Dinoflagellates of the family Kryptoperidiniaceae, known as "dinotoms", possess diatom-derived endosymbionts and contain individuals at three successive evolutionary stages: a transiently maintained kleptoplastic stage; a stage containing multiple permanently maintained diatom endosymbionts; and a further permanent stage containing a single diatom endosymbiont. Kleptoplastic dinotoms were discovered only recently, in Durinskia capensis; until now it has not been investigated kleptoplastic behavior and the metabolic and genetic integration of host and prey. Here, we show D. capensis is able to use various diatom species as kleptoplastids and exhibits different photosynthetic capacities depending on the diatom species. This is in contrast with the prey diatoms in their free-living stage, as there are no differences in their photosynthetic capacities. Complete photosynthesis including both the light reactions and the Calvin cycle remain active only when D. capensis feeds on its habitual associate, the "essential" diatom Nitzschia captiva. The organelles of another edible diatom, N. inconspicua, are preserved intact after ingestion by D. capensis and expresses the psbC gene of the photosynthetic light reaction, while RuBisCO gene expression is lost. Our results indicate that edible but non-essential, "supplemental" diatoms are used by D. capensis for producing ATP and NADPH, but not for carbon fixation. D. capensis has established a species-specifically designed metabolic system allowing carbon fixation to be performed only by its essential diatoms. The ability of D. capensis to ingest supplemental diatoms as kleptoplastids may be a flexible ecological strategy, to use these diatoms as "emergency supplies" while no essential diatoms are available.

BACKGROUND:Bilophila wadsworthia, a strictly anaerobic, sulfite-reducing bacterium and common member of the human gut microbiota, has been associated with diseases such as appendicitis and colitis. It is specialized on organosulfonate respiration for energy conservation, i.e., utilization of dietary and host-derived organosulfonates, such as taurine (2-aminoethansulfonate), as sulfite donors for sulfite respiration, producing hydrogen sulfide (H2S), an important intestinal metabolite that may have beneficial as well as detrimental effects on the colonic environment. Its taurine desulfonation pathway involves the glycyl radical enzyme (GRE) isethionate sulfite-lyase (IslAB), which cleaves isethionate (2-hydroxyethanesulfonate) into acetaldehyde and sulfite.RESULTS:We demonstrate that taurine metabolism in B. wadsworthia 3.1.6 involves bacterial microcompartments (BMCs). First, we confirmed taurine-inducible production of BMCs by proteomic, transcriptomic and ultra-thin sectioning and electron-microscopical analyses. Then, we isolated BMCs from taurine-grown cells by density-gradient ultracentrifugation and analyzed their composition by proteomics as well as by enzyme assays, which suggested that the GRE IslAB and acetaldehyde dehydrogenase are located inside of the BMCs. Finally, we are discussing the recycling of cofactors in the IslAB-BMCs and a potential shuttling of electrons across the BMC shell by a potential iron-sulfur (FeS) cluster-containing shell protein identified by sequence analysis.CONCLUSIONS:We characterized a novel subclass of BMCs and broadened the spectrum of reactions known to take place enclosed in BMCs, which is of biotechnological interest. We also provided more details on the energy metabolism of the opportunistic pathobiont B. wadsworthia and on microbial H2S production in the human gut.

Diplo-diploid parthenogenesis (thelytoky) is a widespread phenomenon in the mite taxon Sarcoptiformes, and is unusually frequent in the suborder Oribatida, where it characterizes almost 10% of extant species, including whole genera and families. Based on molecular and cytological data, terminal fusion automixis with an inverted meiotic sequence based on holokinetic chromosomes has been suggested as the reproductive mode in these mites. However, unequivocal structural evidence for meiosis is missing. The model organism Archegozetes longisetosus, a thelytokous member of the parthenogenetic family Trhypochthoniidae, was studied to gain ultrastructural insight in oocyte progression and meiotic processes. In this study, ovarian nuclear organization of its tritonymphal instar was examined by transmission electron microscopy (TEM). Numerous synaptonemal complexes were observed in the ovary, unequivocally confirming automixis (meiotic thelytoky) in oribatid mites for the first time. No recombination nodules were found. The nuclei are transcriptionally active in late prophase. Inverted meiosis is discussed as a result of the spatial arrangement of chromatid segregation.

