Acute toxicity of broflanilide on neurosecretory system and locomotory behavior of zebrafish (Danio rerio)

Epigenetic Responses Induced by Transgenerational and Multigenerational Exposure Alter the Plasticity of Fish to Neurotoxic Effects of Triclosan

Triclosan (TCS), a common antimicrobial agent, is widely detected in the global environments nowadays globally. Using marine medaka as a model, this study investigated and compared the transgenerational and multigenerational neurotoxic effects on fish. The environmentally realistic concentration of TCS can induce hyperlocomotor activities and increase heart rate, while higher concentrations (>500 μg/L) can inhibit hatching and cause cardiovascular malformations and neurotransmitter imbalances. Parental (F0) exposure to TCS resulted in transgenerational effects on locomotor activities manifested in F2, alongside with alterations in phototransduction and cell adhesion pathways. Global DNA methylation analyses indicated that the observed transgenerational effects are mediated through relevant epigenetic changes. Multigenerational exposure to TCS increased locomotor activities from F1 to F3, which is associated with changes in the expression of genes related to eye structure, phototransduction, and lipid and retinol metabolisms, thereby affecting energy metabolism and visual function. Results of this study highlight the difference between transgenerational and multigenerational effects of TCS exposure, and potential biases incurred in current risk assessment based exclusively on data derived from F0, which presents challenges for environmental management and regulatory standards.

Broflanilide induces zebrafish neurobehavioral defects by interfering with synaptic homeostasis

Broflanilide is a novel bisamide insecticide that is extensively used. Previous study reported that broflanilide induced neurotoxicity during zebrafish embryonic development, however, its behavior impact and the involved neural cell heterogeneous mechanism remains largely unknown. Here, we performed a series of neuro-behavior test for adult zebrafish that were exposed to 5 and 25 μg/L broflanilide for 30 days. We found that 25 μg/L broflanilide could induce abnormal locomotion and cognitive defect. These changes were accompanied by synaptic homeostasis inference (decreased number of synaptic knobs), and neuron loss. Simultaneously, a targeted metabolomic assay showed that the glutathione metabolism and GABAergic synapses in brain were significantly altered, indicating an altered synaptic transmission, which is consistent with the synaptic injury. Single-cell RNA sequencing of zebrafish brain showed changed cell composition after exposure, including a decreased ratio of neuron and oligodendrocyte, and an increased proportion of astrocytes. Meanwhile, genes involved in synaptic functional pathways were altered in neuron, astrocyte and oligodendrocytes, which partly explained the disruption of synaptic homeostasis. These findings reveal the long-term risk of broflanilide toward neural health of aquatic organisms and suggest an across-cell types transcriptional regulation in mediating the neurotoxicity.

Chronic chlorothalonil exposure inhibits locomotion and interferes with the gut-liver axis in Pelophylax nigromaculatus tadpoles

Chlorothalonil is a widely used fungicide that has a negative effect on individual movement, but its impact pathway needs further refinement. Here, the effects of exposure to chlorothalonil on the locomotion behavior of Pelophylax nigromaculatus tadpoles (GS23) were measured at three different levels (0 µg/L, 10 µg/L, and 50 µg/L), and the possible pathways of its effects were analyzed from the gut-liver axis. Chlorothalonil exposure levels of 10 µg/L and 50 µg/L significantly reduced the average speed of P. nigromaculatus tadpoles by 26% and 32.7%, respectively, and significantly decreased the locomotor frequency by 27.1% and 58.6%, respectively. Gut microbiota analysis revealed chlorothalonil exposure significantly increased the abundance of Firmicutes, while significantly decreased the abundance of Actinobacteriota, Pseudomonas, and Rhodococcus. Metabolomics analysis identified that chlorothalonil treatment changed amino acid-related metabolism pathways in the gut and liver and altered the glycerophospholipid metabolism pathway in the liver. This study indicated that chlorothalonil can affect individual locomotor abilities and interfering with the gut-liver axis of aquatic animals. These findings establish that chlorothalonil compromises aquatic organism motility through a multi-target mechanism involving gut microbiota modulation, amino acid metabolic interference, and hepatic lipid pathway disruption.

