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Background: Entamoeba gingivalis (E. gingivalis) is an anaerobic protozoan that is strongly associated with inflamed periodontal pockets. It is able to invade the mucosal epithelium of the human host, where it can feed on epithelial cells and elicit a severe innate immune response. Unlike other Entamoeba species, it is considered that E. gingivalis cannot form cysts, because it is a non-infectious protozoan. The lack of encystation capability would make it susceptible to periodontal treatment. However, it is not clear how the human host becomes infected with E. gingivalis trophozoites. We investigated the ability of E. gingivalis to encapsulate in response to an unfavorable environment in vitro. Methods: Different strains of E. gingivalis, isolated from inflamed periodontal pocket samples, were cultured for 8 days in the presence or absence of the antimicrobials amoxycillin and metronidazole. To reveal cyst formation, we investigated the morphology and ultrastructure of the amoeba by light, fluorescence, transmission and scanning electron microscopy. We also used the fluorescent dye calcofluor white M2R to demonstrate chitin present in the cyst wall. Results: We observed exocysts and an intra-cystic space separating the encapsulated trophozoite from the environment. Remarkably, cysts showed a smooth surface, polygonal edges and smaller size compared to free-living trophozoites. In addition, encapsulated trophozoites that detached from the cyst wall had a dense cytoplasma without phagocytic vesicles. The cyst walls consisted of chitin as in other Entamoba species. The encapsulated trophozoids were mononuclear after antibioticinduced encapsulation. Discussion: We conclude that E. gingivalis cyst formation has significant implications for dissemination and infection and may explain why established treatment approaches often fail to halt periodontal tissue destruction during periodontitis and peri-implantitis.

This volume deals exlusively with the results of the research field trip of the Humboldt-Universität zu Berlin to the AWI Wattenmeerstation List, Sylt (Germany) from 27.09. - 05.10.2022

This volume deals exlusively with the results of the research field trip of the Humboldt-Universität zu Berlin to the AWI Wattenmeerstation List, Sylt (Germany) from 04.04. - 15.04.2022

While cellulose is the most abundant macromolecule in the biosphere, most animals are unable to produce cellulose with the exception of tunicates. Some tunicates have evolved the ability to secrete a complex house containing cellulosic fibers, yet little is known about the early stages of the house building process. Here, we investigate the rudimentary house of Oikopleura dioica for the first time using complementary light and electron microscopic techniques. In addition, we digitally modeled the arrangement of chambers, nets, and filters of the functional, expanded house in three dimensions based on life-video-imaging. Combining 3D-reconstructions based on serial histological semithin-sections, confocal laser scanning microscopy, transmission electron microscopy, scanning electron microscopy (SEM), and focused ion beam (FIB)-SEM, we were able to elucidate the arrangement of structural components, including cellulosic fibers, of the rudimentary house with a focus on the food concentration filter. We developed a model for the arrangement of folded structures in the house rudiment and show it is a precisely preformed structure with identifiable components intricately correlated with specific cells. Moreover, we demonstrate that structural details of the apical surfaces of Nasse cells provide the exact locations and shapes to produce the fibers of the house and interact among each other, with Giant Fol cells, and with the fibers to arrange them in the precise positions necessary for expansion of the house rudiment into the functional state. The presented data and hypotheses advance our knowledge about the interrelation of structure and function on different biological levels and prompt investigations into this astonishing biological object. Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659

Oikopleura dioica (Appendicularia) is a model organism to understand the evolution of chordates. Although its nuclear genome has been sequenced, its mitochondrial (mt) genome has not been determined, probably because of their fast evolutionary rate and extensive RNA editing. We sequenced cDNA of the cox1 gene and nuclear genomes (using Illumina) from O. dioica and Fritillaria pellucida. Mapping the resulting DNA reads onto the cox1 cDNA sequences, we confirmed the previously-published observation that, at DNA level, long poly-T stretches interrupt the mt ORFs, hampering their identification. In addition, we noticed that mitogenomic poly-T correspond at RNA level to TTTTTT (6T) regions in O. dioica but to shorter TTTT (4T) regions in F. pellucida, leading to hypothesize species-specific RNA editings by deletion. Remarkably, different editing sites were observed between Mediterranean and Japanese populations of O. dioica suggesting a rapid evolution of these sites.While tRNAs usually punctuate the protein-coding genes in chordate mt genome, only one tRNA, tRNAmet, was identified among O. dioica mt contigs assembled from published cDNA reads. To test if mt tRNAs could have been lost, we searched the genomic assembly for the presence of mt aminoacyl tRNA synthetase (aaRS) genes, which encode the proteins responsible for the aminoacylation of its cognate tRNA. No specific mt aaRS genes were found in the nuclear genome assembly of O. dioica except for mt-MetRS, which catalyzes the mt-tRNAMet aminoacylation. This suggests that the mt genome of O. dioica encodes only the single tRNAMet.

