Integrative Taxonomy of Dermacentor variabilis (Ixodida: Ixodidae) with Description of a New Species, Dermacentor similis n. sp

Dermacentor variabilis is the most widely distributed three-host tick in North America, and transmits a variety of pathogens. Within the United States, this species has a discontinuous distribution, widespread east of the Rocky Mountains and with a few populations west of the Rockies. Phylogenetic evidence based on individual markers or relatively small data sets has suggested that populations at both sides of this geographic barrier may correspond to two different species. In this study, we further explore this hypothesis using an integrative taxonomy framework. Both molecular (mitochondrial and nuclear markers) and morphological analyses of specimens collected from central-eastern and western states were performed to explore species delimitation in this taxon. Results from these analyses were consistent, and provide strong evidence that D. variabilis actually corresponds to two species. Herein, the western populations are described as a new species, Dermacentor similis n. sp. The usefulness of integrative taxonomy in the context of species delimitation is also discussed.

Morphological and molecular identification of medically important questing Dermacentor species collected from some recreational areas of Peninsular Malaysia

Questing is a situation when a tick is seeking to get closer or ambush its potential host. However, information on questing tick species in Malaysia is still lacking, thus the association with tick-borne diseases (TBD) is not completely understood. The aim of this study was to investigate the tick species from five most frequently visited recreational areas in Pahang and Terengganu states, which were recorded to have high potential of TBD cases. By implementing handpick method, a total of 18 males and 15 females belonging to five Dermacentor Koch, 1844 species, were collected, namely D. compactus Neumann 1901, D. tricuspis (Schulze, 1933), D. auratus Supino 1897, D. steini (Schulze, 1933), and D. falsosteini Apanaskevich, Apanaskevich & Nooma respectively. The specimens were collected and identified based on morphological characters prior to obtaining the molecular data of COI and 16S rDNA. The D. compactus was the most abundant species collected in this study, while D. falsosteini was the least. All species were distinctly separated on the Neighbor Joining and Maximum Parsimony tree topologies and supported with high bootstrap values. Furthermore, a low intraspecific variation (0.00 - 0.01) was observed amongst the individuals of the same species in both genes. Meanwhile, each Dermacentor species was genetically different, with interspecific values ranging from 0.13-0.19 and 0.11-0.20 for COI and 16S rDNA. These findings had successfully recorded the tick species that were potentially associated with TBD, and which might be circulated among humans and animals. This study also has some implications on the diversity and geographical extension of Dermacentor ticks, thus should warrant further investigation as a potential vector of tick-borne diseases and public health importance.

Morphometric Analysis of Adult Dermacentor parumapertus Neumann (Acari: Ixodidae) From Various Locations Within its Geographical Range

Dermacentor parumapertus Neumann (Acari: Ixodidae), a tick primarily associated with rabbits which occurs over much of the western United States, has a fairly large north-to-south distribution, being found from central Idaho southward into northern Mexico. This mostly obscure tick species has recently been the focus of attention due to the discovery of a unique strain of Rickettsia parkeri associated with it which appears closely related to a Rickettsia sp. found in the Atlantic rainforest of Brazil. Historically, a morphological variety of this species was reported in the literature based on significant variation in ornamentation of the tick throughout its range. This study examines several key morphological characters to determine if there are indeed more than one distinct population of this species throughout its range.

Description of a New Dermacentor (Acari: Ixodidae) Species from Thailand and Vietnam

A new tick species belonging to the genus Dermacentor Koch, 1844, namely, Dermacentor filippovae n. sp., is described. All stages of this species are similar to those of D. auratus Supino, 1897, D. compactus Neumann, 1901, and D. limbooliati Apanaskevich and Apanaskevich, 2015 with which it was previously confused. Males of D. filippovae may be distinguished from those of D. auratus, D. compactus, and D. limbooliati by the following suite of characters: conscutum broadly oval with convex lateral sides, widest posteriorly; trapezium-like shape of pseudoscutum; central brown patch on conscutum indistinct; coxa I with internal spur narrowly triangular with tapering apex and external spur fairly long, narrowly triangular with tapering apex; numerous internal spurs on coxa IV; and trochanter I with moderate, broadly triangular spur with tapering apex. Females of D. filippovae may be distinguished from those of D. auratus, D. compactus, and D. limbooliati by the following suite of characters: central patch of scutum narrow, distinct line interrupted around midlength; more rounded shape of scutum; long and distinct alloscutal setae; moderately broad U-shaped genital aperture with preatrial fold bulging anteriorly and thereafter sharply sloping to flat surface posteriorly; coxa I with internal spur narrowly triangular with tapering apex and external spur fairly long, narrowly triangular with tapering apex; and trochanter I with moderate, broadly triangular spur with tapering apex. Dermacentor filippovae is known from Thailand and Vietnam where the adults were collected from wild boar, Sus scrofa L., and vegetation.

