Asexual organogenesis and neuro-muscular system of basal bryozoans

Seit Jahrzehnten steht die phylogenetische Stellung der Bryozoen unter Debatte. Traditionell wurden sie gemeinsam mit den Brachiopoden und Phoroniden als ‚Tentakulata’ oder ‚Lophophorata’ zusammengefasst. Neuere Analysen konnten diese Beziehung nicht bestätigen und eine Schwestergruppe fehlt derzeit. Bisher konnten molekulare phylogenetische Analysen zu dieser Thematik kaum etwas beisteuern und nur wenige neuere morphologische Arbeiten mit phylogenetischer Fragestellung sind vorhanden. Zusätzlich zu der fragwürdigen Stellung des Stammes innerhalb der Bilateria, sind auch die internen Beziehungen der drei Bryozoenklassen zueinander nicht geklärt. In dieser Arbeit wurden zwei morphologische Merkmale von Bryozoen analysiert, die bisher nicht untersucht wurden oder revidiert werden müssen: Die Organogenese während des Knospungsvorgangs und sowohl die Myoanatomie als auch das serotonerge Nervensystem adulter Vertreter. Diese beiden Charaktere wurden bei Vertretern der Phylactolaemata und Ctenostomata untersucht. Von einem phylogenetischen Blickwinkel stellen diese beiden Gruppen die vielversprechendtsen dar. Die gegenwärtigen Ergebnisse liefern neue Merkmale, wie zum Beispiel Ähnlichkeiten während der Bildung der Organe im asexuellen Knospungsvorgang und die Verteilung des serotonergen Nervensystems, welche die Monophylie der Bryozoen untermauern. Bezüglich der Muskelsysteme der Bryozoen zeigen vor allem die Apertur-Muskeln eine große Ähnlichkeit innerhalb der Bryozoen und bestehen immer aus zwei Gruppen von Muskeln. Die Gymnolaemen und Phylactolaemen besitzen deutliche Unterschiede in ihrer Darmtraktmuskulatur, wobei Erstere wesentlich mehr glatte Muskulatur aufweisen als Letztere. Die komplizierte Muskulatur im Bereich der Lophophorbasis scheint vielversprechend für phylogenetische Rückschlüsse zu sein, jedoch liegt ein Mangel an vergleichbaren Daten vor. Ein Vergleich der in dieser Arbeit untersuchten Merkmale mit jenen anderer, möglicherweise verwandten Stämmen erweist sich als schwierig, da ebenfalls vergleichbare Daten fehlen. Von all den Stämmen, die öfters in nähere Verwandschaft mit Bryozoen gezogen werden, sind die Kamptozoen die am besten untersuchten. Deren asexuelle Entwicklung zeigt jedoch nur oberflächliche Ähnlichkeiten und deren Neuro-muskuläres System weist deutliche Unterschiede auf.The phylogenetic position of bryozoans has been in dispute for decades. Traditionally they were considered related to the Brachiopoda and Phoronida as ‘Tentaculata’ or Lophophorata. More recent analyses found no evidence for this relationship and a sister-group of bryozoans is currently wanting. Molecular phylogenetic studies have so far not been able to aid very much for this cause and recent morphological studies with phylogenetic background are few. In addition to the questionable position of the whole phylum within the Bilateria, internal relationships of the three different clades of bryozoans are not clear as well. In this thesis I analyse two morphological traits of bryozoans previously not studied or considered in need for revision: The organogenesis during the budding process and the myoanatomy and serotonergic nervous system of adult specimens. Both of these characters were analysed in representatives of the Phylactolaemata and the Ctenostomata. From a phylogenetic point of view the latter two clades are the most promising ones for gaining more insight into their basal evolution. The current results add new characters such as trends in the formation of organ systems during the asexual budding process and the distribution of the serotonergic nervous system that support the monophyly of the Bryozoa. Concerning muscular systems of bryozoans, the apertural muscles show high similarity within Bryozoa and always consist of two sets of muscles. Gymnolaemates and Phylactolaemates show clear differences within their digestive tract musculature, the former showing smooth and longitudinal muscles to a much greater extent than the latter. The complex musculature at the lophophoral base appears promising for inferring phylogenetic relationships, but sufficient comparative data are currently lacking. Comparing the analysed traits with potentially related phyla remains difficult because of a lack of data. From the commonly suggested candidate phyla, the Kamptozoa are the best studied phylum. However, their asexual development only superficially resembles those of bryozoans and their neuro-muscular system is significantly different

