Liver damage and lipid metabolic dysregulation in adult zebrafish (Danio rerio) induced by spirotetramat.

Spirotetramat, an insecticide derived from cycloketone and extensively utilized in agricultural production, has been reported to be toxic to an array of aquatic organisms. Previous studies have indicated that spirotetramat can cause toxicity such as impaired ovarian development and apoptosis in zebrafish, but its toxicological effects on lipid metabolism and liver health in zebrafish remain unclear. In this study, we explored the effects of spirotetramat exposure on zebrafish (Danio rerio) by examining key markers of lipid metabolism, alterations in gene expression related to this process, and histological characteristics of the liver. Spirotetramat significantly reduced the condition factor, triglycerides and low-density lipoprotein cholesterol levels at 2 mg/L. The expression of genes related to fatty acid synthesis (acacb), ß-oxidation (acox1, pparda) and pro-inflammatory cytokines (tnf-α, il-1ß) was downregulated. However, the expression of genes related to lipid transport and uptake (cd36, ppara) and output (apob) was upregulated. The activity of alanine aminotransferase was significantly inhibited. Histopathology results showed that spirotetramat exposure led to liver cell vacuolation and necrosis. In addition, molecular docking results of spirotetramat and lipid transport related protein (ACC, ApoB) in both zebrafish and human showed the binding energy of human proteins is lower than that for zebrafish, and that the number of hydrogen bonds formed was higher. It is speculated that spirotetramat may also pose a significant potential hazard to humans, potentially affecting human lipid metabolism and health. This study expunge shed light on the ecological toxicity of spirotetramat by showing how it disrupts lipid metabolism and causes tissue damage specifically in zebrafish liver, contributing to a deeper understanding of its harmful effects in aquatic environment.

Effects of injudicious use of spirotetramat on Encarsia formosa's ability to control Bemisia tabaci.

The excessive and frequent use of insecticides has led to serious problems with insecticide residues, impacting nontarget organisms such as the parasitoid Encarsia formosa. This study examined the growth, development, and enzyme activity of E. formosa exposed to spirotetramat at LC10, LC30, and LC50. The regression equation for the toxicity of spirotetramat toward E. formosa was Y = 5.25X-11.07. After exposure to spirotetramat, the survival rates of E. formosa sharply decreased, which occurred earlier than those in the control batch. Although the maximum daily parasitism quantity of E. formosa increased and the average parasitism number, enumerated from the 1st to the 5th day, was 53.97 after being exposed to spirotetramat at LC10, the life span of its F1 generation adults was only 8.47 days, which was significantly shorter than that in the control batch. After being exposed to spirotetramat at LC50, the average parasitism number of E. formosa was 63.30, and the developmental time of its F1 generation, enumerated from the 1st to the 5th day after exposure to spirotetramat, was significantly longer than that of the control batch. The activities of mixed function oxidase, acetylcholinesterase, carboxylesterase, and catalase increased significantly, and the rate of increase in enzyme activity was directly proportional to the increase in the concentration of spirotetramat. These results revealed that the parasitic ability of E. formosa decreased after exposure to spirotetramat at LC10, LC30, and LC50. This leads to a change in parasitoid control of pests, revealing the potential environmental threat of insecticide residues to nontarget organisms.

Basal levels of biochemical biomarkers in the freshwater prawn Palaemon argentinus and their alterations due to the exposure of both insecticides cypermethrin and spirotetramat.

The aim of this study was to evaluate the sensitivity of the prawn Palaemon argentinus to the pyrethroid cypermethrin (CYP) and the tetramic acid spirotetramat (STM). These treatments were compared with prawns collected at a reference site to define their basal physiological state. Initially, physicochemical parameters and several pollutants at the selected site were analyzed. The LC50-96 h was determined in adult prawns. Then, prawns were exposed for 96 h to sublethal concentrations of CYP (0.0005 µg/l) and STM (0.44 mg/l) to evaluate the effects on some biochemical endpoints. A treatment combining both pesticides was also added at 5 % of these values. Controls with and without solvent (acetone) were included. The LC50-96 h values were 0.005 µg/l and 4.43 mg/l for CYP and STM, respectively. Moreover, some biomarkers linked to oxidative and energy metabolism were analyzed in the hepatopancreas and muscle of both essayed prawns and those at the basal state. The STM caused a significant decrease in total protein content (32 %) in contrast to the increase of protein carbonyl content (71 %) (p < 0.05). Also, glutathione S-transferase (52 %) and catalase (61 %) activities in the hepatopancreas of exposed prawns were higher compared to both the control and state basal groups (p < 0.05). In muscle, only a significant decrease in the lactate content (69 %) was caused by STM (p < 0.05). In addition, CYP caused a significant increase in the lactate dehydrogenase activity (110 %) in muscle and triacylglycerol content (73 %) in the hepatopancreas (p < 0.05). The integrated biomarker index (IBRv2) analysis showed that STM caused greater damage than CYP. Besides, the combined treatment showed an antagonistic interaction between both insecticides. The differential response of biomarkers to both CYP and STM exposure with respect to their basal levels shows a high sensitivity of P. argentinus demonstrating its potential role as a bioindicator organism.

