Perception of breath components by the tropical bont tick,Amblyomma variegatum Fabricius (Ixodidae)

Wall-pore olfactory sensilla located in the capsule of Haller's organ on the tarsus of Amblyomma variegatum ticks bear cells responding to vertebrate breath: one of these sensilla contains a CO2-excited receptor and a second sensillum has a CO2-inhibited receptor. Each of these antagonistic CO2-receptors, which display typical phasic-tonic responses, monitors a different CO2-concentration range. The CO2-inhibited receptor is very sensitive to small concentration changes between 0 and ca. 0.2%, but variations of 0.01% around ambient (ca. 0.04%) induce the strongest frequency modulation of this receptor. An increase of just 0.001-0.002% (10-20 ppm) above a zero CO2-level already inhibits this receptor. By contrast, the CO2-excited receptor is not so sensitive to small CO2 shifts around ambient, but best monitors changes in CO2 concentrations above 0.1%. This receptor is characterized by a steep dose-response curve and a fast inactivation even at high CO2-concentrations (greater than 2%). In a wind-tunnel, Amblyomma variegatum is activated from the resting state and attracted by CO2 concentrations of 0.04 to ca. 1%, which corresponds to the sensitivity range of its CO2-receptors. The task of perceiving the whole concentration range to which this tick is attracted would thus appear to be divided between two receptors, one sensitive to small changes around ambient and the other sensitive to the higher concentrations normally encountered when approaching a vertebrate host.     

Perception of breath components by the tropical bont tick,Amblyomma variegatum Fabricius (Ixodidae)

Summary Wall-pore sensilla in the capsule of Haller's organ on foreleg tarsi of the tick, Amblyomma variegatum, show multicellular responses upon stimulation with human and bovine breath. Filtering breath through charcoal removes the stimulant for some of these receptors. Analysis by gas chromatography coupled with olfactory sensillum electrophysiological recordings indicates that an ethanol extract of the breath components trapped on charcoal contains a major stimulant eluting at the same retention time as H₂S. Two types of H₂S-sensitive receptors have been identified. They are housed in separate sensilla, and are called sulfide-receptor 1 and 2.Although, both receptor types are characterized by a high sensitivity to H₂S with an estimated threshold of ca. 0.1 ppb and a response range covering 5–6 log orders of magnitude, their overall response to sulfides and mercaptans is nevertheless dissimilar. The type 1 receptor fires slightly more upon stimulations with H₂S than type 2, whereas ethylmercaptan induces a stronger response from type 2, and dimethyl sulfide activates only receptor 2.In a bioassay, H₂S tested at concentrations of ca. 0.02 ppm and 1 ppm equally arouses 60% of resting ticks. Two-thirds of these ticks quest the air with their first pair of legs, and the remainder start active search. By contrast, H₂S at ca. l ppm in a mixture with CO₂ severely diminishes the locomotor stimulating effect of CO₂.     

Responses of the tropical bont tick, Amblyomma variegatum (Fabricius), to its aggregation-attachment pheromone presented in an air stream on a servosphere

Male Amblyomma variegatum ticks feeding on a host release a mixture of o -nitrophenol and methyl salicylate which serves to attract conspecifics. The behavioural responses of A. variegatum on a servosphere to these volatiles presented in an air stream are detailed here. In still air, ticks walked on all eight legs, but with long halts. In contrast, the air stream caused continuous walking and induced a reaching response where the forelegs actively sampled the air. Such reaching increased the angular velocity and reduced walking speed, effects that were amplified in the presence of vapours from o -nitrophenol and methyl salicylate in the air flowing over the ticks. Vapour from a 1:1 mixture of o -nitrophenol and methyl salicylate was attractive over a 10⁴-fold concentration range providing an increase in upwind displacement of 20–40%, significantly higher than the natural ratio where o -nitrophenol vapour predominates. Although the responses to o -nitrophenol vapour were variable when presented alone, this chemical was consistently attractive when delivered with steer hair odour – unattractive on its own. Moreover, the upwind walk to this combination did not cause a change in speed or angular velocity. This supports the hypothesis that the response to the pheromone is enhanced by host odour. Accepted: 16 October 1999     

Underwater survival in the dog tick Dermacentor variabilis (Acari:Ixodidae)

