Enhanced anaerobic digestion performance and sludge filterability by membrane microaeration for anaerobic membrane bioreactor application.

Slow dissolution/hydrolysis of insoluble/macromolecular organics and poor sludge filterability restrict the application potential of anaerobic membrane bioreactor (AnMBR). Bubble-free membrane microaeration was firstly proposed to overcome these obstacles in this study. The batch anaerobic digestion tests feeding insoluble starch and soluble peptone with and without microaeration showed that microaeration led to a 65.7-144.8% increase in methane production and increased critical flux of microfiltration membrane via driving the formation of large sludge flocs and the resultant improvement of sludge settleability. The metagenomic and bioinformatic analyses showed that microaeration significantly enriched the functional genes and bacteria for polysaccharide and protein hydrolysis, microaeration showed little negative effects on the functional genes involved in anaerobic metabolisms, and substrate transfer from starch to peptone significantly affected the functional genes and microbial community. This study demonstrates the dual synergism of microaeration to enhance the dissolution/hydrolysis/acidification of insoluble/macromolecular organics and sludge filterability for AnMBR application.

The regulation of the PD-1/PD-L1 pathway in imiquimod-induced chronic psoriasis itch and itch sensitization in mouse.

PD-1/PD-L1 inhibitors have been demonstrated to induce itch in both humans and experimental animals. However, whether the PD-1/PD-L1 pathway is involved in the regulation of chronic psoriatic itch remains unclear. This study aimed to investigate the role of the PD-1/PD-L1 pathway in imiquimod-induced chronic psoriatic itch. The intradermal injection of PD-L1 in the nape of neck significantly alleviated chronic psoriatic itch in imiquimod-treated skin. Additionally, we observed that spontaneous scratching behavior induced by imiquimod disappeared on day 21. Still, intradermal injection of PD-1/PD-L1 inhibitors could induce more spontaneous scratching for over a month, indicating that imiquimod-treated skin remained in an itch sensitization state after the spontaneous scratching behavior disappeared. During this period, there was a significant increase in PD-1 receptor expression in both the imiquimod-treated skin and the spinal dorsal horn in mice, accompanied by significant activation of microglia in the spinal dorsal horn. These findings suggest the potential involvement of the peripheral and central PD-1/PD-L1 pathways in regulating chronic itch and itch sensitization induced by imiquimod.

Optimization of track and field training methods based on SSA-BP and its effect on athletes' explosive power.

Digitalization and informationization are important trends in the development of the sports industry. The study first introduced the sparrow search algorithm to improve the generalization ability of traditional neural networks, optimizing the assignment of initial weights and thresholds of neural networks; Secondly, the chicken swarm algorithm is introduced to optimize the training combination, period, and intensity of athletes based on the evaluation results, improving the subjective limitations of traditional training methods. The results of model performance analysis show that the sparrow search algorithm is better than other intelligent optimization algorithms in finding fitted parameters, and the solution error is less than 0.50. The evaluation model performs well in terms of accuracy, recall, average relative error, and R2 evaluation indicators. The model has high repeatability and is suitable for evaluating track and field training methods. The accuracy and computational speed of the chicken swarm algorithm are relatively good; Compared with other optimization models, the chicken swarm algorithm has better optimization ability and accuracy. Friedman test found significant differences in the chicken swarm algorithm, and the optimized training method has a significant positive impact on the explosive power of athletes, and the training period and intensity arrangement are reasonable and more helpful to the improvement of athletic performance. This study improves the scientific rationality of the development of track and field training methods, which is conducive to optimizing the training effect of track and field sports, and facilitates the risk management and personalized training of athletes. At the same time, it greatly promotes the integration and development of sports and computer disciplines.

Comparative analyses of mitogenomes in the social bees with insights into evolution of long inverted repeats in the Meliponini.

