The colonisation of new houses by house dust mites (Acari: Pyroglyphidae)

House dust mites,Dermatophagoides species (Acari: Pyroglyphidae), produce allergens, known for the provocation of asthma and other allergic reactions. To determine the time needed for complete colonisation of a new house by house dust mites, dust samples were collected from carpets of houses varying from 2 weeks to 2 years in age. In contrast to the expectation, no relation was found between age of the houses on the one hand and average levels of mite-allergensDer pI andDer pII and mite numbers on the other. However, presence of dogs appeared to be positively related to allergen levels. Furthermore, carpets in bedrooms appeared to contain more allergens than carpets in living-rooms. Finally, the age of the mattress was not related to allergen levels of bedroom floors.     

A review of biology and allergenicity of the house-dust miteEuroglyphus maynei (Acari: Pyroglyphidae)

Euroglyphus maynei is a commonly occurring mite species in house dust throughout the world, but studies of its biology and allergenicity have been relatively scarce because it is difficult to culture, and because species of the genusDermatophagoides have attracted most attention of research workers.Euroglyphus maynei has been inereasingly recognized as an important source of mite-derived allergens to which patients with house-dust mite allergy are exposed. There is a need for knowledge of its bilogy and allergenicity, in order to be able to grow it in vitro, and to establish whether or not it produces any unique allergens which do not cross-react with those ofDermatophagoides spp. and which may be of clinical significance. This article reviews published and unpublished data on taxonomy and identification, geographical and habitat distribution, seasonal population fluctuations, life-history and the effects of temperature and humidity, culture techniques and allergenicity ofE. maynei.     

Identification of house-dust mites

The term house-dust mite usually refers to those species of the mite family Pyroglyphidae, that are known to commonly occur, although sometimes regionally, in the dust of human dwellings. These species belong to five genera:Dermatophagoides, Euroglyphus, Hirstia, andMalayoglyphus. Related species ofDermatophagoides have the most world-wide occurrence, the commonest being:D. farinae, D. microceras, andD. pteronyssinus. A correct taxonomic identification of house-dust mites is very important, not only from a biological stand point, but also regarding the consequences of their respective allergenical properties. Several immuno-chemical studies revealed differences between the products of two hard to distinguish sibling species. A preliminary practical taxonomic key for the most common and important house-dust mites is presented.     

Effect of certain socio-ecological factors on the population density of house dust mites in mattress-dust of asthmatic patients of Calcutta, India

Allergy to house dust mites, particularly tothe genus Dermatophagoides is a fairlycommon problem in Calcutta and its adjoiningareas since last two decades. Both the commonspecies of the genus Dermatophagoidesi.e. D. farinae and D.pteronyssinus are found to be abundant in thedust samples collected from beds of patientssuffering from nasobronchial allergic disordes.The presence of these mites in quite a goodnumber in the patients' beds are clinicallycorrelated with the aetiopathology of variousallergic manifestations like bronchial asthma.Dermatophagoides mites may occupydifferent niches in the homes of asthmatics andare more common in beds than elsewhere in thehouse, however, the distribution and abundanceof these mites are influenced by somesocio-ecological factors. The aim and objectiveof the present study is to assess the impact ofsome common socio-ecological managementpractices like the age of house, age ofmattress, type of mattress, frequency ofcleaning of the mattress and even the economicstatus of the patients on the growth,multiplication and finally accumulation ofthese mites in the patients' surroundings.Proper identification of offending allergensand subsequent reduction of load of these miteallergens from the patient's environment may behelpful for the prophylactic management ofthese diseases in Calcutta metropolis.     

A review of recent immunochemical studies ofBlomia tropicalis andEuroglyphus maynei allergens

Exposure to mites other thanDermatophagoides spp., particularlyBlomia tropicalis andEuroglyphus maynei, has been increasingly recognized as a cause of asthma. Positive skin tests and serum IgE antibodies toB. tropicalis have been reported in asthmatic patients from several areas of the world, including São Paulo (Brazil), Hong Kong and Tampa (Florida, USA). Analysis ofB. tropicalis extracts showed undetectable levels of the major Group I and Group IIDermatophagoides spp. allergens. Immunoabsorption experiments showed that most of the IgE antibodies toB. tropicalis ( 70%) reacted with species-specific allergens. Murine monoclonal antibodies toB. tropicalis could present antigens that were recognized by human IgG antibodies. Sensitization toE. maynei has been reported in Europe, North and South America and Australia. Analysis of four differentE. maynei extracts by ELISA and RIA showed thatE. maynei produces an allergen that is antigenically related toDermatophagoides Group I allergens. The amino acid sequence of this allergen (Eur m I) has recently been reported. Further identification and purification ofB. tropicalis andE. maynei allergens is required to develop specific assays for measuring these allergens in dust samples. This will make it possible to investigate the relationship between exposure toB. tropicalis orE. maynei and the development of sensitization and allergic disease.     