The fate and ecological risk of mefentrifluconazole in the water-sediment system: A systematic analysis at the enantiomer level

Triazole fungicides occupy a significant position in the global fungicidal market. Mefentrifluconazole (MFZ) is a new-generation chiral triazole fungicide with broad applications. It can effectively control several rice fungal diseases; thus, its wide application increases its risk of entering the water and sediment in ecosystems. In this study, the stereoselective fate and risk of MFZ in the water-sediment system were investigated. The results showed stereoselective differences in the acute toxicity and fate of MFZ enantiomers (S-MFZ and R-MFZ) in the water-sediment system, with S-MFZ being more toxic and persistent. Both R-MFZ and S-MFZ induced significant decreases in the oxidation-reduction potential (ORP) value and organic matter (OM) content of the sediment. Additionally, soil enzyme activity in the sediments changed in varying degrees during exposure. Further microbiome sequencing results showed that both R-MFZ and S-MFZ induced changes in the composition of sediment microbial communities and decreased species diversity, which, in turn, affected the metabolic processes of microorganisms and the function of glycosyltransferase (GT) enzymes, especially S-MFZ. Correlation analysis showed that stereoselectivity in the interaction between the MFZ enantiomers and GT enzymes induced a difference in the synthesis of lipopolysaccharides; thus, affecting the abundances of the relevant bacterial genera and carbohydrate metabolic pathways. Exposure to MFZ enantiomers induced an increase in the abundance of anaerobic bacteria, such as Methylophilus and Rhodoferax, which exacerbated the anaerobic environment of the sediment system, leading to acidification and accelerated nutrient decomposition.

Environmental concentrations of 6PPD and 6PPD-Q cause oxidative damage and alter metabolism in Eichhornia crassipes

N-(1,3-dimethylbutyl)-N '-phenyl-p-phenylenediamine (6PPD) and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q) are ubiquitous in the environment and can cause toxicity to aquatic animals. However, research on the toxicological effects of 6PPD and 6PPD-Q on aquatic plants remains limited. The present study investigated the physiological, biochemical, and metabolic responses of the floating aquatic plant Eichhornia crassipes (E. crassipes) to environmentally relevant concentrations (0.1, 1, and 10 μg·L-1) of 6PPD and 6PPD-Q. We found that 6PPD and 6PPD-Q elicited minimal effects on plant growth, but 6PPD induced a concentration-dependent decrease in the content of photosynthetic pigments. Low doses (0.1 μg·L-1 and 1 μg·L-1) of 6PPD-Q significantly elevated Reactive Oxygen Species (ROS) content in E. crassipes roots, indicating oxidative damage. Furthermore, 6PPD-Q induced a more pronounced osmotic stress compared to 6PPD. Metabolic analyses revealed that carbohydrates were significantly altered under 6PPD and 6PPD-Q treatments. The findings of this study enhance the understanding of the environmental risks posed by 6PPD and 6PPD-Q to plants and reveal the potential mechanisms of phytotoxicity.

Aged polystyrene microplastics exposure affects apoptosis via inducing mitochondrial dysfunction and oxidative stress in early life of zebrafish

