0.001). Variations in the cellular parameters analysed were attributed to the physiological acclimatization of fish to the pesticide exposed. Based on the results it is concluded that organic pesticides may be preferred for rice field application considering safety aspects.

Fenpropathrin induces neurotoxic effects in common carp (Cyprinus carpio L.)

Fenpropathrin (FEN) is a synthetic pyrethroid that has been frequently detected in aquatic environments, yet the neurotoxic impacts and underlying mechanisms on nontarget organisms are lacking. In this experiment, common carp were exposed to 0.45 and 1.35 μg/L FEN for 14 d and exhibited abnormal locomotor behaviour. Biochemical and molecular analysis results indicated that FEN altered the contents of tight junction proteins (claudin-1, occludin, and ZO-1), disturbed Na+-K+-ATPase and AChE activities, caused abnormal expression of neurotransmitters (ACh, DA, GABA, 5-HT, and glutamate) and caused histological damage in the brain, suggesting that FEN may damage the blood-brain barrier and induce neurotoxicity in carp. Furthermore, FEN also promoted an increase in ROS, changed SOD and CAT activities, and generally upregulated the contents of MDA, 8-OHdG, and protein carbonyl in the brain, indicating that FEN can induce oxidative stress and cause damage to lipids, DNA, and proteins. Moreover, inflammation-related indicators (TNF-α, IL-1β, IL-6, and IL-10), mitophagy-related genes (PINK1, parkin, ulk1, beclin1, LC3, p62, tfeb, and atg5), and apoptosis-related parameters (p53, bax, bcl-2, caspase-3, caspase-8, and caspase-9) were also significantly changed, suggesting that inflammation, mitophagy, and apoptosis may participate in FEN-induced neurotoxicity in carp. This study refines the understanding of the toxicity mechanism of FEN and thus provides data support for the risk assessment of FEN.

Teratogenic effects of the dicamba herbicide in Zebrafish (Danio rerio) embryos

Dicamba has been used worldwide for 60 years, but few studies have been conducted on its environmental safety and health effects. Therefore, this study aims to evaluate the acute toxicity, teratogenic effects, oxidative stress, and neurotoxicity of Dicamba in zebrafish embryos. Embryos were exposed to concentrations of 4.5, 18, 72, and 288 mg/L of Dicamba for 96 h. Among the teratogenic effects, yolk sac edema predominated, besides malabsorption of nutrients (grayish yolk sac). The presence of edema may indicate problems with circulation and water efflux from the embryos, which may be related to kidney and cardiovascular problems. Other effects such as hemorrhage, spinal and eye malformations, and dwarfism were also observed. The hatching rate was reduced in the highest concentration, and in the other concentrations, a decrease was noticeable indicating a delay in development. Neurotoxic effects were also observed. Oxidative stress analysis showed a significant decrease in SOD at all concentrations and an increase in GPx, GSH, and LPO at 288 mg/L of Dicamba. It was observed that the herbicide is capable of causing teratogenic effects, developmental delay, and oxidative stress. These results show that exposure to Dicamba, in a commercial formulation, can bring risks during embryonic development. In addition, it highlights the need for further studies on the effects of the herbicide and a reassessment of toxicity categorization.

Omics techniques reveal the toxicity mechanisms of three antiepileptic drugs to juvenile zebrafish (Danio rerio) brain and liver

Epilepsy, a neurological disorder, is characterized by seizures that are an appearance of excessive brain activity and is symptomatically treated with antiepileptic drugs (AEDs). Oxcarbazepine (OCBZ), lamotrigine (LTG), and carbamazepine (CBZ) are widely used AEDs in clinics and are very often detected in aquatic environments. However, neither the sub-lethal effects nor the specific mechanisms of these AEDs' action on the fish are well understood. In this study, juvenile zebrafish were exposed to a sub-lethal concentration (100 μg/L) of OCBZ, LTG, and CBZ for 28 d, after which indicators of oxidative stress (i.e. superoxide dismutase (SOD) activity, catalase (CAT) activity, and malondialdehyde (MDA) level) and neurotoxicity (i.e. acetylcholinesterase (AChE) activity, γ-aminobutyric acid (GABA) level, and glutamic acid (Glu) level) were measured. Brain SOD activity was significantly increased by three AEDs, while brain CAT activity was significantly inhibited by LTG and CBZ. Liver SOD activity was significantly enhanced by CBZ, and liver CAT activity was significantly induced by OCBZ and LTG. Liver MDA level was significantly increased by three AEDs. Brain AChE activity was significantly increased by LTG and CBZ, and brain GABA level was significantly enhanced by three AEDs. However, there were no significant alterations in the levels of MDA and Glu in zebrafish brain. To ascertain mechanisms of AEDs-induced toxicity, brain transcriptomics and liver metabolomics were conducted in zebrafish. The brain transcriptomics results showed that lots of differentially expressed genes (DEGs) were enriched in the sensory system, the immune system, the digestive system, the metabolic processes, and others in three AEDs treated groups. The metabolomics data indicated dysregulation of glycerophospholipid signaling and lipid homeostasis in zebrafish liver after three AEDs exposure. The overall results of this study improve understanding of the sub-lethal effects and potential molecular mechanisms of action of AEDs in fish.

