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PubMedDate not supplied

[Sexual dimorphism of the nymphal phase of ixodid tick species in the genus Dermacentor].

In four studied Dermacentor species at preimaginal phases sexual dimorphism hardly reveals itself in body size and mass of individuals. The formation of sexual distinctions at the nymphal phase concerns different characters as in different species so in populations of one species. In D. niveus male and female nymphs differ in the length of II-III palpal joints and width of gnathosoma, in D. ushakovae in the length of scutum and its proportions, in the width of gnathosoma and hypostome and in the diameter of peritreme. The sex of D. silvarum nymphs can be identified by the width of gnathosoma, length of hypostome and diameter of peritreme. Female and male nymphs of D. marginatus from the Stavropol Territory and Armenia differ in the scutum proportions and populations from the western Pamirs in the length of scutum and gnathosoma.

Animals↗
PubMedDate not supplied

[Histopathological changes in the skin of the rabbit fed on by preimaginal phases of the tick, Alveonasus lahorensis (Argasidae)].

During the feeding of larvae and nymphs of A. lahorensis haemorrhagic inflammation develops in the rabbit's skin. Lymphocytes and macrophages are the dominant cell elements in the reaction while during the feeding of nymphs eosinophilous leucocytes are observed in great number in the infiltrate. Around the oral parts of the tick an infiltration of collagenous fibres of the connective tissue is formed, which serves for a more firm attachment of the parasite, while beneath the proboscis a light band is formed from which the tick sucks the food substratum. By the end of the feeding of nymphs III in the place of skin affection a crust can be formed on account of the host's atrophied tissues, and in the integuments there are formed necrotic foci due to the hystolitic and toxic effect of the saliva.

Animals↗
PubMed1978

The life cycle of the tick Hyalomma marginatum rufipes Koch (Acarina: Ixodidae) under laboratory conditions.

The life cycle of Hyalomma marginatum rufipes Koch was studied under laboratory conditions at 26 +/- 1 C. The preoviposition period was 7.1 +/- 0.23 days. The mean (+/- SE) number of eggs was 6,867 +/- 2,609 (max. 13,180, min. 3,184). The greatest egg production was recorded on day 3 (avg 1,170 egg/female). The incubation period was 29.3 +/- 2.96 days. The feeding time of larvae and nymphs of this 2-host tick was 22.8 +/- 0.13 days. Nymphs producing males weighed less (23.1 +/- 0.748 mg) than those producing females (26.8 +/- 1.19 mg); the combined larval-nymphal feeding time of the former was shorter (21.9 +/- 0.1 days) than that of the latter (22.9 +/- 1.12 days). The premolting period of nymphs to adults of both sexes was similar.

Animals↗
PubMed1984

Demonstration of the inclusion appendage of Anaplasma marginale in nymphal Dermacentor andersoni.

Dermacentor andersoni nymphs were placed in stockinettes and allowed to feed on a splenectomized calf with experimentally induced anaplasmosis when the parasitemia was 3%-5%. Nymphs were selected on each of the 6 days of feeding and every 5 days from repletion through molting to the adult stage (25 days postrepletion); they were killed and midgut tissues were processed and examined by light and electron microscopies. No stages of A marginale were seen in tissues of feeding ticks. Visualization of individual components of gut contents was difficult owing to presence of the concentrated, electrondense blood meal containing hemoglobin. Inclusion appendages were observed in midgut tissues of nymphs at 5 and 10 days postrepletion, but not at 20 or 25 days. The morphology of the appendages was similar to that described for inclusion appendages commonly associated with anaplasmal inclusions in bovine erythrocytes. Some appendages were free in the lumen of the midgut and occurred either alone or with clusters of small vesicular particles. Occasionally, initial bodies like those generally found in bovine erythrocytes were seen with the appendage, but most of them were swollen and appeared to be degenerating. Frequently, inclusion appendages were observed attached to the luminal surface of the midgut cell membrane by a blunt, electron-dense attachment complex. The attachment of the appendage appeared to be extracellular, with the pointed end extending into the lumen. Often, small particles were observed immediately across the cell membrane from where the appendages were attached; the small particles appeared to be generated from the appendage itself and to have passed through the membrane of the midgut cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaplasma↗
PubMed1983

Haematophagous behaviour of Menacanthus eurysternus (Mallophaga, Amblycera).

