Differences in Mitochondrial Cytochrome b Binding Mediate Selectivity of Bifenazate toward Phytophagous and Predatory Mites.

Bifenazate, a potent acaricide that targets mitochondrial complex III, exhibits selective toxicity (>280-fold) toward phytophagous mites versus predatory mites. Here, a systematic study was conducted to clarify the selective mechanism. Nontarget factors were excluded through epidermal penetration tests and assessment of detoxification enzymes' activities. Quantification of IC50 values, ATP content, and reactive oxygen species (ROS) levels revealed that differences in drug-target binding determine the toxicity selectivity. Structural modeling and molecular docking revealed that variations in key amino acid sites within the cytochrome b (cytb) target might regulate this selectivity, which was validated through a microscale thermophoresis assay. Significant disparities were observed in the binding affinity between bifenazate and recombinant cytb proteins derived from phytophagous mites and predatory mites. Mutating isoleucine 139 to leucine notably reduced the binding affinity of bifenazate to cytb. Insights into bifenazate selectivity between phytophagous and predatory mites inform a basis for developing compounds that target cytochrome b.

Integrated Transcriptome and Metabolome Dynamic Analysis of Galls Induced by the Gall Mite Aceria pallida on Lycium barbarum Reveals the Molecular Mechanism Underlying Gall Formation and Development.

Galls have become the best model for exploring plant-gall inducer relationships, with most studies focusing on gall-inducing insects but few on gall mites. The gall mite Aceria pallida is a major pest of wolfberry, usually inducing galls on its leaves. For a better understanding of gall mite growth and development, the dynamics of the morphological and molecular characteristics and phytohormones of galls induced by A. pallida were studied by histological observation, transcriptomics and metabolomics. The galls developed from cell elongation of the epidermis and cell hyperplasia of mesophylls. The galls grew quickly, within 9 days, and the mite population increased rapidly within 18 days. The genes involved in chlorophyll biosynthesis, photosynthesis and phytohormone synthesis were significantly downregulated in galled tissues, but the genes associated with mitochondrial energy metabolism, transmembrane transport, carbohydrates and amino acid synthesis were distinctly upregulated. The levels of carbohydrates, amino acids and their derivatives, and indole-3-acetic acid (IAA) and cytokinins (CKs), were markedly enhanced in galled tissues. Interestingly, much higher contents of IAA and CKs were detected in gall mites than in plant tissues. These results suggest that galls act as nutrient sinks and favor increased accumulation of nutrients for mites, and that gall mites may contribute IAA and CKs during gall formation.

Effects of in-house and commercial extracts of the allergenic mite Tyrophagus putrescentiae on murine and human cell responses.

Mites are among the major sources of domestic and occupational allergens worldwide, and continuous exposure to these allergens leads to chronic airway inflammation. One of the most allergenic species is the storage mite Tyrophagus putrescentiae (Schrank). Protein extracts are produced from this mite for tests that help the clinical diagnosis (via prick test), treatment, and monitoring of disease progression in patients who had positive results for allergic reactions. Therefore, the aim of the present study was to evaluate the cell viability of RAW 264.7 and L929 cells when exposed to in-house raw protein extracts of T. putrescentiae compared to a commercial product, as well as quantify TNF-α secretion by RAW 264.7. Additionally, this study quantified the effect of these extracts in IgE secretion in total blood of people affected by this mite. The study found similarity between the in-house extract and the commercial extract as they had equivalent TNF-α secretion. Additionally, viabilities of RAW 264.7 and L929 exposed to the in-house extract were compatible with viabilities of cells exposed to the commercial extract, with no cytotoxicity at the concentrations tested. Results corroborated the hypothesis that the extract produced in-house would be equivalent to the commercial extract in allergic patients when the IgE was quantified. This study is the first to show the cytotoxicity of T. putrescentiae extracts, and to provide a quantitative analysis of TNF-α and IgE.

High value-added application of a renewable bioresource as acaricide: Investigation the mechanism of action of scoparone against Tetranychus cinnabarinus.

