Environmental parameters determining water mite assemblages in Costa Rica

This paper presents an ecological analysis of the water mite fauna of 350 streams, rivers, springs and standing waters from all main regions, ecosystems and elevations in Costa Rica. From 509 sample sites about 20,000 water mites representing 74 genera in 21 families were collected. 17 habitat types were distinguished and 11 further environmental parameters were measured. The significance of the particular parameters was analysed using canonical correspondence analysis (CCA). Habitat type, elevation, temperature and velocity were identified as major factors determining water mite assemblages. The analyses showed the existence of characteristic water mite coenoses in different neotropical habitats and the suitability of neotropical water mites for biomonitoring programmes.     

Distribution patterns and environmental correlates of water mites (Hydrachnidia, Acari) in peatland microhabitats

In Europe peatlands are wetlands of postglacial origin. Because of climatic changes and agricultural activities (i.e. drainage and peat extraction), they are one of the most endangered ecosystems worldwide. Water mites are well known as indicators of changing environments in other ecosystems such as springs and lakes. For our study we selected seven peatlands located in North-Western Poland and focused on water mite distribution and associated habitat and water quality variables. We described water mite fauna in various microhabitats (aquatic and semiaquatic) along the mineral-richness gradient to test whether this gradient is reflected in the composition of water mite assemblages. We selected conductivity, pH and vegetation as variables reflecting the poor-rich gradient. Additionally, we measured water depth, temperature and dissolved oxygen, which are often important parameters for water mites. We also noted presence of prey and host taxa of particular water mite species. Based on physicochemical parameters we identified three types of habitats harbouring three distinctive species groups of water mites. We were able to distinguish species that appear to be typical of spring fens (e.g. Hygrobates norvegicus, Lebertia separata), connected with acidic, nutrient poor pools (e.g. Arrenurus neumani, A. pustulator) and species seemingly typical of temporary habitats dominated by Sphagnum mosses (e.g. Piersigia intermedia, Zschokkea oblonga, A. stecki). The poor-rich gradient is strongly reflected in the composition of water mite assemblages. We also found strong correlations between the water mite fauna and both conductivity and pH gradient. Our results show that water conductivity is the most important of the examined factors, driving mite-species distribution in peatlands.     

Parasite-host associations and life cycles of spring-living water mites (Hydrachnidia, Acari) from Luxembourg

Larval water mites are parasites of various insect species. The main aim of the present study was to analyse the host range of spring dwelling water mites. The investigation focuses on seven spring sites in Luxembourg. Some 24 water mite species were recorded either from the benthos or as parasites attached to flying insects captured in emergence traps. For 20 mite species 35 host species from four Nematocera (Diptera) families were recorded. About 80% of the host species and over 90% of the host individuals were Chironomidae, the others were Limoniidae, Dixidae and Simuliidae. For all water mite species recorded we present the observed host spectrum and/or potential hosts as well as the intensity of parasitism and the phenology of the mites. For 10 mite species the hosts were previously unknown. For another ten species the known host spectrum can be confirmed and extended. The host spectrum ranged from one host species (e.g. for Sperchon insignis) to at least 10 host species (for Sperchon thienemanni, Ljania bipapillata), but the effective host range could not be definitively estimated due to the lack of corresponding data. The hypothesised host preference of the water mites, of which most are strictly confined to spring habitats, for similarly spring-preferring hosts could not be proven. The mean intensity of parasitism was highest for Thyas palustris (10.8 larvae/host) and lowest for Sperchon insignis and Hygrobates norvegicus (1.2 larvae per host for each). The hydryphantid mite Thyas palustris occurred at maximal intensity (41 larvae per host) and the two abdominal parasites Ljania bipapillata and Arrenurus fontinalis showed higher mean intensities than the thoracic parasites did. Larval water mites parasitising chironomids did not exhibit a preference for host sex. The phenology of the larval mite species was varied, some species were only present in samples early in the year and others exclusively in the summer. Another species showed two peaks of occurrence, springtime/early summer and late summer/autumn. In conclusion, the water mite larvae in the studied springs showed differences in host spectra and phenology but there are no clear evidences in both for host partitioning. Maybe, the relative low species diversity of water mites in individual springs and the low inter-specific competition for suitable hosts in combination with the high host abundances and species richness makes springs such favourable habitats for the mites.     