Reinstatement of Dermacentor bellulus (Acari: Ixodidae) as a Valid Species Previously Confused with D. taiwanensis and Comparison of All Parasitic Stages

Re-examination of Dermacentor taiwanensis Sugimoto, 1935 specimens in the United States National Tick Collection revealed that two morphologically distinct Dermacentor species were identified under this name. One of them corresponds to Sugimoto's description of D. taiwanensis, while another species is identical to Schulze's Dermacentor bellulus (Schulze, 1935). The latter species has not been considered valid by recent workers. D. bellulus is reinstated here as a valid species and all its stages are redescribed. The adults of D. taiwanensis are also redescribed, and its immature stages are described for the first time. Males and females of D. bellulus can be distinguished from those of D. taiwanensis by the shape of the conscutum and scutum, color pattern, genital structures, size of the palpi and cornua, and the spurs of coxa I. Nymphs of D. bellulus can be distinguished from those of D. taiwanensis by the shape of the scutum, basis capituli, and the hypostomal dentition. Larvae of D. bellulus can be differentiated from those of D. taiwanensis by the shape of the basis capituli, and the degree of development of the auriculae and spur on palpal segment III ventrally. D. bellulus has been recorded from China, Japan, Nepal, Taiwan, and Vietnam; adults have been collected from wild boars, bears, panda, dog, and human; the immature stages are known from rodents, hares, ferret-badger, and bamboo-partridge. D. taiwanensis is found in China, Taiwan, and Vietnam; adults have been collected from wild boars; the immature stages are known from rodents, hares, mustelids, and domestic dog.

Description of New Dermacentor (Acari: Ixodidae) Species from Malaysia and Vietnam

A new tick species belonging to the genus Dermacentor Koch, 1844, namely, Dermacentor limbooliati n. sp., is described. Adults of this species are similar to those of Dermacentor auratus Supino, 1897 and Dermacentor compactus Neumann, 1901, with which it was previously confused. Males of D. limbooliati may be distinguished from those of D. auratus and D. compactus by the following suite of characters: relatively broad conscutum with slightly straightened lateral sides, conscutum widest approximately at mid-length, oval shape of pseudoscutum, central brown patch in the center of pseudoscutum broad and diffused and not continuous with central patch in posteromedian area, conscutum posterior to pseudoscutum rugose, wide and blunt internal spur on coxa I, relatively long, narrow, and pointed external spur on coxa I, numerous internal spurs on coxa IV and trochanter I with moderate and broadly triangular spur with tapering apex. Females of D. limbooliati may be distinguished from those of D. auratus and D. compactus by the following suite of characters: rounded shape of scutum, central brown patch broad and diffused in the center of scutum, relatively long alloscutum setae, genital aperture moderately narrow V-shaped with preatrial fold bulging, wide and blunt internal spur on coxa I, relatively long, narrow, and pointed external spur on coxae I and trochanter I with moderate and broadly triangular spur with tapering apex. D. limbooliati is known from Malaysia and Vietnam where the adults were collected from vegetation, Sus scrofa resting beds, a human, and clothing. The immature stages remain unknown.

Description of a new Dermacentor (Acari: Ixodidae) species, a parasite of wild mammals in Central America

A new tick species belonging to the genus Dermacentor Koch, 1844, Dermacentor panamensis n. sp., is described. All stages of this species are similar to those of Dermacentor halli McIntosh, 1931, with which it was confused for a long time. Males of D. panamensis can be distinguished from those of D. halli by the following suite of characters: narrower conscutum, broader basis capituli, shorter dorsal cornua, narrower palpi, palpal segment III tapering to its apex, legs poorly ornate: ivory colored patches present only on dorsal aspects of leg segments (mostly on legs III and IV), and internal spur of coxae I narrower and more tapering. Females of D. panamensis can be distinguished from those of D. halli by the following suite of characters: narrower and less ornate scutum, broader basis capituli, shorter dorsal cornua, larger porose areas, narrower palpi, palpal segment III tapering to its apex, legs poorly ornate: ivory colored patches present only on dorsal aspects of leg segments (mostly on legs III and IV), and internal spur of coxae I narrower and more tapering. Nymphs of D. panamensis can be distinguished from those of D. halli by clear posterolateral projections of scutum and by absence of coxal "pore" on coxae I-IV, while larvae of D. panamensis can be distinguished from those ofD. halli by shorter and less sharp lateral projections of basis capituli dorsally and slightly sharp anterior angle of basis capituli. D. panamensis is known from highlands of Costa Rica, Guatemala, Honduras, Nicaragua, and Panama where the adults were collected from porcupines and unidentified sloth and mouse while nymphs and larvae were found on various rodents and a bat.

First description of the nymph and larva of Dermacentor raskemensis (Acari: Ixodidae), parasites of pikas and other small mammals in Central Asia

Dermacentor raskemensis Pomerantzev, 1946 is one of the rare Asian species in this genus. The immature stages of this species have never been described. Reexamination of D. raskemensis holdings stored in the United States National Tick Collection revealed a collection lot containing reared nymphs and larvae of this species. This collection made it possible for us to find numerous nymphs and larvae of D. raskemensis among previously unidentified material collected in the field. Both immature stages of D. raskemensis are described here for the first time. Nymphs of D. raskemensis can be distinguished from those of other Dermacentor species in the region by small spiracular plate, relatively short and obtuse lateral projections of basis capituli dorsally, relatively short spurs on coxa I and the internal spur is characteristically very broadly rounded at its apex, and very small spur on coxa IV, whereas larvae of D. raskemensis can be distinguished from other Dermacentor by relatively short and obtuse lateral projections of basis capituli, approximately 6 denticles in the median files on hypostome, and relatively short, broad, and rounded spur on coxa I. The nymphs and larvae of D. raskemensis studied originate from Afghanistan, India, Iran, and Pakistan, where they were collected from pikas and other small mammals.

