Experimental and Applied Acarology最新文献

Superfamily Eriophyoidea is a group of highly miniaturized and host-specific phytophagous acariform mites closely related to the soil-dwelling nematalycid mites. Limited number of reliable morphological characters, multiple homoplasies, and numerous cryptic species impede systematics of this group. Most recent multigene phylogenies of Eriophyoidea suffer from incomplete sampling, inclusion of erroneous sequences, and unreliable alignments resulting in biologically inconsistent results. In this study, we obtained five new mitogenomes of eriophyoids and reanalyzed the mitogenomic dataset by Zhang et al. (2024) in order to test their conclusion on the polyphyly of the subfamily Cecidophyinae. We found out that it was based on the wrong identification of the phyllocoptine sequence OQ615736 as a cecidophyine taxon. Our analysis showed that a group of seven mitogenomic sequences assigned to cecidophyine genera Cecidophyes, Cecidophyopsis, Coptophylla, Cosetacus, and Glyptacus form a monophyletic group, which was itself divided into two clades corresponding to previously recognized tribes Colomerini and Cecidophyini. However, no mitochondrial gene clusters unique to Cecidophyinae were found. Gene order variability in Cecidophyinae is low and concerns only positions of the control region and tRNA genes trnC and trnI. Analysis of nucleotide diversity showed that three mitochondrial protein coding genes (COX1, COX3 and CYTB) are promising molecular markers for future eriophyoid studies, whereas genes ATP8, NAD4L, NAD5, NAD6 are hypervariable and should be used with caution or even excluded (ATP8) from multigene phylogenetic analyses. Finally, we identified numerous sequences of Eriophyoidea in GenBank with incorrect taxonomic affinities, underscoring the urgent need for a comprehensive revision of all eriophyoid mite sequences deposited in public databases.

Mass rearing of the predatory mite Euseius scutalis (Athias-Henriot) using natural prey is costly and labor-intensive, limiting its application in biological pest control. Artificial diets may serve as alternative food sources; however, some studies should be previously conducted, to evaluate the possible biological consequences of their adoption. In this study, we compared the suitability of eight artificial diets, including a basic artificial diet (A) consisting of a combination of 10% honey, 10% sucrose, 5% tryptone, 5% yeast extract, 10% egg yolk, and 60% distilled water (w/w), along with seven other diets, each consisting of 80% of diet A enriched with date palm pollen (B), Typha pollen (C), Ephestia kuehniella eggs (D), Helicoverpa armigera hemolymph (E), a mixture of date palm pollen and E. kuehniella eggs (F), Tetranychus turkestani adults (G), and hen's liver (H). The data showed that E. scutalis was able to complete its development on all tested diets. Oviposition of the predator was observed on all diets, except for diets E and H. Females reared on diets B and F had the shortest adult pre-oviposition period (APOP), while those on diet B had the shortest total pre-oviposition period (TPOP). Furthermore, the number of oviposition days and fecundity were highest on diets B, D and F. Diets B and F resulted in significantly higher intrinsic (r) and finite (λ) rates of increase than the other diets, with values statistically similar to those obtained on D. The lowest values of r and λ were recorded on diet G. Based on our results, date palm pollen, E. kuehniella eggs or their mixture added to the basic diet A are more beneficial than other options for use in artificial diets for the mass rearing of E. scutalis.

Ticks of the genus Amblyomma parasitize a wide variety of terrestrial vertebrate hosts, including humans. In Nicaragua, 14 species of ticks of the genus Amblyomma have been recorded. To our knowledge, no published records of ticks on sloths exist. However, A. varium, which parasitizes these hosts, was reported without an associated host. During 2023 and 2024, five sloths of two species (Bradypus variegatus and Choloepus hoffmanni) were rescued from four localities belonging to three Departments of Nicaragua. Two species of ticks were collected from the sloths, Amblyomma geayi and Amblyomma varium. Both records of ticks represent the first for Nicaragua in association with sloths. In this way, the richness of ticks of the genus Amblyomma in Nicaragua increases to 15 species.