Haematophagous nature of some mallophagan species is of great concern to the scientists working in the field. Such species cause harm to the host directly by reducing vitality and productivity and indirectly by acting as reservoir and transmitter of pathogenic strains of infectious diseases. Menacanthus eurysternus infesting common myna Acridotheres tristis feeds exclusively on host blood obtained by piercing the quill of pin feathers and by gnawing through the epidermis. As much as 88.56% adults, 73.91% third instar nymphs, 66.66% second instar nymphs and 83.21% first instar nymphs were found feeding on the host blood, when examined microscopically. This mallophagan species does not harbour any triturating agent and is not involved in cannibalism or predation.

Animals↗
PubMed1980

Ultrastructure of ANaplasma marginale Theiler in Dermacentor andersoni Stiles and Dermacentor variabilis (Say).

Cattle were inoculated with a Virginia isolate of Anaplasma marginale Theiler and served as an infective source for laboratory-reared Dermacentor andersoni Stiles and D variabilis (Say) nymphs. Anaplasma marginale was demonstrated by electron microscopy in gut tissues of replete nymphal ticks and in unfed, incubated, and feeding adult ticks that were exposed to the organism as nymphs when they fed on an infected cow. The A marginale organism in replete nymphs and adult feeding ticks were morphologically similar to A marginale described previously from infected bovine erythrocytes. Colonies of A marginale were demonstrated by light and electron microscopy in midgut epithelial cells of unfed adult D andersoni and D variabilis that had been incubated at 37 C for 3 days. Anaplasma marginale organisms in colonies were very pleomorphic. Small electron-dense particles were demonstrated in all infected tick stages studied, but were most evident in colonies from incubated, unfed ticks. They may represent a reproductive form of A marginale.

Anaplasma↗
PubMed1981

Life cycle in the laboratory and seasonal activity of the tick Rhipicephalus glabroscutatum (Acarina: Ixodidae).

The life cycle of Rhipicephalus glabroscutatum Du Toit was studied under laboratory conditions at 26 C +/- 1C. The preoviposition period was 6.0 +/- 0.12 days. The mean number of eggs was 2,044 +/- 186 (maximum 3,053, minimum 748), and the greatest production was recorded on day 3 (234 eggs/female). The incubation period was 37.4 +/- 0.32 days (maximum 41, minimum 35). The feeding time of larvae and nymphs of this two-host tick was 20.2 +/- 0.33 days (16-28). Nymphs producing males weighed less (4.09 +/- 0.07 mg) than those producing females (6.62 +/- 0.08 mg). The combined larval-nymphal feeding time of the former was shorter (19.3 +/- 0.90 days) than that of the latter (20.4 +/- 0.90 days). The molting period of nymphs to adults of both sexes was similar. Engorged females weighed (mean +/- SE) 204.0 +/- 10.75 mg and the feeding time was 7.9 +/- 0.34 days. Spermatogenesis was completed on day 5 after the commencement of feeding, and pairing between males and females and mating occurred subsequently. The adult ticks were active during early summer and were much more prevalent on kudu than on angora goats and cattle. Immature stages were not found during this study.

Animals↗
PubMedDate not supplied

[Diagnosis of species of the genus Dermacentor Koch from Central Asia by the nymphal phase (Ixodoidea, Ixodidae)].

A key to nymphs to five species of Dermacentor from central Asia is given. To recognize differential characters laboratory nymph from the parents identified previously by the authors were reared. D. montanus and D. pavlovskyi are studied from one, D. reticulatus and D. niveus from two and D. marginatus from four geographical areas. The shape of scutal scapulae, structure of the anal valve, proportion and topography of peritremes, shape, size and number of scutal setae, shape of alloscutal and pleiral setae, proportions of auricles, hypostome, cheliceral bases and different parameters of palpal joints, structure and size of coxae I-IV and tarsi I, sizes of scutum and different parameters of gnathosoma are taken for specific diagnostic characters. The differential characters were checked on laboratory nymphs of D. reticulatus, D. niveus and D. marginatus and on those collected beyond the territory of Central Asia.

Animals↗
PubMed1995

Ecology of Ixodes ricinus immatures on Apodemus agrarius (Muridae) in the lowland ecosystems conditions.

Ecology of Ixodes ricinus collected on black-striped field mouse (Apodemus agrarius) was studied in the lowland ecosystems. During the study period (1986-1991), 1483 specimens of A. agrarius were examined in southern Slovakia and 1319 larvae and nymphs were collected from hosts. The seasonal pattern--bimodal (peak in spring and autumn)--was distinct for larvae. Both prevalence and abundance of tick infestation of A. agrarius by nymphs were low. Prevailing material of nymphs was collected from May (pooled data from all years) on mature hosts. There were significantly higher infestation in mature males than in females as well as significantly higher tick infestation of mature hosts than immature ones. Higher abundance of tick infestation of A. agrarius in fields is probably influenced by great spatial mobility of hosts and by import of ticks from landscape verdure.

