On the visual perception of the eyes in adult Hyalomma truncatum ticks (Acari: Ixodidae)

Adult Hyalomma truncatum ticks with uncovered and foil-covered eyes were exposed to an upright-positioned rectangle as a target giving a luminance contrast ratio of 5:1 at a sun-simulating radiation. The transmission rate of the foil was less than 0.003%. Significantly (p0.05) more locomotorally active ticks with uncovered eyes (36.6%) responded to the target than ticks with foil-covered eyes (7.3%). When the rectangle was illuminated by monochromatic light at wavelengths ranging between 420 and 648 nm, the target induced a positive scototaxis in ticks with uncovered eyes regardless of the wavelength range. In contrast, ticks with covered eyes did not exhibita positive scototaxis at wavelength ranges of 553–585 and 608–648 nm and very few ticks responded only to other wavelength ranges. The results indicate that the eyes are the only or at least the most essential sense organs in the visual system of adult H. truncatum ticks.     

Morphology of spiracles in adult Hyalomma truncatum ticks (Acari; Ixodidae)

Scanning electron microscopical investigations of fractures and corrosion casts of spirales in adult ticks of Hyalomma truncatum revealed a three-part structure consisting of the spiracular plate forming the outer part followed by the subostial space, which leads into the atrial chamber from which the main tracheal trunks arise. The spiracular plate sonsists of a thin surface plate perforated by aeropyles, an underlying interpedicellar space formed by pedicels and an inner thick base plate. The surface plate is subdivided into a porous and a non-porous area. The macula is surrounded by the porous area and cleft by the ostium, which is bounded by a lip. The lip rests on a stalk which passes through the subostial space and forms the lateral wall of the atrial chamber. The interpedicellar space is chambered comprising four types of chambers. Large pyriform chambers (type 1) open to the atmosphere via a large aeropyle and are connected at their base with a duct traversing the base plate. They correspond numerically and in their position with the large aeropyles and the ducts of the base plate. Each chamber is surrounded by four to six medium-sized tubular chambers (type 2) which are closed at both ends. Small tubular chambers (type 3) open to the atmosphere via a small aeropyle, are closed at their base and correspond in number and position to the small aeropyles. Elongated chambers (type 4) are arranged in two to three rows around the subostial space and are closed at both ends. The front row communicates with the subostial space via large gaps. All chambers interconnect with each other by slit-like fenestrations. Below the macula and surrounding the stalk is the subostial space. Over the medial half, the subostial space opens into the atrial chamber. The lateral wall of the atrial chamber is thick, whereas the opposite wall is thin, folded and can be everted and inverted. Inverted, the medial wall closes up the opening to the subostial space and the main tracheal trunks. The base of the atrial chamber sonsists of the openings of the main tracheal trunks only. It is concluded that the aeropyles constitute the functional openings of a spiracle, the interpedicellar space and the subostial space act as diffusion barrier and the atrial chamber is exclusively responsible for the motory process of in- and expiration and is the only closing device of the spiracle.     

Morphology of the Eyes in adult Hyalomma Truncatum Ticks (Acari: Ixodidae)

The eyes of Hyalomma truncatum ticks are morphologically similar in both sexes. They appear aspaired hemispherical structures situated dorsally between the first and second pair of legs on thelateral scutal margin. Each eye consists of a lens and photoreceptor cells, which are separated by afine fibrillar layer and the hypodermis. The lens contains numerous channels which open beneaththe epicuticle, converge uninterruptedly to the interior of the lens and end below the fine fibrillarlayer. The inner closure of the lens is formed as an oval plateau with a cone-like projectionsituated caudolaterally and eccentrically to the longitudinal axis of the lens. The hypodermis is asingle layer of cells, situated immediately below the fine fibrillar layer. Beneath the hypodermis,directly below the cone-like projection of the inner lens are the photoreceptor cells localized in arosette-like arrangement. Facing the hypodermis, each photoreceptor cell is provided withnumerous microvilli. The microvilli consistently border the microvilli regions of other cells atdifferent angles but are always oriented at a right angle to the lenticular channels. Thephotoreceptor cells are unipolar neurons, whose axons arise from the basal portion of the cell andjoin to nerve fibre bundles forming the optic nerve. It is concluded that the eyes in adult H.truncatum ticks possess all the structures necessary to perceive and conduct light stimuli andvisual signals.     

