The effects of parasitic water mite larvae (Arrenurus spp.) on zygopteran imagoes (Odonata)

Arrenurus larvae, ectoparasitic on zygopteran imagoes, attach to the host's cuticle and tear it to obtain the host's tissue fluids. Within the host's epidermis, each larval mite produces a feeding device, the stylostome, a narrow gelatinous resilient blind sac. Heavy mite infestation brings about several wounds in close proximity, accompanied by loss of more or less extensive areas of the epidermis. Despite wound repair by congregating hemocytes, local lack of epidermis seems to enfeeble the host, presumably owing to desiccation. Heavily mite-loaded zygopterans have lost the typical agility and are easily caught. A mite-induced mortality seems to exist in zygopteran populations; the infestation contributes to reduced longevity. The study of formation and decline of the arrenurid stylostome in zygopterans renders it possible to trace cellular defence reactions under natural conditions. Most stylostomes seem to thwart the ability of the host to recognize them as foreign bodies. The host's defence appears as a two-step reaction: (1) initial hemolymph clotting and deposition of melanin associated with aggregating hemocytes at the penetration site, (2) occasional subsequent melanization and cellular encapsulation of the stylostome.     

Stylostome organization in feeding Leptotrombidium larvae (Acariformes: Trombiculidae)

The stylostome of larvae of the trombiculids Leptotrombidium scutellare (Nagayo et al.), Leptotrombidium fletcheri (Womersley et Heaslip) and Leptotrombidium deliense (Walch) was studied experimentally at different time intervals after larval attachment using the histological method. The stylostome of these species has the same organization and belongs to the epidermal combined with the mixed type, developing more in width than in length. Neither transverse nor conspicuous longitudinal layers are present within the stylostome walls, which stain predominantly in red with Azan, also showing longitudinal portions with blue staining. Larvae tend to attach closely to each other and scabs, consisting of the hyperkeratotic epidermal layers fusing with migrating inflammatory cells, develop around the attachment sites. The dermis shows inflammatory foci with dilated capillaries and inflammatory cells inserting in the connective tissue layer underneath the stylostome. The feeding cavity, which is moderately expressed, may be found either in the epidermis or in the dermis. It contains inflammatory cells and their debris in the liquefied host tissues. The stylostome length depends on the character of the attachment site (the thicker epidermis or scab the longer the stylostome), and does not directly correspond to the stages of larval feeding. Nevertheless, at the 48-h time interval, nearly all attached larvae are found to be fully fed and their midgut cells are filled with nutritional globules.     

A salivary chitinase of Varroa destructor influences host immunity and mite’s survival

Varroa destructor is an ectoparasite of honey bees and an active disease vector, which represents one of the most severe threats for the beekeeping industry. This parasitic mite feeds on the host’s body fluids through a wound in the cuticle, which allows food uptake by the mother mite and its progeny, offering a potential route of entrance for infecting microorganisms. Mite feeding is associated with saliva injection, whose role is still largely unknown. Here we try to fill this gap by identifying putative host regulation factors present in the saliva of V. destructor and performing a functional analysis for one of them, a chitinase (Vd-CHIsal) phylogenetically related to chitinases present in parasitic and predatory arthropods, which shows a specific and very high level of expression in the mite’s salivary glands. Vd-CHIsal is essential for effective mite feeding and survival, since it is apparently involved both in maintaining the feeding wound open and in preventing host infection by opportunistic pathogens. Our results show the important role in the modulation of mite-honey bee interactions exerted by a host regulation factor shared by different evolutionary lineages of parasitic arthropods. We predict that the functional characterization of Varroa sialome will provide new background knowledge on parasitism evolution in arthropods and the opportunity to develop new bioinspired strategies for mite control based on the disruption of their complex interactions with a living food source.     

External structure of cuticle injuries and larval mouth parts of the chiggers Euschoengastia rotundata and Neotrombicula vulgaris (Trombiculidae)

When E. rotundata larvae parasitize the abdominal part of the body of their host (Clethrionomys glareolus), capsules with round terminal opening are formed from which hind part of the mite's body projects forwards. Organization of the capsules shows that their walls are formed by a substance (probably by larval saliva) which differs from host's tissues. At the bottom of the capsules there are larval adhesive sites with openings in the proximal parts of stylostomes which resemble in their structure these of N. vulgaris larvae. The latter do not form capsules when feeding on their natural hosts, Microtus arvalis. Proximal part of stylostome is formed in both cases by amorphous glutinous substance bearing imprints of mite's mobile digits of chelicerae and hypostome. Mouth parts of hungry mites and satiated larvae of both species differ only in relative sizes of constituent parts. Soft apical part of hypostome turns backwards during the feeding and forms a sucker. The feeding of larvae of trombiculids in capsules, which is formally regarded as ectoparasitism, can apparently be considered as a special type of parasitism.     

