Differential detachment from resting hosts of replete larval and nymphal Ixodes ticks

To determine whether replete subadult Ixodes ticks detach more frequently from resting than from active hosts, diverse rodents and lizards were caged in an apparatus designed to record the ticks' sites of detachment relative to the resting site of the host. Replete larval Ixodes ricinus and Ixodes dammini accumulated mainly beneath the resting places of the mice (Apodemus agrarius and Peromyscus leucopus) most frequently parasitized in nature. Although nymphal I. ricinus similarly detached where these mice rested, nymphal I. dammini detached more randomly. When lizards were used as hosts, both subadult stages of I. ricinus tended to detach away from their main resting sites; these ticks detached from squirrels more randomly. Detachment ratios for other rodent hosts, that are abundantly infested by the larvae of these ticks in nature (Apodemus flavicollis and Clethrionomys glareolus), could not be derived because nymphs generally failed to attach. Our observations are consistent with reports that both subadult stages of I. dammini, but not the adult, feed on the same kind of nest-dwelling hosts and that the host range of I. ricinus is less focused. Detachment of mouse-feeding larvae from resting mice promotes subsequent nymphal attachment to conspecific hosts, and the absence of such behavior among nymphs facilitates access of the resulting adults to deer.     

The detection of rickettsia-like microorganisms within the ovaries of female Ixodes ricinus ticks

An ultrastructural study of tick-borne fever (TBF)-infected Ixodes ricinus ticks revealed the presence of rickettsia-like microorganisms within the ooplasm and the mitochondria of developing oocytes. These microorganisms are similar in appearance to the TBF agent and it is possible that although transovarial transmission of the TBF agent apparently does not occur, the rickettsiae are at least able to establish themselves in the ovaries of infected ticks.     

The isolation of Saumarez Reef virus, a new flavivirus, from bird ticks Ornithodoros capensis and Ixodes eudyptidis in Australia.

Strains of a new flavivirus, for which the name Saumarez Reef Virus is proposed, were isolated from seabird ticks collected from four localities. Two strains were isolated from ticks of the species Ornithodoros capensis Neumann 1901 collected from the nests of Sooty Terns, Sterna fuscata Linnaeus 1766 on coral cays off the east coast of Queensland, Australia. The other three strains were isolated from ticks of the species Ixodes eudyptidis Maskell 1885 taken from two dead Silver Gulls Larus novaehollandiae Stephens 1826 in northern Tasmania. The new virus was compared serologically with 50 other flaviviruses at the Yale Arbovirus Research Unit and was found to be most closely related to Tyuleniy virus.     

Genetic variation within the ticks Ixodes holocyclus and Ixodes cornuatus from south-eastern Australia

Ticks from mainland Australia (Victoria, New South Wales and Queensland) and Tasmania, identified morphologically as either Ixodes holocyclus or Ixodes cornuatus, were compared genetically using 24 enzyme loci. The results showed that ticks from three localities in Victoria were genetically similar to I. cornuatus in Tasmania, but both groups had fixed genetic differences at >45% of loci compared with other ticks on the mainland. In addition, there were fixed genetic differences at 0-60% of loci among I. holocyclus from different localities on the mainland. Ixodes holocyclus samples could be divided into four distinct clusters (with fixed genetic differences >15%), three of which were represented by one or two specimens. Nonetheless, these electrophoretic data suggest that I. holocyclus represents a species complex. The results also showed that the morphological criteria used to identify specimens were not always accurate because several specimens had been mis-identified morphologically. Despite limitations with the morphological identification, this study has demonstrated that I. cornuatus can be distinguished from the I. holocyclus species complex using six enzyme loci, providing the foundation for a re-examination of morphological characteristics. The present study has shown that I. cornuatus and the I. holocyclus complexes have a greater distribution than previously reported, with both occurring in sympatry at Cape Patterson, on the southern coastline of Victoria.     

A proteomic approach to the identification of salivary proteins from the argasid ticks Ornithodoros moubata and Ornithodoros erraticus

The saliva of ticks contains anti-haemostatic, anti-inflammatory and immunomodulatory molecules that allow these parasites to obtain a blood meal from the host and help tick-borne pathogens to infect the vertebrate host more efficiently. This makes the salivary molecules attractive targets to control ticks and tick-borne pathogens. Although Ornithodoros moubata and O. erraticus are important argasid ticks that transmit severe diseases, to date only a few of their salivary proteins have been identified. Here we report our initial studies using proteomic approaches to characterize the protein profiles of salivary gland extracts (SGE) from these two argasids. The present work describes the proteome of the SGEs of both tick species, their antigenic spots, and the identification of several of their proteins. The whole number of identifications was low despite the good general quality of the peptide mass maps obtained. In the O. moubata SGE, 18 isoforms of a protein similar to O. savignyi TSGP1 were identified. In the O. erraticus SGE we identified 6 novel proteins similar to unknown secreted protein DS-1 precursor, NADPH dehydrogenase subunit 5, proteasome alpha subunit, ATP synthase F0 subunit 6, lipocalin and alpha tubulin. Finally, the current drawbacks of proteomics when applied to the identification of acarine peptides and proteins are discussed.     

