Regulation of the external mycoflora of the giant Madagascar hissing-cockroach,gromphadorhina portentosa, by its mite associate,gromphadorholaelaps schaeferi, and its implications on human health

The giant Madagascar hissing-cockroach,Gromphadorhina portentosa, and its mite associate,Gromphadorholaelaps schaeferi, constitute an intimate commensalistic symbiosis. While the mite’s very survival is dependent by feeding on cockroach saliva and associated organic debris, the degree that the cockroach benefits from this association is unclear. We investigated the mite’s potential role at regulating surface fungi on the exoskeletons of this insect. Numbers of fungal isolates that resulted were compared between captive-bred cockroaches with and without mites. The mycoflora of both groups consisted of common molds (Alternaria sp.,Aspergillus sp.,Cladosporium sp.,Geotrichum sp.,Mucor sp.,Penicillium sp.,Rhizopus sp.,Trichoderma sp.). The presence of mites reduced the number of isolates by 1/2 in mature females, 1/3 in males, and 1/4 in sixth (final) instar nymphs. Fungus levels continued to drop when mite-free cockroaches were artificially supplemented with mites. A direct correlation was detected between mites and the reduction in the quantity of surface molds up to 20 mites per cockroach. The addition of more mites above 20 per cockroach, even 4x more, had a minimal, but still reducing, effect. Mites regulated all types of fungi, not just a select few taxa. We propose that mites reduce the mycoflora not because they consume fungi, but because mites and molds compete for the same resources in an ecological niche, saliva and organic debris that accumulate in between cockroach’s legs. Cockroaches reared in captivity do not apparently benefit by the removal of surface molds by mites, lending support for a commensalistic symbiosis. This cockroach species has been linked to severe allergic reactions in children, in part, because it harbors antagonistic molds. GivenG. schaeferi’s regulatory role at suppressing fungi, these mites could conceivably impose a small indirect, albeit beneficial role to humans by reducing the amount of fungal inoculum (conidia) that might otherwise be inhaled.     

Spider mites adaptively learn recognizing mycorrhiza-induced changes in host plant volatiles

Symbiotic root micro-organisms such as arbuscular mycorrhizal fungi commonly change morphological, physiological and biochemical traits of their host plants and may thus influence the interaction of aboveground plant parts with herbivores and their natural enemies. While quite a few studies tested the effects of mycorrhiza on life history traits, such as growth, development and reproduction, of aboveground herbivores, information on possible effects of mycorrhiza on host plant choice of herbivores via constitutive and/or induced plant volatiles is lacking. Here we assessed whether symbiosis of the mycorrhizal fungus Glomus mosseae with common bean plants Phaseolus vulgaris influences the response of the two-spotted spider mite Tetranychus urticae to volatiles of plants that were clean or infested with spider mites. Mycorrhiza-naïve and -experienced spider mites, reared on mycorrhizal or non-mycorrhizal bean plants for several days before the experiments, were subjected to Y-tube olfactometer choice tests. Experienced but not naïve spider mites distinguished between constitutive volatiles of clean non-mycorrhizal and mycorrhizal plants, preferring the latter. Neither naïve nor experienced spider mites distinguished between spider mite-induced volatiles of mycorrhizal and non-mycorrhizal plants. Learning the odor of clean mycorrhizal plants, resulting in a subsequent preference for these odors, is adaptive because mycorrhizal plants are more favorable host plants for fitness of the spider mites than are non-mycorrhizal plants.     

Ecological characteristics of insects that affect symbiotic relationships with mites

Parasites and pathogens that begin as symbionts, i.e., organisms living together in the same habitat, are some of the most promising drivers of species evolution. Because insects are highly diverse and important as ecosystem service agents and because mites can exert large effects on insect populations (capable of killing at least juveniles), insect–mite interactions have been analyzed from various perspectives, including evolutionary, ecological and pest‐management perspectives. Here, I review and examine insect–mite symbiotic associations to develop hypotheses concerning the factors that maintain and develop their relationships. Previous studies have hypothesized that insect sociality and mite richness and specificity affect insect–mite interactions. I found that both solitary and social insects, including parasocial and subsocial insects, harbor numbers of symbionts including species‐specific ones but few dangerous mite symbionts in their nests or habitats under natural conditions. Nest size or the amount of food resources in a nest may affect mite richness. On the basis of this review, I hypothesize that the insect characteristics relevant for mite symbiotic hosting are sharing the same habitat with mites and living in a nutrient‐rich habitat. I also suggest that many cases of species‐specific symbiosis began with phoresy. To test these hypotheses, phylogenetic information on mites living with insect groups and quantitative analysis to characterize each insect–mite relationship are necessary.     

