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PubMed1993

Oxygen consumption of engorged nymphs and unfed adults of Hyalomma asiaticum ticks (Acari: Ixodidae) exposed to various photoperiods.

The oxygen consumption of engorged nymphs of Hyalomma asiaticum was measured at various intervals after drop-off from mice hosts. Duration of nymphal development to the emergence of adults was 25-32 days at 25 degrees C. The oxygen consumption was high immediately after completing the blood meal (193-248 mm3 g-1 h-1 but decreased significantly 18 days later (at 25 degrees C) to 45-65 mm3 g-1 h-1. It increased again before ecdysis (81-102 mm3 g-1 h-1, and also after ecdysis in freshly moulted adults (177-220 mm3 g-1 h-1. The oxygen consumption in 8-month-old adult ticks was very variable ranging from 40-42 to 172 mm3 g-1 h-1. Neither engorged nymphs nor unfed adult ticks showed any dependence of their respiratory metabolism on the photoperiodic regimes tested (LD 20:4 and LD 12:12, with or without transfer to an alternative photoperiod after engorgement of nymphs).

Animals↗
PubMed1993

Ticks (Acari: Ixodidae) infesting the Arabian camel (Camelus dromedarius) in the Sinai, Egypt with a note on the acaricidal efficacy of ivermectin.

In this study, tick burdens on camels (Camelus dromedarius) were determined in the vicinity of the St. Catherine monastery, Sinai, Egypt. In total 2,545 ticks (1,491 adults and 1,054 nymphs) were collected and identified. Mean tick burdens were relatively heavy and the range in number of ticks per camel was very broad (6-173). Hyalomma dromedarii was the predominant tick species and accounted for 95.6% of the adult ticks. Other ticks found were H. marginatum subspp. and H. anatolicum excavatum. All nymphs collected were Hyalomma spp. In addition, the effect of ivermectin (Ivomec MSD AGVET) on tick burdens, when given subcutaneously at 0.2 mg/kg-1, was evaluated in nine camels in the date-palm plantation of Kibbutz Yahel in the Arava valley, Israel. Initial tick burdens on these camels (half-body tick counts) ranged from 20-105 ticks per camel. Seven camels from the same herd with half-body tick counts ranging from 40-107 ticks per camel were not treated and served as a control group. Ivermectin was not effective against Hyalomma tick infestation in camels under these conditions.

Animals↗
PubMed1994

Vertical migration of adult Ixodes rubicundus, the Karoo paralysis tick (Acari: Ixodidae).

Mortality due to Karoo paralysis amongst livestock is of considerable economic importance in South Africa. Indications are that the extent of vertical migration of adult ticks, to reach questing positions on grasses, is influenced by sudden climatic changes. Such influences as well as selection of questing substrates were investigated under controlled conditions. Vertical migration of adult Ixodes rubicundus on copper rods was determined in a square metal arena within a closed glass container in a room in which temperature and light could be controlled. Significantly more female and male ticks migrated vertically on 1.5 mm diameter rods than on 4.0 mm rods and on 450 mm long rods than on 100 mm rods. More ticks of both sexes migrated vertically at RH > 80% than at RH < 50% and at 12 degrees C than at 21 degrees C. More female than male and more older than younger ticks migrated vertically in all experiments. The results of this study contribute towards an understanding of the epidemiology of Karoo paralysis.

Animals↗
PubMed1994

Localization of insulin-like immunoreactivity in the synganglion of nymphal and adult Dermacentor variabilis (Acari: Ixodidae).

Immunocytochemical staining based on a peroxidase-antiperoxidase method showed neurosecretory cells (NSC) reactive to bovine insulin in five of 18 paraldehyde fuchsin-positive neurosecretory regions (NSR) in the synganglion of unfed adult Dermacentor variabilis. This is the first report of a neuropeptide in an ixodid tick. The insulin-specific immunoreactive cells included the posterior medial group of the protocerebral center, posterior group of dorsal opisthosomal center, anterior lateral group of the dorso-lateral cheliceral center, dorsal group of the frontal stomodeal center, and anterior group of the ventral palpal center. After feeding and mating, females no longer had immunoreactive cells in three of five NSR found in virgin, unfed females. However, two cells of the posterior group in dorsal opisthosomal center and anterior lateral group of the dorso-lateral cheliceral center remained immunoreactive throughout feeding. Fed, mated males continued to display immunoreactive cells in four of five NSR found in the virgin, unfed males. All developmental stages of nymphs examined had insulin-specific immunoreactive cells in two of the five NSR found in unfed adults, including two positively stained cells of the posterior group in dorsal opisthosomal center and anterior group of ventral palpal neurosecretory center.