The insect mitogenome is typically a compact circular molecule with highly conserved gene contents. Nonetheless, mitogenome structural variations have been reported in specific taxa, and gene rearrangements, usually the tRNAs, occur in different lineages. Because synapomorphies of mitogenome organizations can provide information for phylogenetic inferences, comparative analyses of mitogenomes have been given increasing attention. However, most studies use a very few species to represent the whole genus, tribe, family, or even order, overlooking potential variations at lower taxonomic levels, which might lead to some incorrect inferences. To provide new insights into mitogenome organizations and their implications for phylogenetic inference, this study conducted comparative analyses for mitogenomes of three social bee tribes (Meliponini, Bombini, and Apini) based on the phylogenetic framework with denser taxonomic sampling at the species and population levels. Comparative analyses revealed that mitogenomes of Apini and Bombini are the typical type, while those of Meliponini show diverse variations in mitogenome sizes and organizations. Large inverted repeats (IRs) cause significant gene rearrangements of protein coding genes (PCGs) and rRNAs in Indo-Malay/Australian stingless bee species. Molecular evolution analyses showed that the lineage with IRs have lower d N/ d S ratios for PCGs than lineages without IRs, indicating potential effects of IRs on the evolution of mitochondrial genes. The finding of IRs and different patterns of gene rearrangements suggested that Meliponini is a hotspot in mitogenome evolution. Unlike conserved PCGs and rRNAs whose rearrangements were found only in the mentioned lineages within Meliponini, tRNA rearrangements are common across all three tribes of social bees, and are significant even at the species level, indicating that comprehensive sampling is needed to fully understand the patterns of tRNA rearrangements, and their implications for phylogenetic inference.

RefMetaPlant: a reference metabolome database for plants across five major phyla.

Plants are unique with tremendous chemical diversity and metabolic complexity, which is highlighted by estimates that green plants collectively produce metabolites numbering in the millions. Plant metabolites play crucial roles in all aspects of plant biology, like growth, development, stress responses, etc. However, the lack of a reference metabolome for plants, and paucity of high-quality standard compound spectral libraries and related analytical tools, have hindered the discovery and functional study of phytochemicals in plants. Here, by leveraging an advanced LC-MS platform, we generated untargeted mass spectral data from >150 plant species collected across the five major phyla. Using a self-developed computation protocol, we constructed reference metabolome for 153 plant species. A 'Reference Metabolome Database for Plants' (RefMetaPlant) was built to encompass the reference metabolome, integrated standard compound mass spectral libraries for annotation, and related query and analytical tools like 'LC-MS/MS Query', 'RefMetaBlast' and 'CompoundLibBlast' for searches and profiling of plant metabolome and metabolite identification. Analogous to a reference genome in genomic research, RefMetaPlant provides a powerful platform to support plant genome-scale metabolite analysis to promote knowledge/data sharing and collaboration in the field of metabolomics. RefMetaPlant is freely available at https://www.biosino.org/RefMetaDB/.

Effects of the response to the COVID-19 pandemic in chest trauma patients in China: a multicenter retrospective study.