Light, fluorescence, and electron microscopy were applied to cross sections and -breakage and whole-mount preparations of the anterior hindwing vein of the shield bug Graphosoma italicum. These analyses were complemented by investigations of the basal part of the forewing Corium and Clavus. The integration of structural, histological, and fluorescence data revealed a complex arrangement of both rigid and elastic structures in the wall of wing veins and provided insights into the constitution of transition zones between rigid and elastic regions. Beneath the exocuticular layers, which are continuous with the dorsal and ventral cuticle of the wing membrane, the lumen of the veins is encompassed by a mesocuticular layer, an internal circular exocuticular layer, and an internal longitudinal endocuticular layer. Separate parallel lumina within the anterior longitudinal vein of the hindwing, arranged side-by-side rostro-caudally, suggest that several veins have fused in the phylogenetic context of vein reduction in the pentatomid hindwing. Gradual structural transition zones and resilin enrichment between sclerotized layers of the vein wall and along the edges of the claval furrow are interpreted as mechanical adaptations to enhance the reliability and durability of the mechanically stressed wing veins.

Hingeless shading systems inspired by nature are increasingly the focus of architectural research. In contrast to traditional systems, these compliant mechanisms can reduce the amount of maintenance-intensive parts and can easily be adapted to irregular, doubly curved, facade geometries. Previous mechanisms rely merely on the reversible material deformation of composite structures with almost homogeneous material properties. This leads to large actuation forces and an inherent conflict between the requirements of movement and the capacity to carry external loads. To enhance the performance of such systems, current research is directed at natural mechanisms with concentrated compliance and distinct hinge zones with high load-bearing capacity. Here, we provide insights into our biological findings and the development of a deployable structure inspired by the Flexagon model of hindwings of insects in general and the hierarchical structure of the wing cuticle of the shield bug (Graphosoma lineatum). By using technical fibre-reinforced plastics in combination with an elastomer foil, natural principles have been partially transferred into a multi-layered structure with locally adapted stiffness. Initial small prototypes have been produced in a vacuum-assisted hot press and sustain this functionality. Initial theoretical studies on test surfaces outline the advantages of these bio-inspired structures as deployable external shading systems for doubly curved facades.

This paper presents results of the investigation of two biological role models, the shield bug (Graphosomaitalicum) and the carnivorous Waterwheel plant (Aldrovandavesiculosa). The aim was to identify biological construction and movement principles as inspiration for technical, deployable systems. The subsequent processes of abstraction and simulation of the movement and the design principles are summarized, followed by results on the mechanical investigations on various combinations of fibers and matrices with regard to taking advantage of the anisotropy of fiber-reinforced plastics (FRPs). With the results gained, it was possible to implement defined flexible bending zones in stiff composite components using one composite material, and thereby to mimic the biological role models. First small-scale demonstrators for adaptive façade shading systems – Flectofold and Flexagon – are proving the functionality.

ABSTRACTSmall arthropods show a highly condensed central nervous system, which is accompanied by the loss of the ancestral metameric organization. This results in the formation of one solid mass, a synganglion. Although numerous studies investigated the morphology of Archegozetes longisetosus, the organization of the nervous system is to date unknown. Using synchrotron X‐ray microtomography, we investigated the organization of the nervous system in the adult stage and the development of the synganglion over all five free‐living life stages (larva, proto‐, deuto‐, tritonymph and adult). The general morphology of the synganglion resembles that of other studied mites (in the classic sense) and ticks, being subdivided into a sub‐ and supraesophageal region, and consisting of cortex and neuropil. All nerves entering the walking legs except the first consist of two rami. This split is not based on a functional division into a motor and a sensory ramus, but both rami contain motor and sensory neurites. Within the synganglion, we found structures that resemble the ancestral metameric organization of the nervous system of arthropods. The development of the synganglion of A. longisetosus shows a more or less linear increase in volume, but cortex and neuropil grow at different rates over the five life stages. Between the second and third nymphal stage, the volume of the neuropil increases at a faster rate than the cortex. J. Morphol. 277:537–548, 2016. © 2016 Wiley Periodicals, Inc.