Humidity affects populations of Drosophila suzukii (Diptera: Drosophilidae) in blueberry

Temperature and humidity affect insect physiology, survival, fecundity, reproductive status and behaviour. Complementing previous work investigating the effects of temperature on adult survival and fecundity of the invasive frugivorous pest, Drosophila suzukii (Matsumura), this study was conducted to determine the effect of humidity on D. suzukii larval development, adult survival, fecundity and reproductive status using blueberry as a host substrate. The five constant humidity levels in laboratory bioassays were 20, 33, 71, 82 and 94% RH at 20.6 ± 0.2°C. As RH increased, fecundity and longevity increased. At the higher humidity levels, RH had limited impact on mean generation times (T), larval development and eclosion times. The highest net reproductive rate (R_o = 68) and highest intrinsic rate of population increase (r_m = 0.17) were both recorded at 94% RH. The reproductive status of females, as indicated by the number of mature oocytes per female, was significantly greater at 82 and 94% RH, compared to 71% RH. In addition to the laboratory procedures, we correlated field trap captures over an 81‐day summer period to relative humidity (RH) levels in close proximity to those traps. In the field, low ambient humidity levels resulted in decreased trap captures. A humidity‐dependent population model predicted lower densities of D. suzukii relative to populations at higher humidity. This study supports the hypothesis that cultural practices that minimize lower humidity levels in crops can contribute to the management of D. suzukii. Such methods may include open pruning, drip irrigation and field floor management.     

ABA-deficient (aba1) and ABA-insensitive (abi1-1, abi2-1) mutants of Arabidopsis have a wild-type stomatal response to humidity

In most plant species, a decrease in atmospheric humidity at the leaf surface triggers a decrease in stomatal conductance. While guard cells appear to respond to humidity‐induced changes in transpiration rate, as opposed to relative humidity or vapour pressure difference, the underlying cellular mechanisms for this response remain unknown. In the present set of experiments, abscisic acid (ABA)‐deficient (aba1) and ABA‐insensitive (abi1‐1 and abi2‐1) mutants of Arabidopsis thaliana were used to test the hypothesis that the humidity signal is transduced by changes in the flux or concentration of ABA delivered to the stomatal complex in the transpiration stream. In gas exchange experiments, stomatal conductance was as sensitive to changes in vapour pressure difference in aba1, abi1‐1 and abi2‐1 mutant plants as in wild‐type plants. These experiments appear to rule out an obligate role for either the concentration or flux of ABA or ABA conjugates as mediators of the guard cell response to atmospheric water potential. The results stand in contrast to the well‐established role of ABA in mediating guard cell responses to decreases in soil water potential.     

Predicting the population dynamics of the house dust mite Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) in response to a constant hygrothermal environment using a model of the mite life cycle

A generalised model of the life cycle of a house dust mite, which can be tailored to any particular species of domestic mite, is presented. The model takes into account the effects of hygrothermal conditions on each life cycle phase. It is used in a computer simulation program, called POPMITE, which, by incorporating a population age structure, is able to predict population dynamics. The POPMITE simulation is adapted to the Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) (DP) mite using published data on the egg development period, total development period, adult longevity, mortality during egg development, mortality during juvenile development, and fecundity of individual DP mites held at a range of constant hygrothermal conditions. An example is given which illustrates how the model functions under constant hygrothermal conditions. A preliminary validation of POPMITE is made by a comparison of the POPMITE predictions with published measurements of population growth of DP mites held at a range constant hygrothermal conditions for 21 days. The POPMITE simulation is used to provide predictions of population growth or decline for a wide range of constant relative humidity and temperature combinations for 30 and 60 days. The adaptation of the model to correctly take account of fluctuating hygrothermal conditions is discussed.     

