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PubMed1997

Characteristics of acyrthosiphon pisum virus, a newly identified virus infecting the pea aphid.

A new virus was isolated from the pea aphid, Acyrthosiphon pisum, and tentatively named Acyrthosiphon pisum virus (APV). The isometric virus particles were approximately 31 nm in diameter and contained a single-stranded RNA molecule of approximately 10 kb. Four structural proteins were observed with molecular masses of approximately 23.3, 24.2, 34.5, and 66.2 kDa. The 34.5-kDa capsid protein was the most abundant product in purified virions. Computer-assisted analysis revealed no significant homology between an internal sequence of 37 amino acids of the 34.5-kDa protein of APV and other polypeptides of viral origin. APV was not immunologically related to other ssRNA viruses from hemipteroid insects, such as aphid lethal paralysis virus, Rhopalosiphum padi virus, and Nezara viridula virus type 1. Immunolocalization on ultrathin sections of 3-day-old nymphs of A. pisum showed that APV antigen was predominantly present in the epithelial cells of the digestive tract. Virus particles were also observed associated with the microvilli of the intestine. Occasionally, muscle cells and mycetocyte cells were found infected. Purified APV, fed to 1-day-old A. pisum nymphs, significantly reduced the growth of the aphid and increased the time needed to reach maturity.

Amino Acid Sequence↗
PubMed1983

Adipokinetic hormone and AKH-like peptide demonstrated in the corpora cardiaca and nervous system of Locusta migratoria by immunocytochemistry.

An antiserum was raised against tyrosine-adipokinetic hormone ([Tyr1]-AKH). In immunohistochemical procedures, it revealed the AKH cells in the glandular lobes of the corpora cardiaca (CC) of Locusta migratoria with high specificity. In addition, an immunologically related peptide was detected in certain neurons of the central nervous system which suggests that this AKH-like peptide may have a neurotransmitter function. The glandular lobes contain immunoreactive AKH cells in all post-embryonic stages, and no essential differences in morphology and distribution of the cells in nymphs and adults were seen. The amount of AKH, stored predominantly in the cell projections, differ widely among cells and individuals. The brain of adults and nymphs contains several small populations of intensely stained neurons. In last-instar and adult specimens, each half contains 10-12 "normal"-sized neurons in the protocerebrum (including the optic lobe) and deutocerebrum, and in addition 15-18 small reactive neurons. Their axons and numerous branchings traverse the neuropile of proto-, deuto-, and tritocerebrum, except for the pedunculate bodies and antennal lobes. Some of the axons run into the storage lobe of the CC; it is unknown if their content is released into the haemolymph. Other axons run into the ganglia of the stomatogastric nervous system and into the circumoesophageal connectives. The suboesophageal ganglion also contains 8 immunoreactive neurons. It is unknown to which extent the immunoreactive substances in glandular and nervous tissue are chemically and physiologically related.

Animals↗
PubMed1988

The infection of various tick species with Babesia bigemina, its transmission and identification.

Strains of Boophilus decoloratus and B. microplus were easily infected with a single stock of Babesia bigemina; Boophilus annulatus could be infected less easily, and it was difficult to infect Rhipicephalus evertsi. Two strains of R. appendiculatus and one strain each of R. bursa and Hyalomma anatolicum excavatum were refractory. The same stock of B. bigemina was transmitted by nymphs and adults of B. decoloratus but only by nymphs of R. evertsi. Vertical infection was not observed in R. evertsi, whereas it persisted in B. decoloratus for at least two generations. The sporokinetes in the hemolymph of R. evertsi were significantly shorter than those in the three Boophilus species.

Animals↗
PubMed1987

The development of Amblyomma americanum and Dermacentor variabilis (Acari: Ixodidae) fed on rabbits immunized with tick hemolymph.