Varroa destructor males are attracted by a volatile sex pheromone of female mites. We assume that this pheromone is perceived by the sensory pit organ on the front leg tarsi. To test this hypothesis, the front legs of the males were varnished with nail polish. The behavior of the thus treated males toward attractive female mites was analyzed in our mating bioassay and compared to untreated control males and to males with varnished idiosoma. The control males with the varnished idiosoma revealed the same distinct copulation behavior as untreated males whereas the males with the varnished front legs did not show copulation attempts any more. Hence, the sensory pit organ is responsible for the perception of female signals that elicit the copulation behavior. Additionally, a first scanning electron microscopy (SEM) analysis is presented to characterize the male sensory pit organ.

With about 10,000 described species and densities reaching 400,000 ind/m2, the Oribatida (without Astigmata) represent the most prevalent group of soil mites. However, with the exception of their taxonomy, many aspects of the biology of oribatid mites have been poorly studied. This might be explained in part by the previous lack of a model species. However, in the last 20 years, more and more non-taxonomic studies regarding development, genetics, morphology, chemical ecology and ecotoxicology have become available, with a significant number focused on the trhypochthoniid oribatid mite Archegozetes longisetosus. A well-defined laboratory strain of this pantropical parthenogenetic species was established in 1993 by one of us (RAN), and has since spread through numerous laboratories worldwide. In this review, we summarize the scientific achievements this lineage has enabled while becoming a model system for general zoology, ecology and evolution.

Archegozetes longisetosus is a parthenogenetic oribatid mite and a chelicerate model organism. We examined the localisation of processes between vitellogenesis and embryogenesis as well as the anatomy and histology of involved structures by means of light- and electron microscopy. The proximal oviduct is differentiated into an oviductal bulb, exhibiting a strong secretory epithelium. Here, solidification of the egg shell instantaneously occurs upon passing of the egg from the perivitelline space into the oviductal lumen. This is interpreted as an internalised oviposition with the generation boundary being effectively located at the ovary-oviduct transition, rendering the oviducts into functional brood chambers. The parity mode combines elements of oviparity and ovolarviparity with facultative egg retention.

We studied the development of the internal reproductive organs in juvenile stages of Archegozetes longisetosus. 3D-renderings of organs were obtained from synchrotron X-ray microtomography (SR- µCT). In addition, transmission electron microscopy (TEM) was used to obtain cytological details. The reproductive organs develop from an unpaired, ventral mass of mesodermal tissue in the larva, and development progresses continuously and largely independent from the development of other organs or moltings. Volume increase of the ovary and a growing number of germ cells indicate proliferation of oogonia in the deutonymph. The oviducts develop from dorso-lateral extensions of mesodermal somatic tissue.

Aporrectodea trapezoides is a widely distributed earthworm, consisting of sexual, pseudogamic and parthenogenetic forms. We sampled individuals from five differently reproducing populations: one sexual population (ROB), three parthenogenetic populations (MOL, ALC and SAN), and another population (SHB) in which earthworms had sperm-filled spermathecae (indicating copulation) but seminal vesicles empty of mature sperm (indicating inhibited sperm production). Ultrastructure of spermathecae of ROB, MOL and SHB showed a high number of functional spermatozoa in ROB, no presence of any sperm in MOL, but presence of sperm in SHB, however with morphological evidence for active degradation. Spermiogenesis was complete in ROB, but aberrant in MOL and SHB, which had less germ cells in the seminal vesicles and incomplete maturation of spermatozoa. SHB and MOL also showed a significantly higher amount of lipid droplets than ROB in spermathecae epithelium and seminal vesicles, indicating that the mechanisms involved in nurturing the sperm continues to be functional in SHB and MOL. Molecular analyses of mitochondrial cytochrome c oxidase I and nuclear histone H3 revealed a genetic proximity of the parthenogenetic populations MOL and ALZ to ROB, while SHB and SAN were more divergent and clustered together. Phylogenetic analyses indicated independent origin of uni-parental reproduction.

