Evaluation of standard imaging techniques and volumetric preservation of nervous tissue in genetically identical offspring of the crayfish Procambarus fallax cf. virginalis (Marmorkrebs)

In the field of comparative neuroanatomy, a meaningful interspecific comparison demands quantitative data referring to method-specific artifacts. For evaluating the potential of state-of-the-art imaging techniques in arthropod neuroanatomy, micro-computed X-ray microscopy (μCT) and two different approaches using confocal laser-scanning microscopy (cLSM) were applied to obtain volumetric data of the brain and selected neuropils in Procambarus fallax forma virginalis (Crustacea, Malacostraca, Decapoda). The marbled crayfish P. fallax cf. virginalis features a parthogenetic reproduction generating genetically identical offspring from unfertilized eggs. Therefore, the studied organism provides ideal conditions for the comparative analysis of neuroanatomical imaging techniques and the effect of preceding sample preparations of nervous tissue. We found that wet scanning of whole animals conducted with μCT turned out to be the least disruptive method. However, in an additional experiment it was discovered that fixation in Bouin’s solution, required for μCT scans, resulted in an average tissue shrinkage of 24% compared to freshly dissected and unfixed brains. The complete sample preparation using fixation in half-strength Karnovsky’s solution of dissected brains led to an additional volume decrease of 12.5%, whereas the preparation using zinc-formaldehyde as fixative resulted in a shrinkage of 5% in comparison to the volumes obtained by μCT. By minimizing individual variability, at least for aquatic arthropods, this pioneer study aims for the inference of method-based conversion factors in the future, providing a valuable tool for reducing quantitative neuroanatomical data already published to a common denominator. However, volumetric deviations could be shown for all experimental protocols due to methodological noise and/or phenotypic plasticity among genetically identical individuals. MicroCT using undried tissue is an appropriate non-disruptive technique for allometry of arthropod brains since spatial organ relationships are conserved and tissue shrinkage is minimized. Collecting tissue-based shrinkage factors according to specific sample preparations might allow a better comparability of volumetric data from the literature, even if another technique was applied

Contrasting offspring responses to variation in salinity and temperature among populations of a coastal crab: A maladaptive ecological surprise?

Current understanding of species capacities to respond to climate change is limited by the amount of information available about intraspecific variation in the responses. Therefore, we quantified between- and within- population variation in larval performance (survival, development, and growth to metamorphosis) of the shore crab Carcinus maenas in response to key environmental drivers (temperature, salinity) in 2 populations from regions with contrasting salinities (32-33 PSU: Helgoland, North Sea; 16-20 PSU: Kerteminde, Baltic Sea). We also accounted for the effect(s) of salinity experienced during embryogenesis, which differs between populations. We found contrasting patterns between populations and embryonic salinity conditions. In the Helgoland population, we observed a strong thermal mitigation of low salinity stress (TMLS) for all performance indicators, when embryos were kept in seawater. The negative effects of low salinity on survival were mitigated at increased temperatures; only at high temperatures were larvae exposed to low salinity able to sustain high growth rates and reduced developmental time, thereby metamorphosing with comparable levels of carbon and nitrogen to those reared in seawater. By contrast, larvae from the Kerteminde population showed a detrimental effect of low salinity, consistent with a maladaptive response and a weak TMLS. Low salinity experienced during embryogenesis pre-empted the development of TMLS in both populations, and reduced survival for the Kerteminde population, which is exposed to low salinity. Our study emphasises the importance of evaluating species responses to variation in temperature and salinity across populations; the existence of maladaptive responses and the importance of the maternal habitat should not be underestimated

Brain architecture of the largest living land arthropod, the Giant Robber Crab Birgus latro (Crustacea, Anomura, Coenobitidae): evidence for a prominent central olfactory pathway?