Reinstatement of Dermacentor kamshadalus Neumann (Acari: Ixodidae) as a valid species parasitizing mountain goats and sheep in the United States, Canada, and Russia

Reexamination of Dermacentor albipictus (Packard, 1869) holdings stored in the United States National Tick Collection revealed several collections of a morphologically distinct Dermacentor species. Comparison of these specimens with other Dermacentor taxa showed that they are identical to an old taxon originally described as Dermacentor variegatus kamshadalus Neumann, 1908. For more than a century, this taxon was known only from the male holotype specimen collected in Russia, and the name was considered a junior synonym of D. albipictus. D. kamshadalus is reinstated here to a full species rank, and its male is redescribed and its female and nymph are described for the first time. Adults of D. kamshadalus can be distinguished from those of D. albipictus by a short spur on trochanters I, shorter spurs on coxae I, shorter dorsal cornua, more numerous perforations on spiracular plates, less numerous and shorter setae on idiosoma, especially around spiracular plates, and considerably paler coloration of the conscutum and scutum. The nymph of D. kamshadalus can be differentiated from that of D. albipictus by shorter spurs on coxae I and the numerous perforations on the spiracular plates. Adults and nymphs ofD. kamshadalus are recorded from the United States, Canada, and Russia, where they have been collected from mountain goats, Oreamnos americanus (de Blainville), bighorn sheep, Ovis canadensis Shaw, and sheep, Ovis sp. of which the species was not stated.

Abnormal morphology of an adult Rocky Mountain wood tick, Dermacentor andersoni (Acari: Ixodidae)

During a collection of ticks from vegetation in March 2006, a single adult male Rocky Mountain wood tick, Dermacentor andersoni (Stiles, 1908), was collected that exhibited unique morphological anomalies, including the absence of a leg on the right side of the body. Coxa IV on the right side also was missing in this specimen. Such teratological changes have not been reported previously for D. andersoni.

[Dermacentor reticulatus (Fabricius, 1794)--distribution, biology and vector for Babesia canis in Germany]

This work deals with occurrence, distribution as well as biology and vectorial capacity of the ornate dog tick (Dermacentor (D.) reticulatus). Until 30 years ago this tick has only been described in a few natural foci in southern Germany. Its distribution has however expanded in the course of the last years. With the exception of northern Germany it is now covering large areas of Germany. This is particularly the case in the Upper Rhine Valley, Saarland and the Mark Brandenburg. However, it is endemic in many other areas of Germany as well. The transformation of agricultural land into fallow land, an increase in host reservoirs and climatic changes are discussed as main contributors to this change. Little is known about the role of this species as a vector for virus, rickettsia, bacteria and protozoa as well as its medical and veterinary importance. D. reticulatus is a vector for Babesia canis canis. It is reported here about a case of autochthonous babesiosis in a dog from Berlin/Brandenburg.

Molecular differentiation of metastriate tick immatures

Hard ticks, family Ixodidae, are divided into two groups, the Metastriata and the Prostriata, based on morphological differences. In the United States, there are four medically important genera of the Ixodidae: Ixodes, Amblyomma, Dermacentor, and Rhipicephalus. Ixodes is the only genus in and representative of the Prostriata, whereas the latter three genera are members of the Metastriata. All developmental stages of the Prostriata can be easily differentiated from the Metastriata using morphology. Similarly, the three Metastriate genera are highly identifiable as adults, yet as immatures, the discriminating characteristics can be difficult to use for differentiation, especially if the specimens are damaged or engorged with blood. All three Metastriate genera represent medically important vectors, thus accurate differentiation is necessary. To this end, we have developed a multiplexed-PCR diagnostic assay that, when combined with RFLP analysis will differentiate between the Metastriate genera--Amblyomma, Dermacentor, Rhipicephalus, and Haemaphysalis based on the length of the PCR amplicon and subsequent restriction digestion profile. The intended use for this diagnostic is to verify morphological identifications, especially of immatures, as well as to identify samples destroyed for molecular analysis, which will lead to more accurate field data as well as implication of vectors in disease transmission.

Failure of ticks to transmit Scopulariopsis brevicaulis (Deuteromycota), a common filamentous fungal commensal of ticks

The capacity of ticks to transmit a fungus was examined by analyzing tick saliva, host tissue from feeding sites, and host blood for presence of Scopulariopsis brevicaulis (Sacc.) Bainier, an internal mycosymbiont of the American dog tick, Dermacentor variabilis (Say), and lone star tick, Amnblyomma americanum (L.). Although >85% of ticks were infected with S. brevicaulis, conidia presence was low (0-5% of samples) in microscopic observations and mycological culturing of saliva expressed from larvae, nymphs, and adults. Additionally, the recovery of S. brevicaulis from blood and tissue feeding sites from a rabbit where S. brevicaulis-positive adult ticks had attached and fed was not increased compared with control tissue where no feeding occurred, indicating that transmission does not occur by the blood-feeding route. Tick mouthparts were found to contain S. brevicaulis in addition to Penicillium glabrum (Wehmer) Westling, but these agents were sparse in isolations from the feeding sites, which makes it unlikely that ticks act frequently as a mechanical fungal vector.

