Methods to study organogenesis in decapod crustacean larvae. I. larval rearing, preparation, and fixation

Crustacean larvae have served as distinguished models in the field of Ecological Developmental Biology (“EcoDevo”) for many decades, a discipline that examines how developmental mechanisms and their resulting phenotype depend on the environmental context. A contemporary line of research in EcoDevo aims at gaining insights into the immediate tolerance of organisms and their evolutionary potential to adapt to the changing abiotic and biotic environmental conditions created by anthropogenic climate change. Thus, an EcoDevo perspective may be critical to understand and predict the future of organisms in a changing world. Many decapod crustaceans display a complex life cycle that includes pelagic larvae and, in many subgroups, benthic juvenile–adult stages so that a niche shift occurs during the transition from the larval to the juvenile phase. Already at hatching, the larvae possess a wealth of organ systems, many of which also characterise the adult animals, necessary for autonomously surviving and developing in the plankton and suited to respond adaptively to fluctuations of environmental drivers. They also display a rich behavioural repertoire that allows for responses to environmental key factors such as light, hydrostatic pressure, tidal currents, and temperature. Cells, tissues, and organs are at the basis of larval survival, and as the larvae develop, their organs continue to grow in size and complexity. To study organ development, researchers need a suite of state-of-the-art methods adapted to the usually very small size of the larvae. This review and the companion paper set out to provide an overview of methods to study organogenesis in decapod larvae. This first section focuses on larval rearing, preparation, and fixation, whereas the second describes methods to study cells, tissues, and organs

Exploring larval phenology as predictor for range expansion in an invasive species

Predicting range expansion of invasive species is one of the key challenges in ecology. We modelled the phenological window for successful larval release and development (WLR) in order to predict poleward expansion of the invasive crab Hemigrapsus sanguineus along the Atlantic coast of North America and north Europe. WLR quantifies the number of opportunities (in days) when larval release leads to a successful completion of the larval phase; WLR depends on the effects of temperature on the duration of larval development and survival. Successful larval development is a necessary requirement for the establishment of self‐persistent local populations. WLR was computed from a mechanistic model, based on in situ temperature time series and a laboratory–calibrated curve predicting duration of larval development from temperature. As a validation step, we checked that model predictions of the time of larval settlement matched observations from the field for our local population (Helgoland, North Sea). We then applied our model to the North American shores because larvae from our European population showed, in the laboratory, similar responses to temperature to those of a North American population. WLR correctly predicted the northern distribution limit in North American shores, where the poleward expansion of H. sanguineus appear to have stalled (as of 2015). For north Europe, where H. sanguineus is a recent invader, WLR predicted ample room for poleward expansion towards NE England and S Norway. We also explored the importance of year‐to‐year variation in temperature for WLR and potential expansion: variations in WLR highlighted the role of heat waves as likely promoters of recruitment subsidising sink populations located at the distribution limits. Overall, phenological windows may be used as a part of a warning system enabling more targeted programs for monitoring

Effects of environmental stress on early life history stages of the European shore crab Carcinus maenas Linnaeus 1758 (Brachyura: Portunidae)