Panonychus citri, a major pest mite globally, causes substantial economic damage in the citrus sector. Due to the prolonged use of acaricides, P. citri has developed resistance; thus, identifying alternative control measures is imperative. The study successfully cloned and characterized three genes from the RR-2 subfamily of cuticular proteins (CP) in P. citri, PcCPR14, PcCPR15.7, and PcCPR16.8. These genes exhibited their highest expression in eggs aged 4 and 5 days and showed relatively high expression in larvae and nymphs on day 1. Inhibitin PcCPR16.8 expression in eggs resulted in only 23% hatching success. Similarly, silencing PcCPR16.8 is inhibited in nymphs led to cuticle rupture and a mortality rate of 81.77%. Silencing in female mites reduced the oviposition rate by 31.06% and significantly decreased chitin content and the expression of key chitin metabolism genes in P. citri. This indicates the crucial role of CP genes in the development and reproduction of P. citri. Moreover, exposure to the acaricides spirobudiclofen and etoxazole typically triggers high expression of PcCPR16.8, and silencing this gene increases the mite's sensitivity to these chemicals. CPs are vital in defending against environmental changes, making them potential targets for developing P. citri control strategies.

In insects, farnesyl pyrophosphate synthase (FPPS), a pivotal enzyme in the mevalonate pathway, is crucial in the juvenile hormone (JH)/methyl farnesoate (MF) biosynthesis pathway, particularly regulating the molting process. However, its role in the post-embryonic development and molting in Acari remains unclear. This study therefore investigated the function of TuFPPS in the deutonymphal stage of the two-spotted spider mite, Tetranychus urticae, an important pest in agriculture. Real time quantitative PCR (qPCR) revealed a significant increase in TuFPPS expression in the middle of the quiescent period (28 h). RNA interference (RNAi)-mediated knockdown of TuFPPS caused developmental delays, notably extending the quiescent period and delaying the molting process. Ultimately, the treated mites failed to molt and died with 80% mortality at 108 h before molting, while > 90% of the mites in the control successfully molted. To investigate the potential functions of TuFPPS during the quiescent period and molting process in T. urticae, we performed a genome-wide RNA sequencing following RNAi knockdown of TuFPPS. Four genes were identified based on the thresholds of|FC| ≥ 3 and FDR < 0.05, and these are involved in carbohydrate metabolism, fatty acid and lipid metabolism, amino acid metabolism, and ABC transporters. Altogether, our data suggest that TuFPPS plays a critical role in regulating energy transport, intracellular digestion, and energy supply, as seen in ametabolous insects. These findings lay the foundation for further studies of the molecular mechanism of JH/MF in post-embryonic development and molting in mites, and also identify a potential target for pest control, as demonstrated in T. urticae.

Brazilian spotted fever (BSF) is endemic in southeastern Brazil, where Amblyomma sculptum is the main vector incriminated in the transmission of R. rickettsii to humans. In many BSF-endemic areas capybaras are the main hosts for A. sculptum and also efficient amplifiers of R. rickettsii for this tick species. Capybaras are also primary hosts for Amblyomma dubitatum, a tick species frequently found infected by Rickettsia bellii but with no records of natural infection by R. rickettsii. The present study aimed to evaluate transovarial transmission and vector competence for R. rickettsii in A. dubitatum naturally infected and non-infected with R. bellii. For this purpose, two A. dubitatum colonies were used, one naturally infected by R. bellii, another with no R. bellii infection. Ticks from both colonies were divided into three experimental groups: group GL (ticks fed on R. rickettsii-inoculated guinea pigs in the larval stage), group GN (ticks fed on R. rickettsii-inoculated animals in the nymphal stage) and group GC (ticks never exposed to R. rickettsii). DNA samples from eight to 20 unfed nymphs and adults fed on each guinea pig, and from all engorged females at the end of oviposition, and from their respective eggs (one pool of 20-50 eggs/female) and larvae (10 larvae/female), were subjected to species-specific qPCR protocols for either R. rickettsii or R. bellii detection. Finally, larvae originating from R. rickettsii-infected females were fed on uninfected guinea pigs. In both A. dubitatum colonies, nymphs from group GL and adults from groups GL and GN were able to transmit R. rickettsii to susceptible animals, confirming vectorial competence and transstadial perpetuation of the pathogen. Further, infection by R. rickettsii was detected in eggs and larvae from 18% to 75% of GN and GL R. bellii-uninfected females, and from 25% to 44% of GN and GL R. bellii-infected females, respectively, confirming the transovarial transmission of the pathogen, regardless of R. bellii infection. Finally, larvae originating from engorged females infected with R. rickettsii were able to transmit the pathogen to susceptible animals, confirming the vectorial competence of ticks infected by transovarial transmission.