Introduction: Investigation into the action mechanisms of plant secondary metabolites against pests is a vital strategy for the development of novel promising biopesticides. Scoparone (isolated from Artemisia capillaris), a renewable plant-derived bioresource, displays potent acaricidal activities against mites, but its targets of action remain unclear. Objectives: This study aimed to systematically explore the potential molecular targets of scoparone against Tetranychus cinnabarinus and provide insights to guide the future application of scoparone as an agent for the management of agricultural mite pests worldwide. Methods: The mechanism and potential targets of scoparone against mites were investigated using RNA-seq analysis; RNA interference (RNAi) assays; bioassays; and [Ca2+]i, pull-down and electrophysiological recording assays. Results: RNA-seq analysis identified Ca2+ signalling pathway genes, specifically 5 calmodulin (CaM1-5) genes and 1 each of L-, T-, N-type voltage-gated Ca2+ channel (VGCC) genes, as candidate target genes for scoparone against mites. Furthermore, RNAi and electrophysiological data showed that the CaM1- and L-VGCC-mediated Ca2+ signalling pathways were activated by scoparone. Interestingly, by promoting the interaction between CaM1 and the IQ motif (a consensus CaM-binding domain of L-VGCC), CaM1 markedly enhanced the activating effect of scoparone on L-VGCC. Pull-down assays further demonstrated that CaM interacted with the IQ motif, triggering L-VGCC opening. Importantly, mutation of the IQ motif significantly weakened CaM1 binding and eliminated the CaM1-mediated enhancement of scoparone-induced L-VGCC activation, indicating that the effect of scoparone was dependent on the CaM1-IQ interaction. Conclusion: This study demonstrates, for the first time, that the acaricidal compound scoparone targets the interface between CaM1 and L-VGCC and activates the CaM-binding site, located in the IQ motif at the L-VGCC C-terminus. This work may contribute to the development of target-specific green acaricidal compounds based on L-VGCC.

Comparative analysis of mite genomes reveals positive selection for diet adaptation.

Diet is a powerful evolutionary force for species adaptation and diversification. Acari is one of the most abundant clades of Arachnida, exhibiting diverse dietary types, while the underlying genetic adaptive mechanisms are not fully understood. Based on comparative analyses of 15 Acari genomes, we found genetic bases for three specialized diets. Herbivores experienced stronger selection pressure than other groups; the olfactory genes and gene families involving metabolizing toxins showed strong adaptive signals. Genes and gene families related to anticoagulation, detoxification, and haemoglobin digestion were found to be under strong selection pressure or significantly expanded in the blood-feeding species. Lipid metabolism genes have a faster evolutionary rate and been subjected to greater selection pressures in fat-feeding species; one positively selected site in the fatty-acid amide hydrolases 2 gene was identified. Our research provides a new perspective for the evolution of Acari and offers potential target loci for novel pesticide development.

Purification and characterisation of the dimeric group 12 allergen from Blomia tropicalis heterologously expressed by Escherichia coli Top10F´.

Successful research in the wide-ranging field of allergy is usually achieved by definition not only of physicochemical and immunological properties of natural, but also recombinant allergens. Blomia tropicalis mite is a well-known source for various groups of hypersensitivity-causing proteins. The goal of the present work was to produce, purify and characterise by in silico, biochemical and immunological methods the recombinant group-12 allergen of B. tropicalis. The recombinant Blo t 12 aggregation capacity as well as the affinity to antibodies from BALB/c immunised mice and B. tropicalis-sensitised human donors were investigated through in silico analyses, dynamic light scattering, SDS-PAGE, ELISA and Western blot. The presence of Blo t 12 within B. tropicalis extracts was also determined by ELISA and Western blot. High concentrations of dimeric rBlo t 12 were detected through SDS-PAGE next to other aggregates and the results were confirmed by data from DLS and Western blot. The YITVM peptide was predicted to be the most aggregation-prone region. The IgE-reactivity of rBlo t 12 was not completely abolished by aggregate formation but it was significantly decreased compared to rBlo t 5, or B. tropicalis extracts. Natural Blo t 12 may naturally dimerises, but it was detected in non-delipidified B. tropicalis extracts in low amounts. Given that this allergen may be a specific marker for B. tropicalis allergy, the recombinant Blo t 12 herein obtained is characterised as a mid-tier allergen in Brazilian atopic patients and may be useful for the improvement in precision allergy molecular diagnostic applications.

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.

Fatty acid metabolism in an oribatid mite: de novo biosynthesis and the effect of starvation.