Showing their true colors: a practical approach to volume rendering from serial sections

<p>Abstract</p> <p>Background</p> <p>In comparison to more modern imaging methods, conventional light microscopy still offers a range of substantial advantages with regard to contrast options, accessible specimen size, and resolution. Currently, tomographic image data in particular is most commonly visualized in three dimensions using volume rendering. To date, this method has only very rarely been applied to image stacks taken from serial sections, whereas surface rendering is still the most prevalent method for presenting such data sets three-dimensionally. The aim of this study was to develop standard protocols for volume rendering of image stacks of serial sections, while retaining the benefits of light microscopy such as resolution and color information.</p> <p>Results</p> <p>Here we provide a set of protocols for acquiring high-resolution 3D images of diverse microscopic samples through volume rendering based on serial light microscopical sections using the 3D reconstruction software Amira (Visage Imaging Inc.). We overcome several technical obstacles and show that these renderings are comparable in quality and resolution to 3D visualizations using other methods. This practical approach for visualizing 3D micro-morphology in full color takes advantage of both the sub-micron resolution of light microscopy and the specificity of histological stains, by combining conventional histological sectioning techniques, digital image acquisition, three-dimensional image filtering, and 3D image manipulation and visualization technologies.</p> <p>Conclusions</p> <p>We show that this method can yield "true"-colored high-resolution 3D views of tissues as well as cellular and sub-cellular structures and thus represents a powerful tool for morphological, developmental, and comparative investigations. We conclude that the presented approach fills an important gap in the field of micro-anatomical 3D imaging and visualization methods by combining histological resolution and differentiation of details with 3D rendering of whole tissue samples. We demonstrate the method on selected invertebrate and vertebrate specimens, and propose that reinvestigation of historical serial section material may be regarded as a special benefit.</p

Myoanatomy and serotonergic nervous system of the ctenostome Hislopia malayensis: evolutionary trends in bodyplan patterning of ectoprocta

<p>Abstract</p> <p>Background</p> <p>Ectoprocta is a large lophotrochozoan clade of colonial suspension feeders comprising over 5.000 extant species. Their phylogenetic position within the Lophotrochzoa remains controversially discussed, but also the internal relationships of the major ectoproct subclades -Phylactolaemata, Stenolaemata, and Gymnolaemata - remains elusive. To gain more insight into the basic configuration of ectoproct muscle systems for phylogenetic considerations, we analysed the adult myoanatomy and the serotonergic nervous system as well as myogenesis in budding stages of the ctenostome <it>Hislopia malayensis</it>.</p> <p>Results</p> <p>In adults, the serotonergic nervous system is restricted to the lophophoral base with a high concentration in the cerebral ganglion and serotonergic perikarya between each pair of tentacles. Prominent smooth apertural muscles extend from the basal cystid wall to each lateral side of the vestibular wall. The musculature of the tentacle sheath consists of regular strands of smooth longitudinal muscles. Each tentacle is supplied with two bands of longitudinal muscles that show irregular striation. At the lophophoral base several muscles are present: (i) Short muscle fibres that proximally diverge from a single point from where they split distally into two separate strands. (ii) Proximally of the first group are smooth, longitudinal fibres that extend to the proximal-most side of the lophophoral base. (iii) Smooth muscle fibres, the buccal dilatators, traverse obliquely towards the pharynx, and (iv) a circular ring of smooth muscle fibres situated distally of the buccal dilatators. Retractor muscles are mainly smooth with short distal striated parts. The foregut consists mainly of striated ring musculature with only few longitudinal muscle fibres in the esophagus, while the remaining parts of the digestive tract solely exhibit smooth musculature. During budding, apertural and retractor muscles are first to appear, while the parietal muscles appear at a later stage.</p> <p>Conclusions</p> <p>The apertural muscles show high similarity within Ectoprocta and always consist of two sets of muscles. Gymnolaemates and Phylactolaemates show clear differences within their digestive tract musculature, the former showing smooth and longitudinal muscles to a much greater extent than the latter. The complex musculature at the lophophoral base appears promising for inferring phylogenetic relationships, but sufficient comparative data are currently lacking.</p