Synanthropic Mites of Kolkata, India: An Ecological Appraisal

Ecological observations were made on house dust mites of Kolkata as they form a major part of synanthropic mite community. Dust samples were collected with regard to the abundance of mite in relation to certain socio-ecological parameters like, habitat preference, location of house, construction pattern of house, types of mattresses used and the frequency of cleaning of mattresses. Among two different habitats examined, bed dust contained significantly higher mite population (p < 0.01) than the corresponding bedroom floor dust. The density of total mites and glycyphagids are significantly higher in rural houses in comparison to those of urban houses. In contrast, rural houses contained least number of pyroglyphids/g of dust. The density of total mites as well as pyroglyphid mites/g of dust are higher in mud house in comparison to concrete house. The density of total mites, pyroglyphids and glycyphagids are higher in cotton mattress in comparison to that of foam mattress. The frequency of cleaning has a significant effect on reducing mite densities i.e., the more the frequency of cleaning the lesser are the mite densities.     

Do small animals have a biogeography?

It has been stated that small organisms do not have barriers for distribution and will not show biogeographic discreteness. General models for size-mediated biogeographies establish a transition region between ubiquitous dispersal and restricted biogeography at about 1–10 mm. We tested patterns of distribution versus size with water mites, a group of freshwater organisms with sizes between 300 μm and 10 mm.We compiled a list of all known water mite species for Sierra del Guadarrama (a mountain range in the centre of the Iberian Peninsula) from different authors and our own studies in the area. Recorded habitats include lotic, lentic and interstitial environments. Species body size and world distribution were drawn from our work and published specialized taxonomic literature. The null hypothesis was that distribution is size-independent. The relationship between distribution and size was approached via analysis of variance and between size and habitat via logistic regression. Contrary to expectations, there is no special relationship between water mite size and area size distribution. On the other hand, water mite size is differentially distributed among habitats, although this ecological sorting is very weak. Larger water mites are more common in lentic habitats and smaller water mites in lotic habitats. Size-dependent distribution in which small organisms tend to be cosmopolitan breaks down when the particular biology comes into play. Water mites do not fit a previously proposed size-dependent biogeographical distribution, and are in accordance with similar data published on Tardigrada, Rotifera, Gastrotricha and the like.     

Water mites as indicators of natural aquatic ecosystems of the coastal dunes of the Netherlands and northwestern France

A large number of coastal dune waters in the Netherlands and northwestern France have been investigated for the occurrence of water mites. Dune waters turned out to be very rich in water mite species. In the Dutch dunes, 110 species of water mites have been found; this is 50 % of the total number of water mite species present in the Netherlands. In the French dunes 64 species have been found. The water mites most characteristic of the coastal dunes are the temporary water species. Dune areas with a high-lying hinterland have a water mite composition much different from dune areas with a low-lying hinterland. This can be explained by the existence of a very different hydrology. During the last century human activity affected the ground water of dunes. Afforestation and extraction of ground water for drinking water purposes caused a lowering of the ground water table. As a result, many dune slacks dried out. Moreover, the infiltration of river water caused an eutrophication of the ground water. Nowadays, the dunes most rich in typical water mite species are the dunes in which neither infiltration of river water nor extraction for drinking water purposes, occur. It can be concluded that water mites are good indicators for dune areas with a natural hydrology.     