Phylogenetic position of the house dust mite subfamily Guatemalichinae (Acariformes: Pyroglyphidae) based on integrated molecular and morphological analyses and different measures of support

Based on multilocus phylogenetic analyses (18S, 28S, EF1‐α, SRP54, HSP70, CO1, 10 860 nt aligned), we show that the house dust mite subfamily Guatemalichinae is nested within non‐onychalgine pyroglyphid mites and forms the sister group to the genus Sturnophagoides (bootstrap support 100, posterior probability 1.0). Because high bootstrap support values may be misleading in the presence of incongruence, we evaluate robustness of the Guatemalichinae+Sturnophagoides clade using: (1) internode certainty indices to estimate the frequency of conflicting bipartitions in maximum‐likelihood bootstrap trees, (ii) consensus networks to investigate conflict among different loci; and (iii) statistical hypothesis testing based on information theory, both multi‐scale and regular bootstrap. Results suggest that this grouping is very well supported given the data. The molecular analyses were integrated with detailed morphological study using scanning electron and light microscopy. We suggest that the subfamilial status of Guatemalichinae should be reconsidered, and this lineage should be placed within the subfamily Dermatophagoidinae. The latter subfamily is currently accepted in the literature as a monophyletic group but was here inferred as paraphyletic and was not supported by any morphological synapomorphy. The paraphyly involved the most species‐rich and medically important genus, Dermatophagoides. Our findings suggest the need for a comprehensive revision of the higher‐level relationships of pyroglyphid house dust mites using both DNA sequences and morphology coupled with a broad taxonomic sampling.     

Enzymatic analysis of Blomia tropicalis and Blomia kulagini (Acari: Echimyopodidae) allergenic extracts obtained from different phases of culture growth

The majority of important allergenic extracts from arthropods present enzymatic activity. This activity has been studied particularly in Dermatophagoides house dust mites because of its implication in the stability and immunogenicity of extracts used as tools for the diagnosis and specific treatment of allergic diseases. Extracts from cultures of Blomia tropicalis [van Bronswijk (1973a, b). Acarologia 15:477–489, 490–505] and Blomia kulagini (Zakhvatkin 1936) were used to study enzymatic profiles during three growth periods of the mite population: latency phase, maximum mite concentration during exponential growth, and drop stage. The activities of 19 enzymes were analyzed using the Api Zym system. The results show a large variety of enzymes. Some enzymatic activity was found to be (almost) exclusively attributable to mites. The activity levels of proteases, glycosidases and lipases overlapped with the growth curve. Only phosphatase activity showed no significant change during mite growth when compared with the culture medium. We suggest that the glycosidases (β-galactosidase, β-glucuronidase, β-N-acetylglucosaminidase, α-mannosidase and α-fucosidase) and proteases (leucine aminopeptidase and trypsin) may constitute suitable parameters for inclusion in the quality control process for the production of allergenic mite extracts, and may help define a new index for conducting environmental controls.     

A mite survey in the dumpsters for urban solid rubbish

Summary The presence of house dust mites and storage mites in dumpsters was investigated in 3 different areas of Venice hinterland. The aim of this study was to find a relationship between some reported respiratory symptoms among 6 workers who were responsible for moving the dumpsters to the truck and the bio-aerosol released from such operation. These symptoms were closely related to the work and after allergological evaluation we found sensitisation to house dust mites in all 6 employees. The mine exposure in the workplace was assessed by a standardized sampling and analysis of dust obtained after brushing the inside surfaces of dumpsters. In 50% of the specimens (10/20) we found mites belonging to the following families: Pyroglyphidae (Dermatophagoides spp.), Acaridae (Acarus siro) and a lower amount of Cheyletidae (Cheyletus spp.). An indirect test (guanine test) was also performed and gave positivity in 16 dust samples (80%). The insides of dumpsters showed to be an optimal environment for mites survival and reproduction because of cracks and grooves on the walls, the high humidity level and the presence of mould. These mites probably come from dwelling places and other environments (markets, slaughters-houses, farms, etc.). This suggests that mites allergens can be released during rubbish discharging from the dumpsters and represent a possible risk for the employees.     

Simple mass‐rearing technique of a predatory mite Gaeolaelaps aculeifer (Canestrini) (Acari: Laelapidae)

We developed a simple mass‐rearing technique for a soil‐dwelling predatory mite Gaeolaelaps aculeifer. The rearing container consists of two (inner and outer) plastic boxes. The inner box contains rice husks, and is placed inside the outer box which contains a small amount of water. This system is useful to keep high humidity within the inner box and to prevent mites escaping from the box. The prey mite Tyrophagus putrescentiae was also reared in a similar way using rice bran and provided to G. aculeifer once a week. Rearing condition within the inner box were maintained at 25 ± 1°C, 95 ± 5% relative humidity. In this double box system, G. aculeifer was rapidly grown and overpopulated within two weeks while another predatory mite Stratiolaelaps scimitus require four weeks rearing period. This technique help farmers improve biological control efficacy of soil pests in greenhouse as well as open field cultivation.     