The fatty acid (FA) composition of lipids in animals is influenced by factors such as species, life stage, availability and type of food, as well as the ability to synthesize certain FAs de novo. We investigated the effect of starvation on the neutral lipid (NLFA) and phospholipid (PLFA) fatty acid patterns of the oribatid mite Archegozetes longisetosus Aoki. Furthermore, we performed stable-isotope labeled precursors feeding experiments under axenic conditions to delineate de novo FA synthesis by profiling 13C and deuterium incorporation via single-ion monitoring. Starvation of mites resulted in a decline in the total amount of NLFAs and significantly changed the fatty acid patterns, indicating that NLFAs were metabolized selectively. Biochemical tracer experiments confirmed that oribatid mites, like other animals, can produce stearic (18:0) and oleic acid (18:1ω9) de novo. Mass spectrometric data also revealed that they appear to synthesize linoleic acid [18:2ω6,9 = (9Z,12Z)-octadeca-9,12-dienoic acid]-an ability restricted only to a few arthropod taxa, including astigmatid mites. The physiological and biosynthesis processes revealed here are crucial to understand the potential biomarker function of fatty acids-especially 18:2ω6,9-in oribatid mites and their applicability in soil animal food web studies.

Effects of arthropod inquilines on growth and reproductive effort among metacommunities of the purple pitcher plant (Sarracenia purpurea var. montana).

Many plant species harbor communities of symbionts that release nutrients used by their host plants. However, the importance of these nutrients to plant growth and reproductive effort is not well understood. Here, we evaluate the relationship between the communities that colonize pitcher plant phytotelmata and the pitcher plants' vegetative growth and flower production to better understand the symbiotic role played by phytotelma communities. We focus on the mountain variety purple pitcher plant (Sarracenia purpurea var. montana), which occurs in small and isolated populations in Western North Carolina. We found that greater symbiont community diversity is associated with higher flower production the following season. We then examined geographic variation in communities and found that smaller plant populations supported less diverse symbiont communities. We relate our observations to patterns of community diversity predicted by community ecology theory.

Biosynthesis of the widely distributed hydrocarbon (Z,Z)-6,9-heptadecadiene in astigmatid mites.

Using a crude enzyme solution prepared from astigmatid mites, the conversion reaction to (Z,Z)-6,9-heptadecadiene (6,9-C17) using linoleyl aldehyde (LAld) as a substrate was successful. The mass spectrum of the reaction product using 13C-labeled LAld as a substrate could be assigned as 13C-labeled 6,9-C17. Unlike the findings in other species, the decarbonylase derived from mites did not require a coenzyme.

Identification of B Cell Epitopes of Blo t 13 Allergen and Cross-Reactivity with Human Adipocytes and Heart Fatty Acid Binding Proteins.

Cross-reactivity between allergens and human proteins could have a clinical impact in allergic diseases. Blo t 13 is an allergen from the mite Blomia tropicalis, which belongs to the fatty acid binding protein (FABP) family and has structural homology with human FABPs. This work aimed to map B cell epitopes on Blo t 13 and to identify epitopes involved in cross-reactivity with human heart FABP (FABP3) and adipocyte FABP (FABP4). Sera from 25 patients with house dust mite (HDM) allergy that were sensitized to Blo t 13 were used for testing the reactivity of immunoglobulin E (IgE) and IgG to FABP. The epitope mapping of Blo t 13 was performed using overlapping peptides, and cross-reactivity between Blo t 13 and human FABP was analyzed using human sera and anti-Blo t 13 monoclonal antibodies. IgE antibodies to all FABPs were detected in 14/25 serum samples, and IgG was detected in 25/25 serum samples. The cross-reactivity of Blo t 13 was 42% with FABP3 and 48% with FABP4. Two IgE-binding regions were identified in Blo t 13; one between residues 54 and 72 (the main cross-reacting region) and another between residues 111 to 129. Our results suggest that exposure to the Blo t 13 allergen could induce an auto-reactive response to endogenous FABP in allergic patients sensitized to Blo t 13.

Oppia nitens C.L. Koch, 1836 (Acari: Oribatida): Current Status of Its Bionomics and Relevance as a Model Invertebrate in Soil Ecotoxicology.

