Investigations on life-cycle and host specificity of the Malacosporea (Myxozoa)

Es ist bekannt, dass Parasiten der Klasse Malacosporea (Myxozoa) sowohl Fische als auch Süßwasserbryozoen infizieren, allerdings wurden die meisten Malacosporea bisher nur im Wirbellosenwirt beschrieben. Kenntnisse über Wirtsspektrum, Übertragungsmechanismen und innerartliche Unterschiede in der Empfänglichkeit gegenüber Malacosporea-Erregern sind bislang rar. Daher war es das Ziel dieser Dissertation Biologie und Lebenszyklen einiger Malacosporea-Parasiten intensiver zu untersuchen. Die Übertragung von T. brysalmonae auf Bryozoen war bisher nur mittels infizierter Bachforellen (Salmo trutta) erfolgreich. Daher wurde untersucht, ob neben Bachforellen möglicherweise andere Fischarten geeignete Wirte für T. bryosalmonae darstellen. Es konnte nachgewiesen werden, dass auch Bachsaiblinge (Salvelinus fontinalis) den Parasiten auf Bryozoen übertragen können. Im Gegensatz dazu lösten infizierte Regenbogenforellen (Oncorhynchus mykiss) und Äschen (Thymallus thymallus) keine Infektion bei Letzteren aus. Hechte konnten in diesen Versuchen nicht infiziert werden. Über die Anheftung und die Penetration von Sporen der Malacosporea bei Kontakt mit dem Fischwirt sind nur wenige Details bekannt. Offensichtlich dringen die Sporoplasmen dieser Sporen in die Epithelien des Wirts mittels amöboider Bewegungen ein. Zudem deuten die ultrasturkturellen Untersuchungen darauf hin, dass die Kiemen die Haupteintrittspforte für diesen Parasiten sind. Die Variabilität der Empfänglichkeit von vier Regenbogenforellenstämme und Bachforellen gegenüber T. bryosalmonae wurde mittels quantitativer real-time PCR untersucht. Dabei erwiesen sich Bachforellen als empfänglicher als Regenbogenforellen. In der Anfangsphase des Experiments wiesen zwei der Regenbogenforellenstämme eine geringere Parasitenlast auf als alle anderen Gruppen, allerdings vermehrten sich bei diesen beiden Stämmen die Parasiten schneller, was am letzten Entnahmezeitpunkt letztlich zur Angleichung der relativen Infektionsrate bei allen Stämmen führte. Mittels Immunhistochemie konnten Stadien von T. bryosalmonae in histologischen Schnitten detektiert werden, jedoch war ihre Anzahl gering. Im Gegensatz zu T. bryosalmonae sind die Kenntnisse zu den Lebenszyklen von Buddenbrockia spp. unvollständig und alle bekannten Arten dieser Gattung sind lediglich als Stadien im Bryozoenwirt beschrieben. In der vorliegenden Arbeit konnten bisher unbekannte Infektionen in den Nieren von Karpfen (Cyprinus carpio) und Elritzen (Phoxinus phoxinus) nachgewiesen werden. Der Elritzenparasit konnte als Buddenbrockia plumatellae identifiziert werden, wohingegen es sich bei dem Karpfenparasiten höchst wahrscheinlich um eine unbeschriebene Art handelt. Die Kohabitation von im Labor gezüchteten Bryozoen mit infizierten Karpfen führte nicht zu einem offenen Ausbruch der Infektion. Die Ergebnisse der vorliegenden Arbeit haben in entscheidendem Maße die Kenntnisse über das Wirtsspektrum und die Lebenszyklen von verschiedenen, auch mutmaßlich neuen, Malacosporea-Arten erweitert. Ebenso ergaben sich Hinweise auf Resistenzunterschiede verschiedener Regenbogenforellenstämme gegenüber T. bryosalmonae. Untersuchungen zu Aspekten der Invasion von T. bryosalmonae in den Fisch trugen entscheidend zur weiteren Aufklärung der frühen Infektionsprozesse der Malacosporea bei.The class Malacosporea is the most enigmatic, and probably the basal group of the unique metazoan phylum Myxozoa. They are known to parasitize fish and freshwater bryozoans, but still, most malacosporeans were only described from the invertebrate host. A complete life-cycle is merely known for Tetracapsuloides bryosalmonae, the parasite causing proliferative kidney disease in salmonid fish. Knowledge about host range, transmission mechanisms and intraspecific differences in resistance against malacosporean pathogens remains scarce hitherto. Therefore, the aim of the present thesis was to investigate the biology and the life-cycles of some malacosporean parasites in more detail. Firstly, the necessary culture of freshwater bryozoans to keep the life-cycle of these parasites in the laboratory could be established in the course of this study. Spores obtained from cultured bryozoans infected with malacosporeans thus enabled laboratory transmission experiments. It is well known