Worldwide migration of parasitic mites as a result of bumblebee commercialization

We investigated the status of infestation by a tracheal mite, Locustacarus buchneri, in natural populations of a Japanese native bumblebee species, Bombus hypocrita, collected on Hokkaido Island and in the Aomori prefecture between 1997 and 2001. We also investigated mite infestation in commercial colonies of the European bumblebee, Bombus terrestris, imported from the Netherlands and Belgium, and the Japanese native species, B. ignitus, imported from the Netherlands, between 1997 and 2001. We detected mites in natural populations of the two B. hypocrita subspecies and in the commercial colonies. Analysis of variations in 535 bp sequences of the mitochondrial cytochrome oxidase subunit 1 (CO1) gene showed that the mite haplotypes in the native populations and in the imported colonies did not overlap in 1997–1999, but in 2000–2001 some mites possessing European CO1 haplotypes were detected in the natural populations of Japanese native bumblebees. In addition, many mites possessing Japanese haplotypes were detected in the imported commercial colonies from Europe. Considering the fact that the Japanese native bumblebees, B. hypocrita, were once exported to Europe for commercialization, these results suggest that bumblebee commercialization has caused overseas migration and cross-infestation of parasitic mites among natural and commercial colonies. However, because the Japanese and European CO1 haplotypes were closely related, there was a possibility that the European haplotypes found in the mites in the Hokkaido Island revealed native variation. To clarify the status of mite invasion, further detailed analysis of genetic variation of the mite, using other genetic markers on additional samples, need to be performed.     

Unintentional introductions of microscopic organisms associated with forest insects

International trade and travel are devastating native flora and fauna in many countries through the intentional and/or unintentional introduction of exotic organisms. Pathway control appears to be particularly effective for microscopic organisms such as mites, nematodes, and fungi that are difficult to see with the naked eye. However, taxonomic and ecological information on such organisms is scarce, sometimes causing time lags or failure in eradication programs. Several groups of mites, nematodes, and fungi commonly share a habitat with insects or use them as dispersal agents (phoresy). Some exotic mites and nematodes are introduced simultaneously with exotic insects, sometimes in wood materials. In Japan, mites, nematodes, and fungi have been collected from lucanid beetles introduced as pets from Southeast Asia. While no lethal nematode species have been collected from lucanid beetles, one hemolymph-sucking mite species, inhabiting the sub-elytral space of its native host, is able to easily switch to the Japanese beetle, Dorcus rectus, killing the insect. Yeasts have also been reported on exotic beetles and laboulbeniomycetes have been found on mites associated with the beetles, although their interactions are unknown. Despite the lack of information available about other mites, nematodes, and fungi associated with intentionally and unintentionally introduced forest insects, our analysis of insect species listed by the International Union for Conservation of Nature suggests that unintentional introductions of the microscopic organisms are quite common as a consequence of the existence of symbiotic relationships such as phoresy and parasitism.     

Amphibian chytridiomycosis in Japan: distribution,haplotypes and possible route of entry into Japan

A serious disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis was first found in Japan in December 2006 in imported pet frogs. This was the first report of chytridiomycosis in Asia. To assess the risk of pandemic chytridiomycosis to Japanese frogs, we surveyed the distribution of the fungus among captive and wild frog populations. We established a nested PCR assay that uses two pairs of PCR primers to amplify the internal transcribed spacer (ITS) region of a ribosomal RNA cassette to detect mild fungal infections from as little as 0.001 pg (1 fg) of B. dendrobatidis DNA. We collected swab samples from 265 amphibians sold at pet shops, 294 bred at institutes and 2103 collected at field sites from northern to southwestern Japan. We detected infections in native and exotic species, both in captivity and in the field. Sequencing of PCR products revealed 26 haplotypes of the B. dendrobatidis ITS region. Phylogenetic analysis showed that three of these haplotypes were specific to the Japanese giant salamander (Andrias japonicus) and appeared to have established a commensal relationship with this native amphibian. Many other haplotypes were carried by alien amphibians. The highest genetic diversity of B. dendrobatidis was found in the American bullfrog (Rana catesbeiana). Some strains of B. dendrobatidis appeared to be endemic to Japanese native amphibians, but many alien strains are being introduced into Japan via imported amphibians. To improve chytridiomycosis risk management, we must consider the risk of B. dendrobatidis changing hosts as a result of anthropogenic disturbance of the host‐specific distribution of the fungus.     