Oikopleura dioica . Analytical cell lineage tracing of individual notochordal cells between blastula stage (1 h 17 min pf) and early larval stage (4 h 15 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-63.1. (PDF 2830 kb)

Oikopleura dioica . Analytical cell lineage tracing of individual muscle cells between blastula stage (1 h 17 min pf) and early larval stage (4 h 15 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-70.1. (PDF 3696 kb)

Oikopleura dioica . Analytical cell lineage tracing of individual endodermal cells between blastula stage (1 h 37 min pf) and early larval stage (4 h 15 min pf). A higher resolution version of this Fig. is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-59.1. (PDF 2348 kb)

Phallusia mammillata . Analytical cell lineage tracing of individual trunk lateral cells (TLCs) between blastula stage (3 h 55 min pf) and early tadpole stage (10 h 6 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-71.1. (PDF 721 kb)

Oikopleura dioica . Analytical cell lineage tracing of individual nervous system cells between later gastrula stage (2 h 12 min pf) and early larval stage (4 h 15 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-67.1. (PDF 3697 kb)

A Bifocal 4D-microscope. B Higher magnification of the lower objective that replaces the condenser in the bifocal 4D-microscope. C Adult Phallusia mammillata. Dâ G Pictures of removal of gametes from a hermaphroditic P. mammillata individual during the fertilization process in the laboratory. A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-72.1. (PDF 3653 kb)

Oikopleura dioica . Analytical cell lineage tracing of individual animal-half cells between blastula stage (1 h 37 min pf) and early larval stage (4 h 15 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-61.1. (PDF 5425 kb)

Phallusia mammillata . Analytical cell lineage tracing of individual muscle cells between blastula stage (3 h 55 min pf) and early tadpole stage (10 h 6 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-68.1. (PDF 4703 kb)

Phallusia mammillata . Analytical cell lineage tracing of individual animal-half cells between blastula stage (3 h 55 min pf) and early tadpole stage (10 h 6 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-60.1. (PDF 5844 kb)

Phallusia mammillata . Analytical cell lineage tracing of individual endodermal cells between blastula stage (3 h 55 min pf) and early tadpole stage (10 h 6 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-58.1. (PDF 4316 kb)

Phallusia mammillata . Analytical cell lineage tracing of individual muscle cells between gastrula stage (5 h 38 min pf) and early tadpole stage (10 h 6 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-69.1. (PDF 5654 kb)

Phallusia mammillata. Analytical cell lineage tracing of individual nervous system cells between gastrula stage (5 h 38 min pf) and early tadpole stage (10 h 6 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-65.1. (PDF 8904 kb)

Phallusia mammillata . Analytical cell lineage tracing of individual nervous system cells between blastula stage (3 h 55 min pf) and early tadpole stage (10 h 6 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-64.1. (PDF 2998 kb)

Oikopleura dioica . Analytical cell lineage tracing of individual nervous system cells between earlier blastula stage (57 min pf)and early larval stage (4 h 15 min pf). A higher resolution version of this figure is hosted on MorphDBase at: www.morphdbase.de/?T_Stach_20151119-M-66.1. (PDF 4700 kb)

Xenoturbella bocki has recently been identified as one of the most basal deuterostomes, although an even more basal phylogenetic position cannot be ruled out. Here we report on a polymerase chain reaction survey of partial Hox homeobox sequences of X. bocki. Surprisingly, we did not find evidence for more than five Hox genes, one clear labial/PG1 ortholog, one posterior gene most similar to the PG9/10 genes of Ambulacraria, and three central group genes whose precise assignment to a specific paralog group remains open. We furthermore report on a re‐evaluation of the available published evidence of Hox genes in other basal deuterostomes.

