Microscopic anatomy of the Haller's organ of snake ticks
TL;DR: The surface ultrastructural studies by using scanning electron microscope (SEM) on this olfactory organ of both the species revealed some species specific features like slit pattern.
Abstract: Microscopic anatomy of Haller’s organ of snake inhabiting tick, Amblyomma gervaisi and Amblyomma helvolum is described. The Haller’s organ consists of two parts, the anterior pit and the proximal capsule. The surface ultrastructural studies by using scanning electron microscope (SEM) on this olfactory organ of both the species revealed some species specific features like slit pattern. Anterior pit consists of six sensilla in A. gervaisi and four in A. helvolum. These sensilla at their base region are connected to each other by a channel. Transmission electron microscope (TEM) observation of this organ of A. gervaisi shows that the lumen of each sensilla and the channel are associated with muscles and bunches of nerve fibres, respectively. Proximal capsule consists of few pyramid shaped elevated regions, each of which at their ventral surface bears cluster of one bipolar sensory cell guarded by two lateral supportive cells. Cytomorphology of the sensory cell exhibit distinct nucleus, mitochondria, ...
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TL;DR: The potential fitness loss from reduced F1 growth should be compensated by increased fitness in the F2 indicating adaptive trans-generational modifications, and this assumption was evaluated using individuals of predatory mite Amblydromalus limonicus from the F1 and F2 generation.
Abstract: Heat waves are considered to pose a greater risk to arthropods with their limited thermoregulation abilities than the increase of mean temperatures. Theoretically, within- and trans-generational modifications may allow populations to keep pace with rapidly occurring heat waves. Here, we evaluated this assumption using individuals of predatory mite Amblydromalus limonicus from the F1 and F2 generation, which were exposed to summer or simulated heat wave conditions during juvenile development. Independent of generation, survival and male body size were insensitive to heat waves. Heat stress elongated juvenile development of F1 males and females, and lowered the F1 female size at maturity indicating non-adaptive within-generational effects. Trans-generational modifications speeded up the development of F2 males and females and resulted in larger body size of F2 females deriving from the heat wave-experienced F1 generation. Faster F2 development should be adaptive, because it reduces the exposure time to heat waves and promotes an early beginning of mating activities. Being large at extreme high temperatures maybe a benefit for the F2 females, because large individuals are less vulnerable to dehydration and overheating. Thus, the potential fitness loss from reduced F1 growth should be compensated by increased fitness in the F2 indicating adaptive trans-generational modifications.
6 citations
TL;DR: In this paper , the authors reported the presence of the ixodid tick Amblyomma helvolum on three species of reptiles from Timor-Leste, including four-fingered skinks and two forest skinks.
3 citations
TL;DR: Different applications of EM in identification of ticks were discussed and morphological descriptions, comparative taxonomy, detection of pathogens in tick organs, and drug efficacy on ticks were presented.
Abstract: Electron microscopy (EM) is a very good tool in the biological researches. It is mainly used in the morphological description of adult and immature stages of ticks. In this review, different applications of EM in identification of ticks were discussed. In general, the applications of EM have been presented in four topics: morphological descriptions, comparative taxonomy, detection of pathogens in tick organs, and drug efficacy on ticks. EM was used in the description of a new tick or description of a tick which was described before to clarify additional characters that were not observed before by light microscope (LM). It is obvious that the EM provides all the morphological characters clearly in details. However, ticks have ornamented characters on their scutum, so it is necessary to use LM as well as molecular biology to confirm the morphological characters. EM is also used in detection of ultrastructure of pathogenic organisms in the cell lines or tissues of tick vectors that infected experimentally or naturally by pathogen. EM also helps to know the effect of new drugs or its mode of action by photography of the alterations which may occur on the integument or other tick organs such as the digestive system.
3 citations
Cites background from "Microscopic anatomy of the Haller's..."
...Microscopic anatomy of snake inhabiting ticks Haller’s organ, Amblyomma helvolum, and Amblyomma gervaisi was also described (Ghosh et al. 2017)....
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TL;DR: Absence of festoons at the posterior extremity of female tick and absence of eyes on the antero-lateral sides of the scutum of both sexes of this tick species are the main outcome of this present study, which may provide insight to the traditional identification key of the genus Amblyomma.
