Positive correlation of trophic level and proportion of sexual taxa of oribatid mites (Acari: Oribatida) in alpine soil systems

We investigated community structure, trophic ecology (using stable isotope ratios; (15)N/(14)N, (13)C/(12)C) and reproductive mode of oribatid mites (Acari, Oribatida) along an altitudinal gradient (2,050-2,900 m) in the Central Alps (Obergurgl, Austria). We hypothesized that (1) the community structure changes with altitude, (2) oribatid mites span over four trophic levels, (3) the proportion of sexual taxa increases with altitude, and (4) the proportion of sexual taxa increases with trophic level, i.e. is positively correlated with the δ(15)N signatures. Oribatid mite community structure changed with altitude indicating that oribatid mites occupy different niches at different altitudes. Oribatid mites spanned over 12 δ(15)N units, i.e. about four trophic levels, which is similar to lowland forest ecosystems. The proportion of sexually reproducing taxa increased from 2,050 to 2,900 m suggesting that limited resource availability at high altitudes favors sexual reproduction. Sexual taxa more frequently occurred higher in the food web indicating that the reproductive mode is related to nutrition of oribatid mites. Generally, oribatid mite community structure changed from being decomposer dominated at lower altitude to being dominated by fungal and lichen feeders, and predators at higher altitude. This supports the view that resources from dead organic material become less available with increasing altitude forcing species to feed on living resources such as fungi, lichens and nematodes. Our findings support the hypothesis that limited resource accessibility (at high altitudes) favors sexually reproducing species whereas ample resource supply (at lower altitudes) favors parthenogenetic species.

Morphological confocal microscopy in arthropods and the enhancement of autofluorescence after proteinase K extraction

Procedures to study the molecular and morphological characteristics of microscopic organisms are often incompatible with each other. Therein, the realization of alternatives that make the characterization of these features compatible and simultaneously permit the deposition of the original material as a voucher sample into a reference collection is one of the foremost goals of biodiversity studies. In this study, we show that genomic extraction does not necessarily compromise the detailed study of the external morphology of microscopic organisms, and to do so, we used a group of aquatic mites (Acari, Hydrachnidia) as a test group. Hydrachnidia morphology is difficult to study when specimens have been stored in pure ethanol; however, proteinase K extraction leaves them flexible and easy to dissect, while, at the same time, maintaining all of their diagnostic features intact. Furthermore, autofluorescence is significantly enhanced after proteinase extraction. Our study was conducted with aquatic mites that were stored in absolute ethanol in the field and processed for DNA extraction using a Qiagen QIAamp minikit. Before and after molecular extraction, a laser scanning confocal microscopy morphological examination was carried out.

Ultrastructural detection of proteins, lipids and carbohydrates in oocytes of Amblyomma triste (Koch, 1844) (Acari; Ixodidae) during the vitellogenesis process

The ovary of the tick Amblyomma triste is classified as panoistic, which is characterized by the presence of oogonia without nurse and follicular cells. The present study has demonstrated that the oocytes in all developmental stages (I-IV) are attached to the ovary through a pedicel, a cellular structure that synthesizes and provides carbohydrate, lipids and proteins supplies for the oocytes during the vitellogenesis process. The lipids are deposited during all oocyte stages; they are freely distributed as observed in stages II, III and IV or they form complexes with other elements. The proteins are also deposited in all stages of the oocytes, however, in lower concentration in the stage IV. There is carbohydrate deposition from oocytes in the stage II as well as in stages III and IV. In addition, the present work has demonstrated that the oocyte yolk of A. triste has a glycolipoprotein nature and the elements are deposited in the following sequence: firstly the lipids and proteins, and finally the carbohydrates.

Allergenic cross-reactivity between Blomia tropicalis and Blomia kulagini (Acari: Echymiopodidae) extracts from optimized mite cultures

BACKGROUND

At present, data about the cross-reactivity of Blomia spp. comes from studies made among different genera of mites, and no results have been published involving different species of the genus Blomia.

OBJECTIVE

The aim of this study was to find out the level of cross-reactivity between the two main species of Blomia causing allergy, and its implication in the diagnosis of Blomia sensitization.