In recent years, the toxic effects of microplastics (MPs) on aquatic organisms have been increasingly recognized. However, the developmental toxicity and underlying mechanisms of photoaged MPs at environmental concentrations remain unclear. Therefore, the photodegradation of pristine polystyrene (P-PS) under UV irradiation was used to investigate, as well as the developmental toxicity and underlying mechanisms of zebrafish (Danio rerio) exposed to P-PS and aged polystyrene (A-PS) at environmentally relevant concentrations (0.1-100 μg/L). Mortality, heart rate, body length, and tail coiling frequency of zebrafish larvae were the developmental toxicity endpoints. A-PS had increased crystallinity, the introduction of new functional groups, and higher oxygen content after UV-photoaging. The toxicity results showed that exposure to A-PS resulted in more adverse developmental toxicity than exposure to P-PS. Exposure to A-PS induced oxidative damage, as evidenced by elevated production of reactive oxygen species (ROS) and DNA damage, and led to decreased mitochondrial membrane potential (MMP) and causes the release of cytochrome c (cyt c) from the mitochondria. The caspase-3/-9 activation signaling pathways may cause developmental toxicity via mitochondrial apoptosis. Significant changes in the expression of genes were further explored linking with oxidative stress, mitochondria dysfunctions and apoptosis pathways following A-PS exposure. These findings underscore the importance of addressing the environmental applications of aged MPs and call for further research to mitigate their potential risks on aquatic ecosystems and human health.

Molecular underpinnings underlying behaviors changes in the brain of juvenile common carp (Cyrinus carpio) in response to warming

INTRODUCTION

Global warming is increasing interest in how aquatic animals can adjust their physiological performance and cope with temperature changes. Therefore, understanding the behavioral changes and molecular underpinnings in fish under warming is crucial for both the individual and groups survival. This could provide experimental evidence and resource for evaluating the impact of global warming.

OBJECTIVE

Three genetic families of common carp (Cyprinus carpio) were generated. These juveniles were constructed short-term (4 days) and long-term (30 days) warming groups to investigate the effects of warming on behavioral responses and to elucidate the potential underlying mechanisms of warming-driven behavior.

METHODS

Behavioral tests were used to explore the effects of short- and long-term exposure to warming on the swimming behavior of C. carpio. Brain transcriptome combined with measurement of nervous system activity was used to further investigated the comprehensive neuromolecular mechanisms under warming.

RESULTS

Long-term warming groups had a more significant impact on the decline of swimming behavior in juvenile C. carpio. Furthermore, brain comparative transcriptomic analysis combined with measurement of nervous system activity revealed that genes involved in cytoskeletal organization, mitochondrial regulation, and energy metabolism are major regulators of behavior in the juvenile under warming. Importantly, especially in the long-term warming groups, enrichment analysis of associated gene expression suggested functional alterations of synaptic transmission and signal transduction leading to swimming function impairment in the central nervous system, as revealed by behavioral tests.

CONCLUSIONS

Our study provides evidence of the neurogenomic mechanism underlying the decreased swimming activity in juvenile C. carpio under warming. These findings have important implications for understanding the impacts of climate change on aquatic ecosystems and the organisms that inhabit them.

Sodium p-perfluorinated noneoxybenzen sulfonate (OBS) induced neurotoxicity in zebrafish through mitochondrial dysfunction

Sodium p-perfluorous nonenoxybenzene sulfonate (OBS)-one of the main alternatives to perfluorooctane sulfonate-has been increasingly detected in both aquatic environments and human bodies. Therefore, the pathogenic risks of OBS exposure warrant attention, especially its central nervous system toxicity mechanism under long-term exposure. In this study, the effects and mechanisms of OBS on the zebrafish brain at 40 days post exposure were examined. The results demonstrated that at 3.2 μg/L, OBS had no significant effect on the zebrafish brain, but 32 μg/L OBS caused depression or poor social behavior in zebrafish and reduced both their memory and survival ability. These changes were accompanied by histological damage and cell apoptosis. Furthermore, OBS caused the accumulation of excessive reactive oxygen species in the fish brain, leading to oxidative stress and subsequently cell apoptosis. Moreover, an imbalance of both inflammatory factors (IL-6, IL-1β, IL-10, TNF-α, and NF-κB) and neurotransmitters (GABA and Glu) led to neuroinflammation. Additionally, 32 μg/L OBS induced decreases in mitochondrial membrane potential and Na+-K+-ATPase activity, leading to both mitochondrial structural damage and the emergence of mitochondrial autophagosomes, partly explaining the neurotoxicity of OBS. These results help to analyze the target sites and molecular mechanisms of OBS neurotoxicity and provide a basis for the scientific evaluation of its health risks to humans.