Effect of temperature,humidity and photoperiod on mortality of Mononychellus tanajoa (Acari: Tetranychidae) infected by Neozygites cf. floridana (Zygomycetes: Entomophthorales)

The effect of temperature, humidity and photoperiod on the development of Neozygites cf. floridana (Weiser and Muma) in the cassava green mite, Mononychellus tanajoa (Bondar) was studied in the laboratory. Dead infected mites began to appear 2.5 days after inoculation. At 33 and 28°C peak mortalities were higher and occurred earlier (after 2.5 days), than at 23 and 18°C. Mean LT₅₀ (time for half the infected mites to die) decreased with increasing temperature as follows: 3.9, 3.0, 2.9 and 2.5 days at 18, 23, 28 and 33°C, respectively. When placed under conditions of high relative humidity for a period of 24 h, the percentage of dead infected mites from which the fungus sporulated was highest at 28°C (51.4%) and lowest at 33°C (6.5%). The development of the fungus inside the mite was not significantly affected by ambient humidity or photoperiod. No significant interactions between tested factors were found.     

AN UNUSUAL EPICUTICULAR WAX ULTRASTRUCTURE ON LEAVES OF PROSOPIS TAMARUGO (LEGUMINOSAE)

Studies of Prosopis tamarugo Phil. leaflet surfaces by scanning and transmission electron microscopy disclosed an aggregate coating of basic wax structures of various shapes along with large semi-vertical plates. The basic structures, with some degree of variation, were also present on P. velutina Woot. and on several other Prosopis species which had been previously investigated. However, the plates, about 3 μm in size, were observed only on P. tamarugo. The basic wax structures were first observed on very young leaflets, about 6 h after emergence from the apical bud. The plates appeared after 24 to 72 h. Both plates and basic structures were larger on seedlings grown in a low (20–25%) relative humidity as compared to high (70%) humidity. When grown side-by-side in the greenhouse, leaflets of P. tamarugo seedlings were more isolateral in structure than those of P. velutina, suggesting a greater xeromorphic adaptation. The unusual epicuticular configuration described could be a mechanism that enhances the foliar absorption of atmospheric moisture, or at least minimizes cuticular transpiration, thereby aiding survival of this unique tree in its native habitat of northern Chile.     

Interactions of Adult Stoneflies (Plecoptera) with Riparian Zones I. Effects of Air Temperature and Humidity on Longevity

The effects of constant air temperature and relative humidity on the longevity of three species of gripopterygid stonefly adults from New Zealand were investigated in laboratory experiments, and the results were compared to field measurements of air temperature and humidity obtained during summer. Greatest longevity for Zelandobius furcillatus, Zelandoperla decorata and Acroperla trivacuata was recorded in cool humid conditions (10°C, 100% humidity) for adults fed water and a 5% sucrose solution. Absence of feeding reduced survival by 37–73% at 17°C and 100% humidity. Survival decreased significantly with increasing constant air temperature (10, 17 and 25°C) and decreasing mean relative humidity (100, 81 and 15%). Males survived significantly longer than females in all temperature treatments for Z. furcillatus, but longevity was not influenced by gender in other species or in the humidity experiments. Interpolated LT 50 values over 96 h for female stoneflies in the temperature treatments averaged of 22–23°C. Field measurements at near-ground level and 1.5 m above the streambank during summer indicated that these air temperatures were exceeded for 25% of the time in a pasture catchment compared to <0.1% of the time in a native forest catchment. These findings implicate air temperature as a factor potentially influencing the longevity of adult stoneflies, and suggest that maintenance of appropriate microclimate conditions should be a consideration in riparian management.     

EFFECTS OF DESICCATION AND ILLUMINATION ON PHOTOSYNTHESIS AND PIGMENTATION OF AN EDAPHIC POPULATION OF TRENTEPOHLIA ODORATA (CHLOROPHYTA)1

The photosynthetic rates of Trentepohlia odorata (L.) Martius growing on wall surfaces in Singapore changed throughout the day with a maximum in midmorning and decreasing thereafter during the day. Optimum temperature for photosynthesis was 25° C. Different levels of air humidity also affected photosynthetic rates with low relative humidity reducing the rates and efficiency of photosynthesis. Our results suggested that T. odorata was able to maximize its rate of photosynthesis before photoinhibitory light levels were reached and that its growth might be dependent on high levels of atmospheric relative humidity, which may serve as a source of water supply for the alga.     