The possibility of interfering with the normal function of tick hemolymph using antihemolymph antibodies taken in with the bloodmeal, was investigated. Cell free hemolymph from replete Amblyomma americanum and Dermacentor variabilis ticks was used to immunize rabbits. Immunized rabbits developed high antihemolymph antibody titers (ca. 10(5)) and had no ill side effects. Rabbits were simultaneously infested with larvae, nymphs, and adult ticks. The biological performance of ticks fed on immunized rabbits was virtually identical to that of ticks fed on nonimmunized rabbits. Usually, the mean engorgement weights of nymphs and females and the weights of the egg masses of both species were slightly higher for ticks fed on the nonimmunized rabbits but differences were not significant (P greater than 0.05) due to a large standard deviation. The possibility of deactivating a single hemolymph component with specific antibodies is discussed.

Animals↗
PubMed1990

Gross morphological changes in the salivary glands of Ixodes ricinus (Acari, Ixodidae) between bloodmeals in relation to active uptake of atmospheric water vapour.

The gross morphological changes in the salivary glands of Ixodes ricinus (L.) were investigated at the light microscopic level in various phases off the host with emphasis on the engorged nymph, in order to relate the capability of active vapour uptake in the course of postembryonal development to degeneration and regeneration of salivary-gland alveoli. Agranular alveoli in engorged immatures of I. ricinus, from detachment to the following early pharate phase, do not appear different from those of the unfed instars. This is also true for the female up to approximately the end of oviposition. During moulting, the agranular alveoli of the immatures degenerate and new ones are formed which are apparently already functional in teneral nymphs and adults. In contrast, granular alveoli, much enlarged in freshly detached immature I. ricinus, shrivel in the early post-repletion period and soon reach a highly reduced state which is maintained until apolysis. Subsequently, they disintegrate completely. The finding that engorged and detached immatures of I. ricinus with markedly atrophied granular alveoli are capable of active vapour uptake until some days after initiation of apolysis suggests that only agranular alveoli are responsible for producing the primary secretion involved in vapour uptake.

Animals↗
PubMed1991

Predators of the tick Amblyomma variegatum (Acari: Ixodidae) in Guadeloupe, French West Indies.

Some vertebrate species in Guadeloupe are predators of free or parasitic stages of Amblyomma variegatum (Fabricius). Among birds, 1.9% of the 421 identified animals found in the stomachs of grackles (Quiscalus lugubris), 1.6% of the 364 animals found in the stomachs of free-ranging chickens, and 0.3% of the 4642 animals found in the stomach of cattle egrets (Bubulcus ibis) were A. variegatum ticks. The most efficient predator of ticks was the tropical fire ant, Solenopsis geminata, which was observed to only attack engorged stages of ticks. An average of 8% of the 564 individual ticks or batch of ticks released on the ground, mainly in a grass environment, were attacked by this ant species. Mice (Mus musculus) and mongooses (Herpestes auropunctatus) feed on engorged nymphs and female ticks. None of the 15 strains of entomophagous nematodes, genera Steinernema and Heterorhabditis, experimentally put in contact with engorged larvae and nymphs were able to parasitize them. In the laboratory, the insects Megaselia scalaris (Diptera) and Tineola sp. (Lepidoptera) were occasionally found to feed on engorged and unfed ticks, respectively.

Animals↗
PubMed1991

Seasonal occurrence of the bont tick (Amblyomma hebraeum) in the southern lowveld of Zimbabwe.

The seasonal occurrence of the bont tick Amblyomma hebraeum was recorded over 2 years on 20 Brahman cattle held in a 240-ha paddock at Mbizi in southeastern Zimbabwe. The cattle were infested with all life cycle stages throughout the study period, and no clearly defined seasonal patterns were recorded. Males remained attached for up to about 6 months, and consequently accumulated on the cattle and outnumbered females considerably. The cattle did not acquire resistance to A. hebraeum and the abundance of the adults increased steadily over the 2 years of sampling. The occurrence of adults and nymphs on hosts appeared to be largely independent of weather, and these stages were active over the entire range of temperature and relative humidity recorded during the study period. It was concluded that unfed adults and nymphs are able to engage in host-seeking irrespective of weather conditions as they do not await hosts on the vegetation but emerge from protected microhabitats in response to specific stimuli from hosts, notably, carbon dioxide and the aggregation-attachment pheromone emitted by attached males. This behavior may explain the reported absence of a consistent pattern of seasonal occurrence of A. hebraeum at different locations in southeastern Africa.