Ticks are blood-feeding arthropods known for their long survivability off the host. Although ticks are terrestrial, they can survive extended periods of time submerged underwater. A plastron is an alternative respiration system that can absorb oxygen from water via a thin layer of air trapped by hydrophobic hairs or other cuticular projections. The complex spiracular plate of ticks has been postulated to serve as a plastron but that function has not been verified. This study provides evidence of plastron respiration in the American dog tick, Dermacentor variabilis, and for the first time confirmed the existence of plastron respiration in Ixodidae. Longer survival rates in oxygenated water indicate that underwater respiration requires oxygen. Wetting the spiracular plate with alcohol debilitates any potential plastron function and lowers the survival rate. Survival underwater may also be enhanced by metabolic depression and possibly anaerobic respiration. This study describes the first example of plastron respiration in the Ixodidae.     

Field tests of the response of femaleAmblyomma variegatum (Acari:Ixodidae) to the synthetic aggregation-attachment pheromone and its components

Fifty percent of anAmblyomma variegatum female population were able to find upwind-positioned targets containing the synthetic aggregation-attachment pheromone of this species or the pheromone componento-nitrophenol alone. The ticks were not attracted to the other components of the pheromone: methyl-salicylate and pelargonic acid. The mean time required for the ticks to reach a target at 1 m from the starting point was 3 min and 20 s.     

The role of 2,6-dichlorophenol as sex pheromone of the tropical horse tick Anocentor nitens (Acari: Ixodidae)

The objective of this study was to evaluate the role of2,6-dichlorophenol (2,6-DCP) as sex pheromone of Anocentornitens. Sex pheromones were extracted by submerging 150 females fed for 6 days in hexane (3 ml) for two hours and sonicating them for15 min. The extract was analyzed by GC-MS employing the Single Ion Monitoring (SIM) method. Identification of 2,6-DCP was based on the comparison of mass spectra with a computer search using the NIST library and by matching the mass spectrum of the peak at the retention time of 2,6-DCP from extract sand the synthetic product. In an olfactometer, males were released at 2.5cm from females, control rubber septa and impregnated rubber septa with increasing concentrations of 2,6-DCP (50, 500 and 5000 ng). A higher percentage of orientation and higher frequencies of angles between 0° and 10° were observed for males tested with females than with controls. Attraction of males to dummies impregnated with 2,6-DCP was observed with highest response (100%) at 50 ng. There was a gradual decrease of responsiveness of males with increasing concentration of 2,6-DCP (70 to 75%).This compound stimulated a behavior of mounting and ventral positioning ofA. nitens males at the lowest 2,6-DCP concentration where as dummies impregnated with 2,6-DCP higher than 50 ng concentration inhibited these behaviors. Therefore, we can conclude that 2,6-DCP can elicit the complete behavior sequence of orientation, location, mounting and ventral positioning behaviors and plays a role as an attractant and, as a mounting sex pheromone in A. nitens. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evidence for a mounting sex pheromone in the brown ear tick Rhipicephalus appendiculatus,Neuman 1901 (Acari: Ixodidae)

The presence of a mounting sex pheromone was demonstrated on the surface of fed female Rhipicephalus appendiculatus. This pheromone, which is present on the female cuticle, allows the male to recognise the female. The pheromone was removed by cleaning the female in hexane, resulting in the loss of male mating behaviour in in vitro experiments. Male mating behaviour was resumed when extract made from fed female cuticle was replaced on cleaned females. When the extract was transferred to innanimate objects typical male mating behaviour was released. Preliminary chemical analyses indicated that the active component of the extract was contained in the sterol ester fraction of the extract.     

Anteroposterior gradient during nymphal-adult moulting cycle of the tropical bont tick,Amblyomma variegatum (Acarina: Ixodidae)