Mycorrhiza-induced trophic cascade enhances fitness and population growth of an acarine predator

Research on trophic cascades in terrestrial ecosystems has only recently revealed that root-associated organisms interact with organisms living on aboveground plant parts. Arbuscular mycorrhizal (AM) symbiosis is a ubiquitous phenomenon, yet studies on its effect on aboveground natural enemies of herbivores are scarce and mainly deal with plant-mediated rather than herbivore-mediated interactions. Here, we studied herbivore-mediated effects of AM symbiosis on an acarine predator. We measured life history characteristics and population growth rates of Phytoseiulus persimilis preying on two-spotted spider mites, Tetranychus urticae, which were feeding on bean plants colonized or not colonized by the AM fungus Glomus mosseae. All major life history characteristics of P. persimilis, foremost oviposition rate, minimum prey requirements needed to reach adulthood, and developmental time, were positively affected by AM colonization of the host plant of their prey, together resulting in enhanced population growth rates of the predators. Hence, we hypothesize that a bottom-up trophic cascade may counteract the apparent negative effects of mycorrhizal symbiosis when promoting herbivory by promoting the predation of herbivores due to improved prey quality. We argue that this pathway may be involved in stabilizing plant-mycorrhizal symbiosis in ecosystems over time.     

Leaf domatia and mites on Australasian plants: ecological and evolutionary implications

Leaf domatia, specialized chambers in the vein axils on the underside of leaves of many plant species, have remained an enigma for over a century. In this study we show a strong association between foliar domatia and mites in 37 plant species in Australasia. Overall, mites accounted for 91% of the arthropods observed in domatia. Across all species, a median of 51% of domatia were occupied and 71% of leaves showed mite evidence in domatia. The level of mite association did not depend on domatia type (pit, pouch, pocket, or tuft) or provenance (Papua New Guinea, Queensland, Victoria, or New Zealand). Mite association with domatia commonly varied between plant species, between individuals within species, and between shoots within individuals. The leaf developmental stage probably explains much of the variation in association for many of these species. The presence of a variety of life history stages of mites within domatia indicates that these structures act as shelters for development and reproduction. Furthermore, in 12 of 13 plant species examined, domatia concentrate mites in particular locations on the leaf. Mite taxa that we classify as largely predaceous (e.g. phytoseiids, stigmaeids and tydeids) or fungivorous (e.g. acarids and oribatids) were most common in domatia and dominated the association in 21 of 24 plant species in which the relative abundance of herbivorous, fungivorous and predaceous groups was quantified. We evaluate hypotheses that explain the role of leaf domatia, including non-functional hypotheses (e.g. architectural constraints), physiological function (e.g. gas exchange and water uptake), bacterial symbiosis and antagonistic and mutualistic associations with mites. Our quantitative results confirm anecdotal accounts of mite association with leaf domatia and are most consistent with Lundströem's century-old hypothesis of plant-mite mutualism in which leaf domatia billet predaceous and fungivorous mites that prey on plant enemies. Leaf domatia are widespread among woody angiosperms and abundant in many temperate and tropical regions of Australasia. Mites, an ancient group of arthropods whose diversity and abundance parallels that of insects, are likely to be important selective agents on terrestrial plants. Our results (1) indicate that mite-domatia association represents a relationship of comparable scope to plant-ant associations mediated by specialized plant structures such as extrafloral nectaries, food bodies and specialized domatia; (2) suggest that sociality is not a necessary prerequisite for widespread and diverse mutualisms between arthropods and plants; and, (3) extend the diversity of organisms that produce specialized mite ‘houses’ from lizards, and wasps and bees to woody angiosperms.     

Host specificity among Unionicola spp. (Acari: Unionicolidae) parasitizing freshwater mussels

Water mites of Unionicola spp. are common parasites of freshwater mussels as adults, living on the gills, or mantle and foot of their hosts and using these tissues as sites of oviposition. The present study addresses specialization among North American Unionicola mussel-mites using 2 measures of host specificity: (1) the number of host species used by a species of mite; and (2) a measure that considers the taxonomic distinctness of the hosts utilized by mites, weighted for their prevalence in the different hosts. Results of this study indicate the Unionicola spp. mussel-mites are highly host specific, with most species occurring in association with 1 or 2 species of hosts. If 2 or more host species are utilized, they are typically members of the same genus. These data are consistent with studies examining the dispersal abilities and host recognition behavior for members of the group. When the average values of host specificity for Unionicola subgenera were mapped on a phylogenetic tree for these taxa, a clade comprised of gill mites appeared to be more host specific than a clade consisting of mantle mites. There were, however, no apparent patterns of host specificity within each of the clades. Differences in specificity between the 2 lineages may reflect either a long evolutionary history that gill mites have had with host mussels or the intense competition among gill mites for oviposition sites within unionid mussels, leading to increased host specialization.     