BACKGROUND: An international pandemic of severe coronavirus disease (COVID-19) has been caused by the novel coronavirus SARS-CoV-2. A large number of patients with chest trauma were infected with COVID-19. The COVID-19 pandemic had a significant impact on the management of chest trauma. OBJECTIVE: The present observational study was conducted to evaluate the clinical characteristics and outcomes of chest trauma patients with or without COVID-19 infection. METHODS: A multicenter observational study was performed at three Chinese hospitals between November 1, 2022, and January 31, 2023. All enrolled patients were diagnosed with chest trauma. We analyzed data from existing medical records, including all baseline data and prognostic follow-up data, such as 30-day mortality, hospital stays, hospitalization costs, and complications. RESULTS: All 375 eligible patients completed the follow-up. There was no significant difference in baseline characteristics between chest trauma combined with COVID-19 (p > 0.05). Chest trauma combined with COVID-19 infection may lead to higher 30-day mortality (16.36% vs. 7.14%, p = 0.005), longer hospital stays (22.5 ± 5.9 vs. 12.8 ± 4.2, p < 0.001), larger hospitalization costs (p < 0.001), and increased hospitalization complications, such as pulmonary embolism (10.30% vs. 4.76%, p = 0.039), deep vein thrombosis (DVT, 33.33% vs. 18.57%, p = 0.001), the incidence of 7-day delirium (69.70% vs. 46.19%, p < 0.001), and respiratory failure (38.18% vs. 24.77%, p = 0.005). CONCLUSIONS: Compared to chest trauma alone, it may lead to higher mortality, larger hospitalization costs, and more complications. To better respond to the future of COVID-19 or other similar virus-borne disease pandemics, it is important to understand the clinical characteristics and complications, such as pulmonary embolism, DVT, and respiratory failure after COVID-19 infection. To guide the future treatment of chest trauma combined with COVID-19 infection or other infectious diseases.

Effect of Rapid Hollow Cathode Plasma Nitriding Treatment on Corrosion Resistance and Friction Performance of AISI 304 Stainless Steel.

Low-temperature plasma nitriding of austenitic stainless steel can ensure that its corrosion resistance does not deteriorate, improving surface hardness and wear performance. Nevertheless, it requires a longer processing time. The hollow cathode discharge effect helps increase the plasma density quickly while radiatively heating the workpiece. This work is based on the hollow cathode discharge effect to perform a rapid nitriding strengthening treatment on AISI 304 stainless steels. The experiments were conducted at three different temperatures (450, 475, and 500 °C) for 1 h in an ammonia atmosphere. The samples were characterized using various techniques, including SEM, AFM, XPS, XRD, and micro-hardness measurement. Potentiodynamic polarization and electrochemical impedance spectroscopy methods were employed to assess the electrochemical behavior of the different samples in a 3.5% NaCl solution. The finding suggests that rapid hollow cathode plasma nitriding can enhance the hardness, wear resistance, and corrosion properties of AISI 304 stainless steel.

Cost-effectiveness analysis of physical activity interventions for people with schizophrenia or bipolar disorder: systematic review.

BACKGROUND: Clinical guidelines recommend providing physical activity interventions (PAIs) to people with schizophrenia or bipolar disorder for weight management. However, the cost-effectiveness of PAIs is unknown. AIMS: To evaluate the availability and methodological quality of economic evaluations of PAIs for people with schizophrenia or bipolar disorder. METHOD: Four databases (MEDLINE, Embase, PsycInfo and Scopus) were searched on 5 July 2022. Based on the retrieved studies, forward and backward citation searches were conducted. Two reviewers independently selected studies for inclusion. Study quality was assessed using the Drummond checklist. Review results were presented using narrative synthesis. RESULTS: Fourteen articles reporting nine studies were included. All included studies assessed PAIs within a multicomponent lifestyle intervention. Mixed findings were reported on the cost-effectiveness of multicomponent lifestyle intervention: three studies reported it as cost-effective; four studies reported it as not cost-effective; and two studies did not conclude whether it was cost-effective or not. Very limited evidence suggests that certain patient subgroups might be more likely to benefit from multicomponent lifestyle interventions with a PAI component: men; individuals with comorbid type 2 diabetes; and individuals who have been psychiatric hospital in-patients for ≥1 year. The quality of included studies ranged from moderate to high. CONCLUSIONS: The current economic evidence suggests that not all modalities of multicomponent lifestyle intervention including a PAI component are cost-effective for people with schizophrenia or bipolar disorder; and not all people with schizophrenia or bipolar disorder would benefit equally from the intervention. Future research is urgently needed to identify the cost-effective modality of PAI for different patient subgroups.

Gut microbiome helps honeybee (Apis mellifera) resist the stress of toxic nectar plant (Bidens pilosa) exposure: Evidence for survival and immunity.