Summary The structure of the extensible (alloscutum) and inextensible (scutum) integument of the nymph, Amblyomma variegatum was examined during the whole bloodmeal and the nymphal-adult moulting cycle. Integumental events were tentatively correlated with the ecdysteroid levels measured by radioimmunoassay. We observed that all the integumental events were realised along an anteroposterior gradient. During the 5 days corresponding to the bloodmeal, although the hormone concentration was low, a new endocuticle was deposited on both the alloscutum and scutum. Furthermore, mitoses were initiated in the capitulum. On days 1–2 after the meal, ecdysteroid titres began to increase and reached a first peak corresponding to 4.1 ng 20-hydroxyecdysone equivalents/tick on the 4th day after the ticks dropped off their host. At this time the epidermis of the capitulum was detached and the outline of the adult capitulum was already visible. Mitotic activity in the alloscutum was initiated. On day 6 post-drop, the frontal apolysis was achieved and the ecdysteroid titres declined to basal values. A second peak much higher than the first one (maximum value of 33.7 ng/tick) and identified principally as 20-hydroxyecdysone by HPLC/RIA was noted on the 13th day post-drop. During the period of increase in the ecdysteroid levels (days 9–10 post-drop), the mitotic phase ended in the alloscutum and the apolysis began. Epicuticle was deposited after day 12 postdrop. Then, while the titre fell to low values (about 1.6 ng/tick, days 16–20 post-drop), the exocuticle was deposited and the nymphal cuticle was digested. All adult structures were functional 3 days before ecdysis. In young male as in female adults the mean value of the ecdysteroid levels corresponded to about 2.5 ng/tick. Finally, hydrolysis of tick whole extracts with esterase demonstrated a low increase of RIA-positive material, demonstrating the probable presence of natural ecdysteroid fatty-acid conjugates in this species.     

Infestations of the bont tick Amblyomma hebraeum (Acari: Ixodidae) on different breeds of cattle in Zimbabwe

Infestations of adults and nymphs of Amblyomma hebraeum were counted on Brahman (Br), Brahman x Simmental (BS), Sanga (Sa) and Hereford (He) steers exposed to infested pastures at Mbizi in southern Zimbabwe in 1986–1987. Herefords were always the most heavily infested, while the Sanga tended to carry the fewest ticks with the Brahman and Brahman x Simmental groups being in between. The ratios of the engorged females on the four breeds were 2.3 : 1.4 : 1.4 : 1.0 for He : Br : BS : Sa. The ratios of the standard nymphs were 2.2 : 1.4 : 1.7 : 1.0 for He : Br : BS : Sa. The results confirm earlier observations in Africa and support the view that there are genetic differences between breeds in the expression of resistance to this tick species.Deceased.     

Ticks (Acari: Ixodoidea: Argasidae, Ixodidae) of Chile

The tick species recorded from Chile can be listed under the following headings: (1) endemic or established: Argas keiransi Estrada-Peña, Venzal and Gonzalez-Acuña, A. neghmei Kohls and Hoogstraal; Ornithodoros amblus Chamberlin; Otobius megnini (Dugès); Amblyomma parvitarsum Neumann; A. tigrinum Koch; Ixodes auritulus Neumann; I. chilensis Kohls; I. cornuae Arthur, I. sigelos Keirans, Clifford and Corwin; I. stilesi Neumann; I. uriae White; Rhipicephalus sanguineus Koch. (2) Probably established or endemic: Argas miniatus Koch; Ornithodoros spheniscus Hoogstraal, Wassef, Hays and Keirans; Ixodes abrocomae Lahille; I. neuquenensis Ringuelet; I. pararicinus Keirans and Clifford. (3) Doubtfully established: Argas reflexus Fabricius; Ornithodoros talaje (Guérin-Méneville). (4) Exotic: Amblyomma argentinae Neumann; A. latum Koch, Rhipicephalus (=Boophilus) microplus (Canestrini). (5) Erroneously identified as present in Chile: Amblyomma americanum (Linnaeus); A. maculatum Koch; A. varium Koch; Ixodes conepati Cooley and Kohls; I. frontalis (Panzer); I. ricinus (Linnaeus); Margaropus winthemi Karsch. (6) Nomina nuda: Argas reticulatus Gervais; Amblyomma inflatum Neumann; Ixodes lagotis Gervais. Hosts and localities (including new records) are presented. Argas neghmei, O. amblus, O. megnini, I. uriae and R. sanguineus may cause severe injury to their hosts, including humans. The Chilean Ixodes fauna is unique to the Neotropical Zoogeographic Region, and additional research is needed in order to understand the biological importance of these species.This revised version was published online in May 2005 with a corrected cover date.     