Causal mechanisms underlying host specificity in bat ectoparasites

In parasites, host specificity may result either from restricted dispersal capacity or from fixed coevolutionary host-parasite adaptations. Knowledge of those proximal mechanisms leading to particular host specificity is fundamental to understand host-parasite interactions and potential coevolution of parasites and hosts. The relative importance of these two mechanisms was quantified through infection and cross-infection experiments using mites and bats as a model. Monospecific pools of parasitic mites (Spinturnix myoti and S. andegavinus) were subjected either to individual bats belonging to their traditional, native bat host species, or to another substitute host species within the same bat genus (Myotis). The two parasite species reacted differently to these treatments. S. myoti exhibited a clear preference for, and had a higher fitness on, its native host, Myotis myotis. In contrast, S. andegavinus showed no host choice, although its fitness was higher on its native host M. daubentoni. The causal mechanisms mediating host specificity can apparently differ within closely related host-parasite systems.     

<Emphasis Type="Italic">Wolbachia</Emphasis>-induced cytoplasmic incompatibility in Japanese populations of <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae)

Intracellular bacteria of the genus Wolbachia (alpha Proteobacteria) induce cytoplasmic incompatibility (CI) in many arthropod species, including spider mites, but not all Wolbachia cause CI. In spider mites CI becomes apparent by a reduced egg hatchability and a lower daughter:son ratio: CI in haplodiploid organisms in general was expected to produce all-male offspring or a male-biased sex ratio without any death of eggs. In a previous study of Japanese populations of Tetranychus urticae, two out of three green-form populations tested were infected with non-CI Wolbachia strains, whereas none of six red-form populations harbored Wolbachia. As the survey of Wolbachia infection in T. urticae is still fragmentary in Japan, we checked Wolbachia infection in thirty green-form populations and 29 red-form populations collected from a wide range of Japanese islands. For Wolbachia-infected populations, we tested the effects of Wolbachia on the reproductive traits and determined the phylogenetic relationships of the different strains of Wolbachia. All but one green-form populations were infected with Wolbachia and all strains belonged to the subgroup Ori when the wsp gene was used to determine the phylogenetic relationships of different strains of Wolbachia. Six out of 29 red-form populations harbored Wolbachia and the infected strains belonged to the subgroups Ori and Bugs. Twenty-four of 29 infected green-form populations and five of six infected red-form populations induced CI among the hosts. Thus, CI-Wolbachia strains are widespread in Japan, and no geographical trend was observed in the CI-Wolbachia. Although three red-form populations harbored other intracellular bacteria Cardinium, they did not affect host reproduction.     

Larval aquatic and terrestrial mites infesting a temperate assemblage of mosquitoes

We collected 22,769 adult female mosquitoes, representing 27 species, from light traps in Norfolk, Virginia (2006–2007) and examined them to assess infestation by larval mites. Mosquitoes were parasitized by two species of aquatic (Acari: Arrenuridae: Arrenurus) and three species of terrestrial mites (Acari: Erythraeidae). The prevalence of infestation varied from 0.55% (2006) to 0.17% (2007). The mean intensity of parasitism ranged from 3.6 mites per host (2006) to 1.8 mites per host (2007). The most common host species for aquatic mites was Culex erraticus, while the most common host for terrestrial mites was Anopheles quadrimaculatus. Relationships between biotic and abiotic factors were investigated in an attempt to provide insight into temporal, spatial, and interspecific variation in mite–mosquito interactions. Scanning electron microscopy was used to examine the mode of attachment for larval mites. While the prevalence of aquatic mite parasitism was correlated for Culex erraticus, the invasive mosquito, Aedes albopictus, was never parasitized through the duration of the study. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Constant association of ophiostomatoid fungi with the bark beetle <Emphasis Type="Italic">Ips subelongatus</Emphasis> invading Japanese larch logs