Larval parasitism of spring-dwelling alpine water mites (Hydrachnidia,Acari): a study with particular reference to chironomid hosts

During faunistic investigations on spring habitats in the alpine National Park Berchtesgaden (Bavaria, Germany), water mites were found to be the group with the highest share of species strongly adapted to springs. At four sample sites at two spring complexes, insect emergence was screened for parasitism by larval water mites. A total of at least 36 host species were recorded as being parasitized by 19 water mite species. As in many other habitats, the most important host taxon was shown to be the nematoceran family Chironomidae, both in the number of species and individuals parasitized. Likewise, the number of water mite species attached to chironomids was high. Further host species were found among the Plecoptera, Trichoptera, Coleoptera, Limoniidae and Empididae (Diptera). These taxa were only parasitized by a single water mite species in each case. For 13 mite species, new hosts were recorded for the first time. For another six species, the known host spectrum could be confirmed and/or supplemented. The parasitological data presented (e.g., prevalences, selected attachment sites on the host, larval phenology, intensity of parasitism) provide, in most cases, basic information concerning previously unknown parasite–host associations. At this time, the reason for the strong crenobiosis in water mites cannot be explained by their parasitism.     

Population growth of Varroa destructor (Acari: Varroidae) in commercial honey bee colonies treated with beta plant acids

Varroa (Varroa destuctor Anderson and Trueman) populations in honey bee (Apis mellifera L.) colonies might be kept at low levels by well-timed miticide applications. HopGuard^® (HG) that contains beta plant acids as the active ingredient was used to reduce mite populations. Schedules for applications of the miticide that could maintain low mite levels were tested in hives started from either package bees or splits of larger colonies. The schedules were developed based on defined parameters for efficacy of the miticide and predictions of varroa population growth generated from a mathematical model of honey bee colony–varroa population dynamics. Colonies started from package bees and treated with HG in the package only or with subsequent HG treatments in the summer had 1.2–2.1 mites per 100 bees in August. Untreated controls averaged significantly more mites than treated colonies (3.3 mites per 100 bees). By October, mite populations ranged from 6.3 to 15.0 mites per 100 bees with the lowest mite numbers in colonies treated with HG in August. HG applications in colonies started from splits in April reduced mite populations to 0.12 mites per 100 bees. In September, the treated colonies had significantly fewer mites than the untreated controls. Subsequent HG applications in September that lasted for 3 weeks reduced mite populations to levels in November that were significantly lower than in colonies that were untreated or had an HG treatment that lasted for 1 week. The model accurately predicted colony population growth and varroa levels until the fall when varroa populations measured in colonies established from package bees or splits were much greater than predicted. Possible explanations for the differences between actual and predicted mite populations are discussed.     

北方常见农业土地利用方式对土壤螨群落结构的影响

土壤螨群落与土壤健康状况密切相关,农业土地利用方式会影响土壤螨的生存环境,进而影响螨的群落分布。在北方传统农业区研究了小麦玉米常规轮作农田,1年温室蔬菜大棚、4年温室蔬菜大棚和4年露天菜地下土壤主要理化指标和螨群落结构。研究结果表明露天菜地和温室大棚的利用方式均会提高土壤碱解氮和有机质含量,同时温室大棚的长期利用会增加土壤有效磷含量。螨群落分析显示常规农田中甲螨亚目为优势类群;常规农田转变为温室大棚后,由于施肥造成土壤营养物质含量增加,以及人类对土壤扰动程度的提高,无气门亚目取代甲螨亚目成为温室内螨优势类群。但随着温室年限的延长,螨多样性和粉螨科丰度都要有所下降,这可能是磷累积和强扰动效应的共同后果。常规农田转变为露天菜地后,加强的人类扰动也会降低甲螨亚目丰度,但与温室螨群落相比,4个亚目分布要相对均匀。温室在3种土地利用类型中对土壤螨的负面影响最为明显,从土壤功能的自我维持和修复方面来讲是十分不利的,温室内土壤生物多样性的保护尤其值得人们关注和重视。     

