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  • 1
    Electronic Resource
    Electronic Resource
    Morphology of the foveal glands and foveae dorsales in male Hyalomma truncatum and Rhipicephalus evertsi mimeticus ticks (Acari; Ixodidae) before and during feeding (1996)
    Springer
    Experimental and applied acarology 20 (1996), S. 511-532 
    Details
    ISSN: 1572-9702
    Keywords: Male ticks ; Rhipicephalus evertsi mimeticus ; Hyalomma truncatum ; foveal glands ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048284
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  • 2
    Electronic Resource
    Electronic Resource
    Morphology of the Eyes in adult Hyalomma Truncatum Ticks (Acari: Ixodidae) (1997)
    Springer
    Experimental and applied acarology 21 (1997), S. 21-39 
    Details
    ISSN: 1572-9702
    Keywords: Adult ticks ; Hyalomma truncatum ; eyes ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018489208924
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  • 3
    Electronic Resource
    Electronic Resource
    On the visual perception of the eyes in adult Hyalomma truncatum ticks (Acari: Ixodidae) (1997)
    Springer
    Experimental and applied acarology 21 (1997), S. 307-315 
    Details
    ISSN: 1572-9702
    Keywords: Ticks ; Hyalomma truncatum ; visual signals ; perception ; eyes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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 (p≤0.05) 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018459324370
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Hyalomma truncatum (Acari; Ixodidae): investigations into the scototaxis of unfed adult ticks (1995)
    Springer
    Experimental and applied acarology 19 (1995), S. 53-64 
    Details
    ISSN: 1572-9702
    Keywords: Ticks ; Hyalomma truncatum ; visual behaviour ; scototaxis ; CO2 gradient ; temperature gradient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00051937
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Hyalomma truncatum (Acari; Ixodidae): evidence for the inability of adult ticks to discriminate between colours (1995)
    Springer
    Experimental and applied acarology 19 (1995), S. 155-161 
    Details
    ISSN: 1572-9702
    Keywords: Ticks ; Hyalomma truncatum ; coloured objects ; monochromatic light ; perception ; differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046286
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  • 6
    Electronic Resource
    Electronic Resource
    Morphology of spiracles in adult Hyalomma truncatum ticks (Acari; Ixodidae) (1995)
    Springer
    Experimental and applied acarology 19 (1995), S. 287-306 
    Details
    ISSN: 1572-9702
    Keywords: Ticks ; Hyalomma truncatum ; spiracles ; morphology ; structural organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00052620
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    Paper (German National Licenses)
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