<p>Abstract</p> <p>Background</p> <p>Several lineages within the Crustacea conquered land independently during evolution, thereby requiring physiological adaptations for a semi-terrestrial or even a fully terrestrial lifestyle. <it>Birgus latro </it>Linnaeus, 1767, the giant robber crab or coconut crab (Anomura, Coenobitidae), is the largest land-living arthropod and inhabits Indo-Pacific islands such as Christmas Island. <it>B. latro </it>has served as a model in numerous studies of physiological aspects related to the conquest of land by crustaceans. From an olfactory point of view, a transition from sea to land means that molecules need to be detected in gas phase instead of in water solution. Previous studies have provided physiological evidence that terrestrial hermit crabs (Coenobitidae) such as <it>B. latro </it>have a sensitive and well differentiated sense of smell. Here we analyze the brain, in particular the olfactory processing areas of <it>B. latro</it>, by morphological analysis followed by 3 D reconstruction and immunocytochemical studies of synaptic proteins and a neuropeptide.</p> <p>Results</p> <p>The primary and secondary olfactory centers dominate the brain of <it>B. latro </it>and together account for ca. 40% of the neuropil volume in its brain. The paired olfactory neuropils are tripartite and composed of more than 1,000 columnar olfactory glomeruli, which are radially arranged around the periphery of the olfactory neuropils. The glomeruli are innervated ca. 90,000 local interneurons and ca. 160,000 projection neurons per side. The secondary olfactory centers, the paired hemiellipsoid neuropils, are targeted by the axons of these olfactory projection neurons. The projection neuron axonal branches make contact to ca. 250.000 interneurons (per side) associated with the hemiellipsoid neuropils. The hemiellipsoid body neuropil is organized into parallel neuropil lamellae, a design that is quite unusual for decapod crustaceans. The architecture of the optic neuropils and areas associated with antenna two suggest <it>that B. latro </it>has visual and mechanosensory skills that are comparable to those of marine Crustacea.</p> <p>Conclusions</p> <p>In parallel to previous behavioral findings that <it>B. latro </it>has aerial olfaction, our results indicate that their central olfactory pathway is indeed most prominent. Similar findings from the closely related terrestrial hermit crab <it>Coenobita clypeatus </it>suggest that in Coenobitidae, olfaction is a major sensory modality processed by the brain, and that for these animals, exploring the olfactory landscape is vital for survival in their terrestrial habitat. Future studies on terrestrial members of other crustacean taxa such as Isopoda, Amphipoda, Astacida, and Brachyura will shed light on how frequently the establishment of an aerial sense of olfaction evolved in Crustacea during the transition from sea to land. Amounting to ca. 1,000,000, the numbers of interneurons that analyse the olfactory input in <it>B. latro </it>brains surpasses that in other terrestrial arthropods, as e.g. the honeybee <it>Apis mellifera </it>or the moth <it>Manduca sexta</it>, by two orders of magnitude suggesting that <it>B. latro </it>in fact is a land-living arthropod that has devoted a substantial amount of nervous tissue to the sense of smell.</p

Neuroanatomische und neuroethologische Untersuchungen am größten terrestrischen Gliederfüßer, dem Palmendieb Birgus latro (Linnaeus, 1767) (Crustacea, Anomala), auf der Weihnachtsinsel (Indischer Ozean)