The spirotetramat inhibits growth and reproduction of silkworm by interfering with the fatty acid metabolism.

Spirotetramat is a novel insecticide and acaricide that can effectively control many species of piercing-sucking pests by inhibiting lipid synthesis. The silkworm is an economically important insect and a model organism for genetics and biochemical research. However, the toxic effect on their development and reproduction remain unclear. In this study, we demonstrated the negative effects of spirotetramat on the development, vitality, silk protein synthesis, and fecundity of silkworm. We also compared expression changes of silkworm genes using digital gene expression (DGE). A total of 1567 differentially expressed genes (DEGs) were detected, of which 874 genes were downregulated and 693 genes were upregulated. Gene Ontology (GO) enrichment analysis showed that the DEGs were enriched in the oxidation-reduction process, oxidoreductase activity, and fatty-acyl-CoA reductase activity. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the DEGs were mainly enriched in fatty acid metabolism and lysosome pathways. We detected the relative expression of silkworm genes related to fatty acid synthesis and decomposition pathways and the degradation pathway of juvenile hormone by quantitative real-time PCR. The expression levels of Acetyl CoA carboxylase (ACC), fatty acyl-CoA reductase (FACR), Enoyl-CoA hydratase (ECH), very-long-chain (3R)-3-hydroxyacyl-CoA dehydratase (LCHAD), juvenile hormone epoxide hydrolase (JHEH), and phytanoyl-CoA dioxygenase (PCD) genes were downregulated. These data demonstrate the effects of spirotetramat on silkworm and its effects on genes involved in fatty acid metabolism.

Effect of sublethal Spirotetramat on host locating and parasitic behavior of Encarsia formosa Gahan.

BACKGROUND: The use of chemical insecticides to control Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) is widespread, although it might exert a sublethal effect on its dominant parasitoid, Encarsia formosa Gahan (Hymenoptera: Aphelinidae). To investigate the sublethal effect of spirotetramat on E. formosa, we observed the ability of E. formosa to locate and handle the host, oviposit and preen after exposure to sublethal concentrations of spirotetramat. RESULTS: After exposure to spirotetramat at LC50 , the response time of E. formosa to the volatile reached 223.40 s and was significantly prolonged. Only 56.44% of the wasps were attracted by the volatile and the insect crawled the slowest among all of the treatments. The averages of oviposition posture adopted and host handled by each E. formosa in 1 h decreased significantly to 1.79 and 1.27, respectively. At the sublethal concentration of LC10 , 94.59% of the wasps were attracted by the volatile and the insect crawled the fastest. The average of host handled by each E. formosa was 3.92, and the frequency of drumming while walking and drumming the host was 12.34 times per second and 12.30 times per second, respectively, demonstrating a significant acceleration in these abilities. CONCLUSION: These findings demonstrate that spirotetramat induced hormesis in E. formosa on exposure to its LC10 concentration and accelerated its host locating, host handling and frequency of antennae drumming. These findings could assist in balancing the chemical and biological control of B. tabaci and enhancing the efficacy of E. formosa as a biocontrol agent. © 2021 Society of Chemical Industry.

Ovicidal activity of spirotetramat and its effect on hatching, development and formation of Frankliniella occidentalis egg.

