Intraspecific variability and sympatry in closely related chigger mite species of the genus Hirsutiella (Acari: Trombiculidae)

Intraspecific variability in three closely related chigger mite species of the genus Hirsutiella Schluger et Vysotzkaya, 1970, H. steineri (Kepka, 1966), H. llogorensis (Daniel, 1960), and H. alpina Stekolnikov, 2001 has been studied based on materials collected in Caucasus and Turkey. It is established that both H. steineri and H. llogorensis include Western Caucasian and Asian forms, the first one being larger than the second one. Western Caucasian samples of H. steineri are also split into large and small forms. The large form inhabits screes with larvae occurring mainly on snow voles, and the small form inhabits meadows and forests with larvae parasitizing snow voles as well as mice of the genus Apodemus and pine voles. Asian population of H. steineri include small low-mountain form which is hard to distinguish from H. llogorensis. In the light of the new data on variability, morphological border between these two species are specified. Correlations between some characters and altitude above sea level are shown within the Western Caucasian and Asian forms of both species, and also in H. alpina. All the three species can occur together on the same individual hosts, but they have different sets of main hosts and different distribution among biotopes in the area of sympatria. The border between H. steineri and H. llogorensis in the places of sympatria can be indistinct owing to the presence of small ecological forms of H. steineri. Our results give a basis for the construction of alternative hypotheses concerning the processes of speciation in trombiculids. Chiggers species could be formed in allopatric way, on the base of such geographical forms, as Western and Asian forms of the Caucasian Hirsutiella species, but they could also be formed in sympatric way, distributing among neighbouring biotopes (e.g., screes and meadows, or screes and forests), as large and small forms of Western Caucasian H. steineri do.     

Stylostome formation by Leptotrombidium mites (Acari: Trombiculidae).

The modes of stylostome formation by larvae (chiggers) of Leptotrombidium intermedium, L. fletcheri, L. arenicola, and L. deliense in parasitized mouse skin were studied histologically in relation to their capacity to transmit Rickettsia tsutsugamushi. Three types of stylostome formation were recognized among the different species: the epidermal stylostome formed by the larva of L. intermedium; the mesenchymal stylostome formed by the larva of L. fletcheri; and, the mixed stylostome formed by the larva of both L. arenicola and L. deliense. Dermal inflammations related to the three types of stylostomes were histologically defined. The possible importance of stylostome characteristics to the transmission of rickettsial organisms is discussed.     

Geographical variation in the species Montivagum dihumerale and speciation in chigger mites (Acari: Trombiculidae)

Intraspecific morphological variation of the chigger mite species Montivagum dihumerale (Traub et Nadchatram, 1967) is studied. Eco-geographic rules of the variation are revealed. General size of mites is found to be increased along with the rise of the high-mountain character of the landscape in the collection localities. The numbers of idiosomal setae are varied independently from the size parameters and geographically close populations are proved to be the most similar by these characters. At the same time, numbers of the setae of different types play the leading role in the discrimination of closely related Montivagum species, while the eco-geographical rules have not been found in this genus at the level of interspecific differences. As a result, the hypothesis is set up, that a significant degree of isolation of local populations separated from each other by high mountain ranges of the Central Asia is the main factor of speciation in the genus Montivagum. Regional character of this speciation mode is confirmed by the comparison with other chigger mites taxa.     

The genus Speleocola lipovsky (Acari: Trombiculidae) with descriptions of two new species from Venezuela

Speleocola Lipovsky 1952 is redescribed. New species S. clangula off Rhipidomys sp., Venezuela, and S. nolae off Peropteryx kappleri, Venezuela, are described. A key to the 5 included species is given.     

Stylostome formation in trombiculid mites (Acariformes: Trombiculidae)

Stylostomes of the trombiculid mite larvae Neotrombicula pomeranzevi (Schluger), Hirsutiella zachvatkini (Schluger), Miyatrombicula esoensis (Sasa and Ogata) and Euschoengastia rotundata (Schluger) (Acariformes: Trombiculidae), formed in the host skin during feeding of the parasites on their natural hosts (voles) were studied histologically and histochemically. A stylostome is a variously shaped tube formed of solidified mite saliva that extends from the mouthparts of the parasite through the epidermis into the dermis of the host, and allows the mite to obtain its liquid food. The first step of stylostome formation is deposition of an eosinophilic cone, to which the larva’s chelicerae are glued. Organization of the stylostome depends on the mite species, and its walls may show weakly expressed longitudinal or transverse stratification. Histochemically, the stylostome is composed of complex glycoprotein with varying tinctorial properties through the width or the length of the stylostome’s walls. Beneath the distal end of the stylostome, irrespectively of its localization either in the epidermis or in the dermis of the host, a feeding cavity is formed as a result of the action of the hydrolytic components of the mite’s saliva forced through the stylostome into the wound. An inflammatory dermal reaction of moderate intensity is evolved during larval feeding and stylostome formation. It is manifested by the infiltration of the foci with neutrophiles, lymphocytes and macrophages and by dilation of capillaries of the terminal vessel bed and filling them by erythrocytes and other blood elements. Around the stylostome, necrosis of the epidermal cells occurs, leucocytes come to the damaged area and fuse with the necrotic epidermal cells, leading to the formation of the large scabs on the surface of the host’s skin. In the case of E. rotundata, single capsules having a terminal opening and containing feeding larva are formed on the abdomen of the hosts. The walls of the capsules are composed of the mite’s saliva flowing upon the surface of the host’s skin. At the bottom of the capsule, a stylostome perforating the epidermis is also present.     