Host blood proteins and peptides in the midgut of the tick Dermacentor variabilis contribute to bacterial control

Antimicrobial midgut proteins and peptides that result from blood digestion in feeding American dog ticks Dermacentor variabilis (Say) were identified. Midgut extracts from these ticks showed antimicrobial activity against Micrococcus luteus, regardless of whether they were challenged with peptidoglycan, blood meal components, rabbit blood, Bacillus subtilis, Escherischia coli or Borrelia burgdorferi. However, no peptide band co-migrating with defensin was found in midgut extracts from the challenged ticks. Partial purification of the midgut extracts using C(18) Sep Paks and gel electrophoresis showed the presence of 4 distinct bands with rMW 4.1, 5.3, 5.7 and 8.0 kDa identified by tryptic digestion-mass fingerprinting as digestive fragments of rabbit alpha-, beta-, gamma-chain hemoglobin, and rabbit ubiquitin. No evidence of varisin, a defensin previously identified in the hemolymph of D. variabilis, was found in the tryptic digest, although varisin was found in a hemocyte lysate using the same methods. However, varisin transcript was detected in midgut cell lysates. Also present in all midgut samples was a cluster of 3 overlapping bands with rMW 13.0, 14.1 and 14.7 kDa which were identified by tryptic-digestion LC-MS and MALDI-TOF as rabbit alpha- and beta-chain hemoglobin (undigested) and transtherytin. Lysozyme transcript was detected in midgut cell extracts but the peptide was not. Studies done on other tick species demonstrated that hemoglobin digestion resulted in antimicrobial fragments. Antimicrobial hemoglobin fragments (including fragments larger than any reported previously) also were found in D. variabilis, as well as ubiquitin, a peptide known to occur as part of an antimicrobial complex in vertebrate leukocytes. In addition, we noted that Borrelia burgdorferi spirochetes were not lysed in the midgut lumen, which would be expected if defensin and lysozyme were active in this location. In this respect, the midgut's response to microbial challenge differs from that of the hemolymph. In summary, the midgut's antimicrobial activity appears to be primarily a byproduct of hemoglobin digestion rather than expression of immune peptides and proteins.

Characterization of genetic diversity in Dermacentor andersoni (Acari: Ixodidae) with body size and weight polymorphism

Morphological and discrete genetic differences are found between geographically isolated, allopatric, tick populations. However, we have found differences in sympatric tick populations. Notable differences were found in the body size and weight of Dermacentor andersoni collected from a single location in Montana, USA. These ticks were separated in groups consisting of big (B) and small (S) individuals. The objectives of this study were: (a) to characterize genetic diversity in B and S D. andersoni individuals, (b) to evaluate transmissibility of the character associated with body size and weight, and (c) to correlate morphological differences with biological, physiological, and behavioral characteristics. We found extensive genetic variation in 16S rDNA and ITS2 loci in B and S ticks and demonstrated genetic differentiation between B and S individuals. We further provide some support for Mendelian autosomal dominant transmission of characters associated with tick body size and weight. The results reported herein show that B ticks have a better reproductive success than S ticks and suggest partial reproductive isolation of S ticks.

[Variability of the hard dorsal idiosomal tegument pattern and other phenotypic characters as a manifestation of microevolution in Dermacentor marginatus (Acari: Ixodidae)]

The pattern of male conscutum and female scutum in Dermacentor marginatus has been examined in 6 points of the East-European and Asian parts of its range (Fig. 1). A high rate of modification variability of the pattern has been recovered in each geographical sample. It is shown that populations differ reliably from each other by the length of the dark patches on the marginal flank of the conscutum (nkappabeta, npkappabeta, 3kappabeta); some samples also differ by the number of these patches, complexes of other patches of the scutum and conscutum, and as well (visually) by the color density of light fields and contrast between them and the dark background on the conscutum and scutum (Table 1, 2). Besides, the samples differ reliably at each stage by the complexes of morphometric characters (Table 3, 4). The sample from the Peter the First Ridge is most deviate from others by the color contrast and complex of patches both in males and females. However, by the patches of marginal flank and morphometric characters of both sexes and perimaginal stages this sample differ less from others. The sample from the Stavropol plateau having most variable pattern (Fig. 3, 1-9, 4, 1-3) is characterized by the greater number of statistically reliable differences by the patches (nkappabeta, npkappabeta, 3kappabeta) and morphometric characters of all stages of the ontogenesis from all other samples. Other geographical samples have intermedial position in regard to degree of differences from each other. The samples examined are considered as morphotypes; degree of differences between morphotypes is unequal. The phenotypic differences have mosaic dispersion among ontogenetic stages and do not show a coherent direction in comparing the morphotypes. Differential characters of the morphotypes and related tick species belong to different structures or their different parameters. Possible ways of morphotype's origin and geochronological characteristics of morphotypes are discussed.