Ceratocystiopsis, Ceratocystis, Grosmannia, and Ophiostoma species were isolated from Ips subelongatus and beetle-infested Japanese larch logs collected at several areas in central and northern Honshu Island, Japan, to determine constant associates of I. subelongatus. Ceratocystiopsis minuta, two species of Ceratocystis, three species of Grosmannia, and four species of Ophiostoma were isolated. Of the fungi isolated in the present study, G. laricis, O. brunneociliatum, and O. piceae were constant associates of the beetles. Ceratocystis fujiensis, Ceratocystiopsis minuta, and Ophiostoma sp. F were occasionally isolated with high frequencies of occurrence but were not consistent associates. Ceratocystis fujiensis was most often isolated as the leading fungal invasion in the sapwood of Japanese larch logs invaded by I. subelongatus, confirming that the fungus acts as a primary invader of sapwood in beetle-attacked logs. Contribution No. 221, Laboratory of Plant Parasitic Mycology, Graduate School of Life and Environmental Sciences, University of Tsukuba     

Vertical stratification of feeding by Japanese beetles within linden tree canopies: selective foraging or height per se?

Adult Japanese beetles, Popillia japonica Newman (Coleoptera: Scarabaeidae), tend to aggregate and feed most heavily in the upper canopy of host plants, defoliating them from the top down. We examined characteristics of linden (Tilia cordata L.) foliage from different canopy zones and tested two hypotheses that might account for vertical stratification of feeding by this vagile, polyphagous folivore. In the field, P. japonica caused 4–12 times more damage to upper canopy leaves in full sunlight than to lower canopy leaves in sun or shade. However, this within-tree pattern apparently cannot be explained by differences in nutritional parameters (protein, water, and sugar content) or defensive properties (toughness, tannins) of leaves. Furthermore, beetles did not discriminate between foliage from different canopy zones in laboratory choice tests, nor were fecundity or longevity higher for beetles fed upper canopy, sun-exposed leaves. Clonal grape plants suspended from vertical posts in the field at 3.65, 1.83 or 0 m above ground showed a top-down defoliation pattern identical to that seen in linden trees. This suggests that the height of foliage per se strongly affects initial orientation and attack by P. japonica. Recent related studies have shown that both sexes of P. japonica are strongly attracted to host volatiles induced by feeding of conspecific beetles. We suggest that Japanese beetles begin to feed in the upper canopy for reasons unrelated to host nutritional variation (e.g., behavioral thermoregulation, visual orientation to the host silhouette), and that top-down defoliation follows as additional beetles are attracted to feeding-induced volatiles acting as aggregation kairomones.     

Overwintering phenology of a predacious mite, Typhlodromus vulgaris (Acari: Phytoseiidae), on Japanese pear trees, observed with Phyto traps

Phyto traps were attached to twigs, main branches and trunks of Japanese pear trees in central Japan in autumn of 2004, to evaluate the effectiveness of the trap as a tool to study overwintering phenology of arboreal phytoseiid mites. A subset of the traps was inspected and replaced at two-weeks intervals (“short-term Phyto trap”), in order to evaluate movement of phytoseiid mites on the trees in a short-term. The remaining traps were left undisturbed and collected monthly from January to May 2005 (“long-term Phyto trap”), to know what species overwinter in the traps and when they leave them. Most phytoseiid mites were collected in the traps on twigs. The most abundant phytoseiid species was Typhlodromus vulgaris Ehara. In the short-term traps on twigs, adult females and males of T. vulgaris were collected until mid-November 2004, when the pear trees became completely defoliated, but few mites were collected from December to April. On the other hand, adult females of T. vulgaris were abundant in the long-term traps on twigs sampled from January to April, but other stages of mites were never collected. These results indicate that T. vulgaris had moved to the long-term traps by late November, and that only adult females had overwintered in the traps. These females began to move and reproduce in early May. By that time immature developmental stages of T. vulgaris were also recorded in the short- and long-term Phyto traps. Our results confirmed that the Phyto trap was a useful tool for estimating overwintering phenology of phytoseiid mites on trees.     