Frankliniella occidentalis (Pergande) has become an important vegetable pest worldwide because of its economic damage to crop production. However, it is difficult to control due to its unique living habits. In this study, the eggs of F. occidentalis were used as the target to explore the ovicidal activity of spirotetramat on the thrips and its effect on hatching, development and formation. After the treatment of spirotetramat, the LC50 value descreased with increased egg age using egg dipping method, and showed the same trend as the leaf dipping method verified on living plants. Through ultra-depth-of-field microscopy, scanning electron microscopy and transmission electron microscopy, the egg shell and internal structures of F. occidentalis eggs were studied. Spirotetramat can destroy the egg shells of F. occidentalis, resulting in shrinkage of the egg surface, sunken pores, egg deformities, egg shell rupture and other phenomena. This allows spirotetramat to enter the egg and destroy the egg structure, making the egg internal structure flocculent, fuzzy and unevenly distributed, which affects embryonic development and causes the nymphs to die before hatching. Therefore, the prevention and control of F. occidentalis using spirotetramat before damage is caused to crops should have a better effect.

Control efficacy and joint toxicity of thiamethoxam mixed with spirotetramat against the Asian citrus psyllid, Diaphorina citri Kuwayama.

BACKGROUND: The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is one of the most devastating pests in citrus orchards, and has caused huge economic losses worldwide. Chemical control is the most effective way for psyllid control. Herein, the toxicity of nine insecticides to ACP adults and the joint action of thiamethoxam + spirotetramat were determined by a topical application method in the laboratory; field plot experiments were conducted to evaluate the control efficacy of one self-made thiamethoxam + spirotetramat 40% suspension concentrate (SC) comparing with thiamethoxam 21% SC, spirotetramat 22.4% SC, tolfenpyrad 15% SC and bifenthrin 100 g/L emulsifiable concentrate against ACP using foliar sprays in 2018-2019. RESULTS: The highest toxicity to ACP adults was achieved by beta-cyfulthrin, bifenthrin, thiamethoxam and acetamiprid, with median lethal doses of 0.247 to 1.382 ng/adult at 24 h after treatment. High toxicity was observed by chlorpyrifos, spirotetramat and tolfenpyrad, but moderate toxicity by pyriproxyfen and buprofezin. For mixutres of thiamethoxam and spirotetramat, a 25:15 mass ratio showed the highest synergistic effect, with a co-toxicity coefficient (CTC) of 246.52; while a 10:30 mass ratio exhibited an additive effect, with a CTC of 109.84. Thiamethoxam + spirotetramat 40% SC at 60-80 mg/kg can effectively control ACP with a control efficacy of 72.92 to 99.29% during 3-30 days. Moreover, foliar sprays of all tested insecticides at the tested rates had no phytotoxic effects on citrus trees. CONCLUSION: A one-time foliar spray of thiamethoxam + spirotetramat 40% SC at 80 mg/kg could be recommended to control ACP during its infestation period in citrus groves.

Evaluation of potential miticide toxicity to Varroa destructor and honey bees, Apis mellifera, under laboratory conditions.

The honey bee, Apis mellifera L., is the world's most important managed pollinator of agricultural crops, however, Varroa mite, Varroa destructor Anderson and Trueman, infestation has threatened honey bee survivorship. Low efficacy and development of Varroa mite resistance to currently used Varroacides has increased the demand for innovative, effective treatment tool options that exhibit high efficacy, while minimizing adverse effects on honey bee fitness. In this investigation, the toxicity of 16 active ingredients and 9 formulated products of registered miticides for use on crops from 12 chemical families were evaluated in comparison to amitraz on Varroa mites and honey bees using contact surface and topical exposures. It was found that fenpyroximate (93% mortality), spirotetramat (84% mortality) and spirodiclofen (70% mortality) had greater toxicity to Varroa mites, but high dose rates caused high bee mortality (> 60%). With this in mind, further research is needed to investigate other options to minimize the adverse effect of these compounds on bees. The results also found high toxicity of fenazaquin and etoxazole against Varroa mites causing 92% and 69% mortality, respectively; and were found to be safe on honey bees. Collectively, it is recommended that fenazaquin and etoxazole are candidates for a potential Varroacide and recommended for further testing against Varroa mites at the colony level.

Dysregulation of endocrine disruption, apoptosis and the transgenerational toxicity induced by spirotetramat.