The oribatid soil mite Oppia nitens C.L. Koch, 1836, is a model microarthropod in soil ecotoxicity testing. This species has a significant role in supporting soil functions and as a suitable indicator of soil contamination. Despite its significance to the environment and to ecotoxicology, however, very little is known of its biology, ecology, and suborganismal responses to contaminants in the soil. In the present review, we present detailed and critical insights into the biology and ecology of O. nitens in relation to traits that are crucial to its adaptive responses to contaminants in soil. We used a species sensitivity distribution model to rank the species sensitivity to heavy metals (cadmium and zinc) and neonicotinoids (imidacloprid and thiacloprid) compared with other standardized soil invertebrates. Although the International Organization for Standardization and Environment and Climate Change Canada are currently standardizing a protocol for the use of O. nitens in soil toxicity testing, we believe that O. nitens is limited as a model soil invertebrate until the molecular pathways associated with its response to contaminants are better understood. These pathways can only be elucidated with information from the mites' genome or transcriptome, which is currently lacking. Despite this limitation, we propose a possible molecular pathway to metal tolerance and a putative adverse outcome pathway to heavy metal toxicity in O. nitens. Environ Toxicol Chem 2019;38:2593-2613. © 2019 SETAC.

The major allergen Der p 2 is a cholesterol binding protein.

Der p 2 is a major dust mite allergen and >80% of mite allergic individuals have specific IgE to this allergen. Although it is well characterized in terms of allergenicity, there is still some ambiguity in terms of its biological function. Three-dimensional structural analysis of Der p 2 and its close homologues indicate the presence of a hydrophobic cavity which can potentially bind to lipid molecules. In this study, we aimed to identify the potential ligand of Der p 2. Using a liposome pulldown assay, we show that recombinant Der p 2 binds to liposomes prepared with exogenous cholesterol in a dose dependent fashion. Next, an ELISA based assay using immobilized lipids was used to study binding specificities of other lipid molecules. Cholesterol was the preferred ligand of Der p 2 among 11 different lipids tested. Two homologues of Der p 2, Der f 2 and Der f 22 also bound to cholesterol. Further, using liquid chromatography-mass spectrometry (LC-MS), we confirmed that cholesterol is the natural ligand of Der p 2. Three amino acid residues of Der p 2, V104, V106 and V110 are possible cholesterol binding sites, as alanine mutations of these residues showed a significant decrease in binding (p < 0.05) compared to wild-type Der p 2. These results provide the first direct experimental evidence that Der p 2 binds to cholesterol.

Molecular characterization of ecdysis triggering hormone and its receptor in citrus red mite (Panonychus citri).

Neuropeptide ecdysis triggering hormone (ETH) plays crucial roles in invertebrates by activating a G protein-coupled receptor (GPCR), the ecdysis triggering hormone receptor (ETHR), which has been intensively investigated in Hexapoda. However, the molecular characterization of ETH and ETHR in Chelicerata remains unknown. In this study, we identified and characterized the full-length cDNA of ETH and ETHR in citrus red mite Panonychus citri (McGregor). Phylogenetic analysis indicated that PcETHR was closely related to the insect ETHR subtype B. A calcium mobilization-based functional assay showed that PcETH activated the PcETHR in a dose-dependent manner. Furthermore, a sharp upregulation of PcETH before ecdysis was observed by quantitative real-time PCR (qRT-PCR), and it revealed a tight correlation of ETH signaling and the molting process. These are the first insights into the molecular characterization of ETH and its receptor in mites as P. citri. Our work provides basic information of the ETH and ETHR in P. citri and lays a solid foundation for further physiological functions to better understand the ETH signaling system in mites.

Increased lipid accumulation but not reduced metabolism explains improved starvation tolerance in cold-acclimated arthropod predators.

Predatory arthropods are used for biological control in greenhouses, but there is increasing interest to extend their use to the outdoor environment where temperatures are typically lower. Acclimation at low temperature increases the ability of ectotherms to cope with subsequent more extreme cold, but may involve costs or benefits to other performance traits. A recent study in mesostigmatid mites (Gaeolaelaps aculeifer) showed that starvation tolerance was improved following a period of cold exposure. However, the physiological mechanisms that underlie improved starvation tolerance following cold exposure were not investigated. To examine whether cold acclimation would also improve starvation tolerance in an insect, we repeated the starvation study in another arthropod predator, the pirate bug Orius majusculus, as well as in G. aculeifer. Before tests, the two species were acclimated at 10, 15, or 20 °C for 7 (G. aculeifer) or 16 (O. majusculus) days. We then analyzed the effects of thermal exposure on body composition, consumption, and basal metabolic rate in both species. Our results confirmed that exposure to low temperature improves starvation tolerance in these arthropod predators. Body composition analyses revealed that both species had accumulated larger lipid stores during exposure to colder temperature, which at least in part can explain the larger starvation tolerance following cold exposure. In contrast, consumption and basal metabolic rate were not changed by thermal acclimation. Our study indicates that predatory arthropods exposed to cold increase their physiological robustness and ability to endure environmental challenges, including low temperature and low prey availability.