that most salmonid species are susceptible to T. bryosalmonae-infection, but even in Northern pike (Esox lucius) developmental stages similar to this parasite were described previously. Nevertheless, transmission of this parasite to bryozoans was only achieved with infected brown trout (Salmo trutta). To find out whether other teleosts besides brown trout may also be suitable hosts for T. bryosalmonae, infection experiments with different fish species were conducted in the present study. By cohabitation of T. bryosalmonae-infected fish and laboratory raised bryozoans it was demonstrated that also brook trout (Salvelinus fontinalis) transmitted the disease to bryozoans. In contrast, infected rainbow trout (Oncorhynchus mykiss) and grayling (Thymallus thymallus) did not cause infection of the latter. Peculiarly, pike did not become infected at all in this experiment. For infection of such a wide range of fish species, a general mode of host invasion is necessary. Virtually no details about attachment and penetration of malacosporean spores encountering the fish host were known. To characterize these life-cycle stages ultra-structurally, infection trials and in vitro experiments with T. bryosalmonae actinospores were conducted. In vitro activation experiments, light microscopy and scanning electron microscopy (SEM) showed that sporoplasms of these spores penetrate host epithelia by means of amoeboid movement. Additionally, ultrastructural examinations indicated that the gills are main entry site for this parasite. Upon contact, the spores seemed to impair the gill epithelium to allow the entry of the sporoplasm at these sites. After penetration, the parasite is exposed to the immune system of the host, so the number of stages that enter and the intensity of the host response against the parasite will influence its development and multiplication. This variability in susceptibility was addressed in the present study, as reliable data about intra-specific differences in the response of fish to malacosporean infections was lacking up to this point. Four rainbow trout strains and brown trout were infected with T. bryosalmonae and infection intensity was monitored. According to results from quantitative real-time-PCR analysis, brown trout were more susceptible than rainbow trout. Two rainbow trout strains showed lower relative parasite load than all other groups early during the experiment, but parasites multiplied faster in these strains, resulting in an equal level of relative infection rate for all strains upon final sampling. T. bryosalmonae-stages were found stained by immuno-histochemistry in histological sections although their number was low, unfortunately impeding quantitative evaluation of parasite load. In contrast to T. bryosalmonae, knowledge of life-cycles of Buddenbrockia spp. was incomplete and all known species of this genus were described as stages in bryozoan hosts. In this study, cohabitation challenges with bryozoans containing the peculiar worm-like malaco-sporean stages and fish resulted in novel infections detected in kidneys of common carp (Cyprinus carpio) and minnow (Phoxinus phoxinus). Sequence comparison of 18S rDNA identified the parasite in minnows as Buddenbrockia plumatellae, while the carp infecting malacosporean is very likely a new species. Light and electron-microscopy of kidney samples of infected minnows and carp revealed parasite stages in the kidney tubules. Only single parasite cells were observed in minnow, while in carp, multicellular sporogonic stages were found in sections of kidney tubules. Cohabitation of laboratory raised bryozoans with infected carp did not yield in overt infection. Therefore, the complete life-cycle of this parasite has yet to be established. Phylogenetic analysis of the Buddenbrockia spp. known to date sub-stantiated the split of the B. plumatellae-clade into two lineages, but could not fully clarify the placement of the carp-infecting malacosporean. The results of this thesis fundamentally increased the knowledge on the range of compatible hosts and life-cycles of different, even putatively new, malacosporean species. Also, indi-cations for differential resistance of rainbow trout strains to T. bryosalmonae were found. Investigations on aspects of invasion of fish by T. bryosalmonae spores further clarified the early infection process of malacosporeans

