New species and sympatric relations of the chigger mite species group Talmiensis (Trombiculidae, Neotrombicula)

A revision of chigger mites species being closely related to Neotrombicula talmiensis (Schluger, 1955) has been performed. 2 new species are described: N. pontica sp. n. from Krasnodar Territory (Western Caucasus) and N. sympatrica sp. n. from Krasnodar Territory, Daghestan, Tuva, Armenia, Kirghizia and Turkey (Rize Province). N. pontica sp. n. is closely related to N. carpathica Schluger et Vysotzkaya, 1970 and differs from this species by the larger number of idiosomal setae (NDV = = 75-99 against 63-77), shorter legs (Ip = 782-847 against 844-920, TaIII = 67-74 against 70-80), lesser m-t (0.180 against 0.192), slightly lesser scutum and slightly longer setae. N. sympatrica sp. n. is closely related to N. carpathica and differs from this species by the longer scutal and idiosomal setae (PL = 67-78 against 57-69, H = 65-75 against 57-68, Dmin = 43-52 against 39-48, Dmax = 61-70 against 54-64), longer legs (Ip = 892-973 against 844-920, TaIII = = 77-86 against 70-80) and lesser m-t (0.168 against 0.192). N. carpathica is reported for the first time from Northern Caucasus (Karachai-Cherkess Republic, Kabardino-Balkaria, North Ossetia); N. talmiensis is reported for the first time from Khakasia. Data on joint occurrence of 3 species are reported. The 3 types of sympatric pairs of the species have been found in the Western Caucasus: 1) N. pontica sp. n. and N. sympatrica sp. n., 2) N. sympatrica sp. n., and N. carpathica, 3) N. pontica sp. n., and N. carpathica. Differences between species in that localities, where the joint occurrence was recorded, have been analysed. Sympatric relations between N. sympatrica sp. n. and N. carpathica are characterized by increased value of some general diagnostic characters of these species, such as the length of idiosomal setae and length of legs. Different characters play main distinguishing role in different sympatric localities. Besides that, some local features appear in certain species of sympatric pairs (narrow scutum in 3 samples of N. carpathica, numerous idiosomal setae in 1 sample of N. sympatrica), that differs the populations of the sympatric pair, and also discriminates such aberrant group from other material of the same species. Functions produced by the method of discriminant analysis are proposed for the purpose of diagnostics in talmiensis group. Tests for assumptions of discriminant analysis, such as normality and homogeneity of variances, has been performed beforehand. Verifications of the functions on test samples demonstrated the good quality of its working. Key to species using discriminant functions has been constructed.     

Variability in Leptotrombidium europaeum and two new related chigger mite species (Acari: Trombiculidae) from Caucasus

Two new chigger mite species closely related to Leptotrombidium europaeum (Daniel et Brelih, 1959) are described from small mammals collected in Caucasus and Transcaucasia. L. alanicum sp. n. differs from L. europaeum in having shorter legs (TaIII = 61-81, Ip = 734-927 versus 72-90, and 855-1017), shorter scutal and idiosomal setae (D(min) = = 30-45, D(max) = 48-67, H = 59, PL = 58 versus 40-52, 54-69, 64, 63), slightly smaller scutum (AP = 25, SD = 47, PW = 89 versus 28, 50, 91), and more numerous idiosomal setae (87 versus 81). L. montanum sp. n. differs from L. europaeum in having more numerous idiosomal setae (102 versus 81), longer scutal and idiosomal setae (AM = 61, AL = 44, H = 68, D(max) = 66 versus 56, 41, 64, 62), thicker legs (TaW = 19 versus 18), and broader scutum (PW = 95 versus 91). Exact identification of both new species is possible only using classification functions constructed by means of discriminant analysis. These three Leptotrombidium species expose sympatric distribution in Daghestan (Eastern Caucasus). L. alanicum and L. montanum also occurred together in Krasnodar Territory (Western Caucasus). Each of these species includes a number of local geographical forms precisely distinguished from each other. Morphometric differences between L. alanicum and L. montanum agree with eco-geographical rules being previously found in chigger mites from other genera. However, differences between local forms of these species show other tendencies directed controversially in part. Therefore it is probable that interspecific differences in this case correspond to the variability which took place in the process of speciation.     

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.     

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.     