Developmental toxicity of the emerging contaminant cyclophosphamide and the integrated biomarker response (IBRv2) in zebrafish

The safety of cyclophosphamide (CP) in the early developmental stages is not studied yet; it is important to study the responses at these stages because they might have relevance to CP-administered humans. We studied the developmental toxicity of CP by analysing physiological, morphological, and oxidative stress, neurotransmission enzymes, gene expression and histological endpoints in zebrafish embryos/larvae. The study lasted for 120 hpf at environmentally relevant concentrations of CP. No visible alterations were noticed in the control group. Delayed hatching, slow heart rate, yolk sac oedema, pericardial oedema, morphological deformities, the incompetence of oxidative stress biomarkers, excessive generation of ROS, apoptosis, inhibition of neurotransmitters and histopathological anomalies were observed in CP-treated groups. These alterations were found to be concentration- and duration-dependent effects for physiological and morphological endpoints, whereas concentration-dependent effects were antioxidants, ROS, apoptosis and histological endpoints. Biomarkers and gene expression were standardised using the integrated biomarker response-IBRv2 index. The IBRv2 index showed a concentration-dependent behaviour. A non-lethal developmental and teratogenic effect was observed in CP-treated zebrafish embryos/larvae at the studied concentrations. The studied biomarkers are sensitive, and the responses are interrelated; thus, their responses are useful to assess veiled and unseen hazards of pharmaceuticals.

Evaluation of single and combined effects of mancozeb and metalaxyl on the transcriptional and biochemical response of zebrafish (Danio rerio)

Mancozeb and metalaxyl are fungicidal agents frequently used in combination to control fungi in crops that may affect non-target organisms when entering ecosystems. This study aims to evaluate the environmental effects of Mancozeb (MAN) and Metalaxyl (MET), alone and in combination, on zebrafish (Danio rerio) as an experimental model. The oxidative stress biomarkers and the transcription of genes involved in detoxification in zebrafish (Danio rerio) were assessed after co-exposure to MAN (0, 5.5, and 11 μg L^-1) and MET (0, 6.5, and 13 mg L^-1) for 21 days. Exposure to MAN and MET induced a significant increase in the expression of genes related to detoxification mechanisms (Ces2, Cyp1a, and Mt2). Although Mt1 gene expression increased in fish exposed to 11 μg L^-1 of MAN combined with 13 mg L^-1 of MET, Mt1 expression was down-regulated significantly in other experimental groups (p < 0.05). The combined exposure to both fungicides showed synergistic effects in the expression levels that are manifested mainly at the highest concentration. Although a significant (p < 0.05) increase in alkaline phosphatase (ALP) and transaminases (AST and ALT), catalase activities, the total antioxidant capacity, and malondialdehyde (MDA) contents in the hepatocytes of fish exposed to MAN and MET alone and in combination was detected, lactate dehydrogenase (LDH), gamma-glutamyl transferase (GGT) activities, and hepatic glycogen content decreased significantly (p < 0.05). Overall, these results emphasize that combined exposure to MET and MAN can synergistically affect the transcription of genes involved in detoxification (except Mt1 and Mt2) and biochemical indicators in zebrafish.