Animals↗
PubMedDate not supplied

[The isolation of Borrelia from the tick Ixodes trianguliceps (Ixodidae) and the possible significance of this species in the epizootiology of ixodid tick-borne borrelioses].

Ixodes trianguliceps is a common tick species of the Eurasian forest zone. These ticks live probably in natural foci of ixodid tick-borne borrelioses (ITBB) from Western Europe to Transbaikalia, but their role in circulation of corresponding pathogens remains unclear. This study was performed in a natural ITBB focus located in the Perm region of Russia (near the Urals), where Borrelia garinii and B. afzelii circulate and I. persulcatus serves as their main vector. In July-August of 1994, 296 small mammals (mostly Clethrionomys glareolus) were tested for tick infestation. From these mammals, 49 I. trianguliceps and 252 I. persulcatus ticks were collected (16.3 and 83.7%, respectively). I. trianguliceps ticks were found on 33 rodents of three species: Cl. glareolus, Cl. rutilus, and Microtus oeconomus. The abundance of I. trianguliceps (on average, less than 0.2 ticks per animal) was approximately five times lower than that of I. persulcatus. I. trianguliceps larvae, nymphs, and adults (22, 15, and 5 specimens, respectively) were analyzed for Borrelia infection by plating their internal organs on the BSK-2 medium. Spirochete isolates were obtained from four nymphs. Three infected nymphs were collected from different Cl. glareolus specimens, and one was found on Cl. rutilus. According to the results of RFLP analysis, all four isolates were classified as B. garinii. This experiment is the first successful attempt to isolate one of ITBB pathogens from I. trianguliceps ticks. These ticks do not attack people, and their role in ITBB foci should be analyzed only in terms of epizootiology. The results of previous zoological-parasitological and bacteriological studies performed in the Ural region suggest that I. trianguliceps and I. persulcatus populations are maintained there by the same species of small rodents and insectivores, which mostly belong to the genera. Clethrionomys and Sorex. Many of them were identified as the reservoir hosts of Borrelia. These data, in complex with the fact of B. garinii isolation from I. trianguliceps, suggest that I. trianguliceps ticks are involved in the maintenance of Borrelia circulation in natural ITBB foci. Taking into account the low abundance of these ticks in the Ural forests, they should be regarded as an important but not principal component of the epizootic process. It is suggested that such a conclusion about the significance of I. trianguliceps ticks also pertains to ITBB foci of other regions.

Animals↗
PubMed1998

Borreliacidal factor in the blood of the western fence lizard (Sceloporus occidentalis).

In some populations of the western black-legged tick, Ixodes pacificus, the prevalence of infection with Lyme disease spirochetes (Borrelia burgdorferi) in nymphal ticks exceeds those in adult ticks by 3-4-fold. Experiments were conducted to determine if the reduced spirochetal prevalence in adult ticks is due to the presence of anti-borrelial antibodies or to another borreliacidal factor in the blood of the western fence lizard, Sceloporus occidentalis, a primary host of subadult I. pacificus, or to loss of spirochetes as nymphal ticks molt to the adult stage. Ten lizards were each exposed to the feeding activities of 10 nymphs having a 78% prevalence of B. burgdorferi infection. Five of the lizards had been hyperimmunized first with 10(8) heat-killed spirochetes and 5 were seronegative to B. burgdorferi. After repletion and the transstadial molt, none of 62 resultant adult ticks from both groups of lizards was found to contain spirochetes. In contrast, 11 of 20 (55%) infected nymphs that had fed on 4 preimmune rabbits passed spirochetes to adult ticks. Taken together, these findings demonstrate that host immunoglobulins and the transstadial molt by themselves are not necessary for eliminating B. burgdorferi from infected nymphal ticks. A novel in vitro assay revealed that nearly all spirochetes placed in plasma or sera from lizards died in less than 1 hr, whereas many spirochetes injected into mouse plasma or sera survived for 72 hr. When spirochetes were put in lizard sera that had been preheated (100 C for 10 min) and allowed to cool, survival was extended to 72 hr. We conclude that the blood of S. occidentalis contains a thermolabile, borreliacidal factor, probably a protein, that destroys spirochetes in the midgut diverticula of feeding I. pacificus nymphs.