Hyalomma truncatum (Acari; Ixodidae): investigations into the scototaxis of unfed adult ticks

Under controlled test conditions, unfed male and female Hyalomma truncatum ticks exhibited a positive scototaxis to stationary, two-dimensional targets. Upright-positioned rectangles were the most attractive targets. The attractiveness of these targets increased with their size. Significantly more ticks responded scototactically positively to the targets under a luminance contrast ratio of 5:1, as compared with other luminance contrast ratios. Targets with an elevation angle of 13° were occupied more frequently than objects with higher elevation angles. Scototaxis was the same towards a stationary and a sinusoid oscillating target. When an upright-positioned rectangle was combined with a CO₂ gradient, the number of ticks that migrated into the CO₂ gradient and contacted the target did not increase significantly. The interval between exposure and first locomotion of the ticks, however, was significantly shorter under the influence of a CO₂ gradient than in all other experiments without a CO₂ gradient. A temperature gradient simulating a natural host (cattle) did not alter the scototaxis. The results of these investigations suggest that the positive scototaxis exhibited by adult H. truncatum ticks is not likely to be part of their appetence behaviour but rather searching behaviour to find adequate protection from harsh climatic conditions.     

Hyalomma truncatum (Acari; Ixodidae): evidence for the inability of adult ticks to discriminate between colours

Behavioural investigations into the perception and differentiation of coloured objects by unfed adult Hyalomma truncatum ticks revealed that silhouettes of blue, green, red and yellow colour, under illumination by a sun-simulating waveband spectrum, are perceived by the ticks and responded to equally by a directed response. Two green or dark grey rectangles each with a luminance contrast ratio of 5 : 1 against the white wall of the test arena in combination with an overlapping, equally sized dark grey or green target were consistently reached by ticks in a ratio of 2 : 1. Since the outer targets were occupied by the double number of ticks compared with the central silhouette this shows that the response is independent of the colour of the object. Investigations into target perception under monochromatic radiation of different wavelength ranges which were evenly adjusted in their irradiances revealed that ticks responded equally to a black target irradiated by blue, green, yellow and red light of wavelengths 428–472, 517–563, 549–591 and 606–654 nm, respectively. These results indicate the lack of true colour vision in H. truncatum.     

Beauveria bassiana: Synergistic effect with acaricides against the tick Hyalomma anatolicum anatolicum (Acari: Ixodidae)

Owing to the need to combat the spread of chemical acaricide resistance in ticks, we evaluated the efficacy of a mixture of the entomopathogenic fungus Beauveria bassiana AT17 and acaricides for the control of Hyalomma anatolicum anatolicum in China. A mixture of B. bassiana AT17 at the concentration of 10⁸ conidia/mL and the synthetic pyrethroid deltamethrin at concentrations of 2500, 250, 25, 5, 2.5, 0.5 and 0.25 ppm was tested in vitro. The germination capability, vegetative growth, conidia production, and viability of B. bassiana AT17 were assessed and the efficacy of the mixture in killing engorged H. anatolicum anatolicum females was measured. High mortality rates were achieved when the entomopathogen was combined with different concentrations of deltamethrin. Neither B. bassiana AT17 nor deltamethrin alone at the same concentrations could cause the higher mortality rates seen with the combination. In addition the combination killed the ticks more rapidly than did either agent alone (3–5 days more rapidly). Our results indicate that the mixture of B. bassiana AT17 and deltamethrin has potential as a new type of reagent for integrated control of H. anatolicum anatolicum.     

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.     

Cuticle expansion during feeding in the tick Amblyomma hebraeum (Acari: Ixodidae): The role of hydrostatic pressure

Female Amblyomma hebraeum ticks (Acari: Ixodidae) increase their weight ∼10-fold during a ‘slow phase of engorgement’ (7–9 days), and a further 10-fold during the ‘rapid phase’ (12–24 h). During the rapid phase, the cuticle thins by half, with a plastic (permanent) deformation of greater than 40% in two orthogonal directions. A stress of 2.5 MPa or higher is required to achieve this degree of deformation (Flynn and Kaufman, 2015). Using a dimensional analysis of the tick body and applying the Laplace equation, we calculated that the tick must achieve high internal hydrostatic pressures in order to engorge fully: greater than 55 kPa at a fed:unfed mass ratio of ∼20:1, when cuticle thinning commences (Flynn and Kaufman, 2011). In this study we used a telemetric pressure transducer system to measure the internal hydrostatic pressure of ticks during feeding. Sustained periods of irregular high frequency (>20 Hz) pulsatile bursts of high pressure (>55 kPa) were observed in two ticks: they had been cannulated just prior to the rapid phase of engorgement, and given access to a host rabbit for completion of the feeding cycle. The pattern of periods of high pressure generation varied over the feeding cycle and between the two specimens. We believe that these pressures exceed those reported so far for any other animal.     