[Morphology of tick tarsus (Acari: Ixodida)--modifications connected with life cycle, behaviour, and habitat]

Ticks are ectoparasites of wide variety of vertebrates living in various types of environment all over the world. Morphological, biological, and physiological differences among tick species as well as among tick life stages are the result of tick adaptations to various life conditions. This paper presents morphological adaptations of tick tarsus to the hosts and the life conditions. The authors underline morphological differences of Haller's organ and pretarsus in four tick species: Argas reflexus (Fabricius, 1794), A. persicus (Oken, 1818), Dermacentor reticulatus (Fabricius, 1794), and Ixodes ricinus (Linnaeus, 1758).

[Determination of the physiological age of alive Ixodidae ticks]

A method has been developed for lifetime determination of the physiological age of hungry imagoes on Ixodes and Dermacentor ticks of natural populations. The procedure has been used to study an alive tick in the liquid (water, physiological saline) against the light background. In doing so, some previously described anatomic and age-specific signs of Ixodes are imaged outwards and their overall age-specific signs are employed. The author has proposed the following criteria for determination of the age of ticks: appearance: 1) the body's thickness; 2) the wrinkles and colour of the cuticle, and the combined sign; 3) transcuticular visibility of the viscera. The last sign was earlier found [8, 9], which is basic in the new method. There is a significant generic specificity of its manifestation. Tables have been constructed for determining four main physiological ages (I-IV) of ticks of both genera. The method has been applied to the study of natural populations of I. persulcatus, D. reticulatus and D. marginatus in combination with virological studies. The method developed allows one to proceed to make a mass determination of the physiological age of alive ticks and basically expands the potentialities of its application.

[Morphometric features of tarsus in Dermacentor reticulatus (Fabricius, 1794) (Acari: Ixodida: Ixodidae) larvae from Polish and Slovakian populations]

Dermacentor reticulatus is widely distributed dangerous tick that usually lives in the river valleys, boggy forests, meadows, and wooded pastures. Tick populations from various regions may exhibit morphological differences. In our study we compared morphometric features of tarsus in larvae D. reticulatus from Polish and Slovakian populations. I tarsus width, III tarsus length, and length of dorsal setae of I tarsus were significantly higher in Polish populations. Indices of width to length of tarsus I and tarsus III were also significantly different in both populations. The other examined morphologic features were similar, what may result from the same environmental conditions of both populations.

Morphology and structural organization of gené's organ in Dermacentor reticulatus (Acari: Ixodidae)

Scanning and transmission electron microscopical investigations revealed that Genés organ in unfed and ovipositing females of Dermacentor reticulatus is formed as a double-sac-structure consisting of an outer epithelial and an inner cuticular sac. In ovipositing ticks the latter emerges through the camerostomal aperture to the exterior. Genés organ in unfed ticks consists of a corpus, two posterior horns and a pair of undeveloped glands at each side, which differentiate in ovipositing ticks to compound, branched tubular glands with a main efferent duct for each gland opening into the lumen between the epithelial and the cuticular sac. Genés organ of egg-laying females corresponds basically in morphology and structural organization to that of unfed ticks. Compared with unfed ticks, however, in ovipositing ticks the corpus and horns are longer and broader, the glands are fully developed and the cuticular sac is evertable. The epithelial sac as the outermost part of Genés organ is continuous with the hypodermis of the basis capituli and the scutum, arises at the camerostomal aperture, forms the corpus and the two blind-ending horns, passes into the epithelium of the main excretory ducts of the glands and envelops the cuticular sac. The cuticular sac passes into the cuticle of the basis capituli and the scutum, arises at the camerostomal aperture, is folded, expands into the horn tips and consists inwards of a smooth epicuticula and outwards of a fibrous endocuticula. Muscles originating from the scutum pass caudomedially through the epithelial sac and are inserted into the cuticular sac. The entire surface of the maximally everted cuticular sac is covered with an amorphous mass. In cleaned samples, ledge-like structures appear on the lateral surface. These ledges turn into balloon-like structures which extend over the medial and dorsal surface. The entire surface including the balloon-like structures and the ledges are provided with numerous cribrate pits.

Modus operandi of oviposition in Dermacentor reticulatus (Acari: Ixodidae)

The process of oviposition in D. reticulatus was observed and found to be a sequence of exactly coordinated, interlocking events independent of the phase of oviposition. The average period of oviposition in the investigated ticks was 31.6 days at 20 degrees C and 95% relative humidity. The number of eggs deposited on each day increased until reaching a maximum on the fifth day of oviposition and then decreased continuously. As a result, most of the eggs were deposited during the initial phase of oviposition. The total number of eggs was proportional to the ticks' weight replenishment. Egg-laying commenced with the lowering of the capitulum and the simultaneous spread of the pedipalps which were lowered to the body wall embracing the genital aperture on both sides. Immediately afterwards the cuticular sac of Gene's organ was pushed out and retracted several times. At the cuticular sac's maximum extension, the vestibulum vaginae prolapsed, forming the ovipositor as an extended tube which handed over an egg to the two horns of the cuticular sac after a brief, but intensive, contact with the cuticular sac. Then the vestibulum vaginae invaginated, the pedipalps closed, and the cuticular sac was retracted. Finally, the egg was transported onto the dorsal area of the tick by means of a vigorous rising of the capitulum. During the course of oviposition most of the events, especially the period of egg embracement by the cuticular sac, were prolonged, as was the total time for laying one egg. Similarly, the intervals between successive egg-laying processes increased continuously. The number of eggs deposited was not dependent on the functional ability of Gene's organ, as shown by similar numbers of deposited eggs from ticks with and without mechanical blocking of the cuticular sac. But the participation of the organ in the process of oviposition proved to be a prerequisite for the viability of the eggs. Larvae developed and hatched only from those eggs which were deposited from ticks with an undisturbed Gene's organ. In comparison, eggs without contact to the cuticular sac of Gene's organ dried up and shrivelled immediately after being deposited and did not hatch. Consequently, it strongly suggests, together with the results from other studies, that Gene's organ covers the eggs with a secretion that prevents the loss of water.