Innerhalb der Crustacea evolvierte der Landgang mindestens zehn Mal unabhängig voneinander. Die Evolution des Landganges geht mit einer Vielzahl von morphologischen und physiologischen Anpassungen einher, die sich im Vergleich mit rezenten aquatischen Taxa und ihren nächsten terrestrischen Verwandten rekonstruieren lassen. Im Rahmen des Promotionsprojektes dienten vorangegangene neuroanatomische Untersuchungen am Landeinsiedler Coenobita clypeatus (Fabricius, 1787) und dem nah verwandten Palmendieb Birgus latro (Linnaeus, 1767) sowie auch das wenige Wissen über die Lebensweise des Palmendiebes als Ausgangspunkt, Hypothesen zur Sinnes- und Orientierungsleistung zu entwickeln und mit verschiedenen Verhaltensversuchen im Labor (C. clypeatus) bzw. im Freiland (B. latro) zu testen. Morphologische und verhaltensbiologische Befunde wurden mit Daten anderer Vertreter innerhalb der Anomala, Brachyura und Isopoda verglichen. Für die neuroanatomischen Untersuchungen wurden histologische und immunhistochemische Experimente und deren Analyse mithilfe der Lichtmikroskopie, der konfokalen Laser-Scanning-Mikroskopie durchgeführt und mittels dreidimensionaler Rekonstruktion und Morphometrie gestützt. Zur Evaluierung des Wanderungsverhaltens und der Orientierungsleistung von B. latro wurden verschiedene Freilandversuche auf der Weihnachtsinsel während vier Forschungsreisen im Zeitraum von 2008 bis 2012 vorgenommen. Für die verhaltensbiologische Untersuchung des Palmendiebes wurden Experimente mithilfe von Telemetrietransmittern für die Untersuchung des Wanderungsverhaltens und der Tagesrhythmik genutzt. Die neuroanatomischen Daten terrestrischer Vertreter dieser drei Taxa im Vergleich zu ihren nächsten marinen Verwandten, lassen den Schluss zu, dass die Strukturen des primären olfaktorischen Pfades im Zuge des Landgangs unterschiedlichen morphologischen Transformationen unterlagen. Hierbei fällt auf, dass die Strukturen des primären Riechsystems bei terrestrischen Vertretern innerhalb der Anomala stark vergrößert sind, wohingegen diese innerhalb der Brachyura deutlich geringere Dimensionen aufweisen. Innerhalb der Landasseln (Isopoda: Oniscidea) scheinen die primären Verarbeitungszentren der Olfaktion, die deutocerebralen chemosensorischen Loben im Gehirn, reduziert zu sein, da sie sich mit den hier verwendeten Methoden nicht identifizieren ließen. Die ersten Antennen der terrestrischen Isopoda sind im Vergleich zu den untersuchten marinen Asseln, aber auch im Vergleich zu den anderen beiden Taxa deutlich reduziert. Es wird in diesem Zusammenhang vermutet, dass andere sensorische wie verarbeitende Strukturen des Nervensystems es vermögen, das Fehlen bzw. die starke Reduktion des primären olfaktorischen Systems zu kompensieren. Es wurden Versuche durchgeführt, um die Reaktion des Palmendiebes auf verschiedene Duftstoffe im Freiland zu analysieren. Hierbei zeigten Acetoin, Trimethylamin und Dimethyltrisulfid die höchsten Attraktionswirkungen. Zusätzlich wurden Laborexperimente im Windkanal an Coenobita clypeatus etabliert, die das Ziel hatten, das Duftspektrum dieser dem Palmendieb nahe verwandten Tiere zu evaluieren und geruchsgesteuertes Suchverhalten zu analysieren. Dabei konnte gezeigt werden, dass die Tiere sich bei der Stimulation durch natürliche Duftstoffe entlang der Duftfahne entgegen der Strömungsrichtung zielgerichtet zum Stimulus bewegten. Durch die Telemetrieversuche konnte gezeigt werden, dass der Palmendieb auch außerhalb der Reproduktionszeit zum Teil weite Distanzen zurücklegt, aber auch über eine gewisse Ortstreue verfügt und dieses Verhalten somit als semi-nomadisch charakterisiert werden kann. Während der Wanderungen wird vermutlich die Spurverfolgung als Navigationsstrategie genutzt, wobei auch Hinweise auf Pfadintegration als eine weitere Navigationsstrategie hindeuten. Dabei wird aufgrund der bevorzugten Nachtaktivität der Tiere davon ausgegangen, dass die Orientierung bei der Spurverfolgung chemisch gesteuert sein könnte. Diese These wird auch durch einfache Attraktionsversuche gestützt, bei denen einige Versuchstiere, trotz Blendung, den Köder erfolgreich aufsuchen konnten. Die lokomotorische Aktivität im Tagesgang, welche mithilfe von Beschleunigungssensoren (Akzellerometer) aufgezeichnet werden konnte, scheint besonders unter dem Einfluss der relativen Luftfeuchtigkeit zu stehen. Dabei konnte im Beobachtungszeitraum neben stabilen diurnalen, crepuscularen bis nocturnalen Aktivitätsmustern, auch kathemerales Verhalten dokumentiert werden. Neben individuellen Abweichungen im Tagesgang der lokomotorischen Aktivität, konnte für die meisten der Versuchstiere ein Aktivitätsmaximum während der Zeit des Sonnenuntergangs festgestellt werden, wohingegen während der Mittagszeit das überwiegende Aktivitätsminimum lag. Dies stützt wiederum die Hypothese, dass es einen Zusammenhang zwischen der Dynamik der Aktivität und der Dynamik