The question of fluctuating asymmetry in the blacklegged tick Ixodes scapularis (Acari: Ixodidae)

An analysis of fluctuating asymmetry was conducted on populations of the blacklegged tick Ixodes scapularis. The eight groups used in this study consisted of larvae and nymphs and males and females from the states of Minnesota, Massachusetts, Maryland, Missouri, North Carolina and Georgia and the F1 progenies of reciprocal crosses between ticks from Massachusetts and Georgia. Measurements included 16 larval, 19 nymphal, ten female and 12 male bilateral characters. Only five differences between the right and left bilateral characters had normal distributions with means of zero and differences in variances between the groups. These five characters included three setal lengths of the larvae, the spiracular plate length of females and the coxa I internal spur widths of males. Bivariate plots of character size ((R+L)/2) and asymmetry (R-L) showed no correlation. In the spiracular plate lengths of females and one of the setal lengths, ticks from Massachusetts had significantly less within-group variance than all the other groups. The only character in which fluctuating asymmetry was observed was the coxa I internal spur width of males, in which ticks from Minnesota, Missouri and North Carolina had significantly greater variance than the remaining groups; fluctuating asymmetry in this character may be explained by sexual selection. The cross progeny did not demonstrate any fluctuating asymmetry, as would be expected if the northern and southern forms of I. scapularis were true species. The virtual lack of fluctuating asymmetry in the characters used in this study further supports the conclusions of other studies which concluded that I. scapularis is a species with clinal variation and a broad geographic distribution.     

The genus Hyalomma. VI. Systematics of H. (Euhyalomma) truncatum and the closely related species, H. (E.) albiparmatum and H. (E.) nitidum (Acari: Ixodidae)

The geographic distribution of three closely related Hyalomma species, namely Hyalomma (Euhyalomma) truncatum Koch, 1844, Hyalomma (Euhyalomma) albiparmatum Schulze, 1919 and Hyalomma (Euhyalomma) nitidum Schulze, 1919 is confined to Africa. A detailed comparison of all stages of development of the three taxa reveals that they possess many more shared than distinguishing characters. In fact differentiation between these species is based on single or dual qualitative characters on their adults. These are a conspicuous, ivory-coloured parma on H. (E.) albiparmatum males, and the absence or reduction in clarity of ivory-coloured bands on the leg segments of H. (E.) nitidum adults, as well as the shape of the external cuticular preatrial fold of the genital operculum of females of the latter species. The adults of all three species and the larva of H. (E.) truncatum are redescribed. The nymph of H. truncatum and the larva and nymph of H. (E.) albiparmatum and H. (E.) nitidum are described for the first time. Data on their geographic distributions and hosts are provided.     

Isolation and properties of two forms of thrombin inhibitor from the nymphs of the camel tick Hyalomma dromedarii (Acari: Ixodidae)

Two forms of the nymphal thrombin inhibitors (NTI) 3.2 kDaand 14.9 kDa were purified by chromatography on CM-cellulose,Sephacryl S-300 and Sephadex G-50 columns and designated NTI-1 and NTI-2respectively. The NTI-2 turned out to be homogenous monomeric protein in bothnative-PAGE and denatured SDS-PAGE with M(r) value of 14.9 kDaapproximately and its pI value ranged from 7.2 to 7.5. The NTI-1 and NTI-2displayed anticoagulant activity since they prolonged both the activatedpartialthromboplastin time (APTT) and the prothrombin time (PT) of the camel plasma ina concentration-dependent manner. The potency of NTI-1 toward thrombin was5-fold higher than that toward FXa, while NTI-2 was 3-fold active toward FXathan thrombin. However, both of them did not inhibit any of the other examinedproteases. The types of inhibition of thrombin by NTI-1 and NTI-2 were non-competitive and competitive with inhibition constants (Ki) values of 11.7M and 211 nM respectively. One binding site wasdeduced on thrombin for each inhibitor.     