小麦-玉米轮作农田土壤螨多样性空间分布格局

以农田土壤动物长期监测样地为平台, 阐明土壤动物物种和功能多样性空间分布格局, 是揭示农田土壤动物多样性维持机制、提高农田土壤质量的重要基础。本试验于2020年10月, 对河南商丘农田土壤动物大型固定样地(9 ha)的210个采样点进行土壤样品野外采集和室内分离, 将土壤螨样品鉴定到种并测量其体长体宽数据, 以说明小麦-玉米轮作农田土壤螨多样性及其体长体宽的空间分布格局。结果表明: (1)共捕获成螨个体17,256头, 其中甲螨亚目为优势类群, 其个体数占总捕获量的94.67%; MGP分析表明样地甲螨群落属于P型, 说明受人为因素影响强烈; 生态位宽度和重叠度分析表明, 进化程度越高甲螨的生态位宽度越宽, 进化程度越相近甲螨之间的竞争越激烈。(2) Moran’s I分析显示, 在20-100 m的空间尺度上, 土壤螨群落、优势种的个体数和体长体宽多为显著正相关; 在220-300 m的空间尺度上, 部分为显著负的空间自相关。半方差函数结果表明, 甲螨群落物种数、个体数和体长体宽的空间变异主要受确定性过程影响, 中气门螨群落的空间变异由确定性和随机性过程共同影响。(3)土壤螨个体数与体长体宽存在显著弱的负相关关系, 这种关系普遍存在于土壤螨各群落与优势种中。本研究建议同时开展物种多样性和以体长体宽为代表的功能多样性空间格局研究, 对揭示土壤螨群落维持机制、保护土壤螨多样性具有重要意义。     

The community characteristics of soil mites under different land uses in Changchun metropolitan area, China

Soil mites were investigated under different land uses in Changchun metropolitan area (Jilin Province, China). The soil mites were extracted using modified Tullgren funnels and were identified to the genus level. A total of 8 703 soil mites belonging to 92 genera were found. The community characteristics of soil mites were analyzed using individual density, number of taxon, diversity, abundance, and evenness as well as MGP analysis and the MI index. Litter removal considerably decreased the numbers of soil mite taxon, abundance and diversity, and tillage changed the vertical distribution of soil mite individual density in the soil profile and accelerated their move to lower soil layers. The results suggest that the land-use types significantly affect the community structures of soil mites, and litter removal and conventional cultivation are the main factors in play. The studies also suggest that the type of vegetation above ground appears to have little influence on the ecological structures of the soil mite community.     

The community characteristics of soil mites under different land uses in Changchun metropolitan area, China

Soil mites were investigated under different land uses in Changchun metropolitan area (Jilin Province, China). The soil mites were extracted using modified Tullgren funnels and were identified to the genus level. A total of 8 703 soil mites belonging to 92 genera were found. The community characteristics of soil mites were analyzed using individual density, number of taxon, diversity, abundance, and evenness as well as MGP analysis and the MI index. Litter removal considerably decreased the numbers of soil mite taxon, abundance and diversity, and tillage changed the vertical distribution of soil mite individual density in the soil profile and accelerated their move to lower soil layers. The results suggest that the land-use types significantly affect the community structures of soil mites, and litter removal and conventional cultivation are the main factors in play. The studies also suggest that the type of vegetation above ground appears to have little influence on the ecological structures of the soil mite community.     

Parasitism of the backswimmer Buenoa scimitra (Hemiptera: Notonectidae) by the water mite Hydrachna virella (Acari: Hydrachnellae)

SUMMARY. The life cycle of Hydrachna virella , a water mite parasitic on the notonectid backswimmer Buenoa scimitra , is described. The mite parasitizes immature instars 2–5 as well as adult males and females of the notonectid. Parasitized immature backswimmers spent longer periods of time between moults than unparasitized immature backswimmers. Initially attaching mites appeared to be generally distributed over the host body surface but previously attached mites that reattached after host ecdysis were found primarily on the dorsum of the thorax. The observed frequency distribution of mite larvae on the host was similar to that predicted by the negative binomial distribution.     