根螨属螨类进境风险分析

通过对根螨进境风险进行定性分析,初步认为花叶芋根螨(Rhizoglyphus caladii)、小根螨(R.minutus)、长毛根螨(R.setosus)和单列根螨(R.singularis)为检疫性有害生物;刺足根螨(R.echinopus)和罗宾根螨(R.robini)为限定的非检疫性有害生物。     

The ultrastructure and possible functions of nephrocytes in the trombiculid mite Hirsutiella zachvatkini (Acariformes: Trombiculidae)

The ultrastructure of nephrocytes during the post-larval development of the trombiculid mite Hirsutiella zachvatkini (Schluger) was investigated by means of transmission electron microscopy. Nephrocytes are situated either individually or in groups inside the haemocoelic space and are always ensheathed by a basal membrane. They contain numerous tubular elements, electron-dense inclusions and sometimes electron-lucent vacuoles. Invaginations of the plasma membrane, often in the form of labyrinthine channels, with coated pits of plasma membrane and characteristic slit diaphragms linking adjacent pedicels, typically occupy the peripheral parts of the cells. However, no distinct zonation of organelles in the nephrocytes of trombiculids was observed. The number of nephrocytes in the haemocoel and the intensity of development of their tubular elements and in particular of labyrinthine channels vary significantly during the ontogenesis of mites. The possible functions of nephrocytes and their structure and differentiation in comparison with other arachnids are discussed.     

Sexual selection and mating behavior in spider mites of the genus Tetranychus (Acari: Tetranychidae)

As sexual selection is a coevolutionary process between males and females, various morphological and behavioral traits have evolved in each sex. In the tetranychid mites Tetranychus urticae Koch and T. kanzawai Kishida (Acari: Tetranychidae), males can mate repeatedly, whereas females normally accept only the first copulation for fertilization. Since early times, it had been reported that males engage in precopulatory mate guarding and combat against conspecifics for females to enhance their reproductive success. On the other hand, it was believed that females do not have opportunities to choose their mates. In the last 10 or so years, however, several new findings related to mating behavior were reported. Some of the findings reinforce our established knowledge, whereas some of them explode it. Here, I review the mating behavior of T. urticae and T. kanzawai by incorporating recent findings and then propose a new direction for future research.     

Aerial dispersal of European red mites (Acari: Tetranychidae) in commercial apple orchards

Aerial dispersal of European red mite, Panonychus ulmi (Koch), in commercial apple orchards was estimated by trapping windborne mites. Studies were conducted at four orchards in eastern New York during 1989 and 1990 and at three orchards in western New York during 1989. In each orchard mites were trapped in three locations; the interior of the orchard, at the border of the orchard and in a field or woodlot beyond the orchard. Large numbers of mites were captured, even when the numbers of mites on apple foliage were well below levels where mite injury to leaves was visible (less than five per leaf). The log numbers of mites trapped were linearly related to the log density of mites on leaves and this relationship was consistent for each year and region the study was conducted. The trap captures among the three locations in and outside an orchard were highly correlated. The implications these findings may have on metapopulation dynamics and resistance to acaricide dynamics are discussed.     

A new genus and two new species of chigger mites (Acari: Trombiculidae) from the Laotian rock-rat Laonastes aenigmamus Jenkins, Kilpatrick, Robinson & Timmins (Rodentia: Diatomyidae)

A new chigger mite genus Laotrombicula n. g. and two new species, Laotrombicula khunboromi n. sp. (type-species) and L. fangumi n. sp., are described from the Laotian rock-rat Laonastes aenigmamus Jenkins, Kilpatrick, Robinson & Timmins (Rodentia: Diatomyidae). The new genus is most similar to Trombiculindus Radford, 1948 and Leptotrombidium Nagayo, Miyagawa, Mitamura & Imamura, 1916 and differs from these genera by having the scutum of subhexagonal or semicircular shape vs widely rectangular; pinnatifid dorsocentral idiosomal setae vs foliaceous in Trombiculindus and unexpanded in Leptotrombidium; and by the presence of serrated longitudinal crests in the middle part of scutum.     