Molecular and behavioral toxicity assessment of tiafenacil, a novel PPO-inhibiting herbicide, in zebrafish embryos/larvae

Tiafenacil is a newly registered herbicide and a protoporphyrinogen IX oxidase inhibitor. However, sub-lethal effects of PPO-inhibitors in aquatic species are unknown. Embryos or larvae were exposed to 0.1 µg/L up to 10 mg/L tiafenacil for 7-days post-fertilization. Decreased survival (> 50%) and deformities were noted at concentrations > 1 mg/L. Potency (EC50) of tiafenacil for 5- and 7-day larvae were 818.1 µg/L and 821.7 µg/L, respectively. Pericardial and yolk sac edema were the most frequent deformities observed. Heartbeat frequency at 3 dpf was decreased in zebrafish exposed to > 10 µg/L tiafenacil, coinciding with increased reactive oxygen species. Oxygen consumption rates were not affected by tiafenacil, nor did we detect differences in indicators of apoptosis. The abundance of eighteen transcripts related to oxidative stress and mitochondrial complexes I through V were unchanged. Larval activity was decreased with exposure to 1000 µg/L tiafenacil. These data contribute to risk assessment for a new class of herbicide.

Nano-TiO2 aggravates bioaccumulation and developmental neurotoxicity of difenoconazole in zebrafish larvae via oxidative stress and apoptosis: Protective role of vitamin C

Titanium dioxide nanoparticles (n-TiO₂) could enhance the bioavailability and toxicity of coexisting organic contaminants in the aquatic environment. This study attempted to investigate the combined effects of n-TiO₂ and difenoconazole (DIF) on the neurodevelopment of zebrafish and the underlying mechanisms. In this study, zebrafish embryos were exposed to n-TiO₂ (100 μg/L), DIF (0, 0.1 and 0.5 mg/L) and their mixtures from 4 to 96 h post fertilization (hpf) and neurotoxicity was evaluated. Our results indicated that n-TiO₂ adsorbed DIF into the brain of zebrafish and significantly enhanced the bioaccumulation of DIF and n-TiO₂ in the 0.5 mg/L co-exposure group. 100 μg/L n-TiO₂ was not developmentally toxic to the zebrafish larvae, but it exacerbated DIF-induced neurobehavioral alterations in the zebrafish larvae. n-TiO₂ also aggravated DIF-induced suppression of central nervous system (CNS) neurogenesis in Tg (HuC:egfp) zebrafish, motor neuron axon length in Tg (hb9:egfp) zebrafish, and downregulation of neurodevelopmental genes (elavl3, ngn1, gap43, gfap and mbp). In addition, DIF elevated oxidative stress by accumulation of reactive oxygen species (ROS) and inhibition of antioxidant enzymes, and triggered apoptosis by upregulation of p53, bax, bcl-2 and caspase-3, which were markedly intensified in the presence of n-TiO₂. Moreover, vitamin C (VC) ameliorated n-TiO₂/DIF-induced abnormal locomotor behaviors and neurotoxicity by inhibiting oxidative stress and apoptosis, indicating that oxidative stress and apoptosis are involved in n-TiO₂/DIF-induced neurotoxicity. Taken together, our data indicated that n-TiO₂ enhanced the accumulation of DIF and heightened oxidative stress and apoptosis, thereby inducing neurotoxicity. This study exemplifies the importance of the toxicity assessment of chemical mixtures and novel insights to mitigate their combined toxicity.

Metamifop as an estrogen-like chemical affects the pituitary-hypothalamic-gonadal (HPG) axis of female rice field eels (Monopterus albus)

Metamifop (MET) is a widely used herbicide. It is likely for it to enter water environment when utilized, thus potential impacts may be produced on aquatic animals. Little information is available about its effects on the endocrine system of fish to date. In the current study, female rice field eels (Monopterus albus) were exposed to different MET concentrations (0, 0.2, 0.4, 0.6, 0.8 mg L -1) for 96 h to examine the effect of MET on the hypothalamic-pituitary-gonadal (HPG) axis and sexual reversal. The results showed that high concentrations of MET exposure increased vitellogenin (VTG) levels in liver and plasma, but plasma sex hormone levels were not affected by MET exposure. MET exposure increased the expression of CYP19A1b and CYP17 that regulate sex hormone production in the brain, but the expression of genes (CYP19A1a, CYP17, FSHR, LHCGR, hsd11b2, 3β-HSD) associated with sex hormone secretion in the ovary and the estrogen receptor genes (esr1, esr2a, esr2b) in the liver were all suppressed. In addition, the expression of sex-related gene (Dmrt1) was suppressed. This study revealed for the first time that MET has estrogen-like effects and has a strong interference with the expression of HPG axis genes. MET did not show the ability to promote the sexual reversal in M. albus, on the contrary, the genes expression showed that the occurrence of male pathway was inhibited.