RNA-Seq analysis offers insight into the TBBPA-DHEE-induced endocrine-disrupting effect and neurotoxicity in juvenile zebrafish (Danio rerio)

Tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-DHEE) is the major TBBPA derivative. It has been detected in different environmental samples. Previous studies show that TBBPA-DHEE caused neurotoxicity in rats. In this study, juvenile zebrafish were exposed to various concentrations of TBBPA-DHEE to ascertain the potential neurotoxicity of TBBPA-DHEE, the chemical, and its possible molecular mechanism of action. Behavioral analysis revealed that TBBPA-DHEE could significantly increase the swimming distance and speed in the 1.5 mg/L group compared to the control. In contrast, the swimming distance and speed were significantly reduced in the 0.05 and 0.3 mg/L groups, affecting learning, memory, and neurodevelopment. Similarly, TBBPA-DHEE exposure caused a concentration-dependent significant increase in the levels of excitatory neurotransmitters, namely, dopamine, norepinephrine, and epinephrine, which could be attributed to the change observed in zebrafish behavior. This demonstrates the neurotoxicity of TBBPA-DHEE on juvenile zebrafish. The concentration-dependent increase in the IBR value revealed by the IBR index reveals the noticeable neurotoxic effect of TBBPA-DHEE. Transcriptomic analysis shows that TBBPA-DHEE exposure activated the PPAR signaling pathways, resulting in a disturbance of fatty acid (FA) metabolism and changes in the transcript levels of genes involved in these pathways, which could lead to lipotoxicity and hepatotoxicity. Our findings demonstrate a distinct endocrine-disrupting response to TBBPA-DHEE exposure, possibly contributing to abnormal behavioral alterations. This study provides novel insights into underlying the mechanisms and effects of TBBPA-DHEE on aquatic organisms, which may be helpful forenvironmental/human health risk assessments of the emerging pollutant.

Environmental levels of azoxystrobin disturb male zebrafish behavior: Possible roles of oxidative stress, cholinergic system, and dopaminergic system

A widely applied pesticide of azoxystrobin, is increasingly detected in the water environment. Concern has been raised against its potential detriment to aquatic ecosystems. It has been shown that exposure to azoxystrobin interfere with the locomotor behavior of zebrafish larvae. This study aims to investigate whether exposure to environmental levels of azoxystrobin (2 μg/L, 20 μg/L, and 200 μg/L) changes the behavior of male adult zebrafish. Herein, we evaluated behavioral response (locomotor, anxiety-like, and exploratory behaviors), histopathology, biochemical indicators, and gene expression in male adult zebrafish upon azoxystrobin exposure. The study showed that exposure to azoxystrobin for 42 days remarkably increased the locomotor ability of male zebrafish, resulted in anxiety-like behavior, and inhibited exploratory behavior. After treatment with 200 μg/L azoxystrobin, vasodilatation, and congestion were observed in male zebrafish brains. Exposure to 200 μg/L azoxystrobin notably elevated ROS level, MDA concentration, CAT activity, and AChE activity, while inhibiting SOD activity, GPx activity, ACh concentration, and DA concentration in male zebrafish brains. Moreover, the expression levels of genes related to the antioxidant, cholinergic, and dopaminergic systems were significantly changed. This suggests that azoxystrobin may interfere with the homeostasis of neurotransmitters by causing oxidative stress in male zebrafish brains, thus affecting the behavioral response of male zebrafish.