Animals↗
PubMed2003

Relative effects of the insecticide thiamethoxam on the predator Podisus nigrispinus and the tobacco whitefly Bemisia tabaci in nectaried and nectariless cotton.

The predaceous stinkbug Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) feeds on plants as well as on arthropod prey. The question arises whether feeding on plants might expose the predator to systemic insecticide via ingestion of the active ingredient or its metabolites through plant sap of treated plants. This interaction was investigated with nectaried and nectariless cotton plants cropped in pots and treated with the systemic insecticide thiamethoxam at 0.5, 1.0 and 2.0 mg per plant as a root drench. Development of P. nigrispinus fed on prey and on treated nectaried and nectariless cotton plants and confined at 15, 30 and 45 days after insecticide application, and adult reproduction from nymphs caged 30 days after treatment were determined. Podisus nigrispinus life history traits were unaffected by the type of cotton plant, nectaried or nectariless, but were significantly affected by insecticide dose and time after application. Developmental time was extended and fresh adult body weight was reduced by feeding on prey and treated plants. Nymphs caged on treated plants with the highest thiamethoxam concentration at 15 days after application produced only 13.2% of adults. Females emerged from nymphs caged on both plants and at all thiamethoxam concentrations at day 30 after application presented similar reproductive characteristics, except for age of first oviposition, which was delayed on plants treated with the highest thiamethoxam concentration. Thiamethoxam at 0.5 mg per plant restrained tobacco whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) colonization only during the first 15 days after application to either cotton plant, and similar immature densities were sampled at day 35 after application on treated and untreated plants. However, plants treated with 1.0 and 2.0 mg per plant as a drench and cropped in pots were protected from tobacco whitefly for up to 45 days after exposure to a whitefly colony.

Animals↗
PubMed2001

Differential infectivity of two Pseudomonas species and the immune response in the milkweed bug, Oncopeltus fasciatus (Insecta: Hemiptera).

Pseudomonas aeruginosa and Pseudomonas putida show a profound differential infectivity after inoculation in Oncopeltus fasciatus. Whereas P. putida has no significant impact on nymphs, P. aeruginosa kills all experimental animals within 48 h. Both Pseudomonas species, however, induce the same four hemolymph peptides in O. fasciatus. Also injection of saline solution and injury induced these peptides. In general peptide induction was stronger in nymphs than in adult males. A significantly higher number of nymphs survived a challenge with P. aeruginosa when an immunization with P. putida preceded. The antibacterial properties of the hemolymph were demonstrated in inhibition experiments with P. putida. Two of the four inducible peptides (peptides 1 and 4) could be partially sequenced after Edman degradation and were compared with known antibacterial peptides. Peptide 1, of 15 kDa, showed 47.1% identity with the glycine-rich hemiptericin of Pyrrhocoris apterus. Peptide 4, of 2 kDa, had a 77.8% identity with the proline-rich pyrrhocoricin of P. apterus and a 76.9% identity with metalnikowin 1 of Palomena prasina. Peptides 2 and 3 are also small, with molecular weights of 8 and 5 kDa.

Amino Acid Sequence↗
PubMed1993

Cytokinin-mediated insect resistance in Nicotiana plants transformed with the ipt gene.

The bacterial isopentenyl transferase (ipt) gene involved in cytokinin biosynthesis was fused with a promoter from the proteinase inhibitor II (PI-IIK) gene and introduced into Nicotiana plumbaginifolia. Transcripts of the ipt gene were wound-inducible in leaves of transgenic PI-II-ipt plants. In leaf disks excised from fully expanded leaves, transcript levels increased 25- to 35-fold within 24 h and by 48 h were reduced by about 50%. In flowering plants, message levels were 2- to 5-fold higher than in preflowering plants. These plants were used to test for defensive properties of cytokinins against insects. Manduca sexta larvae consumed up to 70% less of the PI-II-ipt leaf material on flowering plants than larvae feeding on controls. Normal development of Myzus persicae nymphs was also delayed. Approximately half as many nymphs reached adulthood on PI-II-ipt leaves than on controls. Zeatin and zeatinriboside levels in leaves remaining on PI-II-ipt plants after hornworm feeding were elevated by about 70-fold and the chlorophyll a/b content was double that of controls. Exogenous applications of zeatin to the PI-II-ipt leaves enhanced the level of resistance to the tobacco hornworm and almost completely inhibited normal development of the green peach aphid nymphs. Transcript levels of an acidic chitinase gene were low and minimally inducible in PI-II-ipt leaves. The mode of action of the cytokinin gene product on enhanced insect resistance is not clear but may involve the products of secondary metabolic pathways.