Ethalfluralin induces developmental toxicity in zebrafish via oxidative stress and inflammation

Ethalfluralin, of dinitroaniline herbicide family, is an effective weed controller. Following residue detection in herbicide-treated fields, ethalfluralin was reported to interfere with early stages of implantation in some vertebrate species. However, the role of ethalfluralin in the development of zebrafish embryos has not been elucidated yet. Therefore, in the present study, we investigated the morphological and physiological changes that occur in the embryonic development of zebrafish due to ethalfluralin exposure. Results indicated that ethalfluralin decreased survival rate along with reduction in the hatching ratio and heartbeat. It was observed to cause edema in the heart and yolk sac, and apoptosis in the anterior region of the developing zebrafish larvae; as visualized through acridine orange and TUNEL staining. In addition, ethalfluralin increased the expression of the apoptosis-associated genes including tp53, cyc1, casp8, casp9, and casp3. The Seahorse Mito Stress analysis revealed that ethalfluralin slightly reduced mitochondrial respiration in live zebrafish embryos. Reactive oxygen species (ROS) production was also observed to be elevated in zebrafish larvae in response to ethalfluralin. Treatment with ethalfluralin decreased blood vessel formation in brain and intestine in flk1 transgenic zebrafish embryos. The decrease in angiogenesis related gene expression was specifically observed in vegfc, flt1, and kdrl, and in the intestinal vasculature related genes apoa4a, aqp3, fabp2, and vil1. Moreover, an increase in inflammatory genes such as cox2a, cox2b, cxcl-c1c, il8, mcl1a, mcl1b, and nf-κb was observed using real-time PCR analysis. Collectively, these results indicate that oxidative stress generated by exposure to ethalfluralin induced ROS generation, apoptosis, inflammation and anti-angiogenic effects, and therefore, ethalfluralin may be toxic to the development of zebrafish embryos.

Stress related blood values in Scyliorhinus canicula as live-indicators of physiological status after bottom trawling capture activity

The quantification of capture-related physiological stress is an important factor when assessing the potential for post-release survival in sharks that are incidentally captured. In the absence of these biological data and when the post-release fate is unknown, effective management plans cannot be formulated and may lead to highly susceptible shark populations being overfished. Here, we measured the levels of lactate, glucose, alanine amino transferase (ALT), aspartate amino transferase (AST), Ca2+, Na+ K+,Cl - Mg 2+ and Pi in the plasma of mature and immature lesser spotted dogfish (Scyliorhinus canicula, herein dogfish) which were incidentally captured at two depths (shallow: 50-200 m, and deep: 201-500 m) by bottom trawl off the coast of southern Sicily. These values were used as biomarkers and physiological indicators of the secondary stress response associated with capture. This study found that dogfish captured in deeper waters (below 200 m) had elevated levels of glucose, Na+, Ca2+ and K+ compared to those inhabiting depths less than <200 m. We hypothesize that the elevated levels of physiological stress in dogfish captured at greater depths may be related to the prolonged duration of the interactions with the fishing gear in the area off southern Sicily. Our findings provide new data on the capture-related stress in dogfish and increase the understanding of the potential for post-release survival in sharks captured at two depths by bottom trawl, information that is important for improving the general management plans for the fishery. However, our PC Analysis results revealed that Maturity have a positive contribution from the sample weight, sample length, ALT, AST and a negative contribution from Pi.

Ecogenotoxicity of environmentally relevant atrazine concentrations: A threat to aquatic bioindicators

Atrazine (ATZ) is a herbicide that is frequently present in surface waters and may result in damage to the health of various organisms, including humans. However, most scientific literature reports injuries caused by ATZ at high concentrations, which are not found in the environment. Therefore, the scope of this study was to investigate the impacts of realistic concentrations of ATZ found in surface waters (1, 2, 5, 10, 15 and 20 μg/L) using the bioindicators Allium cepa, Daphnia magna and zebrafish (Danio rerio). ATZ elicited a genotoxic effect in A. cepa, manifested by the induction of chromosomal aberrations, and a mutagenic effect with increased incidence of micronuclei formation, promotion of cell death and reduction in nuclear size revealed by flow cytometry analysis. D. magna exposed to 10, 15 and 20 μg/L of ATZ showed significant reduction in body size after 21 days, delayed first-brood release, decreased egg production and total offspring, as well as swimming behavioral changes. ATZ exposure promoted physiological and developmental alterations in zebrafish embryos, including an increased spontaneous movement rate, which led to premature hatching at all concentrations investigated. Increase in total body length, decrease of the yolk sac area, pericardial edema and higher heart rate were also detected in ATZ-treated zebrafish. In summary, environmentally relevant concentrations of ATZ can induce substantial alterations in the three bioindicators investigated. This study evidences the deleterious effects of ATZ on three aquatic bioindicators employing established and current techniques, and may contribute to elucidate the risks caused by this widely used herbicide even at low concentrations and short-to-medium-term exposure.

