Sense organs in post-embryonic stages of Hyalomma marginatum marginatum Koch, 1844 (Acari: Ixodida: Ixodidae). I. Tarsal sensory system.

Light and scanning electron microscopic studies showed the differences in morphology and in size of Haller's organ in larvae, nymphs and adults (females and males) of Hyalomma marginatum marginatum Koch, 1844. The length of the anterior pit setae increases during post-embryonic development. The localization of these setae is the same in all stages. Six setae (one porose seta, two grooved setae, two fine setae, one conical seta) contain anterior pit of various developmental stages. In nymphs and adults more numerous pores appear on the wall surface of porose seta than in the larval stage. The structure of the capsule roof also differs in various developmental stages. Haller's organ of Hyalomma m. marginatum shows great degree of morphological development which is connected with the complicated life cycle and feeding behaviour of this tick species.     

Host-parasite relationships of the genus Hyalomma Koch, 1844 (Acari, Ixodidae) and their connection with microevolutionary process

Host-parasite relationships of Hyalomma species of the world fauna are analyzed. The majority of species infests predominately various mammals. Birds and reptiles are used as preferred hosts by several Hyalomma species, and only on certain stage: adults of H. aegyptium parasitize tortoises; immature stages of H. marginatum parasitize birds. It is hypothesized that relationships of H. aegyptium adults (subgenus Hyalomma s. str.) with reptiles are secondarily in origin. Immature stages of H. aegyptium retain the primary wide diapason of hosts, which are various small mammals, birds and reptiles. The life cycle of this species is the three-host type that is considered as a primary type in ixodid ticks. A typical scheme of relationships with their hosts in all well-examined Hyalommina species has following features: the adult stage parasitize large and medium sized mammals, immature stages parasitize small mammals, three-host life cycle. A variety of preferred hosts and types of life cycle is observed in the subgenus Euhyalomma. All species of this subgenus can be arranged into two groups. In the first group, the immature stages infest only small mammals and birds, and the adults parasitize large mammals; this type of host preferences is probably primary host-parasite relationships of Hyalomma. This group includes: H. albiparmatum, H. asiaticum, H. excavatum, H. franchinii, H. impeltatum, H. impressum, H. lusitanicum, H. marginatum, H. nitidum, H. schulzei, and H. truncatum. Hyalomma marginatum and H. schulzei are two-host species; H. excavatum is two- or three-host tick. All the remaining species (except H. albiparmatum, which life cycle is unknown) are three-host ticks. In the second group, the immature stages as well as the adult stage parasitize large mammals. This group includes: H. dromedarii, H. anatolicum, and H. scupense. These species are two- or one-host ticks.     

Differentiation of subspecies of the polymorphic species Hyalomma marginatum (Acari: Ixodidae) based on immature stages

Study of morphological characters to identify the subspecies of Hyalomma marginatum immature stages is based on material collected throughout all the geographical range of the species. As it was found, the discrimination of subspecies of H. marginatum immature stages needs a complex use of structural and morphometrical characters. Only H. m. marginatum larvae and H. m. isaaci nymphs may be easily differentiated from other subspecies based on the structural (qualitative) characters. Besides, morphometric (quantitative) characters should be used only in combinations for identification of the subspecies. In regard to structural characters of larvae, it was found that the shape and size of coxal spurs of H. marginatum allow differentiating this subspecies from the others (Fig. 3, 5, 6). Based on morphometrical characters of larvae, the following characteristic features of subspecies have been found: in H. m. marginatum, the capitulum is wide, the palpi, hypostome and genua I are short and narrow; in H. m. turanicum, the capitulum is narrow, the palpi are short and narrow, the hypostome is short and wide, the genua I are long and narrow; in H. m. rufipes, the scutum is large, the capitulum is wide, the palpi are long and narrow, the hypostome and genua I are long and wide; in H. m. isaaci, the scutum is small, the capitulum is narrow, the palpi and hypostome are long and narrow, the genua I are short and narrow. Among structural characters of nymph, several discriminative features of subspecies have been found. The shape of the scutum in H. m. isaaci (Fig. 2, 2) clearly differentiates this subspecies from the others (Fig. 2, 1). In H. m. marginatum, the setae of alloscutum as a rule have bluntly rounded apices (Fig. 1, 2), while in the other subspecies these setae are more tapering apically (Fig. 1, 1). The shape of spiracular plates is rather variable within the species, but in H. m. marginatum and H. m. isaaci (Fig. 1, 3) the plates are larger and more perforated than in H. m. rufipes and H. m. turanicum (Fig. 1, 4). In H. m. isaaci, the spurs of coxae I are narrower than in other subspecies (Fig. 1, 8). Based on morphometrical characters of nymphs, the following discriminative features of subspecies have been found: in H. m. marginatum, the capitulum is wide, the palpi are short and wide; in H. m. turanicum, the capitulum is narrow, the palpi are long and narrow; in H. m. rufipes, the scutum is wide, the capitulum is narrow, the palpi are long and narrow, the hypostome is long; in H. m. isaaci, the scutum is long and narrow, the capitulum is wide, the palpi are short and wide, the hypostome is short.     