The attachment and stylostome of Trombidium newelli (Acari: Trombidiidae), an ectoparasitic mite on adults of alfalfa weevil, Hypera postica (Coleoptera: Curculionidae)

Larvae of the mite Trombidium newelli Welbourn and Flessel are ectoparasitic on adult alfalfa weevil, Hypera postica (Gyllenhall), an insect pest of alfalfa. The mite larvae are found under the elytra, attached to the dorsal surface of weevils abdomen. T. newelli larvae use their chelicerae to penetrate the pliable and weakly sclerotized areas of the hosts integument, and to hold on firmly to the host. The attachment sites associated with larval mites of different degrees of engorgement were examined using both light and scanning electron microscopy. The ventral inside surface of parasitized host tergites revealed a characteristic injury as spots varying in color from white-yellow to golden-brown depending on the engorged size of the mite. In addition, spots associated with fully engorged mite larvae showed an aggressive dendritically radiating mass expanding outward from the site of cheliceral penetration. This mass, known as feeding tube or stylostome was branched, with each branch ending in a cluster of closed bulbs. Stylostomes appear to exist independently in the hosts tissue. Stylostome mass corresponded with the engorgement state of the mite, increasing as the mite larva increased in size. The possible nature and mechanism of stylostome formation is discussed.     

Anatomical Injury Induced by the Eriophyid Mite Aceria anthocoptes on the Leaves of Cirsium arvense

Anatomical injury of the leaves of the invasive species, Cirsium arvense (L.) Scop., caused by the eriophyid mite Aceria anthocoptes (Nal.), which is the only eriophyid mite that has been recorded on C. arvense worldwide, is described. The injury induced by the mite feeding on the leaves of C. arvense results in visible russeting and bronzing of the leaves. Other conspicuous deformations are folding and distortion of the leaf blade and curling of leaf edge, as well as gradual drying of leaves. The anatomical injury of the mature leaves of field-collected plants was limited to the epidermis of the lower leaf surface. However, on young leaves of experimentally infested plants, rust mite injuries extend to epidermal cells on both leaf surfaces and to those of deeper mesophyll layers. On these leaves, lesions on the lower leaf surface even affected the phloem of the vascular bundles. Leaf damage induced by A. anthocoptes is discussed with regard to the mite’s potential as a biological control agent of C. arvense.     

Morphological, anatomical and chemical characterization of white spruce ( Picea glauca ‘Conica’) differently aged needles and hypotheses on their influence on Oligonychus ununguis infestation

Our investigations suggest that the usually observed avoidance by O. ununguis of current year’s twigs of P. glauca ‘Conica’ as a place for feeding and development may be connected with their morphological and anatomical structure as well their biochemical composition. Needles of the current year’s twigs were covered with a thicker layer of wax and formed more extensive epidermis cell walls, in comparison with needles of 1-year-old twigs. Young needles also showed lower concentration of reducing sugars and soluble proteins, which might additionally reduce their nutritional suitability for mite development. Differences were also found between the 1-year-old growth and current growth in contribution of essential oils and a range of other compounds. Further analyses of the effect of these compounds on mite behavior may provide additional explanation of the feeding preferences of the mite.

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.     

Lesions associated with metazoan parasites of wild platypuses (Ornithorhynchus anatinus)

Pathological findings associated with helminth and arthropod parasites of four wild platypuses (Ornithorhynchus anatinus) are described. Fourth-stage larval rhabditoid nematodes (?Cylindrocorporidae) found partially embedded in the stratum corneum were associated with mild acanthosis, orthokeratotic hyperkeratosis and inconstant subacute dermatits. A filarioid nematode (?Lemdaninae) was found in hypodermal lymphoid tissue. A larval trichostrongyloid nematode was found in the dermis, with no evidence of host response. An undescribed species of trombiculid mite ("chigger") was found in the pelage and attached to superficial stratum corneum. Focal inclusions of eosinophilic material within stratum corneum, interpreted as mite gel saliva produced during formation of the "stylostome," were also observed. The tick Ixodes ornithorhynchi punctured the epidermis causing adnexal trauma, dermal haemorrhage and chronic active dermatitis. The digenean Mehlisia ornithorhynchi was present in the small intestine of one animal and was associated with mild catarrhal enteritis.     