Spirotetramat (SPT) is a new tetronic acid derivative insecticide used to control scales and aphids; the potential for endocrine disruptor effects in fish could not be finalized with the available data. In this study, zebrafish were selected to assess the endocrine-disrupting effects. Significant decrease of plasma estradiol (E2), testosterone (T) and 11-ketotestosterone (11-KT) were observed in both male and female following the spirotetramat exposure; the vitellogenin (VTG) level in females significantly decreased. The expression of the hypothalamic-pituitary-gonad (HPG) axis genes fshr, lhr and esr1 showed significant increase in the gonads, which expression in males is higher than in females. In addition, the activities of capspase-3 and caspase-9 significantly decreased in both males and females liver, while the capspase-3 and caspase-9 were increased in male testis, the mRNA expression levels of genes expression related to the apoptosis pathway were also significantly altered after the spirotetramat exposure. Additionally, we found the parental zebrafish exposed to spirotetramat induced the development delay of its offspring. Above all, the adverse effects induced by spirotetramat suggesting that spirotetramat is a potential exogenous hazardous agent.

Movento effects on learning and hippocampal brain-derived neurotrophic factor protein of adult male rats.

Spirotetramat is a toxic commercially known as Movento used to control pistachio psylla pests. In the present study, the effects of Movento on passive avoidance learning of rats and their ability to explore the novel object in the novel object recognition test were investigated. The changes in the concentration of hippocampal brain-derived neurotrophic factor (BDNF) proteins were evaluated, too. Male Wistar rats were gavaged at different dosages of the Movento (50, 100, 250, 500, 1000, 1250, and 1500 mg/kg) or saline for 7 days (administered every 2 days). We showed that Movento caused 50 and 100% mortality at the dose of 1250 and 1500 mg/kg, respectively. At the dose of 1000 mg/kg, Movento significantly decreased locomotor activity (P < 0.05). These rats also displayed a significant decrease in the number of training trials in the shuttle box and the ability to recognize a novel object compared with the control group (P < 0.01). The BDNF protein level of hippocampus also showed a significant decrease in the Movento (1000 mg/kg) compared with the control group (P < 0.01) while the number of pancellular necrosis pyramidal CA1 cells increased significantly in the Movento group (P < 0.001). We concluded that exposure to Movento can decline sensory, motor, and learning in rats.

The lipid metabolism alteration of three spirocyclic tetramic acids on zebrafish (Danio rerio) embryos.

Spirocyclic tetramic acids are widely used in controlling phytophagous mite species throughout the world. the data set is incomplete and provides insufficient evidence for drawing the same conclusion for fish. To fill the gap whether these acaricides alter lipid metabolism on vertebrates, zebrafish embryos exposed to a series concentration of pesticides, the developmental effects, enzyme activities and levels of gene expression were assessed, battery of biomarker utilized by the integrated biomarker response (IBRv2) model. The 96 h-LC50 of spirodiclofen, spiromesifen and spirotetramat were 0.14, 0.12 and 5.94 mg/L, respectively. Yolk sac deformity, pericardial edema, spinal curvature and tail malformation were observed. Three spirocyclic acids were unfavouring the lipid accumulation of by inhibited the acetyl-CoA carboxylase (ACC), fatty acid synthesis (FAS), fatty acid binding proteins (FABP2) and lipoprotein lipase (LPL) activity. The total cholesterol (TCHO) level significantly decreased in the 0.072 mg/L spirodiclofen group and 0.015 and 0.030 mg/L in the spiromesifen groups. No expected change in spirotetramat group on the TCHO and triglycerides (TGs) levels for any of the treatments. The mRNA levels of the genes related to lipid metabolism also significantly altered. In both spirodiclofen and spiromesifen, ACC achieved the highest scores among a battery of biomarkers using integrated biomarker response (IBRv2). The results suggest that spiromesifen was the most toxic for embryos development and spirodiclofen was the most toxic for lipid metabolism in embryos. The 0.07 mg/L of spirodiclofen, 0.05 mg/L of spiromesifen and 2.00 mg/L would cause malformation on zebrafish embryos. This study will provide new insight that fatty acid metabolism may be a suitable biomarker for the spirocyclic tetramic acids in fish species.

Biochemical and histological alterations in adult zebrafish（Danio rerio）ovary following exposure to the tetronic acid insecticide spirotetramat.