Concerning the evolution of deuterostomes, enteropneusts (acorn worms) occupy a pivotal role as they share some characteristics with chordates (e.g., tunicates and vertebrates) but are also closely related to echinoderms (e.g., sea urchin). The nervous system in particular can be a highly informative organ system for evolutionary inferences, and advances in fluorescent microscopy have revealed overwhelming data sets on neurogenesis in various clades. However, immunocytochemical descriptions of neurogenesis of juvenile enteropneusts are particularly scarce, impeding the reconstruction of nervous system evolution in this group. We followed morphogenesis of the nervous system in two enteropneust species, one with direct (Saccoglossus kowalevskii) and the other with indirect development (Balanoglossus misakiensis), using an antibody against serotonin and electron microscopy. We found that all serotonin-like immunoreactive (LIR) neurons in both species are bipolar ciliary neurons that are intercalated between other epidermal cells. Unlike the tornaria larva of B. misakiensis, the embryonic nervous system of S. kowalevskii lacks serotonin-LIR neurons in the apical region as well as an opisthotroch neurite ring. Comparative analysis of both species shows that the projections of the serotonin-LIR somata initially form a basiepidermal plexus throughout the body that disappears within the trunk region soon after settlement before the concentrated dorsal and ventral neurite bundles emerge. Our data reveal a highly conserved mode of neurogenesis in enteropneusts that is independent of the developing mode and is inferred to be a common feature for Enteropneusta. Moreover, all detected serotonin-LIR neurons are presumably receptor cells, and the absence of serotonin-LIR interneurons from the enteropneust nervous system, which are otherwise common in various bilaterian central nervous systems, is interpreted as a loss that might have occurred already in the last common ancestor of Ambulacraria.

With approximately 3000 marine species, Tunicata represents the most disparate subtaxon of Chordata. Molecular phylogenetic studies support Tunicata as sister taxon to Craniota, rendering it pivotal to understanding craniate evolution. Although successively more molecular data have become available to resolve internal tunicate phylogenetic relationships, phenotypic data have not been utilized consistently. Herein these shortcomings are addressed by cladistically analyzing 117 phenotypic characters for 49 tunicate species comprising all higher tunicate taxa, and five craniate and cephalochordate outgroup species. In addition, a combined analysis of the phenotypic characters with 18S rDNA ‐sequence data is performed in 32 OTU s. The analysis of the combined data is congruent with published molecular analyses. Successively up‐weighting phenotypic characters indicates that phenotypic data contribute disproportionally more to the resulting phylogenetic hypothesis. The strict consensus tree from the analysis of the phenotypic characters as well as the single most parsimonious tree found in the analysis of the combined dataset recover monophyletic Appendicularia as sister taxon to the remaining tunicate taxa. Thus, both datasets support the hypothesis that the last common ancestor of Tunicata was free‐living and that ascidian sessility is a derived trait within Tunicata. “Thaliacea” is found to be paraphyletic with Pyrosomatida as sister taxon to monophyletic Ascidiacea and the relationship between Doliolida and Salpida is unresolved in the analysis of morphological characters; however, the analysis of the combined data reconstructs Thaliacea as monophyletic nested within paraphyletic “Ascidiacea”. Therefore, both datasets differ in the interpretation of the evolution of the complex holoplanktonic life history of thaliacean taxa. According to the phenotypic data, this evolution occurred in the plankton, whereas from the combined dataset a secondary transition into the plankton from a sessile ascidian is inferred. Besides these major differences, both analyses are in accord on many phylogenetic groupings, although both phylogenetic reconstructions invoke a high degree of homoplasy. In conclusion, this study represents the first serious attempt to utilize the potential phylogenetic information present in phenotypic characters to elucidate the inter‐relationships of this diverse marine taxon in a consistent cladistic framework.

Anthropogenic disturbance is known to be highly influential on ecosystems. Sensitive systems with a high ratio of specialized Fauna and Flora are often more affected than those inhabited with generalists. An example of a sensitive ecosystem is the mudflats located off List on the island of Sylt. To investigate the anthropogenic disturbance of the mudflats, we examined populations of Peringia ulvae and Corophium volutator. In this article we show that already a one-time disturbance of the mudflats leads to a significant reduction of density of P. ulvae. No significant difference could be observed between the area disturbed multiple times and the zone that was disturbed only once, indicating that a single disturbance has drastic effects on the ecosystem. Total numbers of C. volutator increased in zones that were disturbed compared to the control area. While organic mass did not significantly differ between disturbed and control area, disturbance, even a single one, resulted in a visual alteration and a decrease of net animal count.