Do geese fully develop brood patches? A histological analysis of lesser snow geese (<Emphasis Type="Italic">Chen caerulescens caerulescens</Emphasis>) and Ross’s geese (<Emphasis Type="Italic">C. rossii</Emphasis>)

Most birds develop brood patches before incubation; epidermis and dermis in the brood patch region thicken, and the dermal connective tissue becomes increasingly vascularized and infiltrated by leukocytes. However, current dogma states that waterfowl incubate without modifications of skin within the brood patch region. The incubation periods of lesser snow geese (Chen caerulescens caerulescens; hereafter called snow geese) and Ross’s geese (C. rossii) are 2–6 days shorter than those of other goose species; only females incubate. Thus, we hypothesized that such short incubation periods would require fully developed brood patches for sufficient heat transfer from incubating parents to eggs. We tested this hypothesis by analyzing the skin histology of abdominal regions of snow and Ross’s geese collected at Karrak Lake, Nunavut, Canada. For female snow geese, we found that epidermis and dermis had thickened and vascularization of dermis was 14 times greater, on average, than that observed in males (n=5 pairs). Our results for Ross’s geese (n=5 pairs) were more variable, wherein only one of five female Ross’s geese fully developed a brood patch. Our results are consistent with three hypotheses about brood patch development and its relationship with different energetic cost–benefit relationships, resulting from differences in embryonic development and body size.     

Mycophagous mites and their internal associated bacteria cooperate to digest chitin in soil

The greater bulk of soil nitrogen is immobilized in chitinous cell walls of fungi. Mycophagous soil mites participate in chitin decomposition and, hence, in the subsequent mobilization of nitrogen. The source of the chitinolytic enzymes was searched in this study. A multimethodical approach was designed for these studies. Histology, plating and identification of bacteria from mite homogenate and, finally, homogenate and bacterial treatment of the soil fungi were applied. Here the presence and activity of chitinolytic bacteria inside mycophagous mites are reported. These bacteria form an extraintestinal group within the mite’s body and pass their enzymes into the mite’s gut. Our results demonstrate that true mycophagous mites, defined by their ability to digest chitin (i.e. the fungal cell wall), achieve this through internal “cooperation” with chitinolytic bacteria that provide the necessary chitinolytic enzymes. The nitrogen from chitin is thus made available to other soil organisms and plants.     

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.     

An approach for studying the mediators of pathogenesis inMycobacterium tuberculosis

Mycobacterium tuberculosis is an example of an intracellular pathogen that mediates the disease state through complex interactions with the host’s immune system. Not only does this organism replicate in the hostile environment prevailing within the infected macrophage, but it has also developed intricate mechanisms to inhibit several defence mechanisms of the host’s immune system. It is postulated here that the mediators of these interactions with the host are products of differentially expressed genes in the pathogen. B and T cell responses of the host are hence to be used as tools to identify such gene products from an expression library of theMycobacterium tuberculosis genome. The various pathways of generating a productive immune response that may be targeted by the pathogen are discussed     

Why do parasitized hosts look different? Resolving the “chicken-egg” dilemma

Phenotypic differences between infected and non-infected hosts are often assumed to be the consequence of parasite infection. However, pre-existing differences in hosts’ phenotypes may promote differential susceptibility to infection. The phenotypic variability observed within the host population may therefore be a cause rather than a consequence of infection. In this study, we aimed at disentangling the causes and the consequences of parasite infection by calculating the value of a phenotypic trait (i.e., the growth rate) of the hosts both before and after infection occurred. That procedure was applied to two natural systems of host–parasite interactions. In the first system, the infection level of an ectoparasite (Tracheliastes polycolpus) decreases the growth rate of its fish host (the rostrum dace, Leuciscus leuciscus). Reciprocally, this same phenotypic trait before infection modulated the future level of host sensitivity to the direct pathogenic effect of the parasite, namely the level of fin degradation. In the second model, causes and consequences linked the growth rate of the fish host (the rainbow smelt, Osmerus mordax) and the level of endoparasite infection (Proteocephalus tetrastomus). Indeed, the host’s growth rate before infection determined the number of parasites later in life, and the parasite biovolume then decreased the host’s growth rate of heavily infected hosts. We demonstrated that reciprocal effects between host phenotypes and parasite infection can occur simultaneously in the wild, and that the observed variation in the host phenotype population was not necessarily a consequence of parasite infection. Disentangling the causality of host–parasite interactions should contribute substantially to evaluating the role of parasites in ecological and evolutionary processes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Barnacle bonding: Morphology of attachment of Xenobalanus globicipitis to its host Tursiops truncatus