der relativen Luftfeuchtigkeit geben könnte.Within Crustacea, the conquest of land evolved at least ten times convergently. Taxa featuring different degrees of adaptation (grades of terrestrialization) are described within Malacostraca for e.g. the Anomala, in true crabs (Brachyura), and in isopods (Isopoda). The evolution of terrestriality includes a variety of morphological and physiological adaptations. Related character transformations can be reconstructed from recent aquatic taxa by comparison to their nearest terrestrial relatives. Here, only respiration, osmoregulation, mode of feeding, reproduction, as well as sensory physiology are mentioned as functions which require special adaptations compared to an aquatic environment. In this context, this work refers to the anatomy of the brain, and in particular, to the structures involved in olfaction (primary olfactory pathway) and their fundamental morphological adaptations of Anomala, Brachyura, and Isopoda. Within this doctoral project, previous neuroanatomical studies on soldier crabs Coenobita clypeatus (Fabricius, 1787) and its close relatives the coconut crabs Birgus latro (Linnaeus, 1767) in addition with the scarce knowledge about the life-style of B. latro served as motivation to develop hypotheses as well as laboratory (C. clypeatus) and behavioral field experiments (B. latro), respectively. The focus of these experiments lays on the sensory performance and orientation. Morphological and behavioral data of other members of anomalans, brachyurans, and isopods were compared with those of the land hermit crabs (Anomala, Coenobitidae). For the neuroanatomical studies, histological and immunhistochemical experiments were conducted and analyzed using conventional light microscopy and confocal laser-scanning microscopy and were corroborated by three-dimensional reconstruction and morphometry. During a total of four field trips to Christmas Island (Australia, Indian Ocean), from 2008 to 2012, different behavioral field experiments for the analysis of the migrational and orientational behavior of B. latro were conducted. For the ethological study of the robber crab, behavioral experiments using telemetric transmitters were established to analyze behavioral aspects of migration and chronobiology. The comparison of neuroanatomical data between terrestrial members and their close aquatic relatives of all three taxa, allows the conclusion that during the evolution of a terrestrial life-style, structures of the primary olfactory pathway are subject to different morphological transformations. In terrestrial anomalans, the structures of the primary olfactory system are considerably enlarged whereas they are smaller in terrestrial brachyurans. In terrestrial isopods (Isopoda: Oniscidea) it appears that the primary processing centers of olfaction are largely reduced because they were unidentifiable with the methods used. In this context, other sensory systems as well as processing structures are presumed to compensate this loss or rather considerable reduction of the primary olfactory system. Behavioral field experiments testing the response of robber crabs to different odorants were conducted. These experiments have demonstrated the most attractant effects for acetoin, trimethylamine, and Dimethyl trisulfide. In addition, a laboratory setup for behavioral experiments was established, using wind tunnels for analysis of the olfactory spectrum and olfactory guided behavior of Coenobita clypeatus, a close relative of the robber crab. Here, it could be shown that C. clypeatus is capable of following an upwind plume towards the source of attracting chemical stimulation with natural odorants. From telemetric experiments, it could be shown that some robber crabs migrate large distances outside of the reproductive period whereas others show a territorial behavior, which can be characterized as semi-nomadic. During large scale migrations, path following presumably is the primary navigational strategy and there are hints for path integration as a second mode of navigation. Orientation during path following is suggested to be chemically guided, due to the preferred nocturnal activity of robber crabs. This hypothesis is supported by successful odor tracking experiments using chemical attractants while the animals were temporary blinded. By the use of acceleration loggers (accelerometers) it was shown that the relative air humidity seems to be the driving parameter influencing daily locomotory activity. During the observation period, constant diurnal, crepuscular, as well as cathemeral behavior could be documentated. Besides individual abberations of daily activity patterns, the maximum of locomotory activity occured around dusk while the activity drops for most of the animals observed at noon. These daily acitivity patterns seem to be congruent of the daily dynamics of relative humidity