Marine intertidal hard substrates provide an ecologically important habitat for many sessile or semi-sessile organisms. As shelter, food source, nursery or living space, they are of central importance in marine ecosy- stems worldwide (Bellan-Santini et al., 1994). Particularly in the Wadden Sea, dominated by soft substrates and extensive tidal flats, the few hard substrates are essential to many sessile organisms. Therefore, such habitats require special protection. During the last forty years, the pacific oyster became more dominant in the North Sea. While it appears to be in compe- tition with the blue mussel, it could provide potential new niches for sessile organisms, on the other side (Dietrich, 2005). This study aims to make a comparative investigation of the biodiversity on the different types of hard substrates in the intertidal zone of the North Sea on Sylt Island. In total, 53 species belonging to three different ecological guilds (algae, sessile and mobile animals) could be documented on four dif- ferent substrates under two conditions. Besides the attached species’ list, different ecological parameters were calculated, including species abundance, Evenness, and the Shannon-Wiener Index (H). The latter was highest for rocks from the rock-blue mussel reef and lowest in detached rocks taken from the mudflat. In bivalves, the observed biodiversity in sessile organisms was higher in pacific oysters than it was on blue mussels. The opposite is true for mobile organisms, which showed a higher biodiversity on blue mussels found in reef than on isolated oysters. This study has shown that the isolated oysters provide a comparable biodiverse habitat for species living on hard substrate in the Wadden Sea, showing a comparable biodiversity. The native blue mussel as well as the rock reefs shows a great abundance of species, being a shelter for specialist taxa like the hydrozoans. In contrast to the expectations, the oysters offer living space for many native taxa. Therefore, as an extension to the original habitats, they might represent an enrichment of the hard substrate habitat in the Wadden sea on Sylt.

The hermit crab Pagurus bernhardus, which is native to the Wadden Sea, is permanently exposed to water level and associated temperature fluctuations due to the strong tides there. Closely related species, including P. longicarpus, also occur in warmer regions such as Texas. To determine the light and temperature tolerance of P. bernhardus and how the species responds to light stress and an increase in temperature in terms of activity, we studied them at increased light intensity and temperatures between 20 and 25 degrees Celsius. In this study, we did not find significant differences in behavior in relation to light and temperature stress, so we assume that P. bernhardus is a generalist with respect to the constantly changing environmental con- ditions of the Wadden Sea., Der Einsiedlerkrebs Pagurus bernhardus, welcher im Wattenmeer beheimatet ist, ist aufgrund der dort stark ausgeprägten Gezeiten permanent Wasserstands- und damit verbundenen Temperaturschwankungen ausgesetzt. Nah verwandte Arten, darunter P. longicarpus, kommen auch in wärmeren Regionen wie beispielsweise in Texas vor. Um herauszufinden, wie hoch die Licht- und Temperaturtoleranz von P. bernhardus ist und wie die Art auf Lichtstress und einen Temperaturanstieg in Bezug auf ihre Aktivität reagiert, untersuchten wir diese bei erhöhter Lichtintensität und Temperaturen zwischen 20 und 25 Grad Celsius. In dieser Studie konnten wir keine signifikanten Unterschiede im Verhalten in Bezug auf Licht- und Temperaturstress feststellen, weshalb wir davon ausgehen, dass P. bernhardus ein Generalist bezüglich der sich ständig ändernden Umweltbedingungen des Wattenmeeres ist.

The brown shrimp Crangon crangon is an opportunistic feeder that is widely distributed in the Atlantic Ocean. It has a large pray spectrum and uses ambush tactics while hunting. To explore the possibility of memory and learning in this species, we attempted to condition specimens to a light stimulus using food (Mytilus edulis) as a reward. After starving the specimens for 32 hours prior to the experiment, several conditioning rounds (20 s light stimulus followed by 60 s of feeding) were absolved on four consecutive days. After conducting short-term experiments with four replicates as well as a long-term experiment (same group for all four trial days) we could not document a successful conditioning with the chosen experiment set up as there were no significant trends in the development of the specimens‘ behavior. We accredit the lack of conditioning mainly to unfavorable management of holding conditions, feeding management and stimulus application but cannot exclude the possibility of memory or learning in the brown shrimp Crangon crangon.