The novel insecticide broflanilide dysregulates transcriptional networks associated with ion channels and induces hyperactivity in zebrafish (Danio rerio) larvae

Broflanilide is a novel insecticide that is classified as a non-competitive γ-aminobutyric acid (GABA) receptor antagonist. However, indiscriminate use can have negative effects on non-target species. The objective of this study was to determine the sub-lethal toxicity potential of broflanilide in early staged zebrafish. Embryos/larvae were assessed for multiple molecular and morphological endpoints following exposure to a range of concentrations of broflanilide. The insecticide did not affect hatch rate, the frequency of deformities, nor did it impact survival of zebrafish at exposure concentrations up to 500 μg/L over a 7-day period from hatch. There was also no effect on oxidative consumption rates in embryos, nor induction of reactive oxygen species in fish exposed up to 100 μg/L broflanilide. As oxidative stress was not prominent as a mechanism, we turned to RNA-seq to identify potential toxicity pathways. Gene networks related to neurotransmitter release and ion channels were altered in zebrafish, consistent with its mechanism of action of modulating GABA receptors, which regulate chloride channels. Noteworthy was that genes related to the circadian clock were induced by 1 μg/L broflanilide exposure. The locomotor activity of larval fish at 7 days was increased (i.e., hyperactivity) by broflanilide exposure based on a visual motor response test, corroborating expression data indicating neurotoxicity and motor dysfunction. This study improves the current understanding of the biological responses in fish to broflanilide exposure and contributes to risk assessment strategies for this novel pesticide.

Neural System Impairment and Involved Microglia-Neuron Regulation of Broflanilide in Zebrafish Larvae

Broflanilide is widely used to control pests and has attracted attention due to its adverse effects on aquatic organisms. Our previous study showed that broflanilide has a negative impact on the central nervous system (CNS) at lethal dosages; however, its neural effects under practical situations and the underlying mechanisms remain unknown. To elucidate how broflanilide affects the CNS, we exposed zebrafish larvae to broflanilide at 16.9 and 88.0 μg/L (the environmentally relevant concentrations) for 120 h. Zebrafish locomotion was significantly disturbed at 88.0 μg/L, with a decreased moving distance and velocity accompanied by an inhibited neurotransmitter level. In vivo neuroimaging analysis indicated that the nerves of zebrafish larvae, including the axons, myelin sheaths, and neurons, were impaired. The number of neurons was significantly reduced after exposure, with an impaired morphological structure. These changes were accompanied by the abnormal transcription of genes involved in early CNS development. In addition, an increased total number of microglia and an elevated proportion of amoeboid microglia were observed after 88.0 μg/L broflanilide exposure, pointing out to an upstream role of microglia activation in mediating broflanilide neurotoxicity. Meanwhile, increased inflammatory cytokine levels and brain neutrophil numbers were observed, implicating significant inflammatory response and immune toxicity. Our findings indicate that broflanilide interferes with microglia-neuron regulation and induces neurodevelopmental disorders.

Metabolomics and mass spectrometry imaging reveal the chronic toxicity of indoxacarb to adult zebrafish (Danio rerio) livers

Indoxacarb is a widely used insecticide in the prevention and control of agricultural pests, whereas its negative effects on non-target organisms remain largely unclear. Herein, we demonstrated the integrated metabolomics and mass spectrometry imaging (MSI) methods to investigate the chronic exposure toxicity of indoxacarb at environmentally relevant concentrations in adult zebrafish (Danio rerio) liver. Results showed that movement behaviors of zebrafish can be affected and catalase (CAT), glutamic oxalacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) activities were significantly increased after indoxacarb exposure for 28 days. Pathological analysis of zebrafish livers also showed that cavitation and pathological reactions occur. Metabolomics results indicated that metabolic pathways of zebrafish liver could be significantly affected by indoxacarb, such as tricarboxylic acid (TCA) cycle and various amino acid metabolisms. MSI results revealed the spatial differentiation of crucial metabolites involved in these metabolic pathways within zebrafish liver. Taken together, these integrated MSI and metabolomics results revealed that the toxicity of indoxacarb arises from metabolic pathways disturbance, which resulted in the decrease of liver detoxification ability. These findings will promote the current understanding of pesticide risks and metabolic disorders in zebrafish liver, which provide new insights into the environmental risk assessment of insecticides on aquatic organisms.