普通大蓟马聚集信息素的分离和鉴定

【目的】普通大蓟马Megalurothrips usitatus是我国华南地区重要的豆科害虫,给我国豇豆种植产业带来巨大损失。开发利用基于聚集信息素的引诱剂是普通大蓟马的绿色防控措施之一,对于普通大蓟马生物防治具有重要意义。【方法】采用Y型嗅觉仪测定普通大蓟马雌雄成虫对其雌虫和雄虫气味源的嗅觉反应;用顶空固相微萃取法(head space solid-phase microextraction, HS-SPME)和溶液浸提法提取普通大蓟马雌雄成虫挥发物;应用气质联用仪(gas chromatography-mass spectrometry, GC-MS)对收集的气体挥发物和正己烷提取物进行活性成分分离鉴定;应用Y型嗅觉仪测定人工合成聚集信息素组分对雌雄成虫的引诱效果。【结果】行为学试验结果表明,普通大蓟马雄成虫气味源对其雌雄成虫均具有显著的引诱作用,而雌成虫气味源则没有。顶空固相微萃取法和溶液浸提法均可提取雄成虫挥发物主要组分,但顶空固相微萃取法获得的TIC图基线平稳,杂峰少,提取效果优于溶剂浸提法。GC-MS分析结果表明,普通大蓟马雄成虫挥发物中主要含有 1种化合物,为反式,反式-金合欢醇乙酸酯［(E,E)-farnesyl acetate］,该化合物在雌成虫挥发物中不存在。室内行为学实验结果表明,特定剂量的人工合成的(E,E)-farnesyl acetate对普通大蓟马雌雄成虫均具有显著的引诱作用。【结论】本研究证明了普通大蓟马雄成虫可以释放聚集信息素,并鉴定了其主要组分(E,E)-farnesyl acetate,为应用聚集信息素开展普通大蓟马的监测和诱杀提供了基础。     

脐腹小蠹聚集信息素的提取鉴定和引诱效果

为了确定脐腹小蠹Scolytus schevyrewi Semenov的聚集信息素成分,对脐腹小蠹成虫后肠和虫粪的挥发物进行了提取鉴定和引诱试验。经气相色谱-质谱联用仪(GC-MS)鉴定,结果表明:雌成虫后肠挥发物成分有十四烷、十五烷、十六烷、十八烷、十九烷、十二酸和十四酸,其中十四酸含量最高,达到了42.2%;雄成虫后肠挥发物成分有十一烷、十四烷、十五烷、十六烷、十八烷和十九烷,十六烷(23.3%)和十九烷(21.5%)含量最多;雌成虫虫粪挥发物成分有十一烷、十二烷、十四烷、十六烷、十八烷和十九烷,十九烷含量最高,为29.9%;雄成虫虫粪挥发物成分有庚烷、十一烷、十二烷、十四烷、十六烷、十八烷、二十二烷和二十三烷,庚烷(20.5%)相对含量最多。此外,借助触角电位仪测定了脐腹小蠹雌雄虫触角对这些单一物质刺激的反应,结果显示,触角电位相对值较大的为十二酸、十四酸和十八烷。雌雄间比较发现十二酸、十四酸和十九烷刺激后雌雄间触角电位相对值差异达到了显著水平(P0.05)。田间诱捕结果显示,十二酸、十四酸、十九烷对脐腹小蠹的引诱数量雌雄间差异性达到了显著水平(P0.05),成虫诱捕总量最多的是十八烷,诱捕量达32.1头,其后诱捕量较多的为十二酸(24.1头)和十四酸(22.7头)。可以推断,十八烷、十九烷、十二酸和十四酸是脐腹小蠹聚集信息素的主要成分。     

Developmental stages and molecular phylogeny of Hepatozoon tuatarae, a parasite infecting the New Zealand tuatara, Sphenodon punctatus and the tick, Amblyomma sphenodonti

The developmental stages of Hepatozoon tuatarae were elucidated in both the tuatara host, Sphenodon punctatus and the tick, Amblyomma sphenodonti. PCR amplicons from A. sphenodonti samples identified DNA matching H. tuatarae. Dissection of tick samples showed oogenesis and sporogony occurring in the haemocoel of A. sphenodonti with the average mature oocyst size being 236 × 228 μm. Partial sequence data of the parasite’s small subunit ribosomal gene, obtained by PCR, was used for phylogenetic comparison. Characterisation of the H. tuatarae lifecycle will help in conservation management of the tuatara.     

The Argasidae, Ixodidae and Nuttalliellidae (Acari: Ixodida): A World List of Valid Tick Names

The world's argasid tick fauna comprises 183 species in four genera, namely Argas, Carios, Ornithodoros and Otobius in the family Argasidae. The ixodid tick fauna consists of 241 species in the genus Ixodes and 442 species in the genera Amblyomma, Anomalohimalaya, Bothriocroton, Cosmiomma, Dermacentor, Haemaphysalis, Hyalomma, Margaropus, Nosomma, Rhipicentor and Rhipicephalus in the family Ixodidae, with the genus Boophilus becoming a subgenus of the genus Rhipicephalus. The family Nuttalliellidae is represented by the monospecific genus Nuttalliella. The species names of these ticks, based on seven previous complete or partial listings, as well as those of recently described new species, are presented in tabular format. This revised version was published online in July 2006 with corrections to the Cover Date.     