Abstract: A detail surface ultrastructure study on both male and female Amblyomma helvolum, inhabiting on snakes were made by using scanning electron microscope. The study unraveled the clear sexual dimorphism of the tick. Details of the surface ultrastructure were compared with other ixodid tick species as reported so far. Some distinctive surface morphology of A. helvolum was recorded viz., arrangement of hypostomal dentition, pore distribution on scutal surface, presence of festoons, position of male and female genital organ, number of spurs on different appendicular coxa, structure of spiracle and Haller’s organ, number of sensilla on anterior pit of Haller’s organ and distribution of different ventral idiosomal plates were remarkably diverse between sexes. Absence of festoons at the posterior extremity of female tick and absence of eyes on the antero-lateral sides of the scutum of both sexes of this tick species are the main outcome of this present study, which may provide insight to the traditional identification key of the genus Amblyomma.
2 citations
Cites background from "Microscopic anatomy of the Haller's..."
...Later, Ghosh et al. (2017) provided a detail microscopic anatomy of the Haller’s organ of A. gervaisi and A. helvolum by using SEM and TEM....
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TL;DR: During the past ten years, special methods for identifying the pores with a solution of crystal violet applied to the external surface of the insect, examination of the material in a medium with a suitable refrac tive index, and the use of silver-stained sections have permitted the identifi cation of the pores in the sense organs of some species with the light micro scope.
Abstract: The body surface of most terrestrial arthropods is highly impermeable to water; if it were not, the individuals, nearly all of which are small, would quickly succumb to dehydration. The receptor surfaces of the neural ele ments of an olfactory or a gustatory sense organ must be located in a posi tion where the stimulating odor or material in solution will reach them promptly. This is accomplished most efficiently when the moist receptor sur faces are exposed directly to the air or other media to be tested. These op posed necessities, then, that the individual 1. minimize water loss and 2. expose the delicate membranous surfaces of the dendrites to the air is a problem with which insects and other terrestrial arthropods are faced. The problem has been solved in the insects by the exposure of the recep tor surfaces at very small openings or pores in the cuticle. Unlike the rela tively large apertures of the digestive, respiratory, and reproductive systems and of various glands that are intermittently opened and closed, the pores of the chemoreceptors are continuously open. The openings, however, are ex tremely small and their combined surface area presents no serious problem in water conservation (86,87). The openings, indeed, are so small that they could not be seen by earlier workers. It was not until the electron microscope came into use and ade quate methods of preparing materials to be examined with it had been devel oped that the openings were demonstrated for the first time (86,87). Before this it had been believed generally that the chemoreceptor nerve endings were covered by a specialized cuticle through which the stimulating sub stance was able to pass. This view was accepted, at first, by the present writer (61). During the past ten years, special methods for identifying the pores with a solution of crystal violet applied to the external surface of the insect (65), examination of the material in a medium with a suitable refrac tive index, and the use of silver-stained sections have permitted the identifi cation of the pores in the sense organs of some species with the light micro scope. Before the knowledge obtained with the electron microscope became available, the correct interpretation of observations made on such structures with the light microscope was not possible.
300 citations
"Microscopic anatomy of the Haller's..." refers background in this paper
...Those fine structural details are very common among the arthropods (Larsen 1962; Richter 1964; Thurm 1964; Moeck 1968; Coons 1970; Foelix 1970; Slifer 1970)....
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TL;DR: Physiological and morphological results indicate that compression at the site of this body probably acts as the stimulus at the cellular level.
Abstract: The distal nerve process of hair plate sensilla and campaniform sensilla contains a special terminal structure in the form of a bundle of tubules herein designated the "tubular body." Physiological and morphological results indicate that compression at the site of this body probably acts as the stimulus at the cellular level. A ciliary structure separates an outer segment of the distal nerve process from the remaining distal fiber.
236 citations
TL;DR: Hungry adults which are repelled by temperature alone are attracted when both stimuli are presented together; they respond with equal vigour to the scents of dog, rabbit, cow and horse hair.