Animals↗
PubMed1993

Ability of successful attack in two species of ixodid ticks (Acari: Ixodidae) as a manifestation of their aggressiveness.

Patterns of attacking hosts by two closely related species of ixodid ticks (Ixodes persulcatus and I. ricinus) were compared in parallel field tests. The ability of active unfed adults of both sexes to adhere to a flannel flag dragged over grass vegetation and to remain on the flag during this process were estimated. The tests were conducted under two temperature conditions, 6-10 degrees C and 17-22 degrees C. In all test versions, adults of I. persulcatus were more successful both in adhering to the flag and in remaining on it. There were no consistent differences between males and females of the same species. The results demonstrated a differing ability of successful attack in both tick species. This ability is a complex derivative of the tick activity and aggressiveness. An attempt is made to analyse the latter phenomenon, which is considered as a general one for all bloodsucking arthropods. The aggressiveness of arthropods should be taken into account as one of the leading factors influencing the sampling results.

Animals↗
PubMed1994

Comparative reproduction and nonparasitic development of Boophilus microplus and hybridized Boophilus ticks (Acari: Ixodidae) under natural field conditions in subtropical south Texas.

The reproductive biology and nonparasitic development of Boophilus microplus (Canestrini) and hybridized Boophilus ticks (B. annulatus (Say) male x B. microplus female) held under natural field conditions in south Texas throughout the year were compared. Comparisons between the two types of ticks indicated that the ovipositional biology (percentage of ovipositing females and number of eggs laid) of the females favored hybrid ticks during some months and B. microplus ticks during other months. However, on a year long basis, there was virtually no difference in the percentage of ovipositing females or in the number of eggs deposited by hybrid females as compared to B. microplus. The duration of each nonparasitic development period (preoviposition period, incubation period of eggs, and larval longevity) showed that both types of ticks had very similar developmental and survival rates during the year. Generally the difference in duration of each of the nonparasitic parameters was < 8 days, leading to a high degree of synchrony of the nonparasitic developmental rates between the two types of ticks. On the other hand, egg hatchability of hybrid ticks was consistently lower than pure-strain B. microplus throughout the year with significantly lower hatch rates occurring in April, July, August, October, and November. Thus, results obtained on percentage of ovipositing females, number of eggs laid, preoviposition period, incubation period of eggs, and larval longevity provide encouragement for the possible use of sterile hybrid males as a means of eliminating a native B. microplus population. In contrast, results of the egg hatchability of the two types of ticks indicate that the selective advantage afforded to B. microplus could have an adverse affect on the success of a sterile hybrid male program by making the number of hybrid ticks necessary to eliminate a native population prohibitively high.

Animals↗
PubMed1994

Transmission of injected DNA sequences to multiple eggs of Metaseiulus occidentalis and Amblyseius finlandicus (Acari: Phytoseiidae) following maternal microinjection.

The persistence of DNA injected into two species of adult female phytoseiids and its transmission to serial eggs deposited by them was assessed by the polymerase chain reaction (PCR). The effect of DNA concentration on persistence and transmission was examined in Metaseiulus occidentalis. M. occidentalis females were microinjected with plasmid DNA at three different concentrations (250, 500, 750 ng microL-1) and allowed to deposit one to five eggs before the females and their last eggs were analyzed. Plasmid DNA was found in 82% of the females assayed and in 70% of all the eggs analyzed (including the fifth eggs produced after microinjection). Transmission of DNA to multiple eggs was also examined in Amblyseius finlandicus. Females of this species are less traumatized by microinjection allowing analysis of transmission over a more extended number of eggs. Females were microinjected and allowed to deposit eggs until their death. DNA from every fifth egg was analyzed by the PCR. PCR products were amplified from 51% of the eggs and from all egg classes except the 30th egg. The persistence and presence of plasmid DNA in both eggs and females suggests that (1) maternal microinjection is a more efficient method for DNA delivery than traditional egg microinjection, (2) it may be possible to isolate transformants from fewer maternally-microinjected females than originally expected, and (3) maternal microinjection could be useful as a DNA delivery system in other phytoseiids.

Animals↗
PubMed1994

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 appeniculatus. 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 inanimate 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.

Animals↗
PubMed1994

Intraspecific diversity of the Cassava green mite Mononychellus progresivus (Acari: Tetranychidae) using comparisons of mitochondrial and nuclear ribosomal DNA sequences and cross-breeding.