Recognition of the tick genus Anocentor Schulze, 1937 (Acari: Ixodidae) by numerical taxonomy

We report on an evaluation of the systematic position of the tick Anocentor nitens (Neumann), examining particularly whether Anocentor should be regarded as a subgenus of Dermacentor or as a separate genus. Twelve species of Ixodidae were analyzed phenetically by using 24 characters of adult ticks. A phenogram indicated 3 clusters, with Anocentor more closely related to Rhipicephalus than to Dermacentor. The results of this study endorse the validity of the monotypic genus Anocentor.

[The use of the methods of geometrical morphometry in the systematics of ixodid ticks (Ixodidae)]

It is shown that morphological characters, such as a form of gnathosoma, usually considered as qualitative one, may be properly analyzed on a quantitative basis by means of the geometrical morphometric methods. In particular, an extraction of relative warps (RW) from a shape variation using TPSRW computer program makes it possible to run standard statistical procedures over matrices of RW values. This approach is demonstrated by the analysis of gnathosoma shape differences in 4 Ixodes species and 3 Dermacentor species, with a discriminant analysis being employed as a statistical routine. It is shown that differences among I. persulcatus and I. ricinus are statistically significant (by F-criterium) in all ontogenetic phases, while in the case of I. laguri and I. redikorzevi this is true only for the larval phase. Magnitudes of the gnathosoma shape variation among species (by F criterium) are similar within both Ixodes (s, str.) and Serdjukovia subgenera. The differences among subgenera of the genus Dermacentor are more significant.

Genetic evidence against a morphologically suggestive conspecificity of Dermacentor reticulatus and D. marginatus (Acari:Ixodidae)

International Journal for Parasitology 25: 1413-1419. Dermacentor reticulatus and D. marginatus exhibit overlapping phenotypes. The possibility of conspecificity was investigated on the nucleotide level by comparing DNA sequences of the second internal transcribed spacer (ITS 2) of the rDNA gene. The inter-specific polymorphism was more than 20-times greater than the intra-specific polymorphism of 3 D. reticulatus strains of different geographic origins. Furthermore, the degree of polymorphisms between D. reticulatus and D. marginatus was found to be of the same order of magnitude as that between D. andersoni and D. variabilis, for which separate species status is accepted. These genomic findings do not support a possible conspecificity of D. reticulatus and D. marginatus.

Dermacentor rhinocerinus (Denny 1843) (Acari: Ixodida: ixodidae): redescription of the male, female and nymph and first description of the larva

Presented is a diagnosis of the male, female and nymph of Dermacentor rhinocerinus, and the 1st description of the larval stage. Adult Dermacentor rhinocerinus parasitize both the black rhinoceros, Diceros bicornis, and the white rhinoceros, Ceratotherium simum. Although various other large mammals have been recorded as hosts for D. rhinocerinus, only the 2 species of rhinoceros are primary hosts for adults in various areas of east, central and southern Africa. Adults collected from vegetation in the Kruger National Park, Transvaal. South Africa were reared on rabbits at the Onderstepoort Veterinary Institute, where larvae were obtained for the 1st time.

[The correlation variability of the morphometric traits in 4 species of ixodid tick species (Ixodidae)]

Correlation analysis of 10 characters was run in three species of Dermacentor, D. nuttalli, D. ushakovae, D. niveus, and in Ixodes persulcatus, separately for each phase and sex. Correlation coefficients are very low in larvae of all species. In male nymphs correlation coefficients are on the same level in all species while the correlation coefficient level in female nymphs reflects the degree of independence of the development of characters. This defines the degree of manifestation of sexual dimorphism at the nymphal phase: the more rigid the connections between the characters the less number of characters shows sexual differences. At the phase of imago the lowest correlation coefficients are in I. persulcatus. This species displays most distinct differences in the morphology of females and males. On the basis of comparison of correlation and variability coefficients the functional role of the characters is discussed.