Potential biomarker of phenol toxicity in freshwater fish C. mrigala: Serum cortisol, enzyme acetylcholine esterase and survival organ gill

In this modern industrialized era of large-scale production of agrochemicals, various emerging contaminants form the main components of waste water and sludge in most of the developing countries of the world. In this concern, phenol- an inevitable and alarming chemical pollutant in aquatic ecosystem, gains a speedy access into the water bodies as an industrial by-product. Though the detrimental effects of phenol have been studied in various aspects of aquatic life, current study is an initiative to unravel the toxic effects of phenol at molecular level in Cirrhinus mrigala. Plasma cortisol level and acetylcholine esterase activity in fish was estimated by Chemiluminescent immunoassay technique and Ellman assay respectively. Scanning electron microscopic studies were carried out to unravel the gill histopathological alterations in exposed fish. It was observed that phenol (22.32 mg/l) inhibits 50 % of acetylcholine esterase activity in brain thereby affecting the locomotion of the targeted carp. Cortisol elevated during the 7th day in exposed fish, but declined progressively on the forthcoming 21st and 28th days. Manifestations in gill encompass curling, fusion, aberrations, sloughing of gill epithelium, wider inter filamentary space and mucus coating in the primary gill filament. It concludes that the discernable deviations produced in both biochemical parameters and key organ gill can be used as a biomarker and bio-indicator respectively for assessing the existence of emerging toxicants in aquatic ecosystem.

Abamectin promotes behavior changes and liver injury in zebrafish

The indiscriminate use of pesticides is a worldwide concern due to the environment contamination since it can cause deleterious effects to non-target organisms including the fishes. The effects of abamectin, a pesticide from the avermectin family, were evaluated in adult zebrafish (Danio rerio) after exposure to a commercial formula commonly used in Brazil. The animals were submitted to acute (96 h) and to a short-term chronic exposure (15 days) of distinct concentrations of abamectin. LC50 was determined and a histological study followed by an immunohistochemistry analysis for P-gp and HSP70 identification were performed on livers of the animals submitted to the acute and chronic treatment, respectively. Moreover, behavior patterns were observed daily in both trials. A LC50 value of 105.68 μg/L was determined. The histological analysis revealed a morphological alteration of the hepatocytes, glycogen accumulation, degeneration, and disorganization of the cytoplasm, and a pyknotic, irregular, and laterally located nuclei. The immunohistochemistry for HSP70 and P-gp showed strong staining in the hepatocytes of the control groups and progressive decrease as the concentration of abamectin increased. Changes were observed in body posture, movement around the aquarium, opercular activity, body color and search for food in the groups treated with abamectin. The results presented suggest that abamectin can affect the behavioral pattern of the animals, promote morphological changes, and decrease the expression of HSP70 and P-gp in zebrafish liver.

Ecotoxicological Risk Assessment of Actellic 50 EC Insecticide on Non-Target Organisms in Parallel with the Application of Standardized Tests

This paper contributes to the ecotoxicological risk assessment of the Actellic 50 EC insecticide (with 50% pirimiphos-methyl as the active substance) tested on non-target organisms. The insecticide concentrations tested were the same for all organisms (0.1, 0.01, and 0.001 mg L-1 of Actellic 50 EC), with an exposure of 3-5-21 days for plants and 4-5-14 days for animals. The non-target organisms tested were both plants (wheat and two ferns) and animals (the Prussian carp and marsh frog tadpoles). The tested insecticide significantly inhibited the growth of roots in wheat, a result that was also confirmed by a microbiotest application (62% root growth inhibition in sorghum and 100% germination inhibition in white mustard and garden cress). In ferns, even for the lowest concentration, the percentage of germinated spores was inhibited by 40% for Asplenium scolopendrium. The recorded toxicological effects of Actellic 50 EC upon the Prussian carp included a decrease in the respiratory rate and oxygen consumption, an increase in the number of erythrocytes and leukocytes, and an increase in blood glucose levels. The highest concentration (0.1 mg L-1 of Actellic 50 EC) caused a 50% decrease in the survival rate of marsh frog tadpoles after 5 days of exposure, negatively affecting body volume and length. Given the high degree of toxicity of the insecticide Actellic 50 EC, we recommend continuing investigations on non-target species, including both plants and animals, as the sub-chronic effects are quite little known in the scientific literature.