Hyperparasitism has been observed in soft and hard tick species around the world. In Brazil, the phenomenon of hyperparasitism has only been observed conspecifically in hard ticks of the genus Amblyomma. In the present study, we report unprecedented cases of hyperparasitism in soft and hard ticks. Conspecific hyperparasitism is reported for Ornithodoros fonsecai and Ornithodoros tabajara, while interspecific hyperparasitism is reported for Amblyomma sculptum on Rhipicephalus microplus.

The natural immune system of arthropods is an important defense against pathogen infection. Predatory mites, as a highly commercialized group of natural enemies, suffer the threat of pathogen infection during mass rearing processes. However, there is a lack of research on the immune mechanisms of predatory mites in response to pathogen infection. To explore whether the Phytoseiulus persimilis possesses a natural immune response to pathogen, we selected the typical Gram-positive bacterium Acaricomes phytoseiuli to examine the pathogenic impact on P. persimilis fitness and the potential immune-related genes. The results showed that the survival rate, fecundity and predation of P. persimilis were significantly reduced after infection with A. phytoseiuli. Furthermore, fluorescent in situ hybridization was used to identify the pathogen enriched in the ovary and intestinal tract of P. persimilis. To further investigate the natural immune defense of P. persimilis, we analyzed the expression of twelve immune genes selected from the transcriptome. The results showed that the expression levels of four genes, tok, HPB, DUOX, and Peroxidase, were upregulated after one day of pathogen infection. While the expression of other genes showed no significant differences in either the 1st day or 3rd day. Our study provide preliminary exploration of natural immune mechanism of phytoseiid mites, laying a theoretical foundation for further their disease resistance.

The aim of the study was to establish an artificial feeding system (AFS), based on silicon membranes, for Amblyomma sculptum nymphs and compare it to classical feeding systems using laboratory animals. Three cohorts of 60 nymphs were fed on a rabbit, calf, and with the newly established AFS using prewarmed (38 °C) defibrinated bovine blood. The attachment rate (38.3%) as well as the engorgement rate (36.7%) in the AFS were both significantly lower (p = 0.0001; p = 0.0002) than in the animal-based feeding systems (73.3-85%). Subsequent development of engorged nymphs was similar regarding engorgement weight (11.96-16.3 mg) and subsequent molting (78.3-100%) into adults in all three cohorts. The main limitations of the AFS are the low attachment and engorgement rates, which require further optimization to enhance initial attraction to the membrane, for instance, by adding external attractants to the membrane or stimulating agents such as ATP to the bovine blood. Despite these limitations, the developed AFS provides a valuable tool for future research on ticks, tick-borne diseases and drug efficacy.

Citrus leprosis is a major viral disease transmitted by the citrus leprosis mite (Brevipalpus spp.), causing significant economic losses in Brazilian citrus farming. This study developed a sequential sampling plan for Brevipalpus spp. in two citrus cultivation systems. Two plots in an orange orchard ('Pêra Rio' variety) in Capitão Poço, Pará, Brazil, were selected: one under monoculture and the other intercropped with teak. Monthly sampling from September 2015 to August 2016 involved 112 georeferenced plants per plot. Mite counts were performed on six fruits, branches, and leaves from both inner and outer plant parts using a 10 × pocket lens. Aggregation indices, including variance-to-mean ratio, Morisita's index, Green's coefficient, and Taylor's power law, revealed an aggregated distribution for all variables. The k parameter of the negative binomial distribution confirmed aggregation, and this model provided the best fit for both systems. The sequential sampling plan determined that the maximum expected sampling units for decision-making is 21 mites per plant and 28 mites per six branches in both systems. These thresholds were established based on the observed distribution pattern and aim to enhance monitoring efficiency. Although these values may seem low, they indicate the infestation level at which control measures should be implemented to prevent economic losses. These findings contribute to improved monitoring strategies for Brevipalpus spp. in citrus orchards, supporting more effective pest management.