Heat sensitivity of first host and cercariae may restrict parasite transmission in a warming sea

To predict global warming impacts on parasitism, we should describe the thermal tolerance of all players in host–parasite systems. Complex life-cycle parasites such as trematodes are of particular interest since they can drive complex ecological changes. This study evaluates the net response to temperature of the infective larval stage of Himasthla elongata, a parasite inhabiting the southwestern Baltic Sea. The thermal sensitivity of (i) the infected and uninfected first intermediate host (Littorina littorea) and (ii) the cercarial emergence, survival, self-propelling, encystment, and infection capacity to the second intermediate host (Mytilus edulis sensu lato) were examined. We found that infection by the trematode rendered the gastropod more susceptible to elevated temperatures representing warm summer events in the region. At 22 °C, cercarial emergence and infectivity were at their optimum while cercarial survival was shortened, narrowing the time window for successful mussel infection. Faster out-of-host encystment occurred at increasing temperatures. After correcting the cercarial emergence and infectivity for the temperature-specific gastropod survival, we found that warming induces net adverse effects on the trematode transmission to the bivalve host. The findings suggest that gastropod and cercariae mortality, as a tradeoff for the emergence and infectivity, will hamper the possibility for trematodes to flourish in a warming ocean

RNAi screen identifies a role for adaptor protein AP-3 in sorting to the regulated secretory pathway

AP-3 concentrates proteins within large dense-core vesicles to promote regulated exocytosis

The impact of society on management control systems

© 2017 Elsevier Ltd The aim of this study is to investigate whether certain configurations of management controls dominate in certain societies (socio-cultural contexts) and whether the effectiveness of a given archetype of management control systems (MCSs) varies depending on the socio-cultural setting—the society—in which it operates. The study focuses on three socio-cultural groups and the corresponding institutional contexts (an Anglo-Saxon group, a Central European group, and a Northern European group) and three MCS archetypes (delegated bureaucratic control, delegated output control, and programmable output control). We use unique data from a cross-national, interview-based survey encompassing 610 strategic business units from nine countries (seven European countries plus Canada and Australia). The idea that firms tend to adapt MCSs to the socio-cultural context does not gain empirical support in this study. No significant differences in the distribution of MCSs between the three socio-cultural groups are noted. However, we do find that programmable output control has a more positive impact on effectiveness in Anglo-Saxon cultures, while delegated output control has a more positive impact on effectiveness in Northern Europe. Taken together these findings indicate that distinct differences between societies make a particular MCS design more appropriate in a given society, but where such differences are not dramatic (as in the present case), multiple MCS designs can be found in the same society

Jet stream position explains regional anomalies in European beech forest productivity and tree growth.

The mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes. The jet stream latitude (JSL) over the North Atlantic-European domain provides a synthetic and robust physical framework that integrates climate variability not accounted for by atmospheric circulation patterns alone. Surface climate impacts of north-south summer JSL displacements are not uniform across Europe, but rather create a northwestern-southeastern dipole in forest productivity and radial-growth anomalies. Summer JSL variability over the eastern North Atlantic-European domain (5-40E) exerts the strongest impact on European beech, inducing anomalies of up to 30% in modelled gross primary productivity and 50% in radial tree growth. The net effects of JSL movements on terrestrial carbon fluxes depend on forest density, carbon stocks, and productivity imbalances across biogeographic regions

A checklist for assessing the methodological quality of concurrent tES-fMRI studies (ContES checklist): a consensus study and statement