Impact of pharmaceutical products on zebrafish: An effective tool to assess aquatic pollution

Overuse of pharmaceuticals products (PPs) and sometimes ineffective wastewater purification systems have led to the accumulation of these residues in aquatic systems. Raising concerns about the likely harmful effects of these substances both to ecosystems and to human health. Animals as model organisms are nowadays increasingly used to track the health of environmental system around the world. They can be used to understand biological processes, to obtain information on the health status of the environment, and to better understand the effects of xenobiotics on organisms. Among model organisms, the zebrafish (Danio rerio) is one of the best models for studying evolution biology, cancer, toxicology, drug discovery, and genetics. This fish is a multipurpose model organism, due to its easy of maintenance and keeping and the transparency of the embryo during the early stages of development. In this paper, the toxicological effects of typical PPs, and their effects on zebrafish are reviewed. Many PPs have been found to be toxic or even fatal to zebrafish. Showing how these pharmaceuticals compound can affect zebrafish from the larval stage and even in the adult stage. Zebrafish is thus a model for how we can better understand how medications affect not only individual fish but the entire aquatic ecosystem, bringing about perturbations in their behaviour and putting their survival at risk.

Dinitroaniline herbicides: a comprehensive review of toxicity and side effects on animal non-target organisms

The widespread use of herbicides has increased concern about the hazards and risks to animals living in terrestrial and aquatic ecosystems. A comprehensive understanding of their effective action at different levels of biological organization is critical for establishing guidelines to protect ecosystems and human health. Dinitroanilines are broad-spectrum pre-emergence herbicides currently used for weed control in the conventional agriculture. They are considered extremely safe agrochemicals because they act specifically on tubulin proteins and inhibit shoot and root growth of plants. However, there is a lack of toxicity information regarding the potential risk of exposure to non-target organisms. The aim of the present review is to focus on side effects of the most commonly used active ingredients, e.g. pendimethalin, oryzalin, trifluralin and benfluralin, on animal non-target cells of invertebrates and vertebrates. Acute toxicity varies from slightly to high in terrestrial and aquatic species (i.e. nematodes, earthworms, snails, insects, crustaceans, fish and mammals) depending on the species-specific ability of tested organisms to adsorb and discharge toxicants. Cytotoxicity, genotoxicity and activation of oxidative stress pathways as well as alterations of physiological, metabolic, morphological, developmental and behavioural traits, reviewed here, indicate that exposure to sublethal concentrations of active ingredients poses a clear hazard to animals and humans. Further research is required to evaluate the molecular mechanisms of action of these herbicides in the animal cell and on biological functions at multiple levels, from organisms to communities, including the effects of commercial formulations.

Are BPA-free plastics safe for aquatic life? - Fluorene-9-bisphenol induced thyroid-disrupting effects and histopathological alterations in adult zebrafish (Danio rerio)

Fluorene-9-bisphenol (BPFL) is used as an alternative compound for bisphenol A, an endocrine disruptor compound which is present in various materials including plastic bottles and packaging. Although it is used extensively in products that are labelled BPA-free, its effect on wildlife and humans have not been fully studied. Therefore, this study aimed to investigate the effects of BPFL in adult zebrafish. In the preliminary experiments of the study, the median lethal concentration value (LC₅₀) of BPFL was 0.25 mg/L (95 % confidence interval 0.15-0.41) for 96 h. Following exposure to three different sublethal concentrations of BPFL after 96 h and 15 days, T4 hormone levels, expression levels of genes involved in thyroid metabolism and histopathological alterations were assessed. T4 hormone levels were found to be significantly higher in females at the lowest BPFL concentration following 96 h exposure (P < 0.05). Expression levels of trh, tshba and trhrb genes were upregulated following 96 h exposure at 0.025 mg/L concentration and crh was upregulated following 15 days exposure at 0.025 mg/L concentration in female zebrafish (P < 0.05). The most prominent histopathological findings in zebrafish exposed to 0.025 and 0.125 mg/L of BPFL were observed in the gill, liver, kidney and testis tissues. The gill tissues showed some hyperemia, lamellar fusion, hyperplasia, epithelial lifting, and telangiectasis, while passive hyperemia, hydropic degeneration, and necrosis were observed in the liver tissues. The BPFL is highly toxic to zebrafish even in sublethal concentrations according to the molecular and histopathological responses.