Trapped in freshwater: the internal anatomy of the entoproct Loxosomatoides sirindhornae

<p>Abstract</p> <p>Background</p> <p>Entoprocta is a small phylum of tentacle-bearing spiralian lophotrochozoans that comprises mainly marine representatives, with only two known freshwater species. One of them, <it>Loxosomatoides sirindhornae </it>Wood, 2005 was only recently described, and detailed information on its morphology including adaptations to life in freshwater are unknown. We analyzed the internal anatomy of <it>L. sirindhornae </it>using serial semi-thin sections, 3D reconstruction, as well as immunocytochemistry and confocal laserscanning microscopy.</p> <p>Results</p> <p>The nephridial system shows high complexity, strikingly similar to that of <it>Urnatella gracilis</it>, the only other known freshwater entoproct. It is composed of 105-120 large flame-bulb terminal organs that occur in the stalk and calyx. In the stalk they terminate in the epidermis, whereas efferent ducts in each terminal organ in the calyx lead to large, paired terminal ducts that fuse close to the central nervous system and open into the atrium by a nephridiopore. Compared to other stolonate entoprocts, <it>L. sirindhornae </it>shows a different stalk-calyx junction by possessing only a single, multicellular canopy instead of a stack of star cells. A sphincter muscle is situated below the diaphragm of the stalk. The remaining musculature is concentrated in the stalk, while the calyx musculature is sparsely developed. The central nervous system is dumbbell-shaped as in basal entoprocts.</p> <p>Conclusions</p> <p>The nephridial system probably has mainly osmoregulatory function. Previous studies have shown that <it>L. sirindhornae </it>is unable to cope with higher salinities, suggesting that its adaptation to freshwater has reached such a high degree that it is unable to 'turn off' the nephridial system in higher salinities. The current data available show that the architecture of internal organ systems such as the musculature or the calyx-stalk junction hold more promising information for taxonomic and perhaps even evolutionary inferences in Entoprocta than external characters such as spination. Contrary to previous investigations, the longitudinal calyx musculature of the genus <it>Loxosomatoides </it>should not be classified as generally strong or conspicuous, since its extent and site of insertion differs between species.</p

Secure Full-Duplex Device-to-Device Communication

This paper considers full-duplex (FD) device-to-device (D2D) communications in a downlink MISO cellular system in the presence of multiple eavesdroppers. The D2D pair communicate sharing the same frequency band allocated to the cellular users (CUs). Since the D2D users share the same frequency as the CUs, both the base station (BS) and D2D transmissions interfere each other. In addition, due to limited processing capability, D2D users are susceptible to external attacks. Our aim is to design optimal beamforming and power control mechanism to guarantee secure communication while delivering the required quality-of-service (QoS) for the D2D link. In order to improve security, artificial noise (AN) is transmitted by the BS. We design robust beamforming for secure message as well as the AN in the worst-case sense for minimizing total transmit power with imperfect channel state information (CSI) of all links available at the BS. The problem is strictly non-convex with infinitely many constraints. By discovering the hidden convexity of the problem, we derive a rank-one optimal solution for the power minimization problem.Comment: Accepted in IEEE GLOBECOM 2017, Singapore, 4-8 Dec. 201

Midbody-Localized Aquaporin Mediates Intercellular Lumen Expansion During Early Cleavage of an Invasive Freshwater Bivalve

Intercellular lumen formation is a crucial aspect of animal development and physiology that involves a complex interplay between the molecular and physical properties of the constituent cells. Embryos of the invasive freshwater mussel Dreissena rostriformis are ideal models for studying this process due to the large intercellular cavities that readily form during blastomere cleavage. Using this system, we show that recruitment of the transmembrane water channel protein aquaporin exclusively to the midbody of intercellular cytokinetic bridges is critical for lumenogenesis. The positioning of aquaporin-positive midbodies thereby influences the direction of cleavage cavity expansion. Notably, disrupting cytokinetic bridge microtubules impairs not only lumenogenesis but also cellular osmoregulation. Our findings reveal a simple mechanism that provides tight spatial and temporal control over the formation of luminal structures and likely plays an important role in water homeostasis during early cleavage stages of a freshwater invertebrate species