Ultrastructure of the midgut and blood meal digestion in the adult tick Dermacentor variabilis

Digestive cells in the midgut of male and female Dermacentor variabilis (Say) took up the blood meal in coated vesicles and smooth flask-shaped vesicles, and deposited it in endosomes which were digested via heterophagy. Iron was concentrated in residual bodies. Digestion occurred in three distinct phases in mated females: (1) continuous digestion (initiated by feeding) occurred during slow engorgement; (2) reduced digestion (initiated by mating) occurred in mated females during the period of rapid engorgement; (3) a second continuous digestion phase (initiated by detachment from the host) occurred throughout the post-feeding periods of preoviposition and oviposition. It proposed that the stem cells in the midguts of unfed females were progenitor of digestive, replacement, and presumed vitellogenic cells in midguts of mated feeding females. Digestive cells were present in all three digestion phases. Only during the first continuous digestion phase did digestive cells fill up with residual bodies, rupture and slough into the lumen, or did whole cells slough into the lumen. During the other two digestion phases no sloughing of digestive cells was observed. At the end of oviposition the digestive cells were filled with residual bodies. Replacement cells were present only during the first continuous-digestion phase. Presumed vitellogenic cells were present only during the reduced-digestion phase and during the second continuous-digestion phase. Stem cells in unfed males developed only into digestive cells in feeding males. Fed males and fed unmated females had only the first continuous-digestion phase. After being hand-detached from the host, unmated 13-day-fed females went through cellular changes associated with the reduced-digestion phase and second continuous-digestion phase of fed mated females, then began ovipositing. Maximum development of the basal labyrinth system and lateral spaces matched the known time of maximum water and ion movement across the midgut epithelia. Spectrophotometric analyses of lumen contents and midgut cells, sampled after detachment from the host, showed that concentrations of protein and hemoglobin at day 1 post-detachment decreased by one-half at the beginning of oviposition, while hematin increased about twofold by the end of oviposition. This supported the idea of the presence of a second continuous-digestion phase.

[Sexual dimorphism of the nymphal phase of ixodid tick species in the genus Dermacentor]

In four studied Dermacentor species at preimaginal phases sexual dimorphism hardly reveals itself in body size and mass of individuals. The formation of sexual distinctions at the nymphal phase concerns different characters as in different species so in populations of one species. In D. niveus male and female nymphs differ in the length of II-III palpal joints and width of gnathosoma, in D. ushakovae in the length of scutum and its proportions, in the width of gnathosoma and hypostome and in the diameter of peritreme. The sex of D. silvarum nymphs can be identified by the width of gnathosoma, length of hypostome and diameter of peritreme. Female and male nymphs of D. marginatus from the Stavropol Territory and Armenia differ in the scutum proportions and populations from the western Pamirs in the length of scutum and gnathosoma.

[Evaluation of the apron as a taxonomic trait in ixodid ticks of the genus Dermacentor Koch (Ixodoidea, Ixodidae)]

Study of the apron in 9 species of the genus Dermacentor from the fauna of the USSR has revealed differencies in its structure. The subgenus Dermacentor (s. str.) differs from two other subgenera both in the shape of the apron itself and in the shape of the postgenital sclerite and setae of perigenital area. Close species within each of two other subgenera differ in apron proportion, shape and size of denticles along its hind edge, and sometimes in their number. Inspite of the statistically reliable interspecific differences in apron structure a wide range of individual variability of some details and geographical specificity of samples from various places of the area were observed in species with a vast area.

Resistance to ixodid tick infestation induced by administration of tick-tissue culture cells

Primary tissue culture cells of developing larvae of Amblyomma americanum were administered to guinea-pigs never previously exposed to ixodid ticks. Guinea-pigs were given 1 X 10(6) primary culture cells on Days 0, 7 and 21 by subcutaneous injection and challenged with male and female A. americanum on Day 35. A significant degree of induced host tick resistance was expressed by reduced engorgement weight of females, reduced oviposition by those females which did obtain a blood meal, and by death of ticks at the attachment site. Resistance induced by A. americanum primary culture cells stimulated a significant degree of resistance to infestation with Dermacentor andersoni adults.

[Redescription of Dermacentor raskemensis Pomerantzev, 1946 (Ixodidae)--a representative of the mountain fauna of the southern regions of the USSR and adjacent territories]

A redescription of female and male of the little-known species Dermacentor raskemensis Pomerantzev has been made on the holotype (male, West China, Sinkiang) and on collection material of Zoological Institute of the Academy of Sciences of the USSR and Institute of Zoology of Armenian SSR: three females and males from Armenia and western Pakistan. Despite a considerable remoteness of their distribution areas all studied specimens show stability of their specific characters and differ distinctly from the close species D. niveus Neumann and D. everestianus Hirst. The both sexes (especially female) of D. raskemensis differ in having peculiar, most complete (in the ranges of the genus) filing of the dorsal shield area with dense light pigment and by prevalence of very small punctation and the lack of contrast between it and larger punctation. Peritreme of D. raskemensis male has a long narrow dorsal process which is at the right angel to its longitudinal axis and slightly concave along the hind edge. The dorsal process of the female is well developed and is at the right or acute angles to the longitudinal axis. In addition the both sexes have a wide smooth thickening along the anterior edge of the process, the proportions of peritreme are specific in species. In close species the dorsal process of peritreme is at the blunt angle to its longitudinal axis, in D. everestianus the thickening along the anterior edge is missing. Female of D. raskemensis lacks wing-shaped appendages of the genital opening while in D. niveus they are distinct (the structure is not mentioned in the description of D everestianus). D. raskenmensis apparently inhabits highlands and meadow-steppe, steppe and mountain sparce forest zones most part of which is covered by rocks and screes. In Armenia it was recorded from Armenian mouflon and wild goat; in other countries (Iran, Afghanistan, western Pakistan, India and China) it occurs on sheep and goats from alpine pastures. Most collections were done in autumn, winter and spring.