2, 5-dichloro-1, 4-benuinone exposure to zebrafish embryos/larvae causes neurodevelopmental toxicity

2, 5-dichloro-1, 4-benuinone (2, 5-DCBQ) is an emerging disinfection by-product belonging to the class of halobenzoquinones (HBQs). However, there is limited evidence regarding the neurotoxic effects of 2, 5-DCBQ. To better understand the toxicological mechanisms of aquatic organisms, zebrafish embryos were exposed to 0.2 mg/L, 0.4 mg/L, and 0.6 mg/L of 2, 5-DCBQ from 4 h post-fertilization (hpf) to 120 hpf. Developmental defects, such as reduced body length, decreased heart rate, decreased pigmentation, and abnormal motor axon structure was observed. In particular, the locomotor activity of zebrafish larvae reduced with exposure to increasing 2, 5-DCBQ concentrations, and this effect was more pronounced under dark stimulation. The results indicated that the genes associated with neuronal development (gfap, mbp, syn2a, elavl3, ache, and a1-tubulin) were significantly downregulated after treatment with 2, 5-DCBQ. Furthermore, the KEGG result showed the neuroactive ligand-receptor interaction and apoptosis pathways were visibly disrupted, and we found acetylcholinesterase activity was also affected. In summary, the disinfection by-product, 2, 5-DCBQ, exhibits neurodevelopmental toxicity in zebrafish embryos, providing novel evidence for comprehensive analyses of its toxicity.

Zebrafish: an important model for understanding scoliosis

Scoliosis is a common spinal deformity that considerably affects the physical and psychological health of patients. Studies have shown that genetic factors play an important role in scoliosis. However, its etiopathogenesis remain unclear, partially because of the genetic heterogeneity of scoliosis and the lack of appropriate model systems. Recently, the development of efficient gene editing methods and high-throughput sequencing technology has made it possible to explore the underlying pathological mechanisms of scoliosis. Owing to their susceptibility for developing scoliosis and high genetic homology with human, zebrafish are increasingly being used as a model for scoliosis in developmental biology, genetics, and clinical medicine. Here, we summarize the recent advances in scoliosis research on zebrafish and discuss the prospects of using zebrafish as a scoliosis model.

Transcriptome profiling reveals toxicity mechanisms following sertraline exposure in the brain of juvenile zebrafish (Danio rerio)

Sertraline (SER) is one of the most commonly detected antidepressants in the aquatic environment that can negatively affect aquatic organisms at low concentrations. Despite some knowledge on its acute toxicity to fish, the effects of chronic SER exposure remain poorly understood along with any underlying mechanisms of SER-induced toxicity. To address this knowledge gap, the effects of chronic exposure to three SER concentrations from low to high were investigated in zebrafish. Juvenile zebrafish were exposed to three concentrations of 1, 10, or 100 μg/L of SER for 28 d, after which indicators of oxidative stress and neurotoxicity in the brain were measured. Superoxide dismutase (SOD) activity was significantly enhanced by SER at 1 up to 100 μg/L, and catalase (CAT) activity was significantly induced by SER at 1 or 10 μg/L. The activity of acetylcholinesterase (AChE) was significantly induced by 10 and 100 μg/L of SER, and the serotonin (5-HT) level was significantly increased by all three concentrations of SER. To ascertain mechanisms of SER-induced toxicity, transcriptomics was conducted in the brain of zebrafish following 100 μg/L SER exposure. The molecular signaling pathways connected with circadian system and the immune system were significantly altered in the zebrafish brain. Based on transcriptomic data, the expression levels of six circadian clock genes were measured, and three genes were significantly altered in relative abundance in fish from all experimental treatments with SER, including cryptochrome circadian regulator 2 (cry2), period circadian clock 2 (per2), and period circadian clock 3 (per3). We hypothesize that the circadian system may be related to SER-induced neurotoxicity and oxidative stress in the central nervous system. This study reveals potential mechanisms and key events (i.e., oxidative stress and neurotoxicity) associated with SER-induced toxicity, and improves understanding of the molecular and biochemical pathways putatively perturbed by SER.