A revision of chiggers in the vulgaris group (Trombiculidae: Neotrombicula)

A revision of chigger mites species, being closely related to Neotrombicula vulgaris (Schluger, 1955), is given. 2 new species are described: N. aideriensis sp. n. from Western Kopetdagh and N. macrovulgaris sp. n. from Western Caucasus. N. aideriensis sp. n. differs from all other species of the vulgaris group by presence of single barb on the lateral seta of palpal tibia in most specimens. This species differs also from N. vulgaris by lesser width of scutum, shorter setae of scutum and idiosoma and by longer legs. N. macrovulgaris sp. n. differs from all other species of the vulgaris group by longer legs, more numerous idiosomal setae and by larger scutum. N. vulgaris is recorded for the first time in Bulgaria, Turkmenistan (western Kopet-Dag) and Krasnodar Territory, N. baschkirica Kudryashova, 1998--in Chuvashia, Kirov Province, Komi Republic and Tyumen' Province, N. kharadovi Kudryashova, 1998--in Russia (Altai Territory) and in Karaganda Province (Kazakhstan). The latter species is reported from several new hosts. Variation of morphometric parameters in the vulgaris group are investigated by the methods of multivariate analysis, the pattern of correlations between them is shown. A complex of diagnostic features in the group is revised. Discriminant functions produced by the computer program DIADIS (A. L. Lobanov, ZI RAS) allows to determine confidently representatives of the vulgaris group. Ecogeographical component of intraspecific variability and character variance at the specific level is revealed in vulgaris group. N. macrovulgaris characterized by the largest scutum, numerous setae and long legs was found in the most rigorous, cold and damp climate (alpine zone of western Caucasus). On the other hand, N. kharadovi, which have the most fine scutum and shortest setae, inhabits rather dry and warm Middle Asia and neighbouring territories. The sample of N. vulgaris collected in the steppe part of Stavropol' Territory differed from the material collected in mountain forests of Western Caucasus by low values of the most part of measurements. N. kharadovi samples from plains of Middle Asia differed from samples of this species collected in western Pamirs, central Kazakhstan and Altay Territory by more fine scutum and shorter setae.     

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.     

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.     

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.     

Ultrastructure of the integument during moulting of the quiescent tritonymphal instar of trombiculid mite Hirsutiella zachvatkini (Acariformes: Trombiculidae)

The ultrastructure of the integument of the quiescent reduced tritonymph of the trombiculid mite Hirsutiella zachvatkini (Schluger) was investigated by means of transmission electron microscopy. Mites were investigated daily during the 14–16 day tritonymphal period (imagochrysalis). This period includes the deutonymphal moult (1–3 days), the quiescent tritonymph period (2–4 days), and the tritonymphal moult into the adult mite (6–10 days). A distinct recognizable feature of the tritonymphal moulting cycle is a sequence of events independent of precise time intervals. This process involves partial destruction and reorganization of the hypodermis of the previous instar, and formation of a new hypodermis of the subsequent instar from islands of rudimentary hypodermal cells. The integument of the reduced tritonymph differs greatly from that of both larva and active deutonymph and adult. It consists of a simply organized hypodermal layer of varying thickness and a thick clear poorly lamellate cuticle with curved pore canals, and lacking setae. The epicuticle is very thin and without a clear protein layer. The tritonymphal instar as such with its own cuticle situated near the hypodermis is encased within the detached covering of the previous active deutonymph, and may be considered a calyptostasic and entirely pharate instar. There is a tendency for reduced tritonymphal stage to be eliminated from ontogenesis and this stage is not homologous to the pupa of insects.     

A revision of the chigger mite genus Paratrombicula Goff & Whitaker, 1984 (Acari: Trombiculidae), with the description of two new species

The monotypic chigger mite genus Paratrombicula Goff & Whitaker, 1984 is expanded to include five species. Two new species of chiggers, parasitising iguanid lizards in Chile, Paratrombicula chilensis n. sp. and P. goffi n. sp., are described, and two species, P. neuquenensis (Goff & Gettinger, 1995) n. comb. and Paratrombicula plaumanni (Brennan & Jones, 1964) n. comb., are transferred to this genus from Parasecia Loomis, 1966 and Neotrombicula Hirst, 1925, respectively. A key to the species of Paratrombicula is presented.     