Honeybee (Apis mellifera) ingestion of toxic nectar plants can threaten their health and survival. However, little is known about how to help honeybees mitigate the effects of toxic nectar plant poisoning. We exposed honeybees to different concentrations of Bidens pilosa flower extracts and found that B. pilosa exposure significantly reduced honeybee survival in a dose-dependent manner. By measuring changes in detoxification and antioxidant enzymes and the gut microbiome, we found that superoxide dismutase, glutathione-S-transferase and carboxylesterase activities were significantly activated with increasing concentrations of B. pilosa and that different concentrations of B. pilosa exposure changed the structure of the honeybee gut microbiome, causing a significant reduction in the abundance of Bartonella (p < 0.001) and an increase in Lactobacillus. Importantly, by using Germ-Free bees, we found that colonization by the gut microbes Bartonella apis and Apilactobacillus kunkeei (original classification as Lactobacillus kunkeei) significantly increased the resistance of honeybees to B. pilosa and significantly upregulated bee-associated immune genes. These results suggest that honeybee detoxification systems possess a level of resistance to the toxic nectar plant B. pilosa and that the gut microbes B. apis and A. kunkeei may augment resistance to B. pilosa stress by improving host immunity.

The effectiveness of early surgical stabilization for multiple rib fractures: a multicenter randomized controlled trial.

INTRODUCTION: Multiple rib fractures (≥ 3 displaced rib fractures and/or flail chest) are severe chest trauma with high morbidity and mortality. Rib fixation has become the first choice for multiple rib fracture treatment. However, the timing of surgical rib fixation is unclear. MATERIALS AND METHODS: The present study explored whether early rib fracture fixation can improve the outcome of multiple rib fractures. The present research included patients who were hospitalized in three Jiangsu hospitals following diagnosis with multiple rib fractures. Patients received early rib fracture fixation (≤ 48 h) or delayed rib fracture fixation (> 48 h) utilizing computer-based random sequencing (in a 1:1 ratio). The primary outcome measures included hospital length of stay, intensive care unit (ICU) stay, mechanical ventilation, inflammatory cytokine levels, infection marker levels, infection, and mortality. RESULTS: A total of 403 individuals were classified into two groups, namely, the early group (n = 201) and the delayed group (n = 202). Patients belonging to the two groups had similar baseline clinical data, and there were no statistically significant differences between them. Early rib fracture fixation greatly decreased the length of stay in the ICU (4.63 days vs. 6.72 days, p < 0.001), overall hospital stay (10.15 days vs. 12.43 days, p < 0.001), ventilation days (3.67 days vs. 4.55 days, p < 0.001), and hospitalization cost (6900 USD vs. 7600 USD, p = 0.008). Early rib fracture fixation can decrease inflammatory cytokine levels and infection marker levels, prevent hyperinflammation and improve infection in patients with multiple rib fractures. The timing of rib fracture fixation does not influence the surgical procedure time, operative blood loss, 30-day all-cause mortality, or surgical site infection. CONCLUSION: The findings from the present research indicated that early rib fracture fixation (≤ 48 h) is a safe, rational, effective and economical strategy and worth clinical promotion.

Honey bees infer source location from the dances of returning foragers.

Honeybees (Apis mellifera carnica) communicate the direction and distance to a food source by means of a waggle dance. We ask whether bees recruited by the dance use it only as a flying instruction, with the technical form of a polar vector, or also translate it into a location vector that enables them to set courses directed toward the food source from arbitrary locations within their familiar territory. The flights of recruits captured on exiting the hive and released at distant sites were tracked by radar. The recruits performed first a straight flight in approximately the compass direction indicated by the dance. However, this "vector" portion of their flights and the ensuing tortuous "search" portion were strongly and differentially affected by the release site. Searches were biased toward the true location of the food and away from the location specified by translating the origin for the danced polar vector to the release site. We conclude that by following the dance recruits get two messages, a polar flying instruction (bearing and range from the hive) and a location vector that enables them to approach the source from anywhere in their familiar territory. The dance communication is much richer than thought so far.