Antioxidant enzyme activity and pathophysiological responses in the freshwater walking catfish, Clarias batrachus Linn under sub-chronic and chronic exposures to the neonicotinoid, Thiamethoxam®

The hydrophilic nature and resultant persistence of neonicotinoids in aquatic systems increase the exposure duration for non-target organisms. The sublethal toxicity of the neonicotinoid Thiamethoxam® spanning sub-chronic and chronic durations was investigated in Clarias batrachus, a non-target freshwater fish species. 96 h LC₅₀ value of Thiamethoxam® on Clarias batrachus was 138.60 mg L^-1. Pre-determined exposure concentrations of Thiamethoxam® (6.93 and 13.86 mg L^-1) were used and effects were assessed at days 15, 30, and 45 exposure intervals. Biomarker effects were evaluated using antioxidant enzyme responses (CAT, SOD) neurotransmission (acetylcholinesterase activity), haematological and serum biochemistry changes (including haemoglobin content, total erythrocyte count, and serum albumin total leukocyte count, total serum protein, serum globulin, triglyceride, cholesterol, high-density lipoprotein, very low-density lipoprotein, low-density lipoprotein, phospholipid, and total serum glucose), histopathological alterations (gill and liver). Thiamethoxam®-exposed fish showed a marked reduction in haemoglobin content, total erythrocyte count, and serum albumin levels compared to control fish. Similarly, gill and liver antioxidant enzyme activity (CAT, SOD) and neurotransmission (acetylcholinesterase) also showed altered responses between sub-chronic exposure on day-15 and chronic responses on day-45. Histopathological observations in gill tissue revealed alterations ranging from vacuolation, hypertrophy, disruption of primary lamellar architecture, haemorrhage, the fusion of secondary lamella, and sloughing of outer epithelia. For liver tissue of exposed fish histopathological observations included increased sinusoidal spaces (ISS), necrosis of hepatocytes (NOH), nuclear degeneration (ND), disruption of architecture (DOA), macrophage infiltration of the central vein, vacuolation (V), hypertrophied hepatocytes, and haemorrhages. The gradients of toxic responses across exposure concentrations and depictions of impaired fish health with increasing thiamethoxam® exposure duration portend lowered physiological capacity for survival in the wild.

Protective effects of summer savory (Satureja hortensis) oil on growth, biochemical, and immune system performance of common carp exposed to pretilachlor herbicide

There are many reports on the deleterious effects of herbicides on aquatic organisms which lead to tremendous biological, environmental and economical damage. In this regard, in the present study, the protective effect of summer savory (Satureja hortensis) essential oil (SEO) against pretilachlor, one of the most used herbicides was investigated in common carp (Cyprinus carpio). The fish assigned to six treatment groups (T₁: control treatment; T₂: 25% LC₅₀ pretilachlor herbicide; T₃: 50% LC₅₀ pretilachlor herbicide; T₄: 1% SEO; T₅: 25% LC₅₀ pretilachlor herbicide + 1% SEO; and T₆: 25% LC₅₀ pretilachlor herbicide + 1% SEO) for 21 days. The results showed that the SEO-containing treatments significantly increased the survival rate (SR) (P < 0.05). The highest final weight (FW), specific growth rate (SGR), and feed conversion ratio (FCR) were observed in the T₄ treatment (P < 0.05). There was a significant increase in glucose (GLU) level in pretilachlor treatments and a significant decrease in SEO-containing treatments compared to the control (P < 0.05). The significantly highest total protein (TP) content was observed in T₄ treatment containing SEO. Cholesterol (CHOL) and triglyceride (TRIG) levels decreased in SEO-containing treatments with the lowest level in T₄ treatment (P < 0.05). Alternative complement pathway activity (ACH₅₀), activity levels of superoxide dismutase (SOD), and glutathione peroxidase (GP_X) showed an increasing trend in SEO-containing treatments with the highest level in T₄ treatment (P < 0.05). The activity of liver enzymes showed a significantly lowest level in T₄ treatment. To conclude, our findings revealed that the use of SEO in fish exposed to pretilachlor herbicide could improve growth, strengthen the immune system and exert a protective effect on common carp.