Pollution of the oceans by anthropogenic influences is a serious problem that will continue to progress in the coming years. The aim of this study was to investigate whether harbour water, which is presumably affected by increased ship traffic or water mixed with sunscreen has an influence on the hiding and feeding behaviour of Carcinus maenas. The crab is frequently found in the shallow water zones of the Wadden Sea and is therefore used as a model organism. The results of our short-term study showed no significant response of the crabs to the pollution used. However, in order to be able to make a clear statement, the sample size must be significantly increased in future experiments. Die Verschmutzung der Meere durch anthropogene Einflüsse ist ein schwerwiegendes Problem, welches in den kommenden Jahren noch weiter fortschreiten wird. In dieser Studie sollte untersucht werden, ob Hafenwasser, welches vermutlich durch das erhöhte Schiffsaufkommen beeinträchtigt ist oder mit Sonnencreme versetztes Wasser einen Einfluss auf das Versteck- und Fressverhalten von Carcinus maenas hat. Die Strandkrabbe kommt unter anderem häufig in den Flachwasserzonen des Wattenmeeres vor und wird daher als Modellorganismus verwendet. Die Ergebnisse unserer Kurzzeitstudie zeigen keine signifikanten Verhaltensänderungen der Krabben auf die verwendeten Verschmutzungen. Um jedoch eine eindeutige Aussage treffen zu können, muss die Stichprobengröße in zukünftigen Versuchen deutlich erhöht werden.

In this study we investigated the ability to associate chemosensory cues with a stressful event in the common acorn barnacle (Semibalanus balanoides). The ecological benefit of associative learning relies on accurate assessment of predictive cues. There are no reports available on experience-dependent behavioral changes in adult barnacles’ autonomic responses. We demonstrated that repetitive aversive conditioning elicited a significant increase in the retraction rate of the cirrus and closure of the operculum after presentation of a cue. These results indicate that adult acorn barnacles are able to anticipate an aversive event through associative learning.

Hemigrapsus sanguineus and Hemigrapsus takanoi are invasive shore crabs in the German Wadden Sea. The monitoring is an important task to evaluate their impact on the ecosystem. This paper analyzes the preference of Hemigrapsus sp. for different bait types. The results of the chi square test based on Pearson shows a preference for Mytilus edulis as bait. M. edulis is the superior bait type for Hemigrapsus sp.

Mussels provide habitat for many organisms – so called epibionts – of the tidal flats by using the shells as a hard substrate for attachment. The abundance of epibionts on mussel shells can vary by location. In this study, the diversity of epibiont species on mussels in the North Sea tidal flats was investigated. For this purpose, mussels and Pacific oysters were collected from three different sites, mixed mudflats, mudflats and mussel beds, and the occurrence of epibiontic species was compared. Epibiontic animal groups identified included Crustacea, Mollusca, Actiniaria, and Bryozoa. The comparison revealed a difference in epibiont diversity on the two bivalve species. The oysters had higher diversity than mussels. The most abundant species include the barnacle species Austrominius modestus. When comparing epibiont diversity among the three sites, an uneven distribution of species was found and the highest diversity was found in the mixed mudflats. Muscheln bieten für viele Organismen – sogenannte Epibionten – des Wattenmeers Lebensraum, indem die Schalen als Hartsubstrat zum Anheften genutzt werden. Das Vorkommen der Epibionten auf den Muschel- schalen kann nach Standort des Watts variieren. In dieser Studie wurde die Diversität der epibiontischen Arten auf Muscheln im Nordsee-Wattenmeer untersucht. Dazu wurden Miesmuscheln und Pazifische Austern aus drei unterschiedlichen Standorten Mischwatt, Schlickwatt und Muschelbank gesammelt und das Artenvorkommen verglichen. Zu den identifizierten epibiontischen Tiergruppen gehören die Crustacea, Mollusca, Actiniaria und Bryozoa. Bei dem Vergleich konnte ein Unterschied in der Epibiontendiversität auf den zwei Muschelarten festgestellt werden, auch wenn gleiche Arten anzutreffen waren. Die Austern wiesen eine höhere Diversität als Miesmuscheln auf. Zu den am häufigsten vorkommenden Arten zählen die Seepockenart Austrominius modestus. Beim Vergleich der Epibiontendiversität zwischen den drei Standorten wurde eine ungleichmäßige Verteilung der Arten festgestellt und die höchste Diversität im Mischwatt festgestellt.