METHODS

Using extracts from optimal growth phases of Blomia kulagini (Zakhvatkin, 1936) and Blomia tropicalis (van Bronswijk, Cock and Oshima, 1973) as allergenic material, the allergenic cross-reactivity between both house dust mites was evaluated by means of cutaneous tests, specific IgE values, ImmunoCAP-inhibition and SDS-PAGE-IgE-immunoblotting-inhibition.

RESULTS

The results demonstrated that IgE-binding components belonging to both species are very similar from the immunological point of view, showing high correlations between both species when using cutaneous tests (R2=0.915) or specific IgE (R2=0.980). ImmunoCAP-inhibition and SDS-PAGE-IgE-Immunoblotting-inhibition probed with human sera, showed a total inhibition of specific IgE reactions by the heterologous antigens.

CONCLUSION

The results obtained strongly suggest the great resemblance between the allergenic composition of both species.

Simple synthesis of mite pheromone beta-acaridial and its analogs in the secretion of Caloglyphus polyphyllae (Acari: Acaridae)

A simple synthesis of beta-acaridial [(E)-1], the active principle of the sex, alarm and aggregation pheromone among astigmatid mites, was achieved in 5 steps from 1,2,4-butanetriol 2 in a 19% overall yield. Its analog, beta-acariolal 8, was also prepared in a 63% yield by oxidation of the intermediate, beta-acaridiol [(E)-7], with pyridinium dichromate (PDC). This synthetic route also gave beta-(Z)-acaridiol [(Z)-7] by using a Z-selective base in the Wittig reaction. (Z)-7 was oxidized to give a new monoterpene, beta-(Z)-acaridial [(Z)-1], which was detected as a trace component in the secretion of Caloglyphus polyphyllae, together with 8.

(4E)-dehydrocitrals [(2E,4E)- and (2Z,4E )-3,7-dimethyl-2,4,6-octatrienals] from acarid mite Histiogaster sp. A096 (Acari: Acaridae)

A mixture of two monoterpenes was obtained as the opisthonotal gland secretion from unidentified Histiogaster sp. A096 (Acari: Acaridae), and their structures were elucidated to be (4E)-dehydrocitrals [(2E,4E)- and (2Z,4E)-3,7-dimethyl-2,4,6-octatrienals] by GC/MS, GC/FT-IR, UV and 1H-NMR spectra. Both isomers of (4E)-dehydrocitral prepared by syntheses in 4 steps from 3-methyl-2-butenal with 34.2% yields (based on the ylide) were separated by column chromatography into the (2E,4E)- and (2Z,4E)-3,7-dimethyl-2,4,6-octatrienal. Mass spectra together with GC retention times of the purified natural (4E)-dehydrocitrals were identical with those of synthetic (2E,4E)-3,7-dimethyl-2,4,6-octatrienal and (2Z,4E)-3,7-dimethyl-2,4,6-octatrienal. The geometry at the 2-C position of both synthetic (4E)-dehydrocitrals was confirmed by NOESY analyses. This is the first identification of (4E)-dehydrocitrals from the animal kingdom.

Aggregation pheromone activity of the female sex pheromone, beta-acaridial, in Caloglyphus polyphyllae (Acari: Acaridae)

Caloglyphus (= Sancasania) polyphyllae discharges from a pair of opisthonotal glands a characteristic set of volatiles, i.e. three monoterpenes and seven hydrocarbons. Among them, beta-acaridial, which is known as the female sex pheromone of the species and has antifungal activity, was newly identified as the aggregation pheromone for unfeeding and unmating mites. Feeding mites, however, exhibited sexually aroused behavior instead of the tendency to cluster when exposed to beta-acaridial. This is the first example of the compound demonstrating two pheromone functions depending upon the circumstances faced by the mites.

Developmental profile, isolation, and biochemical characterization of a novel lipoglycoheme-carrier protein from the American dog tick, Dermacentor variabilis (Acari: Ixodidae) and observations on a similar protein in the soft tick, Ornithodoros parkeri (Acari: Argasidae)