从日本进境邮寄物中截获伤残短体线虫

【背景】2015年北京出入境检验检疫技术中心植物实验室从日本邮寄进境的鸡爪槭中检出一种短体线虫。【方法】通过采用形态学鉴定、rDNA序列测定及系统进化分析,对该线虫进行鉴定。【结果】将该线虫的形态特征和测计值与已知种群比较,与Pratylenchus vulnus最为接近;系统进化分析表明,其r DNA-ITS区序列特征与P.vulnus序列相似度为99%;系统发育树表明,其与P.vulnus聚为一组,证实该线虫为伤残短体线虫P.vulnus。【结论与意义】伤残短体线虫是一种重要的植物寄生线虫,我国进出境检疫部门曾多次从入境货物中检出该线虫,但从入境邮寄物中检中尚属首次。     

Invasion by a Japanese marine microorganism in western North America

The earliest record in western North America of Trochammina hadai Uchio, a benthic foraminifer common in Japanese estuaries, is from sediment collected in Puget Sound in 1971. It was first found in San Francisco Bay in sediment samples taken in 1983, and since 1986 has been collected at 91% of the sampled sites in the Bay, constituting up to 93% of the foraminiferal assemblage at individual sites. The species is also present in recent sediment samples from 12 other sites along the west coast of North America. The evidence indicates that T. hadai is a recent introduction to San Francisco Bay, and is probably also not native to the other North American sites. Trochammina hadai was probably transported from Japan in ships' ballast tanks, in mud associated with anchors, or in sediments associated with oysters imported for mariculture. Its remarkable invasion of San Francisco Bay suggests the potential for massive, rapid invasions by other marine microorganisms.     

Rearing,release and settlement prospect in Italy of <Emphasis Type="Italic">Torymus sinensis</Emphasis>, the biological control agent of the chestnut gall wasp <Emphasis Type="Italic">Dryocosmus kuriphilus</Emphasis>

Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), is one of the most serious pests attacking chestnut trees. Recently it was incidentally introduced into Northwest Italy and it is now spreading throughout Europe. This pest was successfully controlled in Japan by introducing a parasitoid, Torymus sinensis Kamijo (Hymenoptera: Torymidae), from China’s mainland. Following this successful experience, the parasitoid was introduced into Italy from Japan. One year of preliminary studies led to a successful method of rearing imported galls with a synchronization between the parasitoid’s emergence and the presence of the target galls in the field. In two consecutive years, a total of 2,117 individuals were released in several sites covering most of the infested area. There are encouraging data about the settlement of the parasitoid and its synchrony with the host’s cycle: from about 64,000 host galls collected in the field over 200 T. sinensis were reared. The role of native parasitoids associated with the chestnut gall pest in its Italian distribution range is also discussed.     

A migration analysis of the rice planthopper Nilaparvata lugens from the Philippines to East Asia with three-dimensional computer simulations

Migrations of the rice planthopper Nilaparvata lugens (Stål) (Delphacidae) from the Philippines to Taiwan, southern China, and southern Japan were analyzed using three-dimensional migration simulations. The results strongly suggested that the Southeast Asian population of N. lugens mixes with the East Asian population. This highlighted the possibility that planthoppers from the Southeast Asian population, which have properties different from those in the East Asian population such as feeding of resistant rice varieties and wing polymorphism, could migrate to Japan via southern China and Taiwan. This study, therefore, emphasizes the special care that should be taken to monitor the properties of immigrants to Japan.     

Measuring the host preference of parasites: An aid in evaluating biotypes ofAnagrus epos [Hym.: Mymaridae]

Populations ofAnagrus epos Girault are being imported and evaluated for the biological control of variegated grape leafhopper,Erythroneura variabilis Beamer, a newly introduced pest of grapes in central California. To distinguish different biotypes, a field test was developed that quantifies host preference.E. epos collected from geographically isolated regions of western United States and northern Mexico showed different levels of preference towards the variegated leafhopper and its close relative the grape leafhopper,Erythroneura elegantula Osborn, a native to central California. Host preference values may aid in the identification of relased biotypes using leafhopper eggs on leaves sampled from release sites.      