Effect of host lizard anemia on host choice and feeding rate of larval western black-legged ticks (Ixodes pacificus)

Although ticks are known to exhibit preferences among host species, there is little evidence that ticks select hosts within a species based on physiological condition. It may be beneficial for ticks to choose hosts that are easier to feed upon if the ticks can perceive indicative chemical or other signals from the host. For example, if ticks can detect host hematocrit they may choose hosts with high hematocrit, facilitating a faster blood meal. It may similarly be adaptive for ticks to avoid anemic hosts because it may be difficult for them to obtain an adequate meal and feeding duration may be extended. We tested the hypothesis that larval western black-legged ticks (Ixodes pacificus) detect host hematocrit using external cues and choose healthy over anemic hosts, allowing them to feed more quickly. We presented groups of larval ticks with pairs of healthy and anemic male western fence lizards (Sceloporus occidentalis), allowed them to select a host, and measured the feeding duration of the ticks. We found that the ticks did not exhibit a statistically significant preference for healthy over anemic lizards, but that the ticks fed to repletion significantly faster on healthy hosts than on anemic hosts. Larval ticks may not be able to detect external cues indicating the health of the host, at least not in terms of their hematocrit. The extended feeding duration likely reflects the extra time needed for the ticks to concentrate the blood meal of their anemic hosts.     

Parasitism of different larval stages of Cameraria ohridella

About 20 species of parasitic Hymenoptera havebeen reported from the horse chestnutleafminer, Cameraria ohridella Deschka & Dimic (Lepidoptera: Gracillariidae). Generally,parasitism is low compared to other closelyrelated leafminers and the parasitism levelvaries considerably. Among other reasons,parasitism rates depend on the developmentalstage of the moth and therefore vary with thesampling date. In the current study,investigations on the parasitism of the moth'sfirst generation were carried out in order todetermine which preimaginal stages areparasitized by the most abundant parasiticwasps. Minotetrastichus frontalis (Nees),Pnigalio agraules (Walker) and Chrysocharis nephereus (Walker) (allHymenoptera: Eulophidae) developed as larval orpupal parasitoids and preferred later larvalinstars of the moth. Egg parasitism did notoccur. Overall, the last two of the six larvalinstars (the spinning instars) of the leafminersuffered the heaviest attack. In concordancewith the fairly low parasitism rates, theeffect of the four most abundant chalcidoids onthe leafminer population was negligible, havingno significant influence on the mortality ofC. ohridella. Although the speciescomposition of the parasitoid complex of C. ohridella shows similarities with thesituation found in other closely relatedleafmining moths, it is unlikely that thenaturally occurring chalcidoids will be able toprevent the horse chestnut leafminer fromdeveloping epidemic population densities in thenear future.     

The affinities of mites and ticks: a review

Mites and ticks can be divided into two well-defined clades, Anactinotrichida and Actinotrichida, for which a recent work formalized a suite of putative autapomorphies and reciprocal differences. Whether they are sister-taxa – forming a monophyletic Acari – is more controversial. Earlier supporters of two independent origins for mites largely failed to demonstrate convincing synapomorphies between either of the two lineages and other arachnid orders; although recent work on reproductive biology revealed explicit characters of this nature. Furthermore, some of the characters proposed in support of a monophyletic Acari do not stand up to detailed scrutiny when compared with Arachnida in general. Effective morphological comparisons between mites and other arachnids are hindered by incompatible nomenclature and long-standing, mite-specific characters which are difficult to score for other arachnids. Furthermore, taxon-specific characters restricted to individual mite groups have sometimes been treated erroneously as 'typical' for all Acari. Here, previous hypotheses of mite affinities are reviewed. Historically, authors have debated whether mites are basal arachnids or highly derived. Excluding weakly supported early hypotheses, mites have been resolved – in whole or in part – as sister-group of all other Arachnida (based on tagmosis), closely related to Opiliones (based mostly on genital morphology), Palpigradi (based on controversial interpretations of limb morphology), Solifugae (based mostly on the mouthparts, but now perhaps also reproductive characters) and Ricinulei (based on hexapodal larvae and perhaps mouthparts). We cannot provide a final resolution here, but we aim to highlight important character sets which should be included in subsequent phylogenetic analyses, as well as useful areas for future investigations: particularly tagmosis and the nature of the gnathosoma.     

Losses cause by ixodid and demodectic ticks and mites in the tanning industry

Damage done to skin of cattle and defects of raw leather, which are caused by ixodid and demodecid ticks, parasitic on animals, are described. Losses of tanning industry amount to 1.6 to 3.7 thousand roubles per each thousand of finished box-calf leathers.     