Morphology of the foveal glands and foveae dorsales in male Hyalomma truncatum and Rhipicephalus evertsi mimeticus ticks (Acari; Ixodidae) before and during feeding

The ultrastructure of the foveae dorsales and foveal glands in unfed and attached male Hyalomma truncatum and Rhipicephalus evertsi mimeticus ticks was studied. Both species are provided with a paired foveal gland system, which is similar in unfed as well as in attached ticks. This gland system consists of the fovea dorsalis with pores and pore tubes as the external part, the foveal neck zone as a link between the fovea dorsalis and the lobes of the gland and the bulbous lobes as the innermost part. The fovea dorsalis is located on either side of the dorsal midline in the midsection of the body and appears as a roundish plate containing 15±6.5 and 21±7 slit-like pores in R. evertsi mimeticus (n=210) and H. truncatum (n=210), respectively. Each pore leads into a cuticular lined channel containing a pore tube. Below each fovea, the foveal neck zone is located within a groove of the cuticle and consists of the termini of the pore tubes which enlarge basally to form a cup-shaped ampulla each. Furthermore, secretory lobes are located below the foveal neck zone. Each lobe consists of secretory cells and a central excretory duct which leads into the ampulla. The ducts are lined with microvilli. The secretory cells contain numerous vesicles of varying size with one or more granules. In male ticks of both species the secretory lobe cells remained unchanged in size, structure and granule content irrespective of whether they were unfed or attached for up to 30 days. Axons occur in the fascicles between the secretory lobe cells containing numerous neurosecretory vesicles. A possible role of the foveal glands in the production of pheromones is hypothesized.     

Molecular characterization of the vitellogenin receptor from the tick,Amblyomma hebraeum (Acari: Ixodidae)

We have identified the full-length cDNA encoding a vitellogenin receptor (VgR) from the African bont tick Amblyomma hebraeum Koch (1844). VgRs are members of the low-density lipoprotein receptor superfamily that promote the uptake of the yolk protein vitellogenin (Vg), from the haemolymph. The AhVgR (GenBank accession No. JX846592) is 5703 bp, and encodes an 1801 aa protein with a 196.5 kDa molecular mass following cleavage of a 22 aa signal peptide. Phylogenetic analysis indicates that AhVgR is highly similar to other tick VgRs. AhVgR is expressed in only the ovary of mated, engorged females, and is absent in all other female tissues and in both fed and unfed males. Unfed, adult females injected with a VgR-dsRNA probe to knock-down VgR expression experienced a significant delay in ovary development and started oviposition significantly later than controls. These results indicate that the expression of AhVgR is important for the uptake of Vg and subsequent maturation of the oocytes.     

Parasitism of lizards by immature stages of the blacklegged tick,Ixodes scapularis (Acari,Ixodidae)

From 1982–1985 and 1993–1999, a total of 309 individual reptiles, mostly lizards and snakes, belonging to 12 species (American alligator, six lizard species, five snake species) was captured on St. Catherine's Island, Liberty County, Georgia, USA, and examined for ticks. Three lizard species, the broad-headed skink Eumeces laticeps, southeastern 5-lined skink Eumeces inexpectatus, and eastern glass lizard Ophisaurus ventralis, were severely infested with larvae and nymphs of the blacklegged tick, Ixodes scapularis. Ticks were not found on any of the other reptile species. Overall, 80% of 65 E. inexpectatus examined were parasitized by a mean intensity of 21.5larvae and 88% were parasitized by a mean intensity of 4.8 nymphs. Corresponding figures for E. laticeps (n=56) were 93% and 51.3 for larvae and 89% and 7.4 for nymphs, and for O. ventralis (n=3) were 67% and 22.5 for larvae and 100% and 21.3 for nymphs. Larvae and nymphs attached along the lateral grooves of O. ventralis. Nymphs attached mainly behind the ears and in the foreleg axillae whereas larvae mainly attached to these sites and on the hindlegs in Eumeces spp. Seasonally, both larvae and nymphs were recorded on lizards from April through October. A unimodal larval peak was recorded in May or June. Seasonal data for nymphs did not reveal any distinct peaks but small bimodal peaks in mean intensities may have occurred (one in early summer, the other in late summer)suggesting that some ticks complete their life cycle in one year, and others in two years, on St. Catherine's Island. Potential epidemiological consequences of these findings with respect to Lyme disease in the southeastern United States are briefly addressed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Traffic of the tick embryo basic protein during embryongenesis of the camel tick Hyalomma dromedarii (Acari: Ixodidae)