Repeatability of Feather Mite Prevalence and Intensity in Passerine Birds

Understanding why host species differ so much in symbiont loads and how this depends on ecological host and symbiont traits is a major issue in the ecology of symbiosis. A first step in this inquiry is to know whether observed differences among host species are species-specific traits or more related with host-symbiont environmental conditions. Here we analysed the repeatability (R) of the intensity and the prevalence of feather mites to partition within- and among-host species variance components. We compiled the largest dataset so far available: 119 Paleartic passerine bird species, 75,944 individual birds, ca. 1.8 million mites, seven countries, 23 study years. Several analyses and approaches were made to estimate R and adjusted repeatability (R_adj) after controlling for potential confounding factors (breeding period, weather, habitat, spatial autocorrelation and researcher identity). The prevalence of feather mites was moderately repeatable (R = 0.26–0.53; R_adj = 0.32–0.57); smaller values were found for intensity (R = 0.19–0.30; R_adj = 0.18–0.30). These moderate repeatabilities show that prevalence and intensity of feather mites differ among species, but also that the high variation within species leads to considerable overlap among bird species. Differences in the prevalence and intensity of feather mites within bird species were small among habitats, suggesting that local factors are playing a secondary role. However, effects of local climatic conditions were partially observed for intensity.     

Industrial Symbiosis in Kalundborg, Denmark: A Quantitative Assessment of Economic and Environmental Aspects

As a subdiscipline of industrial ecology, industrial symbiosis is concerned with resource optimization among colocated companies. The industrial symbiosis complex in Kalundborg, Denmark is the seminal example of industrial symbiosis in the industrial ecology literature. In spite of this, there has been no in-depth quantitative analysis enabling more comprehensive understanding of economic and environmental performances connected to this case. In this article some of the central industrial symbiotic exchanges, involving water and steam, in Kalundborg are analyzed, using detailed economic and environmental data. It is found that both substantial and minor environmental benefits accrue from these industrial symbiosis exchanges and that economic motivation often is connected to upstream or downstream operational performance and not directly associated with the value of the exchanged byproduct or waste itself. It is concluded that industrial symbiosis, as viewed from a company perspective, has to be understood both in terms of individual economic and environmental performance, and as a more collective approach to industrial sustainability.     

Diseases of Mites

An overview is given of studies on diseases of mites. Knowledge of diseases of mites is still fragmentary but in recent years more attention has been paid to acaropathogens, often because of the economic importance of many mite species. Most research on mite pathogens concerns studies on fungal pathogens of eriophyoids and spider mites especially. These fungi often play an important role in the regulation of natural mite populations and are sometimes able to decimate populations of phytophagous mites. Studies are being conducted to develop some of these fungi as commercial acaricides.Virus diseases are known in only a few mites, namely, the citrus red mite and the European red mite. In both cases, non-occluded viruses play an important role in the regulation of mite populations in citrus and peach orchards, respectively, but application of these viruses as biological control agents does not seem feasible. A putative iridovirus has been observed in association with Varroa mites in moribund honeybee colonies. The virus is probably also pathogenic for honeybees and may be transmitted to them through this parasitic mite.Few bacteria have been reported as pathogens of the Acari but in recent years research has been concentrated on intracellular organisms such as Wolbachia that may cause distorted sex ratios in offspring and incompatibility between populations. The role of these organisms in natural populations of spider mites is in particular discussed. The effect of Bacillus thuringiensis on mites is also treated in this review, although its mode of action in arthropods is mainly due to the presence of toxins and it is, therefore, not considered to be a pathogen in the true sense of the word.Microsporidia have been observed in several mite species especially in oribatid mites, although other groups of mites may also be affected. In recent years, Microsporidia infections in Phytoseiidae have received considerable attention, as they are often found in mass rearings of beneficial arthropods. They affect the efficacy of these predators as biological control agent of insect and mite pests. Microsporidia do not seem to have potential for biological control of mites.     