Animals↗
PubMed1989

Instar development and disengagement rate of engorged female winter ticks, Dermacentor albipictus (Acari:Ixodidae), following single- and trickle-exposure of moose (Alces alces).

Seven hand-reared moose (Alces alces) calves and one yearling were infested with 30,000 larvae each of the winter tick. Dermacentor albipictus, either by single- or trickle-exposure (1000/day). They were examined weekly for instar changes from September/October until late May. By 2 and 3 weeks post-exposure, most larvae on single- and trickle-infested moose, respectively, had fed and molted to nymphs. Thereafter, tick development was similar between both infestation techniques. Nymphs dominated the tick population from October to mid-February, and adults from mid-February to May. The peak of host disengagement by engorged females was late March in both years. Weights of engorged females from calf moose declined over time during the disengagement period.

Animals↗
PubMed1989

Observations on successive infestations of the rabbit host by the ticks Rhipicephalus appendiculatus and R. zambeziensis (Acari: Ixodidae).

Successive infestation of the rabbit host by instars of the brown ear tick Rhipicephalus appendiculatus resulted in a progressive decline in engorgement and egg weights of adult instars and a reduction in percentage recovery of nymphs and larvae. Repetitive infestation with adults and larvae resulted in increased skin hypersensitivity reactions at the attachment site. Successive infestation with R. zambeziensis caused a more significant decline in engorgement and egg weights of adults than for R. appendiculatus. Percentage recoveries of larvae and nymphs were also significantly reduced. A cross-infestation study indicated that R. appendiculatus and R. zambeziensis share antigenic moieties.

Analysis of Variance↗
PubMed1992

Experimental transmission of Cowdria ruminantium (Rickettsiales) by the American reptile tick Amblyomma dissimile Koch, 1844.

A Senegalese isolate of the rickettsia Cowdria ruminantium was transmitted transstadially by nymphs of the American reptile tick Amblyomma dissimile. Only eight nymphs, fed as larvae on a Saanen goat reacting to heartwater, were required to transmit fatal heartwater to another susceptible goat. Since A. dissimile usually feeds on snakes, iguanas and lizards in central America, the tick is not considered to play a significant role in the transmission of heartwater between ruminants. However, the tick could play a role in maintaining a rickettsial reservoir in reptile populations, since it has been shown that an African reptile can be a subclinical carrier of C. ruminantium, infective to vector ticks.

Animals↗
PubMed1989

Characterization of a non-occluded baculovirus (subgroup C) from the field cricket, Gryllus rubens.

A non-occluded baculovirus was isolated from nymphs of the field cricket, Gryllus rubens. SDS-polyacrylamide gel electrophoresis revealed the presence of 6 major and 11 minor polypeptides in these particles. Restriction endonuclease analysis indicated that the genome, 87.0 +/- 1.8 kilobase pairs, was a closed circular DNA molecule. DNA-DNA hybridization in low strigency conditions revealed no homology with the genomes of Oryctes baculovirus or Autographa california NPV. The virus replicated in nuclei of fat body cells, and was transmitted per os to a small proportion of first instar G. rubens nymphs.

Animals↗
PubMed2002

Description of a new Babesia sp. infective for cattle in China.