Langzeitmessungen zeigen bereits den massiven Einfluss globaler Umweltänderungen auf marine Ökosysteme einschließlich des Planktons. Insbesondere Randmeere wie die Nordsee werden zunehmend von steigender Temperatur betroffen sein. Zusätzlich zur Temperatur ändern sich weitere Faktoren wie beispielsweise Salinität und pH. Diese gleichzeitige Änderung zahlreicher Faktoren zwingt marine Organismen mit der Instabilität ihrer Umgebung umzugehen. Planktonische Larven mariner benthischer Organismen spielen eine zentral Rolle in der Beständigkeit deren Populationen und der Verbreitung einer Art. Gleichzeitig sind Larven das empfindlichste Entwicklungsstadium und daher extrem von sich ändernden Umweltbedingungen beeinflusst. Daher ist es wichtig, die Reaktion dieser Larven auf Änderungen abiotischer Faktoren wie Temperatur und Salinität zu quantifizieren, um die Beständigkeit einer Art in einem sich ändernden Ökosystem abzuschätzen. Dieses Projekt hat zum Ziel, larvale Merkmale am der gemeinen Strandkrabbe Carcinus maenas zu identifizieren, welche von der Kombination aus Temperatur- und Salinitätsstress beeinflusst sind. Dafür wurde die larvale Performance (Überleben und Entwicklungsdauer) unter zwölf verschiedenen Temperatur-Salinitäts-Kombinationen verglichen und die Variation innerhalb einer Population untersucht. Des Weiteren wurde die äußere und innere Morphologie der Larven vergleichend untersucht. Es zeigte sich, dass die Interaktion von Temperatur und Salinität sowohl Überleben als auch Entwicklungsdauer beeinflusst. Die Interaktion erhöhter Temperatur und niedriger Salinität selbst ist antagonistisch; im Zuge dessen verbessert erhöhte Temperatur den negativen Effekt niedriger Salinität. Des Weiteren wurde eine hohe intraspezifische Variation in der Auswirkung abiotischer Faktoren und entsprechend der larvalen Performance festgestellt. Es konnte keine Auswirkung der getesteten Faktoren auf die äußere Morphologie der Larven festgestellt werden. Die Untersuchung der larvalen Organogenese ergab eine graduelle Zunahme in der Größe und Komplexität der einzelnen Organsysteme; die meisten Organe erwachsener Krabben sind bereits in Larvenstadien als Anlagen vorhanden. Massive Lipidinklusionen der Mitteldarmdrüse als Zeichen des Ernährungszustandes erlauben potentiell für die Kompensation erhöhter metabolischer Kosten verursacht durch stressige Umweltbedingungen. Zudem wurde eine vermeintlich funktionelle Antennaldrüse identifiziert, welche in erwachsenen Stadien an der Ionenregulation beteiligt ist und es den Larven unter Umständen erlaubt mit Änderungen der umgebenden Salinität zurechtzukommen. Alles in Allem, könnte die Erwärmung der Meere entsprechend die weitere Ausbreitung von Carcinus maenas in Bereich niedrigerer Salinität durch die antagonistische Interaktion zwischen Temperatur und Salinität und morphologische Anlagen der Larven begünstigen.Climate change threatens marine ecosystems by simultaneous alterations and fluctuations in several abiotic factors like temperature, salinity and pH. Therefore, a strong ability to cope with varying environmental factors is indispensable for marine organisms. Especially, larvae of meroplanktonic species will be affected by predicted alterations in environmental conditions as planktonic larval stages are considered the most sensitive stages during life history (Anger 2001). The European shore crab Carcinus maenas, as an ecological key species, was chosen as a model species to investigate multiple stressor effects on early life history stages of marine meroplanktonic invertebrates. The life cycle of C. maenas is biphasic consisting of five pelagic larval stages (four zoeal and one megalopal stage), followed by benthic juvenile and adult phases. The metamorphic molt from the last zoeal stage to the semi-benthic Megalopa includes dramatic changes in ecology, habitat, behavior, feeding, morphology, and physiology. During life history, zoeal stages of C. maenas are of particular interest in the course of climate change as these stages are more vulnerable than the following developmental stages to alterations in abiotic factors. The aim of the present thesis was to develop an integrative view on effects of long-term exposure, from hatching to metamorphosis, to increased temperature and hypo-osmotic conditions on early life history stages of C. maenas. We wanted to gain insights into larval responses to climate driven environmental variables, more specifically, on how tolerance to low salinity is affected by increased temperatures. Consequently, the present study investigated the effect of long-term exposure to twelve different sub-lethal temperature and salinity combinations in an ecological relevant range on larval development of C. maenas. In a multidisciplinary approach, larval responses in performance (survival and developmental duration) and morphology were measured. Furthermore, analysis on larval ontogeny and organogenesis created the foundation for analysis of larval response to multiple stressors in anatomy. Results of the present thesis demonstrated that despite their different life-styles and external morphology, brachyuran larvae are smaller versions of their adults when regarding their inner organization: the adult bauplan unfolds from organ anlagen compressed into miniature organisms. In addition, they provide an overall picture of seemingly gradual organogenesis across larval development and the metamorphic molt, an insight that contrasts with the abrupt external morphological changes during metamorphosis. Gradual anatomical changes in e.g. osmoregulatory structures like gills and antennal glands allowed for ontogenetic shifts of tolerance to temperature and salinity during zoeal development and successive increase in osmo- and thermoregulatory capability. On the other hand, osmoregulatory structures as seen for adults were underdeveloped during zoeal development and therefore do not qualify for osmoregulatory function for these stages. This potentially explains the higher sensitivity of zoeae to hypo-osmotic conditions. Early life history stages of C. maenas were affected on all response levels by the tested multiple stressors. The interaction of temperature and salinity was of antagonistic type, resulting in general reduced stress for larval stages. Nevertheless, low salinity had a strong negative impact on survival, while increased temperature caused ann acceleration of development. Furthermore, the size of zoeae of C. maenas was driven by the interaction of temperature and salinity, with extreme conditions, causing diminished growth, thus resulting in smaller larval size. On the other hand, larval shape was only slightly affected by changes of abiotic factors. Volume of the digestive gland and the heart of larvae from long-term exposure to sub-lethal temperatures and salinities showed high variability. Larval responses were affected by the stressors intensities: moderately high temperatures lessened the negative effects of low salinities, while extreme high temperatures exceeded the ameliorating effect of temperature on stressful salinity conditions. On the other hand, the tolerance to temperature and salinity increased during larval development indicating an ontogenetic shift in response to multiple stressors with development. In addition, performance, morphology, and multiple stressor interaction showed intrapopulation variability among larvae hatched from different females, and between experimental periods. In conclusion, this study highlighted direct effects of abiotic factors on all investigated response levels in early life history stages of the meroplanktonic larvae of the invertebrate C. maenas. High mortality rates combined with higher sensitivity confirm that planktonic early life history stages are the bottleneck during life history of this species. Nevertheless, early life history stages of C. maenas had the ability to cope with wide ranges of changing environmental factors. The antagonism between temperature and salinity on larval development offers potential for early life history stages to persist in a changing world. Furthermore, anatomical structures allow for slight eurytolerance and potentially for compensation of abiotic stress. Overall, slight increases in temperature, driven by climate change may enable larvae of C. maenas to tolerate exposure to moderately low salinities and, combinedwith intrapopulation variability, potentially allows for population persistence. Summarized, this study emphasizes the importance of testing a wide range of ecologically relevant traits in developing pelagic larvae in order to properly characterize their response to environmental change. Changes in abundance and phenology of planktonic larvae like the zoeae of C. maenas have major potential to change a species‘ population structure significantly, and furthermore indirectly affect whole community and ecosystem structures. Therefore, this thesis may serve as a bridge to future studies in evolutionary and ecological developmental biology

