An insight into the tribe Hexathrombiini (Actinotrichida: Trombidioidea, Microtrombidiidae, Eutrombidiinae) with new data on host-parasite interaction

The status of the genera in the small microtrombidiid mite tribe Hexathrombiini is reevaluated. Type specimens representing all genera were studied and diagnostic characters for Hexathrombiini are reviewed, summarized, and new data and a key to the genera in the tribe are provided: Alhamitrombium, Beronium, Hexathrombium and Hoplothrombium. Hexathrombium is the most speciose genus in the tribe and species recorded from South America are compared, as well as those with a divided pygidial plate. A provisional key to species assigned to Hexathrombium is provided. Finally, Hexathrombium abirami was captured in Peru parasitizing a bright metallic tiger beetle (Tetracha fulgida). A total of 361 larvae were removed parasitizing a single carabid host; this is the highest load of parasites reported in terrestrial Parasitengona mites associated with arthropods. This capture represents a new record of Hexathrombiini mites for Peru. A redescription of He. abirami using all specimens available to date is included

A giant mite in Cretaceous Burmese amber

An unusually large acariform mite is described as Immensmaris chewbaccei gen. et sp. nov. from the Cretaceous (ca. 100&thinsp;Ma) Burmese amber of Myanmar. With an idiosoma plus gnathosoma more than a centimetre long, it represents the largest unequivocal fossil mite ever recorded and approaches the maximum size of the largest living Acariformes today. Although some details of the dorsal idiosoma are equivocal, the new fossil appears to belong to Smarididae (Prostigmata: Parasitengona: Erythraeoidea) and also represents the largest erythraeoid mite ever discovered, indicating a clade of giant, possibly arboreal, mites in the Late Cretaceous of southeastern Asia.</p

Inclusion of juvenile stages improves diversity assessment and adds to our understanding of mite ecology – A case study from mires in Norway

Arachnid orders, Mesostigmata, Trombidiformes, and Sarcoptiformes, commonly known as ‘mites’, are abundant in mires, both as adults and as juveniles. However, due to the challenges of identification, the juvenile forms are often excluded from analyses. This is the first study in mires that included all three mite orders identified to the species level, including juvenile instars. We aimed to compare how diversity and the response to ecological variables differed if only the adults (ad) vs. the total number of specimens (ad+juv) are considered. Samples of 20 Sphagnum species (five subgenera) were collected and mites were extracted using Berlese funnels. Overall, nearly 60,000 mites were analyzed; of these Mesostigmata made up 1.87% of the total, Trombidiformes −0.27%, and Sarcoptiformes −97.86%. The study revealed 154 species (33 Mesostigmata, 24 Trombidiformes, and 97 Sarcoptiformes), the highest diversity of mites ever reported from mires. The inclusion of juveniles increased observed species richness by 6%, with 10 species (one Mesostigmata, six Trombidiformes, and three Sarcoptiformes) represented only by juvenile forms. Seventeen species are new to Norway (four Mesostigmata, one Sarcoptiformes, and 12 Trombidiformes, including five undescribed species of Stigmaeidae and Cunaxidae). Four of these were represented in the samples only by juveniles. Including the juveniles explained a greater amount of the variability of Trombidiformes (explanatory variables account for 23.60% for ad, and 73.74% for ad+juv) and Mesostigmata (29.23% − ad, 52.91% − ad+juv), but had less of an impact for Sarcoptiformes (38.48% − ad, 39.26% − ad+juv). Locality, Sphagnum subgenus and species, wetness, and trophic state significantly affected the mite communities and should be taken into consideration when studying mires. Since juvenile stages contribute significantly to mite diversity in mires, they should also be included in mite studies in other habitats.publishedVersio

Full Waveform Modelling for Converted Waves Seismic Reflections in Mountainous and Marine Environment

The application of seismic waves allows us to achieve adequate results by compressional wave (P-wave) surveys alone. However, in the presence of gas P-wave transmission disrupts and obscures underlying targets. Many reservoirs don’t present sufficient impedance contrast to the overburden and not reflect P-wave strongly to produce an impedance image. High impedance rock such as basalt or hard volcanic rocks are difficult to image with P-wave. To overcome these challenges shear-wave (S-wave) or converted wave (P-S) surveys are usedfor last 20 years by making the use of down going P waves converting to upcoming S waves at the mode conversion boundaries.The processing of converted waves requires studying asymmetric reflection at the conversion point, difference in geometries and conditions of source and receiver, and the partitioning of energy into orthogonally polarized components. Interpretation of P-S sections incorporates the identification of P-S waves, full waveform modelling, correlation with P-wave sections and depth migration.The objectives of this study is to model P-S wave reflections in onshore and offshore environment and to examine the major differences in processing of P and P-S wave surveys together with the identifying converted mode reflections by P-wave sources in anisotropic media. To achieve these, realistic mountainous and marine environment models have been developed and synthetic seismograms are generated by full waveform modelling technique. First a mountain foothill model was studied. A Kirchhoff-based technique that includes anisotropic velocities is used for depth migration of P-S waves. The results from depth imaging show that P-S section help in distinguishing amplitude associated with hydrocarbons from those caused by localized stratigraphic changes. Marine model shows a good correlation with identified converted waves. In addition, the full waveform elastic modellingproves useful in finding an appropriate balance between capturing high-quality P-wave data as well as P-S data challenges in a survey.Key Words: Converted-waves (P-S); P-S Wave; Kirchhoff migration; Depth migration; Gas clouds; Shale diaper

A Re-Description of Balaustium leanderi

Balaustium leanderi (Haitlinger, 2000) comb. nov. (Actinotrichida: Erythraeidae), previously known only from the larval stage is re-described based on material originating from a laboratory culture of specimens collected in Colombia. This is also the first report of Balaustium leanderi (Haitlinger, 2000) in this country. The taxonomic characters of adult (female), deutonymph and larva are provided. The species re-described in this paper, is one of 37 nominal species presently assigned to the genus. With Balaustium leanderi (Haitlinger, 2000) there are just 6 species known both from larvae and active postlarval forms. Palenqustium Haitlinger (2000) is considered a junior synonym of Balaustium, which is one of 12 genera recognized within the Balaustiinae. A modified diagnosis of Balaustium von Heyden, 1826 is provided