The quagga mussel genome and the evolution of freshwater tolerance

Freshwater dreissenid mussels evolved from marine ancestors during the Miocene ∼30 million years ago and today include some of the most successful and destructive invasive species of freshwater environments. Here, we sequenced the genome of the quagga mussel Dreissena rostriformis to identify adaptations involved in embryonic osmoregulation. We provide evidence that a lophotrochozoan-specific aquaporin water channel, a vacuolar ATPase subunit and a sodium/hydrogen exchanger are involved in osmoregulation throughout early cleavage, during which time large intercellular fluid-filled 'cleavage cavities' repeatedly form, coalesce and collapse, expelling excess water to the exterior. Independent expansions of aquaporins coinciding with at least five freshwater colonization events confirm their role in freshwater adaptation. Repeated aquaporin expansions and the evolution of membrane-bound fluid-filled osmoregulatory structures in diverse freshwater taxa point to a fundamental principle guiding the evolution of freshwater tolerance and provide a framework for future species control efforts

Aethozooides uraniae, a new deep-sea genus and species of solitary bryozoan from the Mediterranean Sea, with a revision of the Aethozoidae

Bryozoa is a phylum of about 6000 extant species that are almost exclusively colonial. Few species of the uncalcified Gymnolaemata, the ctenostomes, however, show solitary forms that essentially consist of single zooids. Recently, several specimens of a solitary ctenostome bryozoan were encountered for the first time in the deep Mediterranean Sea, at the edge of an anoxic brine lake. Differences in size, tentacle number, and in the variability of cystid appendages set these specimens apart from all other known solitary species. Moreover, additional morphological autapomorphic traits suggest the erection of a novel genus to allocate the new species. Consequently, the new taxon Aethozooides gen. nov. is proposed in virtue of the general resemblance of the Mediterranean specimens with those of the genus Aethozoon Hayward, 1978. Aethozooides uraniae gen. et sp. nov. shows significant variability in the number and location of cystid appendages that range from two on the basal side to one or two on the zooid mid-peristomial position and/or, rarely, on the terminal frontal side. The polypide possesses a distinct, long tentacle crown always carrying 10 tentacles. The prominent retractor muscle consists of numerous bundles that, in contrast to other known gymnolaemates, attach not only to the lophophoral base but also to various parts of the gut. Distally, the aperture shows a set of four apertural muscles including four parieto-vaginal bands. Reviewing the state and diversity of solitary ctenostomes, we propose a revision of the family Aethozoidae to include the genera Franzenella d\u2019Hondt, 1983, Aethozoon, Aethozooides, and two species currently affiliated to the genus Franzenella (F. monniotae and F. radicans) for which we erected the new taxon Solella gen. nov

Rotational Subgroup Voting and Pose Clustering for Robust 3D Object Recognition

It is possible to associate a highly constrained subset of relative 6 DoF poses between two 3D shapes, as long as the local surface orientation, the normal vector, is available at every surface point. Local shape features can be used to find putative point correspondences between the models due to their ability to handle noisy and incomplete data. However, this correspondence set is usually contaminated by outliers in practical scenarios, which has led to many past contributions based on robust detectors such as the Hough transform or RANSAC. The key insight of our work is that a single correspondence between oriented points on the two models is constrained to cast votes in a 1 DoF rotational subgroup of the full group of poses, SE(3). Kernel density estimation allows combining the set of votes efficiently to determine a full 6 DoF candidate pose between the models. This modal pose with the highest density is stable under challenging conditions, such as noise, clutter, and occlusions, and provides the output estimate of our method. We first analyze the robustness of our method in relation to noise and show that it handles high outlier rates much better than RANSAC for the task of 6 DoF pose estimation. We then apply our method to four state of the art data sets for 3D object recognition that contain occluded and cluttered scenes. Our method achieves perfect recall on two LIDAR data sets and outperforms competing methods on two RGB-D data sets, thus setting a new standard for general 3D object recognition using point cloud data.Comment: Accepted for International Conference on Computer Vision (ICCV), 201