The tick embryo basic protein (TEBP) is present in the nucleus as a counterpart of histones at early embryonic stages of the tick Hyalomma dromedarii. The sharp drop in the TEBP nuclear level and elimination of the N-terminal dipeptide (leucine–serine) between days 12 and 15 after oviposition suggested the transport of TEBP to the cytoplasm for protein turnover. The traffic of TEBP during tick embryogenesis was examined. The level of TEBP was detected in the cytoplasm from the different embryonic stages by the established enzyme-linked immunosorbent assay (ELISA) and confirmed by immunoblotting. At day 12, a 2-fold increase in the cytoplasmic TEBP level coincided with its decrease in the nucleus. This result indicates that TEBP starts to leave the nucleus for the cytoplasm at day 12. The changes in the cytoplasmic leucine aminopeptidase (LAP)-specific activity were followed during tick embryogenesis. The LAP activity started to increase at day 12 and reached its maximum level at day 21. The enzyme displayed an optimum pH between 7.5 and 8.8 and a K_m value of 0.5 M for leucine-p-nitroanilide. The involvement of the exopeptidase activity in the TEBP turnover after its translocation to the cytoplasm is discussed.     

The effect of feeding status on sexual attractiveness of Ixodes ricinus (Acari: Ixodidae) females

Sexual attractiveness of unengorged, semiengorged and fully engorged females of both field and laboratory populations of Ixodes ricinus was studied under laboratory conditions by means of a computerised video tracking system. A male and a female were allowed to walk freely in a glass arena during 1 h and their behavioural interactions were observed. Obtained results revealed that the feeding status of I. ricinus females affects their sexual attractiveness. The highest attractiveness was observed in engorged females, the lowest in unengorged females of the field population. Copulation occurred in all experimental groups with the highest frequency observed in the unengorged virgin laboratory females. Despite engorged females being highly attractive for males on distance, the frequency of copulation was low. Differences between field and laboratory populations were found in both behavioural parameters and frequency of copulation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Identification of species of Hyalomma asiaticum group (Ixodidae) in areas of their sympatry based on immature stages

Morphological characters of immature stages of three closely related tick species, Hyalomma asiaticum Schulze et Schlottke, 1929, H. dromedarii Koch, 1844 and H. schulzei Olenev, 1931, collected mainly in areas of their sympatry (Fig. 1) were investigated. The larvae and nymphs of these three species were collected in Egypt, Iran, Turkmenistan, Uzbekistan, Afghanistan and Tadjikistan: 159 larvae and 137 nymphs of H. asiaticum from 12 localities; 78 larvae and 167 nymphs of H. dromedarii from 5 localities; 30 larvae and 6 nymphs of H. schulzei from one locality. Both qualitative morphological features and measured character (in mkm) were used to discriminate these species. Main discriminant characters for larvae. H. asiaticum (Fig. 3). Scutum: length < 246, width < 389; base of capitulum: width < 158, dorsally hexagonal, apices of lateral projections directed forward; palpae (II and III segments): length < 106, width < 42; hypostome: length < 87, width < 25; the spur of coxa I small, equilateral triangular; patella: length < 154. H. dromedarii (Fig. 4). Scutum: length > 236, width > 379; base of capitulum: width > 158, dorsally almost triangular, apices of lateral projections directed laterally or backward; palpae: length > 110, width < 46; hypostome: length > 87, width < 26; the spur of coxa I large, isosceles triangular; patella: length > 115. H. schulzei (Fig. 5). Scutum: length > 249, width > 407; base of capitulum: width > 162, dorsally hexagonal, apices of lateral projections directed forward; palpae: length > 114, width > 44; hypostome: length > 89, width > 28; the spur of coxa I large, isosceles triangular; patella: length > 164. Main discriminant characters for nymphs: H. asiaticum (Fig. 3). Scutum: small, width < 650, length and width subequal, posterior margin widely rounded, lateral incisions weakly developed; spiracular plates with distinct, pointed dorsal projection, marginal row of perforations distant from the base of dorsal projection, submarginal row with a gap; base of capitulum: lateral projections situated in posterior half of capitulum; palpae (II segment) short and narrow; hypostome short and narrow, width < 69; pore of coxae I-III present. H. dromedarii (Fig. 4). Scutum: large, width > 650, length shorter than width, posterior margin widely rounded, lateral incisions moderately developed; spiracular plates: with distinct and wide dorsal projection, marginal row of perforations distant from the base of dorsal projection, submarginal row present, without gap; base of capitulum: lateral projections situated in the middle part of capitulum; palpae long and narrow; hypostome long and wide, width > 69; coxal pore lacking. H. schulzei (Fig. 5). Scutum: small, width < 630, length larger than width, posterior margin narrow rounded, lateral incisions weakly developed; spiracular plates: with weakly developed dorsal projections, marginal row of perforation situated just behind the base of dorsal projection, submarginal row with a gap; base capitulum: lateral projections situated in posterior half of capitulum; palpae short and wide; hypostome long and narrow, width < 73; coxal pore lacking.     