阜阳地区居室环境中粉螨的群落组成和多样性

目的调查安徽省阜阳地区居室环境中粉螨的群落组成和多样性。方法于2009年7月,选择100户家庭进行样本采集,每居室环境中取4个采样点,对采集到的地面灰尘、床面灰尘、家具灰尘及衣物灰尘进行粉螨的分离、鉴定、计数和数据分析。结果共检获粉螨3609只,隶属于6科15属,共19种。对4类居室灰尘中粉螨群落多样性分析表明:它们的丰富度指数为0.89~2.09,多样性指数为1.28~1.83,均匀度指数为0.65~0.71。结论粉螨群落的结构及多样性与其生境条件直接相关;阜阳地区人居环境粉螨孳生密度较高(48.5%),应加强防螨措施。     

Contrasting structures of plant–mite networks compounded by phytophagous and predatory mite species

Differences in the feeding habits between phytophagous and predatory species can determine distinct ecological interactions between mites and their host plants. Herein, plant–mite networks were constructed using available literature on plant-dwelling mites from Brazilian natural vegetation in order to contrast phytophagous and predatory mite networks. The structural patterns of plant–mite networks were described through network specialization (connectance) and modularity. A total of 187 mite species, 65 host plant species and 646 interactions were recorded in 14 plant–mite networks. Phytophagous networks included 96 mite species, 61 host plants and 277 interactions, whereas predatory networks contained 91 mite species, 54 host plants and 369 interactions. No differences in the species richness of mites and host plants were observed between phytophagous and predatory networks. However, plant–mite networks composed of phytophagous mites showed lower connectance and higher modularity when compared to the predatory mite networks. The present results corroborate the hypothesis that trophic networks are more specialized than commensalistic networks, given that the phytophagous species must deal with plant defenses, in contrast to predatory mites which only inhabit and forage for resources on plants.     

Dynamics of springtail and mite populations: the role of density dependence, predation, and weather

Abstract 1. Ecological theory suggests that density‐dependent regulation of organism abundance will vary from exogenous to endogenous factors depending on trophic structure. Changes in abundance of soil arthropods were investigated at three trophic levels, springtails (Collembola), predaceous mites (Acari), and macro‐arthropods (spider, adult and larval beetles, centipedes). Predictions were that springtails are predator regulated and mites are food limited according to the Hairston et al. (1960) model, which predicts alternating regulation by competition and predation from fungi to springtails to mites to macro‐arthropods. The alternate hypothesis was based on the bottom‐up model of trophic dynamics, which predicts that each trophic level is regulated by competition for resources. 2. The relative contributions to springtail and mite population dynamics of endogenous (i.e. density‐dependent population growth related to food availability) and exogenous (i.e. predation and weather) factors were tested using time‐series analysis and experimental manipulation of water conditions. Box patterns were distributed within an aspen forest habitat located in the Canadian prairies and surveyed weekly from May to September 1997–1999. Each box depressed the leaf litter, creating a microhabitat island for soil arthropods that provided counts of invertebrates located immediately beneath the boxes. 3. Strong evidence was found for endogenous control of springtail and mite numbers, indicated by a reduction in population growth related to density in the previous week. Contrary to predictions, no evidence was found for regulation of springtail numbers by mites, or for regulation of mite numbers by macro‐arthropods. Springtail population growth rate was related positively to current springtail density (8 and 23% variation explained) and related negatively to 1‐week lagged density (85 and 58%), and related negatively to temperature (5 and 5%) for time‐series data and for experimental addition of water respectively. Mite population growth rate was related positively to current mite density (54%) and temperature (4%), and negatively to 1‐week lagged mite density (20%) and precipitation (6%) for time‐series analysis. For experimental addition of water, mite growth rate was related positively to current mite density (44%) and temperature (5%), and negatively to 1‐week lagged density (11%). Results differed from the Hairston et al. (1960) model predictions but were consistent with a bottom‐up view that springtail and mite populations were regulated intrinsically by competition for food and secondarily by temperature as a function of reproduction.     