We studied the process of vitellogenesis in the oribatid mite Archegozetes longisetosus using light and electron microscopy. Both vitellogenesis and the formation of the first egg shell occur within the meroi of the ovary, starting after detachment from the medulla and completing with ovulation of the egg into the oviductal lumen at the ovarial bulb. Numerous microvilli appear on the surface, and abundant endocytotic pits and coated vesicles occur in the peripheral plasma of the oocyte. Accumulation of fatty yolk does not precede accumulation of proteineous yolk. Differentiation of ooplasm and formation of a perivitelline space beneath a continuous follicular epithelium were observed. Vitelline envelope material appears to be uniform. We compare details of vitellogenesis and propose a classification of the ovarian type as panoistic and the vitellogenesis as exogenic in A. longisetosus.

The mode of cleavage in the Acari is generalized as superficial or intralecithal, with a preceding phase of total (holoblastic) cleavage, but the knowledge is fragmentary and conclusions have been inconsistent, even when relating to the same species. Since no data about early embryology is available for the speciose group Oribatida, we studied Archegozetes longisetosus using transmission electron microscopy. We focused on early cleavages and the formation of the blastula, as these are the important and controversial points in early embryology of the Acari. We expected, as postulated for other acarine eggs, the early cleavages to be holoblastic and followed by a superficial preblastoderm stage. The early cleavages of A. longisetosus are holoblastic and blastomeres give rise to yolk-free micromeres and macromeres containing all the yolk. In contrast to expectations, the micromeres do not form a superficial preblastoderm layer. They are scattered along the embryonic surface and form an external, monocellular layer that covers the whole surface of the embryo. Since each of the existing TEM studies of mites shows this same pattern, and since this specialized form of total cleavage seems to be unique in Chelicerata, it may be the general mode of cleavage in Acari. However, the question will require much more investigation, especially since most data relate to the Actinotrichida and very few are currently available for species in the other major group, the Anactinotrichida.

The oribatid mite, Archegozetes longisetosus, serves as a chelicerate model organism due to its relatively short life cycle and ease of laboratory culturing. It is a parthenogenetic species and all cultures recently used in different laboratories are descendants of a single female collected in 1993. While aspects of its developmental and functional biology have been published, knowledge of its reproductive rate and reproductive system is meager, and data on its life history are contradictory. Herein, we present the gross morphology of the reproductive system as obtained by SEM techniques and X-ray synchrotron microtomography, a new tool for studying mite anatomy. We investigated its reproductive rate by isolating 48 females from cultures and observing reproduction and development at 23 °C. Females repeatedly laid eggs in clutches containing 2-30 eggs. Within 51 days, each female produced, on average, 55 offspring with a maximum of 147. The reproductive rate averaged 1.3 eggs/day.

In a recent publication, ZHANG, Fu & WANG (2004) reported a karyotype analysis of two species of brachypyline oribatid mites: Brasilobates spinosus Fujita (Protoribatidae, or Haplozetidae) and Galumna longiporosa Choi (Galumnidae). 3 After studying what they referred to as oocytes, the authors concluded that both species have an XX:XO sex determining mechanism and that the karyotype is 2n=16 for male B. spinosus and 2n=19 for male G. longiporosa. Chromosomes were reported to be monocentric. However, we believe that some of the applied methods and interpretations are questionable, and the authors overlooked important past studies of oribatid mite karyology. Our purpose is to briefly discuss these issues and to highlight the rather dramatic contradictions with published literature. As an example, we present the first data on the karyotype of Archegozetes longisetosus Aoki (Trhypochthoniidae), and discuss why the conclusions of ZHANG et al. cannot represent the general state of cytogenetics in Oribatida.