Xenobalanus globicipitis, a unique type of small pseudo‐stalked barnacle occurs on the appendages of cetaceans, including the common bottlenose dolphin Tursiops truncatus. In this study, we examined attachment structures of X. globicipitis and modifications to the skin of T. truncatus in areas of attachment compared to skin nearby an attachment site. Barnacles and their six calcareous footplates were measured for their length and width. There was a positive correlation of barnacle width and length to footplate width and length. The thickness of the stratum corneum increased significantly in areas of attachment compared to skin nearby a footplate. The mitotic stratum germinativum at the base of the dermal papillae did not change significantly in areas of attachment compared to skin nearby a footplate. The stratum germinativum lining the lateral walls of the dermal papillae was significantly thicker in areas of skin nearby a footplate compared to in areas of attachment. Skin of T. truncatus nearby a footplate, displayed dermal papillae extending from the dermis and pointing roughly perpendicular to the epidermal stratum corneum. At sites of X. globicipitis attachment, the dermal papillae were forced to extend laterally, parallel to the stratum corneum, and the dermal papillae length to width ratio at an attachment site was significantly higher than on skin near an attachment site. Our results show that attachment of X. globicipitis through production of footplates organized into calcareous rings, leads to a thickened stratum corneum of the epidermis, a thinner lateral mitotic stratum germinativum and displaced structures of the upper dermis. These resulting modifications to the epidermis and dermis of the host may add to securing barnacle attachment to its host. J. Morphol., 2012. © 2012 Wiley Periodicals, Inc.     

Regional specificity of anuran larval skin during metamorphosis: dermal specificity in development and histolysis of recombined skin grafts

Summary Skins from back and tail were dissected from tadpoles of Rana japonica prior to resorption of the tail and separated into epidermis and dermis by treatment with neutral protease. Homotypically and heterotypically recombined skins were constructed from the separated epidermis and dermis and transplanted into the tail of the original tadpole. Skin grafts using dermis from tail region degenerated simultaneously with resorption of the tail. However, skin grafts containing dermis from back region survived on the posterior part of the juvenile frog beyond metamorphosis. Furthermore, all epidermis underlaid with dermis from back region formed secretory glands and became flattened epithelia characteristic of adult back skin, regardless of region from which the epidermis came. Even when epidermis isolated from tail skin was cultured inside a back skin graft, the tail epidermis survived forming an epithelial cyst and developed secretory glands. These results suggest that regional specificities of anuran larval skin, i.e., development of back skin and even histolysis of tail skin, are determined by regionally specific dermis. The results also suggest that some of epidermal cells of tail skin are able to differentiate into epithelial cells similar to back skin of the adult under the influence of back dermis.     

Monoclonal antibodies against recombinant Der f 3 reveal localization of Der f 3 in the gut and faecal pellets of <Emphasis Type="Italic">Dermatophagoides farinae</Emphasis>

Home dust mite derived materials are known to be a major source of problematic inhalant allergens. The aim of this study was to determine the localization of the group 3 allergen, Der f 3, within Dermatophagoides farinae, in order to assess the relative importance of excreted materials and nonexcreted body components as allergen sources. Recombinant Der f 3 (rDer f 3) was expressed in bacteria and purified as an immunogen for production of monoclonal antibodies (mAb) against it. Dermatophagoides farinae mites and their faecal pellets were embedded in paraffin, and serial sections were immunoprobed with mAb clone 3D3 against Der f 3. D. farinae midgut mucosa, gut contents and faecal pellets were strongly immunopositive for Der f 3. Der f 3 immunoreactive products were not detected in any other internal organs of the mite. These results suggest that Der f 3 allergen may be synthesized in and secreted from the digestive tract and excreted from the mite’s body in the faecal pellets.     