A novel lipoglycoheme-carrier protein (CP) in the American dog tick, Dermacentor variabilis (Say) has been purified and characterized. CP was purified by native-PAGE from partially fed virgin females. CP has a density of 1.25 g/ml with a molecular weight of 200 K by native-PAGE and 340 K by gel filtration chromatography. CP is comprised of two majour subunits, 98 K and 92 K in molecular weight by SDS-PAGE. Separate amino acid composition of the two subunits indicated high contents of As(x), Gl(x) and leucine. However, the N-terminal amino acid sequence of the two subunits was only 13% identical. The lower molecular weight subunit showed 61% identity to artemocyanin (biliprotein) in fairy shrimps, 46% identity to minor vitellogenin in chickens and 13% identity to vitellin of the black-legged tick. No similarity match was found for the other subunit. CP is a lipoglycoheme-protein as indicated by selective staining of native-PAGE gel for lipids, carbohydrates and heme. Lipid analysis by thin layer chromatography revealed the presence of cholesterol, phospholipids, monoacylglycerides, triacylglycerides and free fatty acids. Heme associated with purified CP demonstrated a lambda(max) of 397.5 nm while the lambda(max) of crude hemolymph plasma was 402.5 nm. The presence of CP in whole body homogenates of eggs, unfed and fed larvae and fed nymphs as well as in the plasma of unfed and fed adults including vitellogenic females was demonstrated by native-PAGE. Although a protein of analogous size was not found in the soft tick, Ornithodoros parkeri Cooley, a high molecular weight protein (500 K) is the predominant plasma protein in both unfed and fed male and female adults of that species as determined by native-PAGE. Also, CP appears to function as a biliprotein which sequesters heme.

Boophilus microplus anticoagulant protein: an antithrombin inhibitor isolated from the cattle tick saliva

An anticoagulant was isolated from saliva of the cattle tick Boophilus microplus. Crude saliva prolonged both recalcification time and prothrombin time in assays with bovine plasma. It also inhibited thrombin, but not fXa, amidolytic activity. We purified the antithrombin activity by a combination of gel filtration, anion exchange, and affinity chromatography. The purified inhibitor has a molecular weight of 60,000 Da, determined by SDS-PAGE. The anticoagulant IC50 varied from 100 nM to 1.1 microM, depending on the thrombin concentration and substrate used (fibrinogen or platelet receptor). The excess of inhibitor in relation to thrombin indicates that it is not a tight-binding inhibitor. Chromogenic assays using a panel of five serine-proteinases suggest that the inhibitor is specific against thrombin.

Nitrophorins and related antihemostatic lipocalins from Rhodnius prolixus and other blood-sucking arthropods

Recent gene sequence and crystal structure determinations of salivary proteins from several blood-sucking arthropods have revealed an unusual evolutionary relationship: many such proteins derive their functions from lipocalin protein folds. Many blood-sucking arthropods have independently evolved the ability to overcome a host organism's means of preventing blood loss (called hemostasis). Most blood feeders have proteins that induce vasodilation, inhibit blood coagulation, and reduce inflammation, but do so by distinctly different mechanisms. Despite this diversity, in many cases the antihemostatic activities in such organisms reside in proteins with lipocalin folds. Thirteen such lipocalins are described in this review, with a particular focus on the heme-containing nitrophorins from Rhodnius prolixus, which transport nitric oxide, sequester histamine, and disrupt blood coagulation. Also described are the antiplatelet compounds RPAI, moubatin, and pallidipin from R. prolixus, Ornithodoros moubata, and Triatoma pallidipennis; the antithrombin protein triabin from T. pallidipennis; and the tick histamine binding proteins from Rhipicephalus appendiculatus.

Cuticular hydrocarbon variation and progeny phenotypic similarity between laboratory breeds of allopatric populations of Argas (persicargas) persicus (oken) (acari: argasidae)

Cuticular hydrocarbons of laboratory breeds of four Argas (Persicargas) persicus (Oken) population samples were studied by gas chromatography. Cuticular hydrocarbon patterns were used to determine Nei's genetic distances among populations, and their average heterozygosity. Sixteen n-alkanes, 37 monomethylalkanes and 26 dimethylalkanes were identified. Mostly quantitative differences were recorded between populations, rarely among males and females of the same population. A low genetic distance (0.0278-0.0781) together with a prominent degree of average heterozygosity (60.37-66.98%) were recorded in the population samples studied. When crossbreeds with adult specimens from the same or different geographical origins are performed, all larval progenies closely correlated within themselves and with their parents in hydrocarbon pattern. A slight matrocliny occurred in larvae coming from crosses of the same geographical source. From cross data it is postulated that hydrocarbons in A. persicus are inherited under a two dominant alleles hypothesis.