Natural co-infection of Babesia caballi and Encephalitozoon-like microsporidia in the tick Anocentor nitens (Acari: Ixodidae)

The present paper reports the occurrence of natural co-infection of Babesia caballi and Encephalitozoon-like microsporidia in the tick Anocentor nitens. Engorged females of ticks, collected from a naturally B. caballi-infected horse, were incubated at 27 degrees C and relative humidity over 83%. After a 6-day incubation period, Giemsa-stained smears prepared from hemolymph were examined microscopically under oil immersion. B. caballi infected ticks were dissected and samples of midgut tissue were examined by transmission electron microscopy, through which free sporokinetes were seen in the cytoplasm of gut epithelial cells. In addition, Encephalitozoon-like microsporidia were observed inside the parasitophorous vacuoles in the same cell in which sporokinetes of B. caballi were found and also in some neighbour cells. They presented different morphological stages, suggesting a sequential phases of development.     

Diversity,ecology, and seasonality of hard ticks (Acari: Ixodidae) in eastern Croatia

The diversity of hard tick fauna was studied in different forest communities in 48 localities of eastern Croatia using the dragging‐flagging method and by hand from ten different vertebrate hosts. A total of 2,225 specimens comprising seven species in three genera were identified. Ixodes ricinus, the most abundant species (72.8% of all collected specimens) was recorded in 44 localities, followed by Dermacentor reticulatus in 19 localities, while the other five species (D. marginatus, H. concinna, H. inermis, I. canisuga, and I. hexagonus) were recorded in fewer localities. The highest ratio (67% of collected ticks) was in the adult stage with the predominance of females. The numbers of collected females, males, and nymphs of I. ricinus and H. concinna differed significantly. Ten new tick‐host associations in Croatia were recorded. Fifty‐three animals were infested with one tick species. Single species infestation with I. ricinus was found in 45.8% of animals, followed by D. reticulatus with 25.4%, D. marginatus with 10.2%, H. inermis and I. hexagonus with 3.4%, and I. canisuga with 1.7%. Coinfestation with two species of ticks were recorded in six animals. Ixodes ricinus, H. inermis, and D. reticulatus showed bimodal seasonal activity; for other species unimodal activity patterns were recorded.     

Fat body cells of Amblyomma cajennense partially engorged females (Acari: Ixodidae) and their role on vitellogenesis process

During the process of Arthropoda reproduction, the synthesis and uptake of proteins, carbohydrates, and lipids by oocytes is termed vitellogenesis. These compounds that will make up the yolk may be in ticks endogenously synthesized by the oocytes and/or exogenously produced by the fat body and pedicel cells. This study examined the fat body of Amblyomma cajennense ticks at the cytochemical ultrastructural level to demonstrate the presence of lipids, proteins and carbohydrates in trophocytes. The lipids were detected in higher quantity than proteins and carbohydrates in the fat body cells, suggesting that the role of the fat body in tick is stored lipids and carbohydrates to convert them in energy, or still they could be used with cell structural purpose. The electrophoresis technique applied at A. cajennense fat body demonstrated specifically the molecular mass of proteins: about 98 kDa. By the other hands, the fat body is not the organ responsible for the synthesis of the yolk protein, role probably performed by the pedicel cells.     

Aggregation pheromone released from the palps of feeding female Phlebotomus papatasi (Psychodidae)

Experiments with 2 feeding chambers: 1 new, the other having been used previously for feeding, showed that an aggregation and feeding pheromone had been secreted onto the chamber membranes by engorging females. Of the different extracts from parts of females or males tested, only the female palps and mouth parts exhibited pheromonal activity. The reaction to the pheromone was shown to be olfactory, and the pheromone itself is volatile. Reaction to the pheromone was dependent on chamber temperature. Pheromone-baited chambers at 28°C elicited a high response and the specific reaction to the pheromone was eliminated at 36°C. Large vacuolated cells in the 3rd and 4th segments and in Newstead's organ in the palps of females are suggested as a source of the pheromone.