Inductive activity of the posterior tip of planula in the marine hydroid <Emphasis Type="Italic">Dynamena pumila</Emphasis>

Activity of organizer regions is required for body plan formation in the developing organism. Transplanting a fragment of such a region to a host organism leads to the formation of a secondary body axis that consists of both the donor’s and the host’s tissues (Gerhart, 2001). The subject of this study, the White Sea hydroid cnidarian Dynamena pumila L. (Thecaphora, Sertulariidae), forms morphologically advanced colonies in the course of complex metamorphosis of the planula larva. To reveal an organizer region, a series of experiments has been performed in which small fragments of donor planula tissues were transplanted to embryos at the early and late gastrula stage, as well as to planulae. Only transplantations of a posterior tip fragment of a donor planula to a host planula of the same age led, in the course of metamorphosis, to the formation of a secondary shoot, which involved up to 50% of the host’s tissues. After transplantations of tissue fragments of the anterior tip and the middle of the planula body, the formation of any ectopic structures was never observed. It was concluded that the posterior tip of the planula has organizer properties in Dynamena.     

Inferring associations among parasitic gamasid mites from census data

Within a community, the abundance of any given species depends in large part on a network of direct and indirect, positive and negative interactions with other species, including shared enemies. In communities where experimental manipulations are often impossible (e.g., parasite communities), census data can be used to evaluate the strength or frequency of positive and negative associations among species. In ectoparasite communities, competitive associations can arise because of limited space or food, but facilitative associations can also exist if one species suppresses host immune defenses. In addition, positive associations among parasites could arise merely due to shared preferences for the same host, without any interaction going on. We used census data from 28 regional surveys of gamasid mites parasitic on small mammals throughout the Palaearctic, to assess how the abundance of individual mite species is influenced by the abundance and diversity of other mite species on the same host. After controlling for several confounding variables, the abundance of individual mite species was generally positively correlated with the combined abundances of all other mite species in the community. This trend was confirmed by meta-analysis of the results obtained for separate mite species. In contrast, there were generally no consistent relationships between the abundance of individual mite species and either the species richness or taxonomic diversity of the community in which they occur. These patterns were independent of mite feeding mode. Our results indicate either that synergistic facilitative interactions among mites increase the host’s susceptibility to further attacks (e.g., via immunosuppression) and lead to different species all having increased abundance on the same host, or that certain characteristics make some host species preferred habitats for many parasite species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A method for the isolation and serial propagation of keratinocytes,endothelial cells,and fibroblasts from a single punch biopsy of human skin

Summary When multiple types of cells from normal and diseased human skin are required, techniques to isolate cells from small skin biopsies would facilitate experimental studies. The purpose of this investigation was to develop a method for the isolation and propagation of three major cell types (keratinocytes, microvascular endothelial cells, and fibroblasts) from a 4-mm punch biopsy of human skin. To isolate and propagate keratinocytes from a punch biopsy, the epidermis was separated from the dermis by treatment with dispase. Keratinocytes were dissociated from the epidermis by trypsin and plated on a collagen-coated tissue culture petri dish. A combination of two commercial media (Serum-Free Medium and Medium 154) provided optimal growth conditions. To isolate and propagate microvascular endothelial cells from the dermis, cells were released following dispase incubation and plated on a gelatin-coated tissue culture dish. Supplementation of a standard growth medium with a medium conditioned by mouse 3T3 cells was required for the establishment and growth of these cells. Epithelioid endothelial cells were separated from spindle-shaped endothelial cells and from dendritic cells by selective attachment toUlex europeus agglutinin I-coated paramagnetic beads. To establish fibroblasts, dermal explants depleted of keratinocytes and endothelial cells were attached to plastic by centrifugation, and fibroblasts were obtained by explant culture and grown in Dulbecco’s modified Eagle’s medium (DMEM) containing fetal bovine serum (FBS). Using these isolation methods and growth conditions, two confluent T-75 flasks of keratinocytes, one confluent T-25 flask of purified endothelial cells, and one confluent T-25 flask of fibroblasts could be routinely obtained from a 4-mm punch biopsy of human skin. This method should prove useful in studies of human skin where three cell types must be grown in sufficient quantities for molecular and biochemical analysis.