Exploring brain diversity in crustaceans: sensory systems of deep vent shrimps

The current report focuses on shrimps from deep hydrothermal vents of the Mid-Atlantic Ridge that live in an environment characterized by high hydrostatic pressure, lack of sunlight, and with hot and potentially toxic emissions of black smoker vents. Malacostracan crustaceans display a large diversity of lifestyles and life histories and a rich repertoire of complex behavioral patterns including sophisticated social interactions. These aspects promote this taxon as an interesting group of organisms for those neurobiologists interested in evolutionary transformation of brain structures and evolutionary diversification of neuronal circuits. Here, we explore how analyzing the nervous system of crustacean species from extreme habitats can provide deeper insights into the functional adaptations that drive the diversification of crustacean brain structure.Innerhalb der höheren Krebstiere (Malacostraca) finden sich Vertreter mit einer großen morphologischen und ökologischen Diversität, die sich außerdem durch eine Vielfalt an unterschiedlichen Lebenszyklen und komplexen Verhaltensweisen auszeichnen. Diese Diversität bietet sehr gute Voraussetzungen, um evolutive Transformationen von Gehirnstrukturen und Sinnessystemen im Spannungsfeld zwischen funktionalen und phylogenetischen Zwängen zu analysieren. Insbesondere die Neurobiologie von Tieren aus extremen Lebensräumen kann uns neue Einblicke in funktionale Anpassungen ermöglichen, die die evolutive Diversifizierung von Gehirnstrukturen antreiben. In diesem Beitrag stellen wir die Sinnessysteme von Garnelen der Tiefsee vor, die eng assoziiert mit „black smoker“ hydrothermalen Quellen des Mittelatlantischen Rückens leben, einem lichtlosen und auf den ersten Blick lebensfeindlichem Habitat, dass durch hohen hydrostatischen Druck und die toxischen Emissionen der heißen Quellen geprägt ist

Establishing Student Publication Seminars in Higher Education

A publication seminar is a course (lecture, seminar, project, etc.) during which students create material with the intent and infrastructure to publish it. The publication concept is broadly understood as ‘making the work publicly available’ and is not limited to publications via publishing houses or journals. This handbook results from the "Student Publication Seminars" project (2022-2023) and gives step-by-step instructions and provides checklists for instructors who want to make student course works publicly visible

Einführung studentischer Publikationsseminare an Hochschulen

Ein Publikationsseminar ist eine Lehrveranstaltung (Vorlesung, Seminar, Projekt etc.), in der Studierende Material mit der Absicht und der Infrastruktur erstellen, es zu veröffentlichen. Das Konzept der Ver¨offentlichung soll weitreichend als “die Arbeit öffentlich zugänglich machen” verstanden werden und ist nicht auf Veröffentlichungen über Verlage oder Fachzeitschriften beschränkt. In dieser Handreichung, die aus dem Projekt "Studentische Publikationsseminare" (2022-2023) entstanden ist, fassen wir Erfahrungen aus verschiedenen Lehrveranstaltungen zusammen und geben Hilfestellungen und Checklisten für Lehrende, die es ihren Studierenden ermöglichen wollen, Seminararbeiten etc. öffentlich zu machen