Intraspecific diversity in Cassava Green Mite Mononychellus progresivus Doreste was examined using individuals collected in Benin and the Congo and in Columbia and Brazil. Comparisons were based on mitochondrial and ribosomal DNA sequences and the results of several cross-breeding experiments. Sequence variation was examined in a total of 1139 base pairs (bp) constituting the ITS2 ribosomal DNA (805 bp) and a fragment of the Cytochrome Oxidase I (COI) gene (334 bp). Sequence divergence is low, ranging from 0% to 2.1% for COI and from 0% to 0.4% for ITS2. Inter-strain comparisons have shown that the two African populations appear to be identical. They were similar to the Colombian population while the Brazilian population was clearly different. The data support the hypothesis of a single introduction of the species in the two African populations. Crossing experiments have shown partial hybrid sterility, suggesting a genetic incompatibility consistent with differences detected by sequence data. The results show the usefulness of molecular markers as a tool for determining taxonomic status and dispersion paths in spider mites.

Animals↗
PubMed1996

Seasonal incidence of Ixodes ricinus ticks (Acari:ixodidae) on rodents in western France.

Data collected from a longitudinal survey carried out over 2 years on four farms in western France were used to assess the incidence and infestation of Ixodes ricinus on rodents. Once a month, on each farm, 25 Sherman live traps were set in hedges bordering selected pastures. A total of 799 micromammals were examined, including Apodemus sylvaticus, Clethrionomys glareolus, Microtus agrestis, Microtus arvalis, and Crocidura spp. Larvae and nymphs of I. ricinus were found. Small numbers of Ixodes (Exopalpiger) trianguliceps were also recovered from each farm. The mean infestation rate of the I. ricinus larvae (1.6-5.9) among all animals examined varied between farms Most animals were infested by only a single tick, but one M. agrestis harboured 43 I. ricinus larvae. Larvae or nymphs were found throughout the year, with peaks from March to October.

Animals↗
PubMed1996

Reproductive bionomics of the soft tick, Ornithodoros turicata (Acari: Argasidae).

The effects of different temperatures and relative humidities (RHs) were tested on various reproductive parameters of Ornithodoros turicata, an argasid tick that inhabits gopher tortoise burrows in Florida, USA. The pre-oviposition, oviposition and incubation periods of the ticks decreased as temperature increased. These periods were also affected by the RH. The number of eggs oviposited was affected significantly by the combined effect of temperature and RH. Fewer eggs were laid by ticks in the 24 degrees C regimes and the 27 degrees C/95% RH regime compared to those in the other temperature/RH groups. There was an inverse relationship between the number of eggs oviposited and the percentage of hatched larvae that was correlated with the temperature and RH. Ticks reared at 27 degrees C/90% RH and 30 degrees C/90% RH laid more eggs than those reared in the other combinations of temperature and humidity but fewer larvae hatched from these eggs. The reproductive fitness index (RFI) values were highest in females held in the 24 degrees C groups and the 30 degrees C/95% RH group, although significantly more larvae hatched at the lower temperatures. The optimum reproductive conditions for O. turicata under laboratory conditions appear to be 24 degrees C and 90-95% RH. While mating occurred at all temperatures, none of the females laid eggs at 22 degrees C. The ticks may move preferentially to low temperatures when not feeding to remain above the critical equilibrium humidity and/or below the critical metabolic level necessary for prolonged survival. However, most female ticks oviposited after 45 days when moved to 27 degrees C/95% RH. Ornithodoros turicata females may have a limited capability to delay oviposition until an optimal microenvironment for egg deposition can be located in the burrow.

Animals↗
PubMed1995

Seasonal incidence and ecology of the tick Ixodes ricinus (Acari: Ixodidae) on grazing pastures in western France.

A longitudinal survey was carried out during a 2 year period in Western France to assess the infestation level of grazing pastures by Ixodes ricinus ticks. Four farms were visited once a month and each of the grazing pastures was sampled in the centre and at the border using the blanket dragging method. A total of 3562 I. ricinus (34 adults, 900 nymphs and 2628 larvae) were collected and the infestation was significantly higher during the first year (p < 0.0001). The infestation level by I. ricinus varied between grazing pastures and farms. Grazing pastures in the vicinity of forest were more infested than the others, all through the study. The seasonal distribution of ticks showed peaks, with low fluctuations between farms, years and stages. Tick abundance could not be related to vegetation, but only to the vicinity of woods.