As a new tetronic acid derivative insecticide, spirotetramat has been reported to be toxic to an array of aquatic organisms. However, the toxic effects of spirotetramat on zebrafish especially at ovary are still obscure. Hereby, the acute toxicity of spirotetramat towards zebrafish（Danio rerio），as well as the changes on biochemical and histological traits of ovary were investigated. The acute toxicity test results showed that the median lethal concentration (LC50) value of spirotetramat were 9.61 mg/L and 7.21 mg/L at 72 h and 96 h, respectively, suggesting spirotetramat has moderate toxicity to zebrafish. In the following sub-lethal toxicity test, the gene expression of superoxide dismutase (SOD), catalase (CAT), and gonadotropic hormone receptor (FSHR and LHR) together with the content of malondialdehyde (MDA) in ovary were measured at 14, 21, and 28 days after exposure to 36, 360 and 720 µg/L. Under high concentration treatment (360 and 720 µg/L), MDA content, the relative transcription CAT and SOD gene level increased significantly in ovary (p < 0.05). That indicated sub-lethal doses spirotetramat caused oxidative stress and lipid peroxidation in zebrafish ovary during the entire experimental period. Under the exposure to spirotetramat at 720 µg/L after 14 days, the relative transcript FSHR gene level was down regulated, and the relative transcript LHR gene level was up regulated. Moreover, spirotetramat affected the oocyte development especially on the diameter size and maturation during the ovary tissue biopsies at 28 days. Taken together, these findings revealed the adverse effects of spirotetramat on fish from the biochemical and histological aspects.

Contribution of cytochrome P450 monooxygenase CYP380C6 to spirotetramat resistance in Aphis gossypii Glover.

The cytochrome P450 monooxygenases play a key role in detoxification mechanism for spirotetramat resistance in Aphis gossypii Glover. However, only one P450 genes (CYP6DA2), among thirty-five P450 genes identified from Aphis gossypii transcriptome database, has been reported to play important role in spirotetramat resistance in previous resistance level until now. In this study, after the confirmation of the rise of resistance level and important roles of P450s in spirotetramat resistance by the synergism analysis, the gene expression changes were determined for P450 genes in spirotetramat susceptible and resistant strains. Compared with the susceptible strain, CYP6CY4, CYP6CY14, CYP6CY18 and CYP6DC1 in CYP3 Clade were up-regulated in resistant nymphs, with the CYP6CY14, CYP6CY4, CYP6DC1, and CYP6CY18 increased to 2.54-, 1.51-, 1.31- and 1.29-fold, respectively. Eight genes in CYP3 Clade, three genes in CYP4 Clade and one gene in Mito Clade were down-regulated. In resistant adult aphids, CYP380C6 in CYP4 Clade, CYP353B1 in CYP2 Clade, and CYP307A1 in Mito Clade were up-regulated under spirotetramat stress, with the CYP380C6, CYP353B1 and CYP307A1 increased to 2.89-, 1.91-, and 1.38-fold, respectively. In contrast, the other P450 genes were almost down-regulated, especially these P450 genes in CYP3 Clade, CYP4 Clade and Mito Clade. RNA interference of CYP380C6 significantly increased the sensitivity of the resistant adults and nymphs to spirotetramat, while suppression of CYP6CY14 could not increase the toxicity of spirotetramat. These results indicate the possible involvement of the CYP380C6 genes in spirotetramat resistance at present very high resistance levels. Screening the expression changes of P450 genes under different spirotetramat resistance levels in the genome-scale will provide an overall view on the possible metabolic factors in the resistance development. The results may facilitate further work to validate the roles of P450 in spirotetramat resistance with heterologous expression.

Energetic contaminants inhibit plant litter decomposition in soil.

Individual effects of nitrogen-based energetic materials (EMs) 2,4-dinitrotoluene (2,4-DNT), 2-amino-4,6-dinitrotoluene (2-ADNT), 4-amino-2,6-dinitrotoluene (4-ADNT), nitroglycerin (NG), and 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) on litter decomposition, an essential biologically-mediated soil process, were assessed using Orchard grass (Dactylis glomerata) straw in Sassafras sandy loam (SSL) soil, which has physicochemical characteristics that support "very high" qualitative relative bioavailability for organic chemicals. Batches of SSL soil were separately amended with individual EMs or acetone carrier control. To quantify the decomposition rates, one straw cluster was harvested from a set of randomly selected replicate containers from within each treatment, after 1, 2, 3, 4, 6, and 8 months of exposure. Results showed that soil amended with 2,4-DNT or NG inhibited litter decomposition rates based on the median effective concentration (EC50) values of 1122 mg/kg and 860 mg/kg, respectively. Exposure to 2-ADNT, 4-ADNT or CL-20 amended soil did not significantly affect litter decomposition in SSL soil at ≥ 10,000 mg/kg. These ecotoxicological data will be helpful in identifying concentrations of EMs in soil that present an acceptable ecological risk for biologically-mediated soil processes.