Background: Low intensity transcranial electrical stimulation (tES), including alternating or direct current stimulation (tACS or tDCS), applies weak electrical stimulation to modulate the activity of brain circuits. Integration of tES with concurrent functional magnetic resonance imaging (fMRI) allows for the mapping of neural activity during neuromodulation, supporting causal studies of both brain function and tES effects. Methodological aspects of tES-fMRI studies underpin the results, and reporting them in appropriate detail is required for reproducibility and interpretability. Despite the growing number of published reports, there are no consensus-based checklists for disclosing methodological details of concurrent tES-fMRI studies. Objective: To develop a consensus-based checklist of reporting standards for concurrent tES-fMRI studies to support methodological rigor, transparency, and reproducibility (ContES Checklist). Methods: A two-phase Delphi consensus process was conducted by a steering committee (SC) of 13 members and 49 expert panelists (EP) through the International Network of the tES-fMRI (INTF) Consortium. The process began with a circulation of a preliminary checklist of essential items and additional recommendations, developed by the SC based on a systematic review of 57 concurrent tES-fMRI studies. Contributors were then invited to suggest revisions or additions to the initial checklist. After the revision phase, contributors rated the importance of the 17 essential items and 42 additional recommendations in the final checklist. The state of methodological transparency within the 57 reviewed concurrent tES-fMRI studies was then assessed using the checklist. Results: Experts refined the checklist through the revision and rating phases, leading to a checklist with three categories of essential items and additional recommendations: (1) technological factors, (2) safety and noise tests, and (3) methodological factors. The level of reporting of checklist items varied among the 57 concurrent tES-fMRI papers, ranging from 24% to 76%. On average, 53% of checklist items were reported in a given article. Conclusions: Use of the ContES checklist is expected to enhance the methodological reporting quality of future concurrent tES-fMRI studies, and increase methodological transparency and reproducibility

Invaders, natives and their enemies: distribution patterns of amphipods and their microsporidian parasites in the Ruhr Metropolis, Germany

Abstract Background The amphipod and microsporidian diversity in freshwaters of a heterogeneous urban region in Germany was assessed. Indigenous and non-indigenous host species provide an ideal framework to test general hypotheses on potentially new host-parasite interactions, parasite spillback and spillover in recently invaded urban freshwater communities. Methods Amphipods were sampled in 17 smaller and larger streams belonging to catchments of the four major rivers in the Ruhr Metropolis (Emscher, Lippe, Ruhr, Rhine), including sites invaded and not invaded by non-indigenous amphipods. Species were identified morphologically (hosts only) and via DNA barcoding (hosts and parasites). Prevalence was obtained by newly designed parasite-specific PCR assays. Results Three indigenous and five non-indigenous amphipod species were detected. Gammarus pulex was further distinguished into three clades (C, D and E) and G. fossarum more precisely identified as type B. Ten microsporidian lineages were detected, including two new isolates (designated as Microsporidium sp. nov. RR1 and RR2). All microsporidians occurred in at least two different host clades or species. Seven genetically distinct microsporidians were present in non-invaded populations, six of those were also found in invaded assemblages. Only Cucumispora dikerogammari and Dictyocoela berillonum can be unambiguously considered as non-indigenous co-introduced parasites. Both were rare and were not observed in indigenous hosts. Overall, microsporidian prevalence ranged from 50 % (in G. roeselii and G. pulex C) to 73 % (G. fossarum) in indigenous and from 10 % (Dikerogammarus villosus) to 100 % (Echinogammarus trichiatus) in non-indigenous amphipods. The most common microsporidians belonged to the Dictyocoela duebenum- /D. muelleri- complex, found in both indigenous and non-indigenous hosts. Some haplotype clades were inclusive for a certain host lineage. Conclusions The Ruhr Metropolis harbours a high diversity of indigenous and non-indigenous amphipod and microsporidian species, and we found indications for an exchange of parasites between indigenous and non-indigenous hosts. No introduced microsporidians were found in indigenous hosts and prevalence of indigenous parasites in non-indigenous hosts was generally low. Therefore, no indication for parasite spillover or spillback was found. We conclude that non-indigenous microsporidians constitute only a minimal threat to the native amphipod fauna. However, this might change e.g. if C. dikerogammari adapts to indigenous amphipod species or if other hosts and parasites invade