A morphological comparative approach of different Barnacle species in Gullmarfjord with special focus on the cirripeds

As a basis for understanding the sympatric occurrence of the balanomorph Semibalanus balanoides, Bala- nus balanus, Balanus improvisus and the verrucomorph Verruca stroemia in the eulittoral and deepwater in Gullmarfjord, we examined the cirral activity and structural morphology of the cirri. All Barnacles showed a rythmical cirral extension of the first three cirripedia, that function as a filter for plankton and detritus. Whereas the cirri of the Balanomorpha built a collective filtration net, also single cirri of the first three cir- ripedia of Verruca stroemia were directed to the mouth orifice. The last three cirri in all examined species functioned as a comb, carrying captured food from the first three cirri to the mouth. As the food spectrum shows no broad differences cirral activity may have little effect on the sympatric occurrence.Als Grundlage für das Verständnis des sympatrischen Vorkommens der Balanomorphe Semibalanus balanoides, Balanus balanus, Balanus improvisus und der Verrucomorphe Verruca stroemia im Eulittoral und Tiefwasser im Gullmarfjord untersuchten wir die Zirraktivität und Strukturmorphologie der Zirri. Alle Seepocken zeigten eine rhythmische cirrale Erweiterung der ersten drei Cirripedien, die als Filter für Plankton und Detritus fungieren. Während die Cirri der Balanomorpha ein kollektives Filternetz bildeten, wurden auch einzelne Cirri der ersten drei Cirripien der Verruca stroemia zur Mundöffnung geleitet. Die letzten drei Cirri bei allen untersuchten Arten fungierten als Kamm, der eingefangenes Futter von den ersten drei Cirri zum Maul transportierte. Da das Nahrungsspektrum keine großen Unterschiede aufweist, kann die zirrale Aktivität einen geringen Einfluss auf das sympatrische Auftreten haben.Peer Reviewe

Ecological Developmental Biology and global ocean change: brachyuran crustacean larvae as models