Hydrolytic Behavior of Novel Pesticide Broflanilide and Its Dissipative Properties in Different Types of Soils

All pesticides are toxic by nature and pose short- or long-term safety risks to human or the environment, especially when they were used extensively and absence of safety measures. As a new insecticidal active compound with a novel mechanism of action, there is a serious inadequate of information on the hydrolytic behavior of broflanilide in the aqueous environment, as well as its degradation pattern in agricultural soils. In particular, the effects of temperature and pH of the aqueous environment on its hydrolytic behaviors and the dissipation pattern in different types of agricultural soils were still in a dark box. And the further understanding and insights into this insecticidal active ingredient were being deeply conditioned by these doubts. The hydrolysis behavior of broflanilide and the dissipation pattern in soil were systematically investigated by constructing hydrolysis systems with different temperatures and pH values, and conducting spiking experiments in different types of agricultural soil in the laboratory. The obtained results showed that the longest hydrolysis half-life of 10 mg/L broflanilide at 25 °C was 43.32 h (in pH 4.0 buffer), while it was only 12.84 h in pH 9.0 buffer. In pH 7.0 buffer, the hydrolysis rate of broflanilide exhibited a significant temperature dependence, as shown by the fact that for every 10 °C increase in the system temperature, the corresponding hydrolysis rate will increase about 1.5 times. The dissipation experiments in soils showed that broflanilide was most rapidly dissipated in fluvo-aquic soil (half-life of 1.94 days), followed by lime concretion black soil (half-life of 2.53 days) and cinnamon soil (half-life of 3.11 days), and slower in paddy soil (half-life of 4.03 days). It was indicated that broflanilide was a readily degradable pesticide in both aqueous environment and agricultural soil, and it was significantly affected by the temperature and pH of the system.

Effects of Broflanilide on Oxidative Stress and Expression of Apoptotic Genes in Zebrafish (Danio rerio) Gill

Broflanilide exerted negative impacts on the gill of zebrafish. Thus, in this study, zebrafish gill was used to assess the apoptosis toxicity of broflanilide by determining the levels of reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) and apoptosis-related genes. The results found that the minimum threshold for the content and time of broflanilide affecting enzyme content and gene expression was 0.26 mg/L after 24 h exposure. After 96 h exposure, broflanilide could cause apoptosis and exerted significantly increased contents of ROS and MDA, while inhibiting the activities of SOD, CAT, and GPx at 0.26 and 0.57 mg/L. Broflanilide also had adverse effects on apoptosis-related genes, such as tumor protein p53 (p53), associated × (Bax), B-cell lymphama-2 (Bcl-2), caspase-3, caspase-9, and apoptotic protease activating factor-1(apaf-1), at 0.26 mg/L and 0.57 mg/L after 96 h exposure, respectively. These results provide new insight into the potential toxicity mechanisms of broflanilide in zebrafish gills.

Photolysis of the novel meta-diamide insecticide broflanilide in solutions: Kinetics, degradation pathway, DFT calculation and ecotoxicity assessment

Broflanilide, as a novel meta-diamide insecticide, presents high bioactivity against agricultural pests. However, there was limited report regarding the photolysis fate of broflanilide. In this study, the photodegradation kinetics and influence factors of broflanilide, including different solvents, pH, iron, S₂O₈^2- and SO₃^2- were investigated under UV condition, and the reaction mechanism and transformation pathway were explored. The reaction rates (k) showed solvent-specificity in ultrapure water (0.015 min^-1), ethyl acetate (0.051 min^-1), methanol (0.084 min^-1) and acetonitrile (0.193 min^-1), correspondingly. The photolysis of broflanilide was slowest in the acid condition (pH = 4.0) compared with that in the neutral (pH = 7.0) and alkaline (pH = 9.0) conditions. The iron (Fe²⁺ and Fe³⁺) presented significant inhibition on the photodegradation due to the light shielding effect. Additionally, the UV/peroxydisulfate (S₂O₈^2-) and UV/sulfite (SO₃^2-) technologies could effectively accelerate the photodegradation of broflanilide, which has the potential for rapid treatment of pesticides in the aqueous environment. Six transformation products (TPs) were detected in water, peroxydisulfate and sulfite solutions, and the possible transformation pathways, including dehalogenation, cyclization, N-dealkylation, oxidation, reduction and hydrolysis, were proposed. Importantly, the reaction mechanism was explained through the analysis of molecular electrostatic potential and molecular orbitals. The predicted toxicity of the TPs indicated that several highly toxic TPs need to pay more attention in future risk assessments. This study provides a new perspective for evaluating the ecological fate and risks of pesticides.