Honeybee (Apis mellifera) resistance to deltamethrin exposure by Modulating the gut microbiota and improving immunity.

Honeybees (Apis mellifera) are important economic insects and play important roles in pollination and maintenance of ecological balance. However, the use of pesticides has posed a substantial threat to bees in recent years, with the more widely used deltamethrin being the most harmful. In this study, we found that deltamethrin exposure significantly reduced bee survival in a dose-dependent manner (p = 0.025). In addition, metagenomic sequencing further revealed that DM exposure significantly reduced the diversity of the bee gut microbiota (Chao1, p < 0.0001; Shannon, p < 0.0001; Simpson, p < 0.0001) and decreased the relative abundance of core species of the gut microbiota. Importantly, in studies of GF-bees, we found that the colonization of important gut bacteria such as Gilliamella apicola and Lactobacillus kunkeei significantly increased bee resistance to DM (survival rate increased from 16.7 to 66.7%). Interestingly, we found that the immunity-genes Defensin-2 and Toll were significantly upregulated in bees after the colonization of gut bacteria. These results suggest that gut bacteria may protect against DM stress by improving host immunity. Our findings provide an important rationale for protecting honeybees from pollutants from the perspective of gut microbes.

Fractal Characteristic-Induced Optimization of the Fixed Abrasive Lapping Plate in Fabricating Bipolar Plate of Proton-Exchange Membrane Fuel Cells.

Purpose: A bipolar plate with fractal-characterized microstructures can realize intelligent energy transmission and obtain a high efficiency of proton-exchange membrane fuel cells. In this paper, fixed abrasive lapping technology is proposed to fabricate a surface microstructure on a bipolar plate with fractal characteristics. Methodology: The kinematics of the fixed abrasive lapping process was developed and employed to numerically investigate the particle trajectories moving on the target surface by considering the different arraying forms of diamonds on the lapping plate. Findings: It was found from an analysis of both the uniformity and the fractal characteristics that the arraying form of diamonds on the lapping plate, with the distribution of latitude and longitude with an angle of 30° and a gap of concentric circles of 40 mm with a minimum radius of 70 mm and maximum radius of 190 mm, can be used to obtain the best uniformity and fractal characteristics in the fixed abrasive lapping of a bipolar plate. Conclusions: The distribution of the latitude and longitude of 40° and 30° considered in this study is expected to realize the best machining performance in the bipolar plate and present good cell performance.

Institution Publication Feature Analysis Based on Time-Series Clustering.

Based on the time series of articles obtained from the literature, we propose three analysis methods to deeply examine the characteristics of these articles. This method can be used to analyze the construction and development of various disciplines in institutions, and to explore the features of the publications in important periodicals in the disciplines. By defining the concepts and methods relevant to research and discipline innovation, we propose three methods for analyzing the characteristics of agency publications: numerical distribution, trend, and correlation network analyses. The time series of the issuance of articles in 30 important journals in the field of management sciences were taken, and the new analysis methods were used to discover some valuable results. The results showed that by using the proposed methods to analyze the characteristics of institution publications, not only did we find similar levels of discipline development or similar trends in institutions, achieving a more reasonable division of the academic levels, but we also determined the preferences of the journals selected by the institutions, which provides a reference for subject construction and development.

Transcriptome analysis of the winter wheat Dn1 in response to cold stress.