Synonymy of Boophilus Curtice, 1891 with Rhipicephalus Koch, 1844 (Acari: Ixodidae)

Recent molecular and morphological studies of the genera Rhipicephalus Koch, 1844 and Boophilus Curtice, 1891 revealed that the five species of Boophilus make the genus Rhipicephalus paraphyletic. Thus, Rhipicephalus Koch, 1844 is not a monophyletic (natural) lineage and some species of Rhipicephalus are more closely related to the species of Boophilus than to other species of Rhipicephalus. Here, we revise these genera: Boophilus is synonymised with Rhipicephalus, and Rhipicephalus (sensu lato) (including Boophilus) is redefined. By synonymising Boophilus with Rhipicephalus, we have changed the nomenclature so that it reflects our understanding of the phylogeny of these ticks. Boophilus is retained as a subgenus of Rhipicephalus, so the synonymy of Boophilus with Rhipicephalus does not result in the loss of the name Boophilus. In addition, Rhipicephalus is a well-known genus and the change proposed is simple -- all five species of Boophilus become members of Rhipicephalus (Boophilus).     

Influence of temperature and humidity on the reproductive efficiency of Ixodes ricinus (Linnaeus, 1758) and Hyalomma marginatum Koch, 1844 (Ixodoidea, Ixodidae)]

Laboratory studies have been carried out on two species of ticks, I. ricinus and H. marginatum, showing different seasonal activity and different geographical distribution in nature. The purpose of the present study has been to investigate the effect of different combinations of temperature and humidity on the oviposition of I. ricinus and H. marginatum. An index of reproduction efficiency (no. eggs/wt female), established to relate the capacity of the females to produce eggs to their body weight, has been calculated; for I. ricinus 5 temperatures (18-20-25-27 and 30 degrees C) have been studied (Fig. 1), for H. marginatum 3 (25-30 and 32 degrees C) (Fig. 2) and for both species 2 R.H. (75-95%). An optimal range of temperature, within which the value of such an index doesn't change, has been demonstrated for both species by statistical testing (Table 1). A critical weight value as the minimum engorged female weight required for egg deposition has been identified with the weight of first female which has laid eggs. This weight, different in each species, is influenced by temperature and humidity.     