Determination and Safety Assessment of Residual Spirotetramat and Its Metabolites in Amaranth (Amaranthus tricolor) and Soil by Liquid Chromatography Triple-Quadrupole Tandem Mass Spectrometry.

With the purpose of guaranteeing the safe use of spirotetramat and preventing its potential health threats to consumers, a QuEChERS extraction method coupled with LC triple-quadrupole tandem MS was applied in this study to determine residual spirotetramat metabolites in different tissues of amaranth (Amaranthus tricolor) and in soil. The results indicate that the spirotetramat degraded into different types of metabolites that were located in different tissues of amaranth and in soil. B-keto, B-glu, and B-enol were the three most representative degradation products in the leaf of amaranth, and B-glu and B-enol were the two major degradation products found in the stem of amaranth; however, only B-enol was detected in the root of amaranth. B-keto and B-mono were the two products detected in the soil in which the amaranth grew. The cytotoxicity results demonstrate that spirotetramat and its metabolite B-enol inhibited cellular growth, and the toxicity of spirotetramat and its metabolite B-enol exceeded than that of the metabolites B-keto, B-mono, and B-glu. This investigation is of great significance to the safe use of spirotetramat in agriculture.

Lethal and Sub-lethal Effects of Four Insecticides on the Aphidophagous Coccinellid Adalia bipunctata (Coleoptera: Coccinellidae).

Conventional insecticide assays, which measure the effects of insecticide exposure on short-term mortality, overlook important traits, including persistence of toxicity or sub-lethal effects. Therefore, such approaches are especially inadequate for prediction of the overall impact of insecticides on beneficial arthropods. In this study, the side effects of four modern insecticides (chlorantraniliprole, emamectin benzoate, spinosad, and spirotetramat) on Adalia bipunctata (L.) (Coleoptera: Coccinellidae) were evaluated under laboratory conditions by exposition on treated potted plants. In addition to investigation of acute toxicity and persistence of harmful activity in both larvae and adults of A. bipunctata, demographic parameters were evaluated, to provide a comprehensive picture of the nontarget effects of these products. Field doses of the four insecticides caused detrimental effects to A. bipunctata; but in different ways. Overall, spinosad showed the best toxicological profile among the products tested. Emamectin benzoate could be considered a low-risk insecticide, but had high persistence. Chlorantraniliprole exhibited lethal effects on early instar larvae and adults, along with a long-lasting activity, instead spirotetramat showed a low impact on larval and adult mortality and can be considered a short-lived insecticide. However, demographic analysis demonstrated that chlorantraniliprole and spirotetramat caused sub-lethal effects. Our findings highlight that sole assessment of mortality can lead to underestimation of the full impact of pesticides on nontarget insects. Demographic analysis was demonstrated to be a sensitive method for detection of the sub-lethal effects of insecticides on A. bipunctata, and this approach should be considered for evaluation of insecticide selectivity.

Side effects of spirotetramat on pupae and adults of a Neotropical strain of Eretmocerus mundus (Hymenoptera: Aphelinidae): Effects on the life parameters and demography.

The negative impact of conventional pesticides on the environment is already extensively discussed worldwide. Although the use of chemical agents for controlling agricultural pests remains as first-line strategy for pest control, novel biorational active insecticides, such as spirotetramat, have appeared in the pesticide market during recent years in Argentina. The aim of this study was to assess the toxicity of spirotetramat on two developmental stages of a Neotropical strain of Eretmocerus mundus, with the conventional insecticide cypermethrin as a positive control, and to determine spirotetramat's side effects on parasitoid demographic parameters. Lethal effects of both insecticides on pupae and adults were evaluated by adult emergency and survival, respectively; whereas sublethal effects on both development stages were assessed by adult longevity, reproduction capacity, sex ratio, and longevity of the first progeny. Spirotetramat proved less harmful than cypermethrin at both developmental stages studied, corroborating once more the high toxicity of this pyrethroid to natural enemies. Although spirotetramat did not affect the emergence and reproductive capacity of adults surviving pupal exposure, the longevity of the first progeny was reduced as was adult survival and longevity after exposure to residues. Spirotetramat also reduced all demographic parameters in the population evaluation. This work is the first report of spirotetramat toxicity at the population level and demonstrates the need to assess the total effect of pesticides on natural enemies.