Chronic toxicity of broflanilide in Daphnia magna: changes in molting, behavior, and gene expression

Broflanilide is a novel pesticide used in agriculture that binds to unique receptors on pests; however, the widespread use of broflanilide has led to toxicity in Daphnia magna. At present, little information on the potential threats broflanilide imposes on D. magna is available. Therefore, the present study examined the chronic toxicity of broflanilide in D. magna by comparing changes in molting, neurotransmitter function, and behavior. The results showed that broflanilide caused chronic toxicity in D. magna at a concentration of 8.45 μg/L, and growth, development, reproduction, and the development of offspring were affected. In addition, broflanilide affected the molting of D. magna by significantly inhibiting the expression of chitinase, ecdysteroid, and related genes. Broflanilide also affected the expression of γ-glutamic acid, glutamine, gamma-aminobutyric acid, 5-hydroxytryptamine, 5-hydroxytryptophan, dopa, and dopamine. Furthermore, the swimming distance and speed of D. magna were reduced. Taken together, the results demonstrate the chronic toxicity and exposure risk of broflanilide in D. magna.

The transcriptomic profile of Spodoptera frugiperda differs in response to a novel insecticide, cyproflanilide, compared to chlorantraniliprole and avermectin

BACKGROUND

Cyproflanilide is a novel chemical that is already undergoing insecticide registration in China and has been categorized as a member of group 30 by the IRAC. Since it was first detected in 2019, the fall armyworm (FAW), Spodoptera frugiperda, has become a serious pest in China. Our laboratory and field efficacy trials indicated that cyproflanilide exhibits high larvicidal activity against FAW. However, the effect of cyproflanilide against FAW remains unknown. And it is worth exploring further before the cyproflanilide becomes commercially available.

RESULTS

We found larvae exposed to cyproflanilide had significantly shorter body length and higher death rates compared to control larvae. Additionally, we found surviving larvae had a significantly longer developmental period compared to control larvae. The potential molecular mechanisms of cyproflanilide against FAW were investigated using comparative transcriptomic analyses on larval samples subjected to three insecticide treatments, including cyproflanilide and two other commonly used insecticides against FAW in China, chlorantraniliprole and avermectin. We found that several subunits of the γ-aminobutyric acid receptor (GABAR), a possible target protein of cyproflanilide, were significantly up-regulated at the transcriptional level during cyproflanilide-induced stress. Additionally, between the control and cyproflanilide-treated samples, we identified 131 differentially expressed genes (DEGs) associated with detoxification metabolism. Of these, we found four P450 genes that were significantly up-regulated under cyproflanilide stress but were not DEGs when exposed to chlorantraniliprole and avermectin, or 23 other pesticides from previous reports. Furthermore, we discovered an interesting gene aggregation region for insect cuticle proteins (CPs) on the 18th chromosome, which is likely related to FAW cross-resistance to cyproflanilide and avermectin.

CONCLUSIONS

Our results contribute to a greater understanding of the mechanisms by which cyproflanilide affects FAW. Additionally, we identified the similarities and differences in transcriptomic profiling of FAW between the novel insecticide cyproflanilide and two other commonly used insecticides.