Parasitism,longevity and progeny production of six indigenous Kenyan trichogrammatid egg parasitoids (Hymenoptera: Trichogrammatidae) at different temperature and relative humidity regimes

Six native Kenyan species/strains of Trichogramma and Trichogrammatoidea, recovered from Helicoverpa armigera were evaluated at six different temperatures (10, 15, 20, 25, 30 and 35°C) and two relative humidity levels (40–50 and 70–80%) with the aim of selecting strains adapted to warmer temperature regimes. The species/strains were collected from low (<700 m), medium (between 700 and 1200 m) and high altitude (>1200 m) locations and were evaluated for parasitism, adult longevity, progeny production and progeny sex ratio at the different environmental regimes. Eggs of the factitious host, Corcyra cephalonica Stainton (Lepidoptera: Pyralidae) were used in the investigations. Temperature and humidity interactions affected parasitism and progeny production. The highest parasitism at the two humidity levels was at 25 and 30°C for all the strains evaluated. Adult longevity was also significantly affected by the interaction of temperature and relative humidity and was longer at the lower than higher relative humidity. Survival followed a type I survivorship curve at lower temperatures and a type III survivorship curve at the higher temperatures. Trichogramma sp. nr. mwanzai from low altitude, Trichogramma sp. nr. mwanzai from medium altitude and Trichogrammatoidea sp. nr. lutea also from medium altitude lived longer than other strains at all the temperatures and relative humidity levels evaluated, including the warmest regimes of 30 and 35°C. These strains appear promising as candidates for augmentative biocontrol of H. armigera in Kenya.     

Survival rates of immature Ixodes pacificus (Acari: Ixodidae) ticks estimated using field‐placed enclosures

Granulocytic anaplasmosis (GA) and Lyme borreliosis are emerging tick‐borne diseases caused by infection with Anaplasma phagocytophilum and Borrelia burgdorferi, respectively, and maintained in rodent‐Ixodes spp. tick cycles, including I. pacificus in the western U.S. Ixodes pacificus has a multiple‐year life cycle and B. burgdorferi and A. phagocytophilum are transstadially, but not transovarially, transmitted within ticks, thus ticks function importantly in maintaining infection in nature. In this study, the survival of larval and nymphal I. pacificus was determined using ticks placed in tubes in leaf litter from June 2005 to September 2006 at two field sites in the California northern coast range mountains and a laboratory control. In all three sites, nymphal and larval survival ranged from 90–400 d, with differences in mean survival among sites. Fewer ticks died in the autumn in the moister field sites compared with the drier incubator control treatment. The first large die‐off event in late autumn occurred at all sites shortly before relative humidity increased from 80–100% and temperature declined from approximately 22–15° C. The concurrent die‐off in the incubator population, subject to relative humidity and temperature regimes that were invariant, suggests that survival time was dependent on other factors in addition to environmental conditions. These results suggested that many ticks exhausted resources or tolerance for relatively low humidity within six months of questing, and that higher humidity prolonged survival. Based on observed longevity, humans and other animals could acquire A. phagocytophilum infection from adult I. pacificus that were infected up to three years earlier.     

The effect of relative humidity on osmoregulation in the squirrel monkey (Saimiri sciureus)

Osmoregulatory balance was studied in four young, tamed squirrel monkeys (Saimiri sciureus, Columbia) after acclimatization to relative humidities (rh) commonly used in laboratories (30% and 50%) and to higher humidities representative of the dry and wet seasons in their natural environment (75% and 95%). The temperature was constant at 25°C and the light-dark cycle was 12:12 hours. The animals were maintained in large metabolism cages and were free moving. Water consumption and urine flow rates increased at each higher humidity from 30% rh to 75% rh and then decreased at 95% rh (p<0.05). Fecal water loss was greater with higher humidity (p<0.05). Evaporative water loss remained relatively constant until a break between 75% and 95% rh, at which point it decreased dramatically (p<0.05). Expressed relative to total water intake, evaporative water loss demonstrated a progressive decrease with increasing humidity: 65%, 56%, 51%, and 42%, at 30%, 50%, 75%, and 95% rh. This indicates that as the humidity approaches maximum saturation, not only is the evaporative water loss component necessarily diminished, but also the apparent precipitation of alternate strategies of thermoregulation leads to a reduction in the overall water requirements of the animals. Potassium/sodium excretion ratios were relatively constant at 30%, 50%, and 95% rh but decreased significantly at 75% rh (p<0.05). As a reflection of adrenocorticosteroid activity, this suggests that at 25°C, 75% rh is an optimal humidity in the maintenance of squirrel monkeys. The significant osmoregulatory alteration occurring between 75% and 95% rh provides further evidence that relative humidity may be an important factor in the seasonal physiological cycles of the squirrel monkey. In conducting the research described in this report the investigators adhered to the “Guide for Laboratory Animal Facilities and Care,” as promulgated by the Committee on the Guide for Laboratory Animal National Academy of Sciences, National Research Council.