Discrimination of subspecies in a polymorphic species Hyalomma marginatum (Acari, Ixodidae) based on adult stage

Morphological characteristics allowing discriminating adult stages of four subspecies of Hyalomma marginatum (H. m. marginatum, H. m. turanicum, H. m. rufipes and H. m. isaaci) are displayed. The subspecies status of all named forms is confirmed. The main discriminating characters for adults of these subspecies are peculiarities of scutal or conscutal punctations and a shape of the dorsal tale of spiracular plates (Fig. 1, 1-4; 2, 4-7; 4, 1, 2; 5, 1, 2, 6, 5-8). Nevertheless, there are a number of facts, which support only the subspecific rank of these taxa. In Turkmenistan, there is a zone inhabited by forms, adult stages of which are morphologically intermedial between H. m. marginatum and H. m. turanicum. A zone of intermedial forms between H. m. turanicum and H. m. rufipes exists in Arabian Peninsula (Hoogstraal e. a., 1981). An absence of clear discriminative characters between immatures of H. m. marginatum, H. m. turanicum and H. m. rufipes also confirms the subspecies level of these taxa. H. m. isaaci is the most differentiated subspecies. It is difficult to estimate relationships between the latter subspecies and H. m. turanicum because of a deficit of materials. However, clear morphological differences of H. m. isaaci immature stages from other subspecies were noticed (Apanaskevich, 2003). Therefore, it is quite probable that H. m. isaaci might deserve the species rank. Further analysis of relationships between subspecies of H. marginatum needs additional materials represented by all stages from zones containing intermedial forms between recently recognized subspecies.     

Studies on the ecology of Amblyomma marmoreum Koch 1844 (Acarnia: Ixodidae).

In the Eastern Cape Province of South Africa, larvae and nymphs of Ablyomma marmoreum Koch occur in habitats in which there is tree cover and herbaceous ground cover. Immatures of A. marmoreum are parasitic on reptiles, birds, and mammals. Adults occur only on reptiles. The major host for all stages is the moutain tortoise (Geochelone pardalis), and in the home areas of tortoises the density of ticks is high. Larvae are active in late summer and autumn. The rate of feeding is temperature-dependent, and some larvae which attach on tortoises in late autumn do not complete feeding until the following spring. Nymphs which occur in the home area of a tortoise become active in response to CO2 in early spring. Adults, and nymphs which occur outside the home area of a tortoise, become active in summer in response to rising temperatures. In nymphs which feed in spring, and hence develop into adults in midsummer, the life cycle is completed in 1 year. In nymphs which fed in midsummer, the life cycle is completed in 2 years.     

The genus Hyalomma Koch, 1844. IX. Redescription of all parasitic stages of H. (Euhyalomma) impeltatum Schulze & Schlottke, 1930 and H. (E.) somalicum Tonelli Rondelli, 1935 (Acari: Ixodidae)

The ticks Hyalomma (Euhyalomma) impeltatum Schulze &; Schlottke, 1930 and H. (E.) somalicum Tonelli Rondelli, 1935 [a species resurrected for “Hyalomma ? species” of Hoogstraal (1956) and H. erythraeum of Kaiser &; Hoogstraal (1968)] are tentatively considered to belong to the H. (E.) asiaticum group of closely related species. Amongst other features that are fairly similar, males of H. impeltatum can be distinguished from those of H. somalicum by the oval posterior margin of the conscutum, a narrow, subtriangular parma, the lack of ventral sclerotised plaques on median, paramedian and 4th festoons, and an incomplete to complete ivory-coloured stripe on the dorsal aspect of the leg segments; whereas males of H. somalicum have a broad but only slightly convex posterior conscutal margin, in most cases no parma, well-developed sclerotised ventral plaques on all festoons, and only a small ivory-coloured spot on the dorsal aspect of the leg segments. Females of H. impeltatum can be distinguished from those of H. somalicum by the bulging rather than flat preatrial fold of the genital aperture. All parasitic stages of both ticks are illustrated and redescribed, and the characteristics that distinguish the adults from those of other closely related species are detailed. Larger domestic and wild ungulates are the principal hosts of the adults of both ticks. Nymphs and larvae of H. impeltatum parasitise rodents, leporids, birds and lizards, whereas the hosts of the immature stages of H. somalicum are unknown. H. impeltatum is widely distributed in Africa north of the equator, Arabia, the Near East and south-western part of Central Asia; in contrast, H. somalicum has a more limited distribution in East Africa and possibly the Arabian Peninsular. Data on their possible disease relationships are also provided.     