BACKGROUND: Heilongjiang Province has a long and cold winter season (the minimum temperature can reach -30 ℃), and few winter wheat varieties can safely overwinter. Dongnongdongmai1 (Dn1) is the first winter wheat variety that can safely overwinter in Heilongjiang Province. This variety fills the gap for winter wheat cultivation in the frigid region of China and greatly increases the land utilization rate. To understand the molecular mechanism of the cold response, we conducted RNA-sequencing analysis of Dn1 under cold stress. RESULTS: Approximately 120,000 genes were detected in Dn1 under cold stress. The numbers of differentially expressed genes (DEGs) in the six comparison groups (0 ℃ vs. 5 ℃, -5 ℃ vs. 5 ℃, -10 ℃ vs. 5 ℃, -15 ℃ vs. 5 ℃, -20 ℃ vs. 5 ℃ and -25 ℃ vs. 5 ℃) were 11,313, 8313, 15,636, 13,671, 14,294 and 13,979, respectively. Gene Ontology functional annotation suggested that the DEGs under cold stress mainly had "binding", "protein kinase" and "catalytic" activities and were involved in "oxidation-reduction", "protein phosphorylation" and "carbohydrate metabolic" processes. Kyoto Encyclopedia of Genes and Genomes enrichment analysis indicated that the DEGs performed important functions in cold signal transduction and carbohydrate metabolism. In addition, major transcription factors (AP2/ERF, bZIP, NAC, WRKY, bHLH and MYB) participating in the Dn1 cold stress response were activated by low temperature. CONCLUSION: This is the first study to explore the Dn1 transcriptome under cold stress. Our study comprehensively analysed the key genes involved in cold signal transduction and carbohydrate metabolism in Dn1 under cold stress. The results obtained by transcriptome analysis could help to further explore the cold resistance mechanism of Dn1 and provide basis for breeding of cold-resistant crops.

A nucleotide signature for the identification of Pinelliae Rhizoma (Banxia) and its products.

BACKGROUND: Ensuring the authenticity of raw materials is a key step prior to producing Chinese patent medicines. Pinellia ternata (Thunb.) Breit. is the botanical origin of Pinelliae Rhizoma (Banxia), a traditional Chinese medicine used to treat cough, insomnia, nausea, inflammation, epilepsy, and so on. Unfortunately, authentic Pinelliae Rhizoma is often adulterated by morphologically indistinguishable plant material due to the insufficient regulatory procedures of processed medicinal plant products. Thus, it is important to develop a molecular assay based on species-specific nucleotide signatures and primers to efficiently distinguish authentic Pinelliae Rhizoma from its adulterants. METHODS AND RESULTS: The ITS2 region of 67 Pinelliae Rhizoma and its common adulterants were sequenced. Eight single nucleotide polymorphisms within a 28-43 bp stretch of ITS2 were used to develop six primer pairs to amplify these species-specific regions. We assayed 56 Pinelliae Rhizoma products sold on the Chinese market, including medicinal slices, powder and Chinese patent medicines, which revealed that about 66% of products were adulterated. The most common adulterants were Pinellia pedatisecta (found in 57% of the assayed products), Arisaema erubescens (9%), Typhonium giganteum (2%) and Typhonium flagelliforme (2%). CONCLUSIONS: A severe adulteration condition was revealed in the traditional medicine market. The species-specific nucleotide assays developed in this study can be applied to reliably identify Pinelliae Rhizoma and its adulterants, aiding in the authentication and quality control of processed products on the herbal market.

Strengthening Performance Optimization of Single Ball Impact Treatment by Evaluating Residual Stress.

Residual stress plays an essential role in affecting the strengthening performance by a surface treatment. Studying the impact of a single ball on a target surface is the basis of shot peening technology in order to obtain the distribution of the residual stress, and to optimize the processing parameters. In this paper, a numerical model has been developed to represent single ball impacts on high manganese steel by considering different processing parameters. It was found that by increasing the ball diameter and impact velocity, the depth of maximum residual compressive stress and the depth of the residual compressive stress layer became significantly enlarged due to increasing kinetic energy of the impacting ball. It was also found from simulation that with an increase in ball impact angle, the maximum residual compressive stress, the depth of maximum residual compressive stress and the depth of the residual compressive stress layer were significantly improved; an exception was the surface residual compressive stress, which showed a decreasing trend. Moreover, by employing quantitative analysis with the entropy method, it was found that within the range of processing parameters considered in the simulation, it is recommended to use a ball with a diameter of 0.6 mm to impact the target, with a velocity of 80 m/s and an angle of 90° for the best strengthening performance.