Ophiostomatoid fungi isolated from Japanese red pine and their relationships with bark beetles

We isolated ophiostomatoid fungi from bark beetles infesting Pinus densiflora and their galleries at 24 sites in Japan. Twenty-one ophiostomatoid fungi, including species of Ophiostoma, Grosmannia, Ceratocystiopsis, Leptographium, and Pesotum, were identified. Among these, 11 species were either newly recorded in Japan or were previously undescribed species. Some of these fungal species were isolated from several bark beetles, but other species were isolated from only a particular beetle species. Thus, it is suggested that some ophiostomatoid fungi have specific relationships with particular beetle species. In addition, fungus-beetle biplots from redundancy analysis (RDA) summarizing the effects of beetle ecological characteristics suggested that the association patterns between bark beetles and the associated fungi seemed to be related to the niches occupied by the beetles.     

Host Selection by the Herbivorous Mite Polyphagotarsonemus latus (Acari: Tarsonemidae)

This study examined the host-selection ability of the broad mite Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae). To make long-distance-shifts from one host plant patch to another, broad mites largely depend on phoretic association with whiteflies. However, the host plants of whiteflies and broad mites are not necessarily the same. We determined the host-preference and acceptance of free-moving and phoretic broad mites using two behavioral bioassays. We used a choice test to monitor host selection by free-moving mites. In the case of phoretic mites, we compared their rate of detachment from the phoretic vector Bemisia tabaci placed on leaves taken from various host plants. The suitability of the plant was further determined by monitoring mite’s fecundity and its offspring development. We compared the mites’ responses to young and old cucumber (Cucumis sativus cv. ‘Kfir’) leaves (3rd and 8–9th leaf from the apex, respectively), and two tomato (Solanum lycopersicum cvs. ‘M82’ and ‘Moneymaker’). Free-moving mites of all stages and both sexes preferred young cucumber leaves to old cucumber leaves and preferred young cucumber rather than young tomato leaves, demonstrating for the first time that broad mites are able to choose their host actively. As for phoretic mated females, although eventually most of the mites abandoned the phoretic vector, the rate of detachment from the whitefly vector was host dependent and correlated with the mites’ fitness on the particular host. In general, host preference of phoretic female mites resembled that of the free-moving female. Cues used by mites for host selection remain to be explored.     

Genetic Diversity Between Japanese and Chinese Threeline Grunt (<Emphasis Type="Italic">Parapristipoma trilineatum</Emphasis>) Examined by Microsatellite DNA Markers

Threeline grunt (Parapristipoma trilineatum) distributes around the southwestern coast of Japan and the east coast of China. The Chinese P. trilineatum was imported by Japan as an aquacultural seed because of its rapid growth compared with that of the Japanese P. trilineatum. The Japanese P. trilineatum differs from the Chinese P. trilineatum in some quantitative traits, and it has been suggested that these two P. trilineatum populations are genetically different. In order to identify the population structures around Japan and China, 5 local populations of the Japanese P. trilineatum and 2 local populations of the Chinese P. trilineatum were analyzed using 4 microsatellite DNA markers. Significant differences were detected between Japanese and Chinese P. trilineatum and among samples of Chinese P. trilineatum; however, among the samples of Japanese P. trilineatum, no significant differences were detected. These results suggest that care must be taken to prevent the escape of the Chinese P. trilineatum from culture cages around the Japanese coast, in order to preserve the genetically different population structures of Japanese and Chinese P. trilineatum.     