Seasonal dynamics and changing sea level as determinants of the community and trophic structure of oribatid mites in a salt marsh of the Wadden Sea.

Global change processes affect seasonal dynamics of salt marshes and thereby their plant and animal communities. However, these changes have been little investigated for microarthropod communities. We studied the effect of seasonality and changes in sea level on oribatid mites in the natural salt marsh and on artificial islands in the back-barrier environment of the island Spiekeroog (Wadden Sea, Germany). Three zones of the artificial islands were filled with transplanted sods from the lower salt marsh zone and thereby exposed to three different inundation frequencies. We hypothesized that oribatid mite communities will differ along the natural salt marsh vegetation zones [upper salt marsh (USM), lower salt marsh (LSM), pioneer zone (PZ)], which are influenced by different tidal regimes. Accordingly, total oribatid mite densities declined from the USM and LSM to the PZ. Similarly, oribatid mite species compositions changed along the salt marsh transect and also responded to variations in inundation frequency in LSM on artificial islands with typical species of the USM, LSM and PZ being Multioppia neglecta (USM), Hermannia pulchella (LSM), Zachvatkinibates quadrivertex (LSM, PZ) and Ameronothrus schneideri (LSM, PZ). Oribatid mite density in the salt marsh and on the artificial islands was at a maximum in winter and spring; this was due in part to high density of juveniles, pointing to two reproductive periods. We hypothesized that oribatid mite trophic structure changes due to variations in abiotic (e.g., tidal dynamics, temperature) and biotic conditions (e.g., resource availability). Stable isotope (15N, 13C) and neutral lipid fatty acid analyses indicated that oribatid mite species have different diets with e.g., Z. quadrivertex feeding on macroalgae and fungi, A. schneideri feeding on microalgae and bacteria, and Scheloribates laevigatus and M. neglecta feeding on dead organic matter, bacteria and fungi. Overall, the results indicate that oribatid mite species in salt marshes are affected by changes in environmental factors such as inundation intensity, with the effects being most pronounced in species with narrow trophic niches and limited niche plasticity. The results also indicate that oribatid mite communities of the LSM respond little to short-term (one year) changes in inundation frequency.

De novo RNA-seq and functional annotation of Ornithonyssus bacoti.

Ornithonyssus bacoti (Hirst) (Acari: Macronyssidae) is a vector and reservoir of pathogens causing serious infectious diseases, such as epidemic hemorrhagic fever, endemic typhus, tularemia, and leptospirosis. Its genome and transcriptome data are lacking in public databases. In this study, total RNA was extracted from live O. bacoti to conduct RNA-seq, functional annotation, coding domain sequence (CDS) prediction and simple sequence repeats (SSRs) detection. The results showed that 65.8 million clean reads were generated and assembled into 72,185 unigenes, of which 49.4% were annotated by seven functional databases. 23,121 unigenes were annotated and assigned to 457 species by non-redundant protein sequence database. The BLAST top-two hit species were Metaseiulus occidentalis and Ixodes scapularis. The procedure detected 12,426 SSRs, of which tri- and di-nucleotides were the most abundant types and the representative motifs were AAT/ATT and AC/GT. 26,936 CDS were predicted with a mean length of 711 bp. 87 unigenes of 30 functional genes, which are usually involved in stress responses, drug resistance, movement, metabolism and allergy, were further identified by bioinformatics methods. The unigenes putatively encoding cytochrome P450 proteins were further analyzed phylogenetically. In conclusion, this study completed the RNA-seq and functional annotation of O. bacoti successfully, which provides reliable molecular data for its future studies of gene function and molecular markers.

Characterization of a hybrid protein designed with segments of allergens from Blomia tropicalis and Dermatophagoides pteronyssinus.