Animals↗
PubMed1995

Host-seeking behaviour by Australian ticks (Acari: Ixodidae) with differing host specificities.

Ticks generally detach from their hosts into sites where they are later exposed to host species which may or may not be suitable for infestation. The question of how four species of ixodid ticks, with differing specificities, behave towards such potential host species was examined. Observations of the generalists, Aponomma hydrosauri and Amblyomma limbatum and the specialists, Aponomma fimbriatum and Aponomma concolor, showed that the generalists were attracted to a wider range of potential host species than the specialists and that the larval stages of all tick species, regardless of specificity, contacted more potential host species than the adults. The interspecific differences may be attributed to reliance on different sets of host cues, while the intraspecific differences may reflect the developmental state of the sensory system.

Animals↗
PubMed1994

Transient expression of a Drosophila melanogaster hsp70 promoter/lacZ construct injected into larvae of two species of predatory mites (Acari: Phytoseiidae).

The Drosophila melanogaster heat shock 70 promoter (hsp70) was used to regulate expression of the Escherichia coli beta-galactosidase gene (lacZ) in transiently-transformed predatory mite larvae. A construct containing the hsp70 promoter upstream of the D. melanogaster alcohol dehydrogenase (adh) translational start site and Escherichia coli lacZ gene fusion (adh/lacZ) was injected into larvae of Metaseiulus occidentalis and Amblyseius finlandicus. LacZ expression was compared to expression of a similar construct lacking any upstream regulatory sequence. Expression from the hsp70 promoter was strong and heat shock-dependent in both species. The Drosophila hsp70 promoter therefore appears useful for regulating expression of exogenous DNA in both phytoseiid species and may be broadly applicable in the Phytoseiidae. Furthermore, the lacZ gene is a useful gene for analysis of expression in both species. Larval microinjection provides a method of assessing transient expression and of examining native regulatory sequences in these two phytoseiids and will likely be useful in other phytoseiid mites with only minor modifications.

Animals↗
PubMed1982

Unusual structural changes in mitochondria during spermiogenesis in the oribatid mite, Hafenrefferia gilvipes (Acari).

During spermiogenesis in the oribatid mite, Hafenrefferia gilvipes, striking alterations in the structure and location of mitochondria in spermatids were observed. The structural changes include formation of a single, distended annular crista, which subsequently becomes tubular. Initially, the mitochondria are located in central regions of the cytoplasm, they then move first to the plasmalemma and subsequently to the nuclear envelope, and finally are engulfed in the nuclear material.

Animals↗
PubMed1978

Moulting and morphogenesis of sensilla in a prostigmate mite (acari, actinotrichida, actinedida: caeculidae) I. Mechanoreceptive bristles.

In the prostigmate mite Microcaeculus steineri delamarei moulting and morphogenesis of mechanoreceptive sensilla were studied by electron microscopy and compared to corresponding sensilla of other arthropods. Dendritic contact with the cuticular parts of old sensilla breaks down during apolysis. Two groups of cells are engaged in the formation of new sensilla: 1) several trichogen and two tormogen cells in a semicircular arrangement, and 2) two sheath cells surrounding the mechanoreceptive dendrites. Cells ensheathing the dendrites do not play any part in the formation of bristles. These observations differ from those on insect sensilla during moulting.

Animals↗
PubMed1980

Regional specialization of the sperm membrane in the tick Amblyomma hebraeum koch (Acari: Ixodidae).

The spermatozoon of Amblyomma hebraeum is about 200 micrometers long and comprises: (l)a thick, club-shaped anterior part, about 20 micrometers long bearing at its apex a "tactile" hemisphere, and (2) an elongated tail-like part, about 180 micrometers long. The surface of the "tactile" hemisphere is covered by numerous bulbous expansions, attached to it by short stalks. The base of the hemisphere is surrounded by a fringe of thin motile processes; the remaining surface of the spermatozoon is covered with long cellular processes which run more or less parallel to one another. The membrane-associated particles found on the membrane beneath the cellular processes are regularly arranged as groups of parallel strands. The external surface of the so-called "peripheral granules", as revealed by freeze-etching, is smooth with a very small number of particles. Internally the particles exhibit a regular hexagonal pattern which has not been observed, so far, on any other membrane of these sperm cells. The regional specialization of the spermatozoon surface membrane in relation to sperm motility is discussed. The results obtained indicate that processes of three types: (1) bulbous expansions, (2) motile processes, and (3) cellular processes are regional specializations, all engaged in aspects of sperm motility.

Acrosome↗