Ornithodoros porcinus ticks, bushpigs, and African swine fever in Madagascar

African swine fever (ASF) has recently made its appearance in Madagascar. Ticks of the Ornithodoros moubata group, considered to be O. porcinus Walton, 1962 were formerly known to occur in western Madagascar, but seem to have disappeared from that region. However, three new sites where they occur were found in the humid and cool central highlands of Anatananarivo province. These ticks are known to be efficient reservoirs and vectors of ASF and constitute a considerable complication to the control of the disease. The authors also discuss another potentially complicating factor, the presence of a species of African bushpig, Potamochoerus larvatus.     

Control of sex ratio by female spider mites

Control of sex ratio in the progenies of mated female spider mites was investigated in two laboratory experiments. In Experiment I, a single strain of Tetranychus urticae Koch was reared in four different environments. In Experiment II, 4 different geographic strains of T. urticae were reared in a single environment.Results indicated that spider mite females were able to control the sex ratio of their progeny at two levels: an initial control of mean population ratio according to ovipositional environment. In addition, a secondary control resulted in an approximately uniform daily ratio. Although each parental female produced a varying number of eggs from day to day, a more or less constant fraction of those eggs were fertilized every day. It is concluded that both of these characteristics are probably important to the colonizing ability of the species.

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Résumé L'étude de la régulation du sexe de la descendance de femelles inséminées d'acariens est basée sur deux expériences de laboratoire. Dans l'expérience I, une lignée de Tetranychus urticae a été élevée dans deux conditions différentes de qualité des feuilles pendant le développement des parents, d'une part, pendant leur ponte et le développement de la descendance d'autre part. Dans l'expérience II, quatre souches géographiques différentes de T. urticae ont été élevées dans les mêmes conditions.Il est apparu nettement que les femelles dans des conditions différentes ont donné des descendances avec des taux sexuels variant dans certaines limites. Ces différences étaient statistiquement significatives dans les duex lots de données expérimentales. Les taux sexuels des populations d'acariens variaient aussi avec les conditions écologiques. Dans les bonnes conditions, la proportion de femelles dans la descendance était la plus élevée. Les taux sexuels des populations variaient aussi entre les quatre souches géographiques.Les analyses ont aussi révélé que les femelles d'acariens sont capables de contrôler le taux sexuel à deux niveaux: une régulation initiale du taux de la population en fonction des conditions écologiques ou de la lignée géographique et un contrôle secondaire qui s'est traduit par un taux quotidien approximativement uniforme.En utilisant un argument mathématique simple incorporant la fécondité caractéristique des acariens, nous avons conclu que ces deux caractéristiques de la rulation sont probablement d'une importance capitale pour le pouvoir colonisateur de cette espèce.

     

Ixodes ticks: serum species sensitivity of anticomplement activity

Ixodid ticks feed for extended periods of up to 2 weeks or more. To complete engorgement, they must overcome their host's innate immune mechanisms of which the complement system is a major component. Using in vitro assays, salivary gland extracts of the ixodid ticks, Ixodes ricinus, I. hexagonus, and I. uriae, were shown to inhibit activity of the alternative pathway of complement. The ability of the different Ixodes species to inhibit complement activity varied with the animal species used as a complement serum source. Serum species sensitivity correlates to the reported host range of the tick species tested.     

Loss of larval parasitism in parasitengonine mites

Larval Parasitengona are typically parasites, yet at least 29 species of water mites and one species of Trombidiidae forgo larval feeding and any association with a host. Species with non-feeding larvae are isolated cases within species groups or genera where the remaining species have parasitic larvae. Species without larval parasitism occur in at least 14 genera, eight families and four superfamilies of water mites; the loss of larval parasitism is presumably polyphyletic, having occurred at least 21 times. Lineages of water mites with non-feeding larvae frequently exist in parallel with almost identical populations or species that have parasitic larvae. Thus, there is tremendous potential for studies comparing the relative merits of the two life history strategies. Comparisons indicate that adults from lineages with non-parasitic larvae produce smaller numbers of larger eggs; the extra nutrition included in larger eggs permits the larvae to forgo feeding. Non-feeding larvae frequently have wider dorsal plates but reduced leg length, setal length and sclerotization when compared to parasitic larvae from sister lineages. The adults of lineages with non-feeding larvae are frequently smaller in comparison to adults of sister lineages with parasitic larvae. There is no apparent pattern in relation to habitat: lineages lacking larval parasitism occur in streams, temporary ponds and the littoral and planktonic regions of permanent lakes. © Rapid Science Ltd. 1998     

Borrelia burgdorferi sensu lato in the female cement plug of Ixodes persulcatus ticks (Acari,Ixodidae)

Borrelia burgdorferi sensu lato was detected in one out of five cement plugs of female Ixodes persulcatus ticks. The spirochetes were found by dark field microscopy as early as 18 h after attachment of the ticks to the skin of a white mouse. The relevance of this finding is discussed in relation to the epidemiology of Lyme Borreliosis.