Abstract: 1. Posture The unfed sheep tick when at rest adopts either a ‘questing’ attitude with the forelegs extended or an attitude of repose with the forelegs folded. While walkingthe hungry tick waves the forelegs in the manner of antennae. 2. Sensory responses ( a ) Gravity . A tick walking on a 24 cm. vertical glass rod, which serves as a satisfactory model of natural grass or rush stems, usually climbs from the base to the tip, quests, then walks up and down near the tip before finally coming to rest there. This response involves a taxis (upward-turning near the tip) and a kinesis. Negative geotaxis may be of some significance, but reasons are given for supposing that this pattern of behaviour is partly a tactile response following arrival at the tip. ( b ) Humidity . The humidity behaviour is greatly influenced by the physiological state. When their water balance is normal, unfed ticks avoid higher humidities but come to rest with equal readiness in moist or dry air. The avoiding response (taxis) disappears after desiccation and is replaced by a kinesis: the tick is then intensely active in dry air, but soon comes to rest in moist air. On remaining in damp air the water balance is restored by water uptake through the cuticle. The first response then reappears. The operation of the kinesis does not seem to depend on sensory stimulation. The taxis is weakly developed in normal engorged ticks, but the kinesis is again strongly manifested after desiccation. ( c ) Tactile responses . Unfed ticks with their legs folded respond to vibrations by questing instantly: they readily cling to any object which brushes against them. The formation of densely packed larval clusters is a further response to contact stimulation ( d ) Temperature . Hungry ticks orienting to an odourless tube at 37°C. either approach it eagerly and climb on, or avoid it. This stimulus is usually attractive to larvae and nymphs, but repellent to adult ticks. The response is to a gradient of air temperature and not to radiant heat. Objects at any temperature higher than that of the surroundings may prove attractive, but avoiding responses are always elicited by temperatures higher than 42°C. In a linear gradient extending from 8 C.to 45°c. ticks aggregate rapidly in the coldest region after previous exposure to 25°C. Fewer cold-adapted ticks are trapped in this way; those remaining outside the coldest region show no definite ‘preferendum’ within the range 11-41° C. ( e ) Smell . Below 20°C. ticks are indifferent to the odour of sheep wool alone; above 20°C. wool is slightly attractive. In the presence of a temperature gradient (wool wrapped round a tube at 37° C.) this odour becomes highly attractive. Thus, hungry adults which are repelled by temperature alone are attracted when both stimuli are presented together. They respond with equal vigour to the scents of dog, rabbit, cow and horse hair. ( f ) Light . Unfed ticks at rest on a glass rod respond to a sudden fall in light intensity by questing (shading section). Engorged ticks are strongly photonegative; newly moulted ticks also avoid a directed filumination, but become indifferent as they age 3. Sense organs The following sensory structures are borne on the forelegs: (a) Huller9s organ. This composite organ includes groups of sensilla in the anterior pit and posterior capsule which are morphologically distinct and have an independent innervation. The sensilla of the anterior pit are the humidity receptors responsible for the taxis while the peg-like chemoreceptors of the capsule are olfactory. ( b ) The temperature sensilla are short, thick-walled hairs borne on the dorsal and lateral aspects of the leg. ( c ) Tactile bristles are restricted to the ventral surface of the distal articles; their stimulation by vibrations of the substratum leads to the questing response. The palpal organ , situated at the tip of the palps, is a chemoreceptor with a high threshold of stimulation. Its function lies in the attachment response rather than in orientation. Temperature sensilla and tactile bristles are also present on the other legs and on the palps. The reactions to light are due to a dermal sense. 4. Attachment By offering warm or cold membranes of various types as sites for attachment, temperature, smell and a factor of the fleece which is perceived as a contact stimulus by the palpal organ, were found to provide the necessary stimulation for inducing attachment. Most ticks still attach to the natural host if the forelegs or the palps are amputated; none attach if both are lacking. 5. Orientation mechanisms A questing response to light or vibration is often followed by movement. This mechanism (orthokinesis) is also very important in the humidity behaviour of the desiccated tick. Random changes in the direction of locomotion (klinokinesis) rarely occur. The usual response to favourable or unfavourable stimuli (e.g. temperature, smell and humidity) is directed and involves successive comparisons of intensity by the sensilla borne on the forelegs (klinotaxis). There is no tropotactic component, for ticks lacking one foreleg can still locate such stimuli accurately. 6. Orienting responses in the natural environment An important physical feature of the rough moorland grazings which form the main habitat of the sheep tick is the steep humidity gradient within the vegetation layer. Near the roots, where the tick remains quiescent for long periods, the atmosphere is permanently moist; at the tips of the vegetation, where the tick comes to rest during the ‘active’ period, humidities are variable but generally lower. All the sensory perceptions are of value in promoting surpival or host-finding. ( a ) First, certain reactions guide the tick to a situation--the vegetation tips--favourable for encountering the host. Of particular value in this respect is the upward-turning response summarized under § 2 ( a ). The tendency to remain near the tips is assisted at first by the humidity response, for ticks walking on the stem lattice avoid the high humidity near the roots. After an unsuccessful period of waiting the tick becomes desiccated and the kinesis comes into play: walking downwards the tick comes to rest at the roots, takes up water from the damp atmosphere, and is then prepared for a further period of activity at the tips. ( b ) Secondly, responses to tactile stimuli (unusual movements of the vegetation) and to light (shading) provide warning of the imminent approach of the host. c Thirdly,orientations ot the warmth and scent of the skin take place when the host is very near: the tick then catches hold and climbs on. After dropping from the host the movements of the engorged tick down into the deeper layer of the vegetation are guided by the avoidance of directed illumination and to some extent by sensations of contact.