The effect of sub-floor heating on house-dust-mite populations on floors and in furniture

It is well known that dehydrating conditions for house dust mites can be created by simply raising the temperature, causing loss of body water and eventually death. Thus, it can be expected that conditions for dust mites are less favourable on floors supplied with sub-floor heating. This was examined in a study of 16 houses with sub-floor heating and 21 without. The pattern of changes in air humidity and temperature on the floors was investigated and compared to known data of the tolerance of dust mites. Also the resident mite populations were compared. Floors with sub-floor heating had, on average, fewer mites, but the difference with unheated floors was small. It was remarkable that mite numbers were also lower in upholstered furniture. Another important observation was that some houses with sub-floor heating had high mite numbers, indicating that this type of heating is compatible with a thriving mite population. Temperature and humidity conditions of heated floors may allow mites not only to survive, but also to remain active in winter. A moderate increase in temperature, a moderate decrease inf (absolute) air humidity, or a combination of both, will suffice to keep the humidity all winter below the Critical Equilibrium Humidity, the level of air humidity that is critical for mite growth and reproduction, hence for allergen production. However, it is argued that measures to suppress allergen production by house dust mites are likely to be far more effective if taken in summer rather than in winter. This revised version was published online in July 2006 with corrections to the Cover Date.     

Complete sequence analysis of 18S rDNA based on genomic DNA extraction from individual Demodex mites (Acari: Demodicidae)

The study for the first time attempted to accomplish 18S ribosomal DNA (rDNA) complete sequence amplification and analysis for three Demodex species (Demodex folliculorum, Demodex brevis and Demodex canis) based on gDNA extraction from individual mites. The mites were treated by DNA Release Additive and Hot Start II DNA Polymerase so as to promote mite disruption and increase PCR specificity. Determination of D. folliculorum gDNA showed that the gDNA yield reached the highest at 1 mite, tending to descend with the increase of mite number. The individual mite gDNA was successfully used for 18S rDNA fragment (about 900 bp) amplification examination. The alignments of 18S rDNA complete sequences of individual mite samples and those of pooled mite samples ( ≥ 1000mites/sample) showed over 97% identities for each species, indicating that the gDNA extracted from a single individual mite was as satisfactory as that from pooled mites for PCR amplification. Further pairwise sequence analyses showed that average divergence, genetic distance, transition/transversion or phylogenetic tree could not effectively identify the three Demodex species, largely due to the differentiation in the D. canis isolates. It can be concluded that the individual Demodex mite gDNA can satisfy the molecular study of Demodex. 18S rDNA complete sequence is suitable for interfamily identification in Cheyletoidea, but whether it is suitable for intrafamily identification cannot be confirmed until the ascertainment of the types of Demodex mites parasitizing in dogs.     

Biological control of the two-spotted spider mite Tetranychus urticae on strawberries by the predatory phytoseiid mite Typhlodromus pyri (Acari, Tetranychidae, Phytoseiidae)

The ‘Mikulov’ strain of the predatory mite Typhlodromus pyri Scheuten from south Moravian vineyards was released on cultivated strawberries infested with the two-spotted spider mite, Tetranychus urticae Koch. The strawberries were grown in field plantations and under glass. Typhlodromus pyri on vine shoots were successfully introduced into the field strawberry plantation but they produced no demonstrable control of the spider mites and they eventually declined in density with their prey. In contrast, T. pyri gave good control of spider mites in the glasshouse despite the occurrence of low humidity and water stress of the plants.     

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.