中国云南洱海周边大足鼠的体表寄生螨

用U检验和相关分析的统计方法对2003～2004年云南洱海(中国滇西北著名的淡水湖泊)周边251只大足鼠体表寄生螨进行了调查.调查点是我国11大鼠疫自然疫源地之一,也是我国恙虫病和出血热的流行地区.大足鼠已经被鉴定为鼠疫、汉坦病毒、恙虫病和流行性出血热的储存宿主.我们的研究发现大足鼠携带好几种与人兽共患病有关的螨类.为了丰富大足鼠体表寄生螨的研究,在此,对大足鼠的体表寄生螨群落和体表寄生螨医学和兽医学的重要性进行了描述.有191只大足鼠寄生有体表寄生螨,侵染率为76%.采集到的体表寄生螨有35种,包括15种恙螨和20种革螨.其中6种以前已经被证明是人类疾病的主要媒介.因此大足鼠很显然成为流行性出血热和恙虫病等病原体的贮存宿主.     

Within-plant distribution of twospotted spider mites (Acari: Tetranychidae) on impatiens: development of a presence-absence sampling plan

The twospotted spider mite, Tetranychus urticae Koch, is an important pest of impatiens, a floricultural crop of increasing economic importance in the United States. The large amount of foliage on individual impatiens plants, the small size of mites, and their ability to quickly build high populations make a reliable sampling method essential when developing a pest management program. In our study, we were particularly interested in using spider mite counts as a basis for releasing biological control agents. The within-plant distribution of mites was established in greenhouse experiments and these data were used to identify the sampling unit. Leaves were divided into three zones according to location on the plant: inner, intermediate, and other. On average, 40, 33, and 27% of the leaves belonged to the inner, intermediate, and other leaf zones, respectively. However, because 60% of the mites consistently were found on the intermediate leaves, intermediate leaves were chosen as the sampling unit. These results lead to the development of a presence-absence sampling method for T. urticae by using Taylor coefficients generic for this pest. The accuracy of this method was verified against an independent data set. By determining numerical or binomial sample sizes for consistently estimating twospotted spider mite populations, growers will now be able to determine the number of predatory mites that should be released to control twospotted spider mites on impatiens.     

Antigenic characterization of Psoroptes spp. (Acari: Psoroptidae) mites from different hosts

Immunoblotting with defined antigens and antisera revealed extensive and nearly complete antigenic cross-reactivity between Psoroptes spp. mites from a bighorn sheep, a mule deer, a cow, and a rabbit. Antigenic differences were not detected between mites from the sympatric bighorn sheep and mule deer. However, minor antigenic differences between mites from the cow and rabbit suggested that these mites were distinct from each other, as well as from the mites from the bighorn sheep and mule deer. These results are consistent with earlier morphologic studies of these populations of mites and provide additional support for the hypothesis that putative populations and/or species of Psoroptes mites may not be reproductively or ecologically isolated, particularly when their hosts are sympatric.     

Of spates and species: responses by interstitial water mites to simulated spates in a subtropical Australian river

The 'hyporheic refuge hypothesis' predicts that the hyporheic zone, the saturated sediments below and alongside rivers and streams, is a refuge from the scouring effects of spates for many aquatic invertebrates including water mites. We tested this hypothesis in two lateral gravel bars and two riffles in a subtropical Australian river by collecting water mites from the hyporheic zone at two depths (10 and 50 cm) at two 'pre-flood' sampling times before experimentally diverting water through the sites for 14 h to simulate a spate. Taxon richness of mites washigh (46 taxa) and dominated by the Prostigmata, with nearly half the species being new to science. Oribatids were also common at the four sites. Samples were collected twice during each 'spate', and again soon after flow was returned to normal. The experimental spate induced changes in the strength and even direction of subsurface-surface water exchange; however, these changes seldom persisted after the experiment, nor after a subsequent natural spate. The hyporheic refuge hypothesis was not supported by our water mite data. Neither during nor shortly after the experimental spates did we find more epigean (surface-dwelling) water mites in downwelling zones where surface streamwater enters the hyporheic zone, demonstrating that these mites were not using the hyporheic zone as a refuge at these locations. There was also no evidence for a 'wash out' effect, because hyporheic mitedensities did not significantly decline late in the spate. Our data indicate that floods of the low magnitude simulated in this study apparently do not pose a lasting disturbance for hypogean water mites. The fact that the same response was found at four sites indicates that the hyporheic refuge hypothesis may not always be an appropriate explanation for rapid post-flood recolonisation. Possibly, the use of the hyporheic zone as a refuge from floods may be dictated by the strength of the disturbance and substrate composition and stability.     