A Babesia species has been identified and shown to be transmitted by Hyalomma anatolicum anatolicum in China. When larvae, nymphs and adults developed from engorged females H. a. anatolicum collected from cattle in Xinjiang province were infested onto the Babesia-free calves, piroplasms of Babesia sp. were seen in blood smears from cattle infested with nymphs (2 calves), but not from the calves infested with larvae (1 calf or adult ticks (2 calves). This Babesia sp. proved to be of low virulence, causing 3% parasites which lasted 3-4 days.

Animals↗
PubMed2002

Existence of phenol oxidase in the argasid tick Ornithodoros moubata.

Phenol oxidase (PO, EC 1.10.3.1) activity was detected in the hemolymph of the fourth instar nymphs of the argasid tick, Ornithodoros moubata, with peak levels corresponding to the days before the majority of the nymphs had molted, suggestive of a protective role of PO during the ecdysial phase. Higher PO activity was detected in plasma relative to the hemolymph and was negligible in hemocytes. The concentration of the hemolymph and plasma assayed clearly influenced the level of PO activity, and was significantly reduced ( P<0.005) after treatment with 1-phenyl-2 thiourea, a specific PO inhibitor. This is the first report of the existence of PO in the hemolymph and plasma of a soft tick species. The regulation of PO activity and its precise role in soft tick immunity, particularly during the ecdysial phase, are interesting and need to be examined further.

Animals↗
PubMed2007

Phenotypically plastic responses of green frog embryos to conflicting predation risk.

Predators have been shown to alter the timing of switch points between life history stages, but few studies have addressed switch point plasticity in prey exposed simultaneously to conflicting predation pressure. We tested hatching responses of green frog (Rana clamitans) embryos subject to perceived predation risk from chemical cues released by two stage-specific predators, predicting that these predators would elicit: (1) directional hatching responses when presented independently, and (2) intermediate phenotypic responses when presented simultaneously. R. clamitans embryos in outdoor exclosures were exposed to cues from an egg predator (freshwater leeches; Nephelopsis obscura), a larval predator (dragonfly nymphs, Aeschna canadensis), and both predators in a 2 x 2 factorial experiment, and changes in hatchling size, hatchling developmental stage, and hatching time were compared to those for control embryos. Leeches alone induced embryos to hatch at a smaller size and an earlier developmental stage than controls, while dragonfly nymphs elicited a delay in egg hatching time that was associated with larger size and later developmental stage at hatching. Embryos failed to respond to simultaneous exposure to both predators, implying that responses to each occurred concurrently and were therefore dampened. Our results indicate that prey under threat from conflicting predators may manifest intermediate defensive phenotypes. Such intermediate responses may result in elevated rates of prey mortality with possible consequences at the population level.

Adaptation, Physiological↗
PubMed2006

The phylogenetic position of Ixodes stilesi Neumann, 1911 (Acari: Ixodidae): morphological and preliminary molecular evidences from 16S rDNA sequences.

The female of Ixodes stilesi Neumann, 1911 (Acari Ixodidae) is redescribed and the male and nymph are described from specimens collected from Pudu puda (Molina) (Artiodactyla: Cervidae) in Chile. Both sexes of I. stilesi have characteristics of the subgenera Ixodes Latreille, 1795 and Ixodiopsis Filippova, 1957. The females of I. stilesi are peculiar in having the combination of the sinuous scutum outline, rounded porose areas with distinct borders separated by the width of one area, slender and long palpi, and two subequal spurs on coxa I. The male is unique in having a combination of a posteriorly wrinkled marginal folder, a basis capituli longer than wide, a non-crenulate hypostome toothed portion, two spurs on coxa II to IV and the presence of a pseudoscutum. The nymph of I. stilesi has blunt anterior and posterior processes on palpal article I (characteristics of the subgenus Ixodiopsis and some Pholeoixodes Schulze, 1942) and a wing-shaped basis capituli with a prominent triangular cornua. Phylogenetic analyses based on 16S mitochondrial rDNA sequences of 12 Neotropical and two Australian Ixodes species, plus three argasids, were carried out to clarify the position of I. stilesi. The results of phylogenetic analyses and morphological characters indicate a close relationships between I. stilesi and two other Neotropical species of uncertain subgeneric status, I. neuquenensis Ringuelet, 1947 and I. sigelos Keirans, Clifford & Corwin, 1976.