202 citations
"Microscopic anatomy of the Haller's..." refers background in this paper
...Further investigations (Nuttall et al. 1908) showed that this organ – which was named after its discoverer consists of two parts – a cluster of short sensory setae, termed the “accessory pit” (“anterior pit”, Lees 1948) and immediately proximal a “capsule”, which have several sensilla inside....
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...Several behavioural studies (Totze 1933; Lees 1948; Zolotarev and Elizarov 1963, 1964) supported latter concept in their view....
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...Lees (1948) obtained good evidence that the anterior pit functions as a humidity receptor while the capsule subserves olfaction....
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TL;DR: The female Argas (P.) arboreus coxal organ consists of a nitration chamber, a tubular system, and an accessory gland that serves for passive fluid transport and fluid osmoregulation.
Abstract: The female Argas (P.) arboreus coxal organ consists of a nitration chamber, a tubular system, and an accessory gland. The nitration chamber, formed of ramified podocytes with thin, membranous diaphragms between successive pedicels, serves for passive fluid transport. The tubular system is formed of proximal and distal segments consisting of epithelial cells with morphological characteristics of those involved in active transport and fluid osmoregulation. The accessory coxal gland consists of 20–25 alveoli interconnected by alveolar ducts leading to the main coxal duct, which opens to the exterior via the coxal pore (between coxa I and II). Each alveolus contains 1 type of granule-secreting cell, interstitial cells, and cap cells, which may maintain the structural integrity of the alveolus during secretion. The coxal gland secretory cycle is under neural control.
112 citations
"Microscopic anatomy of the Haller's..." refers background in this paper
...vioural studies (Totze 1933; Lees 1948; Zolotarev and Elizarov 1963, 1964) supported latter concept in their view. Lees (1948) obtained good evidence that the anterior pit functions as a humidity receptor while the capsule subserves olfaction....
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...According to Roshdy et al. (1972), such plugged pores on the cuticular wall of the sensillum have not been reported earlier....
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TL;DR: The role of compounds secreted into the external environment that mediate important aspects of tick behaviour are addressed, including pheromones, attraction–aggregation–attachment (AAA), allomones and kairomones (used for host identification and location).
Abstract: This review addresses the role of compounds secreted into the external environment that mediate important aspects of tick behaviour. Known as semiochemicals, these information-containing compounds include pheromones (used for conspecific communication), allomones (defence secretions) and kairomones (used for host identification and location). An impressive body of knowledge has accumulated concerning the identification of the compounds that comprise these semiochemicals. Pheromones are the best known and intensively studied, including arrestment (=assembly) pheromones, attraction-aggregation-attachment (AAA) pheromones and sex pheromones. Arrestment behaviour is mediated by contact with excreta from other ticks. In contrast, aggregating and sexual behaviours comprise a hierarchy of responses to different types of chemical compounds that must be recognized in a sequential order to achieve the end result. Ixodid ticks also produce an allomone that protects against certain insect predators. Finally, ticks use kairomones for host identification, e.g. volatiles such as CO2 and NH3 and various oils such as glandular secretions from deer. Knowledge of tick pheromones has been used to develop innovative new technologies for tick control. These products incorporate tick pheromones and small amounts of pesticide to attract and kill ticks on their hosts or in vegetation. The kairomones and the tick allomone also may be of interest for use in controlling ticks.
109 citations