The Australasian Barnacle Austrominius modestus possesses a great number of chemical receptors and is able to discriminate between chemical mixtures based on their single compounds. Prior studies showed that related barnacles (Semibalanus balanoides) have the ability to memorize chemical cues and connect them with specific reactions. The aim of the present study was to confirm this capacity in barnacles and further investigate whether it lasts over a longer period of time or decreases with time. For this the Australasian Barnacle Austrominius modestus was used as a model organism. The results of the previous study could be reproduced in this species as well and showed that barnacles can be conditioned with a neutral stimulus. Furthermore, the study demonstrated that this conditioning lasts at least 3 hours with a slight decrease over time. The ability to learn is of great advantage for the barnacles in a continuously changing environment., Die Australische Seepocke Austrominius modestus besitzt eine große Anzahl an chemischen Rezeptoren und ist in der Lage chemische Gemische aufgrund ihrer Teilstoffe zu unterscheiden. Bereits vorangegangene Veröffentlichungen zeigten außerdem die Fähigkeit einer verwandten Seepockenart (Semibalanus balanoides) sich chemische Reize zu merken und diese mit spezifischen Reaktionen zu verknüpfen. Ziel dieser Studie war es, die Fähigkeit des Lernens und Verknüpfens bei Seepocken zu bestätigen und weiterhinzu untersuchen, inwieweit diese Fähigkeit über längere Zeit anhält bzw. abnimmt. Dazu wurde die Australische Seepocke Austrominius modestus als Versuchtier ausgewählt. Die Daten konnten die Ergebnisse der vorherigen Studie auch bei dieser Art reproduzieren und zeigen, dass Seepocken auf einen neutralen Stimulus konditioniert werden können. Desweitern wurde herausgefunden, dass diese Konditionierung über mindestens 3 Stunden anhält, wobei ein leichter abnehmender Trend nach dieser Zeit erkannt wurde. Die Fähigkeit zu Lernen ist in der sich ständig ändernden natürlichen Umgebung der Seepocken von großem Vorteil.

The Wadden Sea a habitat with extreme variability of abiotic factors. In spring, green gelatinous egg capsules of the polychaete Phyllodoce maculata can be found attached to the sediment, algae or hard substrates. The eggs and the newly hatched larvae have to be resistant against multiple changes of abiotic factors in their habitat. In this study we investigate the influence of changes in the abiotic environment on the early deve- lopmental stages of P. maculata. We tested their reaction to changes in salinity, drought, light conditions, and temperature. We show that the egg capsules and the larvae are resistant against changes in temperature and lighting conditions. The embryos inside the egg capsules and the larvae can tolerate decreased salinity in the sea water of up to 50% for at least 48h. Further decrease in salinity leads to increased lethality of embryos and larvae. In larvae inside the egg capsules, dry conditions lead to further development of the larvae, but the larvae seem to be compromised. For free-swimming larvae, drying out is lethal. Additionally, we show that the early stage trophophora larvae are positively phototactic and prefer open water over sediment.

Die Brachyura umfassen ca. 7000 Arten. Die Variationsbreite ihrer morphologischen Merkmale spiegelt sich in den männlichen und weiblichen Reproduktionssystemen wider und machen sie zu einem herausfordernden Untersuchungsgegenstand. Obwohl sich zahlreiche Studien mit der Phylogenie der Brachyura befasst haben, fehlen eindeutige Ergebnisse. Manche Studien stützen sich weiterhin auf deren Teilung in die Podotremata, die Heterotremata und die Thoracotremata (die beiden letzteren bilden die Eubrachyura), die auf der Position der Gonoporen basiert. In dieser Arbeit wurden die männlichen Kopulations- und weiblichen Reproduktionssysteme von vier eubrachyuren Arten untersucht. Zur Analyse ihrer inneren Morphologie, wurden die Gonopoden in der ersten und zweiten Studie μCT-gescannt und 3D-rekonstruiert. Zusätzlich wurden in allen Studien rasterelektronenmikroskopische Untersuchungen angewendet, um Informationen über die Oberflächenstrukturen der Gonopoden zu erhalten. Alle Untersuchungen des weiblichen Systems wurden mit bewährten histologischen Methoden und Lichtmikroskopie durchgeführt. In der ersten und zweiten Studie wurde diese detaillierte Strukturanalyse durch 3D-Rekonstruktion ergänzt. Die Ergebnisse dieser Studien wurden in Zusammenhang mit der vorhandenen Literatur interpretiert, um Merkmale des männlichen und weiblichen Reproduktionssystems zu definieren und deren Potenzial für phylogenetische Untersuchungen zu diskutieren. Außerdem wird ein evolutives Scenario bezüglich der Transformation der hier vorgeschlagenen Merkmalszustände des weiblichen Reproduktionssystems diskutiert. Die Gonopoden sind wertvoll, um Artenzugehörigkeiten zu Brachyurengruppen zu identifizieren, sind aber für Untersuchungen großskaliger Brachyurenphylogenie ungeeignet. Einige der weiblichen Merkmale können ausschließlich heterotremen oder thoracotremen Weibchen zugeordnet werden. Die vorgeschlagenen Szenarien deuten darauf hin, dass einige dieser Charaktere mehrfach entstanden sind. The Brachyura comprise approximately 7000 species. The variability of their morphological traits is reflected in the male copulatory and the female reproductive systems that make them a challenging object of investigation. Numerous studies addressed the brachyuran phylogeny but unambiguous results have yet to be presented. Some studies still rely on the division of Brachyura into the Podotremata, the Heterotremata and the Thoracotremata (the latter two forming the Eubrachyura) that is based on the position of the male and female gonopores. In this work, the male copulatory and female reproductive systems of four eubrachyuran species were investigated. In the first and the second study, the gonopods were µCT-scanned and 3D-reconstructed to analyse their internal morphology. Additionally, in all studies scanning electron microscopy was used in order to obtain information about the surface structures of the gonopods. All investigations of the female system were conducted using approved histological methods and light microscopy. In the first and second study, this detailed structural analysis was complemented by 3D-reconstruction. The results of these studies are evaluated in comparison with the existing literature in order to define characters of the male copulatory and female reproductive system and discuss their potential for phylogenetic investigations. Additionally, an evolutionary scenario of the transformations of the herein proposed character states of the female reproductive system is discussed. Without additional information from the female reproductive system, the gonopod morphology is valuable to identify species affiliations to certain groups but remains inconclusive for large-scale brachyuran phylogeny. Some of the female characters found in these studies can explicitly be assigned to heterotreme or thoracotreme females. The proposed scenarios suggest, that some, if not all of these characters probably have evolved multiple times.