Evaluation of antidesmone alkaloid as a photosynthesis inhibitor.

Antidesmone, isolated from Waltheria brachypetala Turcz., owns special structural features as two α,ß-unsaturated carbonyl groups and a side alkyl chain that can compete with the quinones involved in the pool of plastoquinones at photosystem II (PSII). In this work, we showed that the alkaloid is an inhibitor of Hill reaction and its target was located at the acceptor side of PSII. Studies of chlorophyll (Chl) a fluorescence showed a J-band that indicates direct action of antidesmone in accumulation of QA- (reduced plastoquinone A) due to the electron transport blocked at the QB (plastoquinone B) level similar to DCMU. In vivo assays indicated that antidesmone is a selective post-emergent herbicide probe at 300µM by reducing the biomass production of Physalis ixacarpa plants. Furthermore, antidesmone also behaves as pre-emergent herbicide due to inhibit Physalis ixacarpa plant growth about 60%. Antidesmone, a natural product containing a 4(1H)-pyridones scaffold, will serve as a valuable tool in further development of a new class of herbicides.

Effects of spirotetramat treatments on fecundity and carboxylesterase expression of Aphis gossypii Glover.

Spirotetramat is a novel tetramic acid-based insecticide, belonging to keto-enol pesticide family, with a novel mode of action; it interferes with lipid biosynthesis. Its insecticide activity against various agricultural pest insects have been demonstrated (e.g. on Myzus persicae, Bemisia tabaci and Tetranychus urticae). However, information available is currently limited on the efficacy of spirotetramat on the cotton aphid, Aphis gossypii, a key cotton pest worldwide. We assessed the spirotetramat toxicity on A. gossypii and evaluated its effects on aphid fecundity when exposed to a sublethal concentration (LC10) and to increasing lethal concentrations (LC25, LC50, and LC75). A key mechanism involved in insecticide resistance in aphids relates to esterase activity. We estimated the CarE activity and a CarE gene expression in aphids in response to spirotetramat exposure, then we tested tolerance of offspring to spirotetramat when the parents were exposed to the highest concentration tested in our study (LC75). Results showed that spirotetramat showed increasing toxicity to A. gossypii with exposure duration to treated leaves; LC50 ranged from 23,675.68 to 12.27 mg/L for 1 to 5-days exposure. In addition, spirotetramat reduced aphid daily fecundity, in all concentration treatments, especially with up to 90 % reduction in case of exposure to LC75. Total CarE activity increased dramatically and CarE mRNA expression was also up regulated in aphids after exposure to LC75 spirotetramat. Finally, the tolerance to spirotetramat in offspring (when parents were exposed to the LC75) showed a 2.5-fold increase when compared to control aphids. Consequently, spiroteramat showed potential for pest management of cotton aphids owing to both lethal and sublethal activities, notably strong impact on aphid fecundity. However, we also demonstrated that increased tolerance of A. gossypii to spirotetramat may happen through increased CarE- activity and subsequent metabolic degradation of the insecticide in aphids' body.

Peptide bond-forming reagents HOAt and HATU are not mutagenic in the bacterial reverse mutation test.

The peptide bond-forming reagents 1-hydroxy-7-azabenzotriazole (HOAt, CAS 39968-33-7) and O-(7-Azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU, CAS 148893-10-1) either have structural alerts, unclassified features or are considered out of domain when evaluated for potential mutagenicity with in silico programs DEREK and CaseUltra. Since they are commonly used reagents in pharmaceutical drug syntheses, they may become drug substance or drug product impurities and would need to be either controlled to appropriately safe levels or tested for mutagenicity. Both reagents were tested in the bacterial reverse mutation (Ames) test at Covance, under GLP conditions, following the OECD test guideline and ICH S2(R1) recommendations and found to be negative. Our data show that HOAt and HATU-common pharmaceutical synthesis reagents-are not mutagenic, and can be treated as ordinary drug impurities.