Three new species of oribatid mites of the genus Pergalumna (Acari: Oribatida: Galumnidae) from India

Three new oribatid mite species of the genus Pergalumna (Galumnidae) are described from growing mosses on rocks near a water stream in India. Pergalumna paraclericata sp. n. is very similar morphologically to Carinogalumna clericata (Berlese, 1914), however, it differs from the latter by the structure of lamellar lines and number of notogastral porose areas. Pergalumna minipora sp. n. is very similar morphologically to Pergalumna bifissurata Hammer, 1972, however, it differs from the latter by the body size and the presence of prodorsal ridges and a median pore. Pergalumna paracattienica sp. n. is very similar morphologically to Pergalumna cattienica Ermilov & Anichkin, 2011, however, it differs from the latter by the number of notogastral porose areas and the body integument on the ventral plate.     

Biology, ecology, and management of the bulb mites of the genus Rhizoglyphus (Acari: Acaridae)

Bulb mites of the genus Rhizoglyphus (Claparède) (Acari: Acaridae) have been identified as pests of many crops and ornamentals in storage, in the greenhouse, and in the field. The most importanthosts are species in the family Liliaceae (e.g. Allium spp.), but bulb mites will often attack otherimportant crops such as potatoes (Solanum sp.) and carrots (Daucus carota). Despite their economicimportance and broad distribution, the systematics of the genus remains in a state of confusion and is inneed of a comprehensive revision. In addition, the field biology and ecology of these mites is not wellunderstood, and methods for sampling, monitoring, and loss assessment are limited. Management of bulbmites is complicated by their short generation time, high reproductive potential, broad food niche,interactions with other pests and pathogens, and unique adaptations for dispersal. Historically, control ofthese acarine pests has relied on the use of synthetic miticides and insecticides, but this option is nowlimited due to documented resistance and withdrawal of registration of some products. Alternativecontrol strategies, including cultural and biological control, have shown limited success, but need to befurther developed and implemented.     

On systematics of mites of the genus Syringophiloidus (Acari: Syringophilidae) from the european part of Russia

A new species Syringophiloidus delichonum sp. n. (Acari: Syringophilidae) is described from quills of Delichon urbica (Hirundinidae) and S. glandarii (Fritsch, 1958) from Garrulus glandarius (Corvidae) is redescribed. Syringophiloidus glandarii, female: body length 650-680, width 160-180. Peritremes: longitudinal branch with 11-14 chambers, lateral--with 2 chambers. All propodosomal setae slightly serrate. Length of setae: vi 33-36, ve 87-96, sci 150-180, sce 180-240, h 200-230, dl 210-230, d2 140-170, d4 25-32, d5 33-40, l1 190-210, l2 150-170, l4 250-280, l5 310-320, pg1 140-150, pg2 120-160, pg3 190-200, g1, g2 40-45, a1, a2 25-33. Male. Body length 500-520, width 150-170. Peritremes: longitudinal branch with 13-14 chambers, lateral with 4 chambers. Length of setae: vi 32-36, ve 50-56, sci 74-80, sce 120-135, h 90-100, d1 135-140, d2 13-22, d5 20-22, l1 24-45, l2 13-22, l5 180-200, pg1 90-110, pg2 70-90. S. glandarii is closely related to S. presentalis Chirov et Kravsova, 1995. It is distinguished from the latter species by following characters. In female S. glandarii, setae vi, ve are thick and serrate, ve 87-96 in length. In female S. presentalis, setae vi, ve are thin and nude, ve 40-70 in length. Syringophiloidus delichonum sp. n., female (holotype): body length 900, width 135. Peritremes: longitudinal branch with 8 chambers, lateral--with 1-2 chambers. All setae nude. Length of setae: vi 45, ve 90, sci 200, sce 200, h 225, d2 90, d4 35, d5 33, l1 140, l2 ?, 155-160 in paratypes, l4 230, l5 320, pg1 135, pg2 120, pg3 170, g1, g2 40, a1, a2 17. Male Body length 506, width 135. Peritremes: longitudinal branch with 9 chambers, lateral with 2 chambers. Length of setae; vi 33, ve 78, sci 90, sce 123, h 130, d1 135, d2 15, d5 17, l1 22, l2 15, l5 180, pg1 105, pg2 45. S. delichonum sp. n. is closely related to S. presentalis, but differs by following characters. In female S. delichonum sp. n., body length is 850-920; longitudinal branch of peritreme includes 6-8 chambers; setae ve 85-90 in length; in male, longitudinal branch of peritreme include 9 chambers. In female S. glandarii, body length 630-700; longitudinal branch of peritreme include 10-11 chambers; setae ve 40-70 in length; in male, longitudinal branch of peritreme include 11-13 chambers.