The distribution of ticks (Acari: Ixodidae) of domestic livestock in Portugal

This paper introduces the first countrywide faunistic study of the tick parasites on ruminants in Portugal. The aim of this study was to map accurately the distribution of the ticks Dermacentor marginatus, Rhipicephalus (Boophilus) annulatus, R. bursa, Hyalomma m. marginatum, H. lusitanicum and Ixodes ricinus in Portugal. Additional information about the abiotic preferences of these species has been obtained through the use of abiotic (temperature- and vegetation-derived) variables have been recorded from remotely sensed information at a nominal resolution of 1.1 km². A further aim was the development of predictive models of distribution using Classification and Regression Trees (CART) methodologies. Four species (R. annulatus, R. bursa, D. marginatus and H. m. marginatum) are mostly restricted to south-eastern parts of the country, under hot and dry climate conditions of Mediterranean type. H. lusitanicum has been collected almost only in the southern half of Portugal. I. ricinus has a very patchy distribution and is mainly associated with vegetation of Quercus spp., found in southern zones of the country, but it is present also in the more humid western part. A variable number of abiotic variables, mainly temperature derived, are able to describe the preferences of the tick species. It is remarkable that variables derived from maximum values of the Normalized Derived Vegetation Index (yearly or summer-derived) only apply to discriminate areas where I. ricinus has been collected. CART models are able to map the distribution of these ticks with accuracy ranging within 75.3 and 96.4% of actual positive sites.     

Ultrastructure of the nymphal integument in the camel tick Hyalomma (Hyalomma) dromedarii (Ixodoidea: Ixodidae)

The ultrastructure of the nymphal integument in the ixodid tick Hyalomma (Hyalomma) dromedarii is compared for stages of development during and after feeding, and up to the first step of molting, apolysis. The integument comprises a cuticular layer and underlying epidermal cells. The body cuticle, which consists of both sclerotized and non-sclerotized parts, is divided into an outer, thin epicuticle, and an inner, thick, fibrillar procuticle. Pore canals in the procuticle are continuous with wax canals which traverse the epicuticle. As feeding progresses, the parallel, extensible epicuticular folds disappear due to the gut filling with ingested blood. The procuticular zone, however, becomes subdivided into an exocuticle, similar to the previously seen procuticle, and a lamellate endocuticle. Pore canals lose their parallel pattern and appear to have become deformed by stretching of the cuticle. The flat epidermal cells grow asynchronously during feeding; their cytoplasm becomes packed with well-developed rough endoplasmic reticulum (RER), while the cell apices project long microvilli extending deep into the procuticle. The RER undergoes ultrastructural changes indicating synthetic activity. Dense material released through the microvilli may serve to lyse the endocuticle and thus cause separation of the cuticle from the epidermis during apolysis. The lysed area, the exuvial cavity, is filled with lysed components which are probably withdrawn by endocytosis into the apical coated vesicles which appear in epidermal cells. Two types of integumental glands, which may participate in wax production, are observed in this study. The ultrastructure of their previously undescribed cuticular ducts is described, in addition to other hypodermal structures including epidermis-muscle attachments and sensory receptors.