Description of a new species of Dermacentor Koch, 1844 (Acari: Ixodidae) from Laos and Thailand

Systematic Parasitology - Dermacentor laothaiensis n. sp. (Acari: Ixodidae) is described based on adults ex wild boar and vegetation from Laos and Thailand. Adults of D. laothaiensis n. sp. are...     

Amblyomma triste (Koch, 1844) (Acari: Ixodidae): morphological description of the ovary and of vitellogenesis

The present study presents the morphology, histology, and the dynamics of vitellogenesis in females of the tick Amblyomma triste. The ovary in this species is of the panoistic type, therefore it lacks nurse cells. It is composed of a layer of epithelial cells that outwardly form the wall of the ovary, but also originate the pedicel, the structure that attaches the oocytes to its external margin, as well the oocytes themselves. In Amblyomma triste, the oocytes develop in four synchronic stages, which differs from the process in other tick species. The classification of the stages of the oocytes was carried out based on the presence of four morphologic characteristics: cytoplasm appearance; site of the germ vesicle; presence, quantity, and constitution of the yolk granules and presence of chorium.     

Towards a diagnostic view of Hyalomma (Hyalomma) aegyptium (Acari,Ixodidae)

The diagnostic characters of larval, nymphal and adult Hyalomma aegyptium (L., 1758) based on specimens from the territory of most part of the area are given. In the diagnoses of immature stages, was used the characters, which were formerly tested by the author for diagnostics of other Hyalomma species occurring in the former USSR. Commonly used characters and those which were revealed by the author as useful for the majority of Euhyalomma Filippova, 1984 and Hyalommina Schulze, 1919 species, have been used in the diagnoses of male and female. Differential diagnosis of Hyalomma aegyptium. Female: genital orifice as wide arch with straight posterior margin (fig. 2, 5); vestibular part of vagina funnel-like, greatly swollen (fig. 2, 5); setae of alloscutum stick-like, tapering in apical one (figs 2, 3, 4); second segment of palps with proximal narrowing (figs 3, 1, 2); spurs of coxae I widely separated, triangular, wide, subequal in size (fig. 3, 5). Male: any grooves of conscutum absent, except short and pit-like cervical ones (fig. 4); punctation sparce and impressive (fig. 4); adenal shields short and wide, without inner branch, posterior part widened, anteromedian margin straight (fig. 5, 4); spurs of coxae I widely separated, triangular, wide, subequal in size (fig. 6, 5). Nymph: posteromedian setae of alloscutum stick-like and, as a rule, with indented apices (fig. 7, 2); spurs of coxae I large, median spur as equilateral triangle and shorter than lateral one (fig. 7, 8); spurs of coxae II-IV well developed, with acute apices (fig. 7, 8). Larva: posterior part of scutum (behind the eyes) heavy elongated, its apex straight, postero-lateral incisions weakly developed (fig. 8, 1); spurs of coxae I as equilateral triangle in shape and with rounded apices, spurs of coxae II-III very large (fig. 8, 5).     

Brazilian distribution of Amblyomma varium Koch, 1844 (Acari: Ixodidae), a common parasite of sloths (Mammalia: Xenarthra)

Amblyomma varium, commonly known in Brazil as the "carrapato-gigante-da-pregui a" (sloth's giant tick) is found from southern Central America to Argentina. The present study adds information on the geographical distribution of A. varium, as well as on their hosts, based on material deposited in the main Brazilian collections and on the available literature. Eighty-two vials, containing 191 adult specimens, deposited in five Acari collections between 1930 and 2001, were examined. These vials included data on the host and collection localities. The biology of A. varium is unknown. However it is known that, during the adult stage, the tick presents a high host specificity and is found almost exclusively on the sloths Bradypus tridactylus, B. variegatus, B.torquatus (Bradypodidae), Choloepus hoffmanni and C. didactylus (Megalonychidae). Based on the material examined, the states of Rond nia, Amazonas, Bahia and Alagoas are newly assigned to geographic distribution of A. varium in Brazil.