Tunicata umfasst 3000 marine Arten, mit sehr unterschiedlichen Lebensstrategien. Als eines der drei großen Taxa innerhalb der Chordata, stellt die Evolution der Tunikaten eine Schlüsselkomponente bei der Aufklärung der Evolution der Chordaten und Cranioten dar. Dafür ist ein Verständnis der Merkmalstransformationen innerhalb der Tunikaten notwendig. Leider sind die internen Verwandtschaftsverhältnisse der fünf großen Tunikatentaxa in verschiedenen molekularphylogenetischen Studien widersprüchlich. Bisher gibt es nur wenige morphologische phylogenetische Analysen. Ein Schwerpunkt dieser Arbeit liegt auf der Untersuchung neuroanatomischer Merkmale, da das Nervensystem wahrscheinlich phylogenetische Informationen enthält. Durch das Anwenden moderner morphologischer Methoden, wie hochauflösende konfokale Laserscan- und Elektronenmikroskopie (REM und TEM), und 3d Rekonstruktionen basierend auf lichtmikroskopischen Schnitten, wurde die Verfügbarkeit neuroanatomischer Daten wesentlich verbessert. Die Ergebnisse zeigen, dass die Variation neuroanatomischer Merkmale größer ist als bisher angenommen und dass sich die Gehirnanatomie und die Verteilung von Neurotransmittern in den zwei Stadien der Thaliaceen unterscheidet. Neue unabhängige Merkmale des Nervensystems wurden in einer Matrix kodiert. Ergänzt mit traditionellen in der Tunikatentaxonomie verwendeten Merkmalen, entstand die bisher umfangreichste morphologische Datenmatrix, die 116 Merkmale für insgesamt 54 Arten umfasst. Die kladistische Analyse ergab monophyletische Tunicata, in denen die Appendicularia die Schwestergruppe der übrigen Tunikaten bildet. Ascidiacea ist monophyletisch, während „Thaliacea“ paraphyletisch ist. Zusätzlich wurde eine kombinierte phylogenetische Analyse basierend auf den morphologischen Daten und 18S rDNA-Sequenzen durchgeführt. Eine stufenweise stärkere Gewichtung phänotypischer Merkmale zeigt, dass die morphologischen Daten das Ergebnis der kladistischen Analyse stark beeinflussen., Tunicata comprises 3000 marine species with diverse life-history strategies. As one of the three major chordate taxa, the evolution of tunicates plays a key role to elucidate chordate and craniate evolution. Therefore, a broader understanding of character transformations within tunicates is essential, but the interrelationships of the five main tunicate subtaxa in previous molecular phylogenetic analyses were contradictory. Morphological phylogenetic analyses are rare. In this comparative study emphasis was given to neuroanatomical characters, as the nervous system probably contains phylogenetic information. Applying modern morphological techniques like high-resolution confocal laser scanning microscopy and electron microscopy (SEM and TEM), serial sectioning for light microscopy, and digital 3d reconstruction, the number of available tunicate neuroanatomical data was considerably increased. It was revealed that the variation of neuroanatomical characters is higher than previously assumed, a specific pattern of serotonin-like immunoreactive cells in ascidians is present, and that brain anatomy and distribution of neurotransmitters in the two thaliacean life-cycle stages differs. Novel independent characters of the central nervous system were coded in a matrix for a cladistic analysis. Including traditional morphological from tunicate literature this effort resulted in the largest morphological data matrix to date, containing 116 phenotypic characters and 54 species. The cladistic analysis resulted in monophyletic Tunicata, with Appendicularia the sister taxon to the remaining tunicates. Furthermore, the monophyly of Ascidiacea is supported, whereas “Thaliacea” are paraphyletic. An additional phylogenetic analysis combining morphological and 18S rDNA-sequence data was performed. A reevaluation of this dataset with a successively increased weighting of the phenotypic data showed that morphological data strongly influence the outcome of the cladistic analysis.