Electrochemical Strategy for High-Resolution Nanostructures in Laser-Heat-Mode Resist Toward Next Generation Diffractive Optical Elements.

For achieving high-resolution nanostructures for next-generation diffractive optical elements (DOEs) using an environmentally friendly process, an electrochemical development strategy is proposed and developed using AgInSbTe-based laser heat-mode resist (AIST-LHR). Based on the electrical resistivity difference of amorphous and crystalline phases for this resist, an etching selectivity ratio of ≈30:1 (i.e., the etch ratio between the amorphous and crystalline ones) is achieved through the oxidation of Fe3+ ions with the assisted pitting activation etching using Cl- ions in an acid medium. Nanostructures with a minimum feature size down to 41 nm are successfully generated, including grating patterns, meta-surface optical structures, gears, and English characters. Using a post-plasma etching process, the nanostructures are successfully transferred from the AIST-HLR onto silica substrate, and X-ray grating patterns with a line space of 80 nm are created as a demonstration for its potential applications in DOEs.

Higher toxin tolerance to triptolide, a terpenoid foraged by a sympatric honeybee.

The thunder god vine, Tripterygium hypoglaucum, is a toxic nectar plant distributed across China. A terpenoid, called triptolide (TRP), found in nectar can impair honeybees' foraging responses, dance communication, and olfactory learning. In the present study, we tested the tolerances of the native honeybee Apis cerana and the introduced honeybee A. mellifera to short-term and long-term exposure to TRP. The results showed that introduced A. mellifera is more vulnerable in fatality to high concentrations of TRP sucrose solution (5 and 10 µg TRP mL-1) than A. cerana. We also compared the short-term and long-term exposure effects of TRP on olfactory learning and memory between the two honeybee species, and the olfactory learning and memory of both honey bee species showed impaired performance after both 2 h or 7 days of being fed with TRP sucrose solution. However, A. cerana showed a higher tolerance and resistance to TRP toxin than A. mellifera. Our results support a coevolution hypothesis in that the native species A. cerana has higher toxin tolerance than the introduced species A. mellifera.

The cell invasion preference of Varroa destructor between the original and new honey bee hosts.

Honey bees (Apis) are important pollinators for food crops and wild plants, but are facing great threats from pathogens and parasites, especially an obligate ectoparasitic mite, Varroa destructor. Cell invasion is a key step for V. destructor to reproduce, and the parasite displays remarkable host preference in this process. Varroa destructor made its host-shift from its original host, the Asian honey bee Apis cerana, to the new host, the European honey bee Apis mellifera several decades ago. However, it remains largely unstudied whether V. destructor shows a cell invasion preference between the two host species. Using cell invasion bioassays on a modified four-well arena, we showed that V. destructor significantly preferred to invade the worker and drone larvae of A. mellifera rather than A. cerana, suggesting that the new host is much more attractive to the parasite than the original one. Using gas chromatography-mass spectrometry (GC-MS), we revealed significant differences between the cuticular hydrocarbon (CHC) profiles of worker and drone larvae of the two bee hosts. The amounts of methyl-branched alkanes and alkenes (unsaturated CHCs), but not n-alkanes, were significantly different, and A. mellifera worker and drone larvae were found to express significantly higher amounts of methyl-alkanes, while A. cerana larvae produced higher amounts of alkenes. Cell invasion bioassays with glass dummies showed that the mites preferred the glass dummies coated with the CHCs of A. mellifera worker or drone larvae, which indicates a role of larval CHCs in mediating the preferential cell invasion of Varroa. The findings from this study extend our understanding of the host preference of V. destructor, and can potentially contribute to the development of effective strategies for mite control.