Are hippoboscid flies a major mode of transmission of feather mites?

Feather mites (Astigmata) are distributed around the world, living on the feathers of birds, but their mechanisms for transmission among hosts are not fully understood. There is anecdotal evidence of feather mites attached to louseflies (Diptera: Hippoboscidae), suggesting that feather mites may use these flies as a mode of phoretic transmission among birds. Two bird-lousefly associations (alpine swift Apus melba-Crataerina melbae and feral pigeon Columba livia-Pseudolynchia canariensis) were inspected to test the hypothesis that feather mites use hippoboscid flies as major mode of transmission. Both bird species showed a high prevalence and abundance of feather mites and louseflies. However, no feather mites were found attached to the 405 louseflies inspected, although skin mites (Epidermoptidae and Cheyletiellidae) were found on louseflies collected from feral pigeons. This study suggests that feather mites do not use hippoboscid flies as a major mode of transmission among birds.     

The early‐life environment and individual plasticity in life‐history traits

We tested whether the early‐life environment can influence the extent of individual plasticity in a life‐history trait. We asked: can the early‐life environment explain why, in response to the same adult environmental cue, some individuals invest more than others in current reproduction? Moreover, can it additionally explain why investment in current reproduction trades off against survival in some individuals, but is positively correlated with survival in others? We addressed these questions using the burying beetle, which breeds on small carcasses and sometimes carries phoretic mites. These mites breed alongside the beetle, on the same resource, and are a key component of the beetle's early‐life environment. We exposed female beetles to mites twice during their lives: during their development as larvae and again as adults during their first reproductive event. We measured investment in current reproduction by quantifying average larval mass and recorded the female's life span after breeding to quantify survival. We found no effect of either developing or breeding alongside mites on female reproductive investment, nor on her life span, nor did developing alongside mites influence her size. In post hoc analyses, where we considered the effect of mite number (rather than their mere presence/absence) during the female's adult breeding event, we found that females invested more in current reproduction when exposed to greater mite densities during reproduction, but only if they had been exposed to mites during development as well. Otherwise, they invested less in larvae at greater mite densities. Furthermore, females that had developed with mites exhibited a trade‐off between investment in current reproduction and future survival, whereas these traits were positively correlated in females that had developed without mites. The early‐life environment thus generates individual variation in life‐history plasticity. We discuss whether this is because mites influence the resources available to developing young or serve as important environmental cues.     

Observations on the initiation and stimulation of oviposition of theVarroa mite

FemaleVarroa mites were collected from adult bees and were classified as swollen or not swollen. After introduction of these mites into recently sealed worker brood cells the average number of offspring of reproducing swollen mites was similar to that of naturally invaded mites, but the non-swollen mites produced a significantly lower number of offspring. This suggests that the oviposition of adult mites is stimulated by a preceding stay on adult bees. When (non-swollen) mites collected from brood cells were kept for 35 days in Eppendorf test tubes containing a larva or a pupa, their reproduction was similar to that of swollen mites.Contact of young mites, collected from brood cells, with adult bees was not essential for the initiation of oviposition. However, the number of offspring of reproducing mites, even after a third or fourth introduction into brood cells, was as a rule lower than that of mites that had been in contact with adult bees.The period of artificial introduction into sealed brood cells proved to be essential for subsequent reproduction. When introduced 48–52 h or 72–76 h after cell sealing, the mites did not produce eggs. When introduced 0–4 h after cell sealing a high percentage of the mites reproduced. Contact of the mites with a spinning larva seems necessary for initiation of oviposition.     

The use of volatile cues in recognition of kin eggs by predatory mites

1. Several animal species are known to distinguish between their own eggs and eggs of unrelated conspecifics. However, the cues involved in this discrimination are often unknown. These cues were studied using the predatory mite Gynaeseius liturivorus Ehara.
2. Adult females of these predatory mites oviposit in clusters and avoid oviposition close to eggs laid by other females, resulting in reduced cannibalism between offspring. Because predatory mites are blind, it was tested whether volatiles of eggs were used as a cue for egg recognition.
3. Adult female predatory mites were offered volatile cues of their own eggs and of unrelated conspecific eggs, and females were prevented from contacting the eggs. Predatory mites oviposited closer to their own eggs than to unrelated eggs. This preference was observed even when one own and one unrelated egg were offered as a volatile source.
4. These results suggest that adult female predatory mites can determine kinship using volatiles released from the eggs.