Resistance and cross-resistance of guinea pigs to Dermacentor andersoni Stiles, D. variabilis (Say), Amblyomma americanum (Linnaeus), and Ixodes scapularis Say

The ability of guinea pigs to acquire resistance to Dermacentor andersoni and Amblyomma americanum was determined by repeatedly infesting separate sets of guinea pigs with tick larvae. Resistance was measured in terms of reduced numbers successfully engorging and reduced weight of those ticks that engorged. An 83% reduction in numbers of larvae engorging and a 64.5% reduction in the weight of engorged larvae were seen between the first and second infestations with D. andersoni. Guinea pigs exhibited considerably less resistance to A. americanum the third time they were exposed to this species than did guinea pigs infested twice with D. andersoni. Feeding success was only 30.8% less than the initial percentage that engorged, and the percentage weight reduction was 35. During the challenge infestations, sizable fluid-filled vesicles formed on ears of the guinea pigs used as hosts for D. andersoni or A. americanum. Cross-resistance was evaluated by dividing D. andersoni-resistant animals into groups and challenging them with D. andersoni D. variabilis, A. americanum, or Ixodes scapularis. Appreciable cross-resistance was apparent between the two Dermacentor species. The weights of the A. americanum and I. scapularis were significantly reduced, but not the number that engorged. When A. americanum-resistant guinea pigs were challenged, they were cross-resistant to D. variabilis but not to D. andersoni. Skin tests on guinea pigs in which extracts of tick salivary glands were used as the antigens did not conclusively reflect the same patterns of cross-reactions noted in the tests of cross-resistance.

[Diagnosis of species of the genus Dermacentor Koch from Central Asia by the nymphal phase (Ixodoidea, Ixodidae)]

A key to nymphs to five species of Dermacentor from central Asia is given. To recognize differential characters laboratory nymph from the parents identified previously by the authors were reared. D. montanus and D. pavlovskyi are studied from one, D. reticulatus and D. niveus from two and D. marginatus from four geographical areas. The shape of scutal scapulae, structure of the anal valve, proportion and topography of peritremes, shape, size and number of scutal setae, shape of alloscutal and pleiral setae, proportions of auricles, hypostome, cheliceral bases and different parameters of palpal joints, structure and size of coxae I-IV and tarsi I, sizes of scutum and different parameters of gnathosoma are taken for specific diagnostic characters. The differential characters were checked on laboratory nymphs of D. reticulatus, D. niveus and D. marginatus and on those collected beyond the territory of Central Asia.

Ultrastructure of some cutaneous sense organs in Dermacentor marginatus nymphs

The fine structure of the integumentary glands and mechanoreceptory setae in Dermacentor marginatus nymphs is described. The integumentary gland is localized in the epidermal layer and secretory products pass through the duct lumen and two cuticular lips to the surface. Ultrastructure of cuticular cavity represents triangular form with lateral folds. The mechanoreceptor setae are composed of glandular cells localized in the epidermal layer and cuticular setae movably articulated to the cuticle by means of a compact fibrillar ring around the base.

Neurosecretory system of the American Dog Tick, Dermacentor variabilis (Acari: Ixodidae). ii. Distribution of secretory cell types, axonal pathways and putative neurohemal-neuroendocrine associations; comparative histological and anatomical implications

Histological observations using specialized techniques reveal neurosecretory cells in 18 centers throughout the rind (cortex) of the central nerve mass or synganglion of Dermacentor variabilis. Many cells contribute to complicated networks of neurosecretory pathways and tracts in pre- and post-esophageal portions of the synganglion. The four types of neurohemal-neuroendocrine associations found in Dermacentor resemble structures found in soft ticks (Argasidae) and in other Arachnida, but are more diverse than those described from any other single species. Neurosecretory terminals are distributed diffusely and in two concentrated associations within the perineurium of the synganglion and major peripheral nerves. Terminals are also distributed in the perineurial layers of lateral segmental organs which lie in the general hemocoel at the level of the pedal nerves. A retrocerebral organ complex surrounds the esophagus at its junction with the midgut. The complex includes dorsal and ventro-lateral lobes (containing neurosecretory terminals and intrinsic secretory cells1 and the proventricular (neurohemal) plexus. This plexus seems to be a modified (concentrated) cardioglial association. Cardioglial associations are also formed by the neurosecretory innervation of vascular walls of the dorsal aorta and circulatory sinuses which envelope the synganglion and major peripheral nerves. Inferential considerations of neurosecretory and endocrine interactions in the Acari are based on these anatomical and histological data which also provide the basis for evolutionary considerations of anatomical relationships and specializations in the neurosecretory systems of other Arachnida.

Larvae of the British Metastriata (Ixodoidea: Ixodidae)

Detailed descriptions are given of the larvae of the three species of British metastriatan ticks, with particular reference to the arrangement and dimensions of setae.