Larvae of chigger mites Neotrombicula spp. (Acari: Trombiculidae) exhibited Borrelia but no Anaplasma infections: a field study including birds from the Czech Carpathians as hosts of chiggers

Chigger mites were collected from 1,080 wild birds of 37 species at Certak (Czech Republic), in the western Carpathian Mountains, from 29 July to 24 September 2005. The prevalence of infestation with chigger larvae was 7%. A total of 325 chigger specimens from 10 bird species was identified and three chigger species were found: Neotrombicula autumnalis, N. carpathica, and N. inopinata, the latter two species being reported on new hosts. Neotrombicula carpathica is reported in the Czech Republic for the first time. A total of 509 chigger larvae found on 79 host specimens were examined by polymerase chain reaction (PCR) for the presence of Borrelia burgdorferi s.l. DNA (fragments of the rrf (5S)—rrl (23S) intergenic spacer), and Anaplasma phagocytophilum DNA (epank1 gene). A fragment of specific Borrelia DNA was amplified through PCR in one sample, and the PCR product was further analyzed by reverse line blotting assay, whereby both genospecies of B. garinii and B. valaisiana were proved. This sample pooled five chigger larvae collected from one Sylvia atricapilla on 11 August 2005. No A. phagocytophilum DNA was amplified. We conclude that larvae of the genus Neotrombicula can be infected with Borrelia genospecies originated from their present or former hosts.     

Liacarus paraborealis, a new oribatid mite species (Acariformes, Oribatida) from Khabarovsk Territory

A new species, Liacarus paraborealis sp. n., was found in Khabarovsk Territory. It is characterized by the presence of a long, covering rostrum and connivent but completely divided lamellae with parallel inner margins; by the absence of translamella and the middle tooth between the lamellae; by the presence of a long spire of the trichobothrium; and by the presence of relatively short interlamellar hairs.     

Redescription of Neotrombicula naultini (Dumbleton, 1947) and descriptions of two new species of chiggers from New Zealand (Acari: Trombiculidae)

Abstract

Neotrombicula naultini (Dumbleton, 1947) was redescribed from the type specimen and additional specimens collected off Hoplodactylus granulatus (= Dactylocnemus granulatus), Hoplodactylus maculatus, and Hoplodactylus pacificus in New Zealand. Neotrombicula sphenodonti and Microtrombicula hoplodactyla were described, as new species, from specimens collected from New Zealand reptiles.     

New species of the primitive oribatid mite families Brachychthoniidae and Phthiracaridae (Acariformes, Oribatida) from the Caucasus

Seven new species and a new subspecies of the families Brachychthoniidae Thor, 1934 and Phthiracaridae Perty, 1841 from the Caucasus are described: Liochthonius murtazalievi sp. n., Sellnickochthonius ilyinae sp. n., Atropacarus achmedovi sp. n., A. kremenitsai sp. n., A. yarovenkoi sp. n., A. chernovae sp. n., A. obesus minimus ssp. n., and Steganacarus (Tropacarus) adelaidae sp. n., and also the species Synchthonius elegans Forsslund, 1957, Atopochthonius maimaensis Grishina, 1971, and Atopochthonius artiodactylus Grandjean, 1949 from the Caucasus are figured.     

The origin of parasitism in trombiculid mites (Acariformes: Trombiculidae)]

On the basis of literary data and original investigations some phylogenetic, ecological and morphological aspects of the origin of parasitism in trombiculid mites are carefully considered for the first time. It is shown that parasitism in this group of trombidiform mites is a relatively young historical phenomenon and was formed after their ontogenesis had differentiated into active and quiescent stages. Therefore, in the life pattern of trombiculid mites the character of individual development, that defines their biotopical restriction, is much more important than the phase parasitism. Primitive organization of the digestive system and extraintestinal digestion, so characteristic of this group, are one of the main reasons of the origin of their parasitism. Under pasture conditions trombiculid mites, that initially were predators-entomophages with bite-sucking mouth parts, pass easily to parasitism on vertebrate animals and become primary lymphophages. They use the vertebrate host's organism exclusively as a source of food and by the extent of polyphagia are very close to free-living blood-sucking insects. Stylostome, that develops during feeding of trombiculid larvae and some other closely related groups of trombidiform mites, is a universal structure for achieving a large amount of food on a wide range of animals during a relatively short period of time and reflects wide host-parasite specificity of these parasitic mites. From the historical view the larvae of trombiculid mites did not pass from one group of hosts to the others, but owing to morphological preadaptation to parasitism passed in a definite historical period, not earlier than Paleogene, to parasitism on all classes of terrestrial vertebrates, especially on mammals, their primary hosts.