BACKGROUND: Sensitization to allergens of the house dust mites Dermatophagoides pteronyssinnus and Blomia tropicalis is an important risk factor for asthma and allergic diseases. Allergen-specific immunotherapy is currently based on natural allergen extracts, however, in the last years recombinant allergens with different modifications have shown promising immunological properties that may be advantageously applied for developing novel allergy vaccines. METHODS: A hybrid molecule (MAVAC-BD-2) containing epitopes of B. tropicalis (Blo t 5, Blo t 8 and Blo t 10) and D. pteronyssinus (Der p 1, Der p 2, Der p 7 and Der p 8) allergens was constructed, expressed in Escherichia coli and purified by affinity chromatography. Its folding was analyzed by circular dichroism. Antibody reactivities were evaluated by ELISA and non-denaturing dot blot assays using a battery of sera from mite allergic patients and non-allergic subjects. ELISA inhibition and dot blot assays with monoclonal antibodies were used to detect B-cell epitopes. Human basophil activation and induction of IgG-blocking antibodies in mice immunized with the hybrid protein were also evaluated. RESULTS: MAVAC-BD-2, expressed as a 22.8 kDa protein, showed a lower frequency and strength of IgE reactivity compared to Blo t 5, Der p 1, Der p 2 and the extracts of B. tropicalis and D. pteronyssinus. MAVAC-BD-2 inhibited 26% of IgE reactivity to Der p 2 and Blo t 5, reacted with anti-Der p 1 and anti-Der p 2 monoclonal antibodies and did not induce relevant basophil activation. MAVAC-BD-2 immunized mice produced specific antibodies that reacted against mite extracts and the purified allergens, as well as IgG antibodies that blocked the human IgE reactivity to mite extracts. CONCLUSION: MAVAC-BD-2 has hypoallergenic characteristics and in mice induces IgG antibodies that block the human IgE reactivity to mite extracts.

A Saliva Protein of Varroa Mites Contributes to the Toxicity toward Apis cerana and the DWV Elevation in A. mellifera.

Varroa destructor mites express strong avoidance of the Apis cerana worker brood in the field. The molecular mechanism for this phenomenon remains unknown. We identified a Varroa toxic protein (VTP), which exhibited toxic activity toward A. cerana worker larvae, in the saliva of these mites, and expressed VTP in an Escherichia coli system. We further demonstrated that recombinant VTP killed A. cerana worker larvae and pupae in the absence of deformed-wing virus (DWV) but was not toxic to A. cerana worker adults and drones. The recombinant VTP was safe for A. mellifera individuals, but resulted in elevated DWV titers and the subsequent development of deformed-wing adults. RNAi-mediated suppression of vtp gene expression in the mites partially protected A. cerana larvae. We propose a modified mechanism for Varroa mite avoidance of worker brood, due to mutual destruction stress, including the worker larvae blocking Varroa mite reproduction and Varroa mites killing worker larvae by the saliva toxin. The discovery of VTP should provide a better understanding of Varroa pathogenesis, facilitate host-parasite mechanism research and allow the development of effective methods to control these harmful mites.

Trophic predator-prey relationships promote transport of microplastics compared with the single Hypoaspis aculeifer and Folsomia candida.

Although the roles of earthworms and soil collembolans in the transport of microplastics have been studied previously, the effects of the soil biota at different trophic levels and interspecific relationships remain poorly understood. Here, we examine three soil microarthropod species to explore their effects on the transport of microplastics. The selected Folsomia candida and Hypoaspis aculeifer are extensively used model organisms, and Damaeus exspinosus is a common and abundant indigenous species in China. A model food chain (prey-collembolan and predator-mite) was structured to test the role of the predator-prey relationship in the transport of microplastics. Commercial Polyvinyl chloride (PVC) particles (Diameter: 80-250 µm) were selected as the test microplastics, because large amounts of PVC have persisted and accumulated in the environment. Synchronized soil microarthropods were held in plates for seven days to determine the movement of microplastics. The 5000 microplastic particles were carefully placed in the center of each plate prior to the introduction of the animals. Our results clearly show that all three microarthropod species moved and dispersed the microplastics in the plates. The 0.54%, 1.8% and 4.6% of the added microplastic particles were moved by collembolan, predatory mite and oribatid mite, respectively. Soil microarthropods (<0.2 cm) transported microplastic particles up to 9 cm. The avoidance behavior was observed in the collembolans in respect of the microplastics. The predatory -prey relationship did promote the transport of microplastics in the plates, increasing transport by 40% compared with the effects of adding single species (P < .05). Soil microarthropods commonly occur in surface soils (0-5 cm) and, due to their small body size, they can enter soil pores. Our results therefore suggest that the movement of microplastics by soil microarthropods may influence the exposure of other soil biota to microplastics and change the physical properties of soils.