We discuss several forms of developmental plasticity exhibited by marine crabs, in the context of ecological developmental biology (EcoDevo), and seek to motivate research in EcoDevo by addressing some key questions of the field. We summarise the diversity of plastic developmental responses exhibited during crab development, identify gaps in knowledge and highlight the importance of EcoDevo research in the light of current climate change. Marine crabs show a suite of plastic responses including transgenerational plasticity (e.g., maternal effects), as well as developmental plasticity both within the larval phase and across the larval-juvenile life history transition (e.g., latent effects). Given the potential ecological and evolutionary consequences we think that there is much potential for research in the field of EcoDevo using brachyuran crabs as model organisms

Akzeptanz von Energiesuffizienzpraktiken im Haushalt : Auswertung einer quantitativen Befragung ; im Rahmen des Forschungsprojekts "Energiesuffizienz - Strategien und Instrumente für eine technische, systemische und kulturelle Transformation zur nachhaltigen Begrenzung des Energiebedarfs im Konsumfeld Bauen/Wohnen"

Im Rahmen des Forschungsprojekts "Energiesuffizienz - Strategien und Instrumente für eine technische, systemische und kulturelle Transformation zur nachhaltigen Begrenzung des Energiebedarfs im Konsumfeld Bauen/Wohnen" wurden vielfältige denkbare Suffizienzentscheidungen und -handlungen beobachtet, analysiert, beschrieben und systematisiert. Doch welche dieser Entscheidungen und Handlungen werden bereits heute breit praktiziert, welche werden möglicherweise zukünftig akzeptiert und welche Rahmenbedingungen müssen sich dazu ändern? Eine zentrale Forschungsfrage des Projektes war es zu untersuchen, welche Akzeptanz und Akzeptabilität für bestimmte Suffizienzentscheidungen und –handlungen in der deutschen Bevölkerung besteht. Wie offen sind Menschen für das Teilen von Waschmaschinen oder für einen Umzug in eine kleinere Wohnung, wenn die eigene Wohnung durch Veränderungen der Personenzahl des Haushalts zu groß geworden ist? Wie schätzen Menschen, die eine sehr große Wohnfläche haben, diese selbst ein? Suffizienzentscheidungen und -handlungen müssen in der Regel von der haushaltsführenden Person initiiert und getragen werden und können direkt oder indirekt zu einem höheren Arbeitsaufwand führen. Deshalb sind insbesondere die Akzeptabilität der Optionen für die Haushaltsvorstände sowie deren Akzeptanz und die Einstellung dieser Personengruppe zu Suffizienzentscheidungen und -handlungen von besonderer Relevanz. Um die Beantwortung der o. g. Forschungsfrage quantitativ zu untermauern, wurde deshalb eine Breitenbefragung konzipiert und durchgeführt, in der 601 haushaltsführende Personen als zentrale Akteure suffizienzrelevanter Entscheidungen im Haushalt interviewt wurden

Unmasking intraspecific variation in offspring responses to multiple environmental drivers

Understanding organismal responses to environmental drivers is relevant to predict species capacities to respond to climate change. However, the scarce information available on intraspecific variation in the responses oversimplifies our view of the actual species capacities. We studied intraspecific variation in survival and larval development of a marine coastal invertebrate (shore crab Carcinus maenas) in response to two key environmental drivers (temperature and salinity) characterising coastal habitats. On average, survival of early larval stages (up to zoea IV) exhibited an antagonistic response by which negative effects of low salinity were mitigated at increased temperatures. Such response would be adaptive for species inhabiting coastal regions of freshwater influence under summer conditions and moderate warming. Average responses of developmental time were also antagonistic and may be categorised as a form of thermal mitigation of osmotic stress. The capacity for thermal mitigation of low-salinity stress varied among larvae produced by different females. For survival in particular, deviations did not only consist of variations in the magnitude of the mitigation effect; instead, the range of responses varied from strong effects to no effects of salinity across the thermal range tested. Quantifying intraspecific variation of such capacity is a critical step in understanding responses to climate change: it points towards either an important potential for selection or a critical role of environmental change, operating in the parental environment and leading to stress responses in larvae

Proceedings in Marine Biology

“Proceedings in Marine Biology” is an international journal publishing original research by graduate students on all aspects of marine biology. Subjects covered include: ecological surveys and population studies of oceanic, coastal and shore communities; physiology and experimental biology; taxonomy, morphology and life history of marine animals and plants. Papers are also published on techniques em- ployed at sea for sampling, recording, capture and observation of marine organisms.Zeitschrift zur Kursabschlussreise der Humboldt-Universität zu Berlin (Deutschland) im Bereich Elektronenmikroskopie.Peer Reviewe