Alkyl and Aryl Transferases↗
PubMed1987

Value of first-instar triatomines (Hemiptera; Reduviidae) in comparative xenodiagnosis of Trypanosoma (Schizotrypanum) cruzi.

A direct correlation was shown between bloodmeal intake in xenodiagnosis and subsequent infection rate with Trypanosoma (S.) cruzi, in first-stage nymphs of Panstrongylus megistus Burmeister. The parasitaemia of different hosts, or of the same host at intervals, thus can be compared indirectly by the proportion of first-stage nymphs infected in xenodiagnosis, if uniform distribution and infectivity of bloodstream trypomastigotes is assumed. This indirect comparison of host parasitaemia provides important information not obtainable otherwise, since parasitaemia often is too low for quantitative measurement. Infection rates were compared of first-instar P. megistus in experimental xenodiagnosis of patients and animals. All T. cruzi stocks originated from an endemic area of Brazil (Bahia state). Several batches of nymphs were fed sequentially on some hosts, to assess fluctuations of parasitaemia with time; in others, particularly the patients, xenodiagnosis was carried out only once.

Animals↗
PubMed1989

Development rates, fecundity and survival of developmental stages of the ticks Rhipicephalus appendiculatus, Boophilus decoloratus and B. microplus under field conditions in Zimbabwe.

To determine development rates, fecundity and survival of Rhipicephalus appendiculatus, Boophilus decoloratus and B. microplus, a study was carried out in long and short grass in the highveld of Zimbabwe. Engorged adult females of the three species and engorged larvae and nymphs of R. appendiculatus were buried beneath the soil in small cages in the rainy, cool and hot seasons in 1980 and 1981. Half the number of cages were examined regularly to determine development rates and half were left undisturbed to determine survival rates and the fecundity of engorged females. Development was most rapid during warm conditions and slowest during cool conditions, but high temperatures appeared to prolong the preoviposition periods of all species. The relationship between fluctuating temperatures and rate of development in the field was defined using a least-squares procedure. Survival of engorged females was usually high, but was reduced by predation when they were not protected. Fecundity was reduced in long grass during the cool season and in short grass during the hot season. A higher percentage of eggs hatched in the rainy season than in the cool or dry seasons. The survival of engorged larvae and nymphs was usually high in all seasons. Engorged nymphs were the hardiest stage and eggs the most suceptible stage to adverse microclimatic conditions.

Animals↗
PubMed1983

Rhipicephalus zambeziensis as a vector of bovine Theileriae.

Rhipicephalus zambeziensis was shown experimentally to transmit Theileria parva parva in cattle from nymph to adult and Theileria parva lawrencei, Theileria parva bovis and Theileria taurotragi from larva to nymph and nymph to adult. In a single trial the tick failed to transmit Theileria mutans. The tick is believed to be a vector of T. parva lawrencei in the field in Zimbabwe.

Animals↗
PubMed2002

Estimating population size and transmission bottlenecks in maternally transmitted endosymbiotic bacteria.

Many species of bacterial endosymbionts are acquired by animal hosts before birth, through direct transmission from mothers to eggs or embryos. This vertical transmission imposes a reduction in numbers or "bottleneck," and the size of this bottleneck affects the population structure and evolution of symbiotic lineages. We have estimated the size of the transmission bottleneck in Buchnera, the bacterial symbiont of aphids, using basic light and electron microscopy techniques. By serial-sectioning whole aphid abdomens, their eggs, and embryos, we determined the following parameters: (i) The average size of a Buchnera cell is 2.9 mm in diameter. (ii) The total number of Buchnera in an Acyrthosiphon pisum embryo was around 36700 whereas a first instar nymph contained more than 119000. (iii) The number of symbionts per bacteriocyte was around 800 in an embryo and 3200 in a first instar nymph. (iv) The total number of Buchnera transmitted to each sexual egg ranged from 850 in Nasonovia to 1800 in A. pisum to more than 8000 in Uroleucon ambrosiae. (v) The total number of secondary endosymbionts in A. pisum was 12170 for an embryo and 18360 for a first instar nymph. Secondary symbionts were arranged both extracellularly and in clusters of 2000-8000 bacteria inside bacteriocytes. These numbers are consistent with the few previous estimates of symbiont population sizes based on counts of gene copies.

Animals↗