Varroa jacobsoni (Acari: Varroidae) is more than one species

Varroa jacobsoni was first described as a natural ectoparasitic mite of the Eastern honeybee (Apis cerana) throughout Asia. It later switched host to the Western honeybee (A. mellifera) and has now become a serious pest of that bee worldwide. The studies reported here on genotypic, phenotypic and reproductive variation among V. jacobsoni infesting A. cerana throughout Asia demonstrate that V. jacobsoni is a complex of at least two different species. In a new classification V. jacobsoni is here redefined as encompassing nine haplotypes (mites with distinct mtDNA CO-I gene sequences) that infest A. cerana in the Malaysia–Indonesia region. Included is a Java haplotype, specimens of which were used to first describe V. jacobsoni at the beginning of this century. A new name, V. destructor n. sp., is given to six haplotypes that infest A. cerana on mainland Asia. Adult females of V. destructor are significantly larger and less spherical in shape than females of V. jacobsoni and they are also reproductively isolated from females of V. jacobsoni. The taxonomic positions of a further three unique haplotypes that infest A. cerana in the Philippines is uncertain and requires further study.Other studies reported here also show that only two of the 18 different haplotypes concealed within the complex of mites infesting A. cerana have become pests of A. mellifera worldwide. Both belong to V. destructor, and they are not V. jacobsoni. The most common is a Korea haplotype, so-called because it was also found parasitizing A. cerana in South Korea. It was identified on A. mellifera in Europe, the Middle East, Africa, Asia, and the Americas. Less common is a Japan/Thailand haplotype, so-called because it was also found parasitizing A. cerana in Japan and Thailand. It was identified on A. mellifera in Japan, Thailand and the Americas.Our results imply that the findings of past research on V. jacobsoni are applicable mostly to V. destructor. Our results will also influence quarantine protocols for bee mites, and may present new strategies for mite control.     

Deformed wing virus associated with <Emphasis Type="Italic">Tropilaelaps mercedesae</Emphasis> infesting European honey bees (<Emphasis Type="Italic">Apis mellifera</Emphasis>)

Mites in the genus Tropilaelaps (Acari: Laelapidae) are ectoparasites of the brood of honey bees (Apis spp.). Different Tropilaelaps subspecies were originally described from Apis dorsata, but a host switch occurred to the Western honey bee, Apis mellifera, for which infestations can rapidly lead to colony death. Tropilaelaps is hence considered more dangerous to A. mellifera than the parasitic mite Varroa destructor. Honey bees are also infected by many different viruses, some of them associated with and vectored by V. destructor. In recent years, deformed wing virus (DWV) has become the most prevalent virus infection in honey bees associated with V. destructor. DWV is distributed world-wide, and found wherever the Varroa mite is found, although low levels of the virus can also be found in Varroa free colonies. The Varroa mite transmits viral particles when feeding on the haemolymph of pupae or adult bees. Both the Tropilaelaps mite and the Varroa mite feed on honey bee brood, but no observations of DWV in Tropilaelaps have so far been reported. In this study, quantitative real-time RT-PCR was used to show the presence of DWV in infested brood and Tropilaelaps mercedesae mites collected in China, and to demonstrate a close quantitative association between mite-infested pupae of A. mellifera and DWV infections. Phylogenetic analysis of the DWV sequences recovered from matching pupae and mites revealed considerable DWV sequence heterogeneity and polymorphism. These polymorphisms appeared to be associated with the individual brood cell, rather than with a particular host.     

Potential role of parasitism in the evolution of mutualism in astigmatid mites: Hemisarcoptes cooremani as a model

Phoresy is a symbiotic interaction that results in dispersal, benefiting the relocated organism without negatively impacting the phoretic host. It has long been considered that phoresy among astigmatid mites is somehow an intermediate precursor to the evolution of parasitism within the group. In astigmatid mites, only the heteromorphic deutonymph (hypopode) participates in phoretic dispersal, and the plesiomorphic hypopode may be the key to understanding the dynamics of the evolution of that parasitism. Hypopodes of Hemisarcoptes cooremani (Acari: Acariformes) and their phoretic beetle host Chilocorus cacti (Coleoptera: Coccinellidae) have become the experimental focus for studies concerned with the potential forces that influence the transition of a free-living life style into various coevolved relationships. Previous radiolabeling studies applied to H. cooremani and C. cacti determined that hypopodes of H. cooremani acquired resources from adults of C. cacti while in transit, negating the paradigm that the heteromorphy was purely phoretic. To further probe this relationship, we tested whether materials could be passed from the mites to their hosts. We report here a study using a tritium radiolabel, which indicated that beetles also acquire resources from the hypopodes. These results have implications for understanding the complex relationship between H. cooremani and C. cacti. We propose that this relationship should now correctly be defined as mutualistic (not phoretic) and develop a general model for the potential role of parasitism in the evolution of mutualism among the Astigmata.