Für eine umfassende Untersuchung der Phylogenie der Decapoda wurden von mir die mitochondrialen Genome von 13 Dekapoden sequenziert. Zusammen mit den in der GenBank verfügbaren Sequenzen von 31 Dekapoden und dem von der Universität Bonn zur Verfügung gestellten mitochondrialen Genom von Dromia personata deckt dieser Datensatz alle großen Teilgruppen der Decapoda ab. Maximum likelihood (ML)-Analysen und Bayesian inference (BI)-Analysen der Nucleotidsequenzen und Aminosäuresequenzen ergaben bezüglich der Verwandtschaft der hochrangigen Taxa ähnliche Topologien: (((((((Anomala, Brachyura), Thalassinida: Gebiidea) Thalassinida: Axiidea), Astacidea), Achelata), Stenopodidea), Caridea), Dendrobranchiata). Gleichwohl wurde mit den Polychelida ein problematisches Taxon mit ungewissen Verwandtschaftsbeziehungen identifiziert. Auf der Eben der Unterordnungen sind die Thalassinida paraphyletisch, was mit einigen morphologischen und einigen jüngeren molekularen Studien konsistent ist, alle anderen gebräuchlichen Taxa sind monophyletisch. Es handelt sich um eine Inversion, die sich vom S-E-F tRNA cluster bis zum I-Q-M tRNA cluster erstreckt und in Procambarus fallax f. virginalis und Homarus gammarus auftritt. Im Vergleich mit dem Genarrangement des Limulus polyphemus zeigen beide Astaciden in dieser Region exakt dieselbe Inversion wie der Priapulide Priapulus caudatus, die daher innerhalb der Ecdysozoa als konvergent angenommen werden muss. Auch neben dieser Inversion innerhalb der Astacidea zeigen die Genarrangements aller verfügbaren Dekapoden mehrere interessante Eigenschaften. Um die beobachteten einzigartigen genomischen Eigenschaften zu erklären, schlage ich mit dem „inversion triggered duplication“ Model ein neues Modell für Gen-Rearrangements vor. For a comprehensive study of decapod phylogeny at the mitochondrial genome level, I have sequenced the mitochondrial genome of 13 decapods. Together with available sequences of 31 decapods from GenBank, and the mitochondrial genome of Dromia personata provided by the Bonn University, the dataset now cover all major decapod taxa. Maximum likelihood (ML) and Bayesian inference (BI) of the nucleotide and amino acid datasets reveal similar topologies at the higher level relationships: (((((((Anomala, Brachyura), Thalassinida: Gebiidea) Thalassinida: Axiidea), Astacidea), Achelata), Stenopodidea), Caridea), Dendrobranchiata). Nevertheless, one problematic taxon, Polychelida, with ambiguous affinities is recognized. At the lower level, most taxa are monophyletic, whereas the Thalassinida is paraphyletic, which is consistent with some morphological and molecular results. An inversion spanning from S-E-F tRNA cluster to the I-Q-M tRNA cluster occurred in Procambarus fallax f. virginalis, Homarus gammarus, and one priapulid Priapulus caudatus. Compared with the gene arrangement of the horseshoe crab Limulus polyphemus, both astacids and the priapulid exhibit the same inversion, which is therefore supposed to be a convergent event of the clade Astacidea and Priapulida among Ecdysozoa. Other than this notable feature observed in astacids, the gene arrangements in all available decapods show some interesting characters. To explain these unique genomic features observed here, a new gene rearrangement model is proposed, which is called the “inversion triggered duplication” model.