Animals↗
PubMed2005

Reduction of Theileria annulata infection in ticks fed on calves immunized with purified larval antigens of Hyalomma anatolicum anatolicum.

Larval antigen of Hyalonmma anatolicum anatolicum, the vector of Theileria annulata, was purified by two-step affinity chromatography using anti-tick gut-specific rabbit IgG and IgG from immunized cattle. The purified antigen showed the presence of a single polypeptide of 37 kDa (GHLAgP) on SDS-PAGE. Two groups (I and II) of naive crossbred calves (Bos taurus x B. indicus) were immunized with I mg of GHLAgP in three divided doses. Immunized calves of group I were also infected with a sublethal dose of T annulata along with a group of non-immunized calves (group III). Animals in groups I, II, III as well a control group (group IV) were challenged with live nymphs of H. a. anatolicum on the 10th day of immunization. There was a significant reduction in the number of emerging adults of 56.9% +/- 1.67%, in calves of group I (p < 0.01) and 63.09% +/- 1.26% in calves of group II (p < 0.001) compared to the controls. The calves of groups I and II showed antibody responses to tick antigen up to day 70 post immunization. Infection with T. annulata was determined in the salivary glands of adult ticks that developed from the nymphs used for challenge infection. In ticks taken from group I calves, there was a 75.0% +/- 0.00% infection compared with only 85.0 +/- 2.88% infection in ticks taken from calves of group III. Using PCR, a lower infection (83.33% +/- 3.33%) was detected in ticks that developed from calves of group I compared with calves from group III (90.00% +/- 2.88%). The ground-up tick supernatants (GUTS) of the ticks taken from calves of group III yielded higher infection rate and exhibited higher infectivity titre in in vitro infection assay of bovine mononuclear cells than the GUTS of the ticks taken from calves of group I. The results suggest a partial reduction in growth rate of T. annulata in ticks feeding on calves immunized with GHLAgP.

Animals↗
PubMed1985

Trypanosoma cruzi: kinetics of metacyclogenesis in adult and nymphal Panstrongylus megistus.

Adult triatomine insects, Panstrongylus megistus, naturally infected with the protozoa, Trypanosoma cruzi, contained significantly more metacyclic trypomastigote forms in their digestive tracts than did P. megistus nymphs. Metacyclics were scarce in all stages of triatomines fed once on infected mammalian hosts and subsequently starved. In contrast, triatomines fed repeatedly on infected mammalian hosts developed prolific T. cruzi infections. Repeatedly fed adults contained 14 X more metacyclics than similarly fed nymphs. Nutritional factors appear to play a key role in regulating metacyclogenesis. Control campaigns designed to alter the age structure of populations of triatomines must take notice of the high transmission potential of the adult stage.

Animals↗
PubMed1991

Development, survival, fecundity and behaviour of Haemaphysalis (Kaiseriana) longicornis (Ixodidae) at two locations in southeast Queensland.

The free-living stages of the tick Haemaphysalis (Kaiseriana) longicornis were studied at Mt Tamborine (526 m altitude) and Amberley (25 m altitude) in southeast Queensland between 1971 and 1980. Data are presented on the number of eggs and larvae produced, the moulting success of engorged larvae and nymphs and the survival and behaviour of unfed larvae, nymphs and adult females. Temperature, moisture, daylength, grass length and age of unfed ticks were investigated as sources of variation in development rates, fecundity or survival. At Mt Tamborine the life cycle was well synchronized with the seasons to produce one generation per year. At Amberley higher temperatures accelerated development rates and would have delayed diapause, so disrupting the life cycle.

Animals↗