Coprophagous features in carnivorous Nepenthes plants: A task for ureases

Most terrestrial carnivorous plants are specialized on insect prey digestion to obtain additional nutrients. Few species of the genus Nepenthes developed mutualistic relationships with mammals for nitrogen supplementation. Whether dietary changes require certain enzymatic composition to utilize new sources of nutrients has rarely been tested. Here, we investigated the role of urease for Nepenthes hemsleyana that gains nitrogen from the bat Kerivoula hardwickii while it roosts inside the pitchers. We hypothesized that N. hemsleyana is able to use urea from the bats' excrements. In fact, we demonstrate that 15N-enriched urea provided to Nepenthes pitchers is metabolized and its nitrogen is distributed within the plant. As ureases are necessary to degrade urea, these hydrolytic enzymes should be involved. We proved the presence and enzymatic activity of a urease for Nepenthes plant tissues. The corresponding urease cDNA from N. hemsleyana was isolated and functionally expressed. A comprehensive phylogenetic analysis for eukaryotic ureases, including Nepenthes and five other carnivorous plants' taxa, identified them as canonical ureases and reflects the plant phylogeny. Hence, this study reveals ureases as an emblematic example for an efficient, low-cost but high adaptive plasticity in plants while developing a further specialized lifestyle from carnivory to coprophagy

Seismic characterization of a rapidly-rising jökulhlaup cycle at the A.P. Olsen Ice Cap, NE-Greenland

Rapidly-rising jökulhlaups, or glacial outburst floods, are a phenomenon with a high potential for damage. The initiation and propagation processes of a rapidly-rising jökulhlaup are still not fully understood. Seismic monitoring can contribute to an improved process understanding, but comprehensive long-term seismic monitoring campaigns capturing the dynamics of a rapidly-rising jökulhlaup have not been reported so far. To fill this gap, we installed a seismic network at the marginal, ice-dammed lake of the A.P. Olsen Ice Cap (APO) in NE-Greenland. Episodic outbursts from the lake cause flood waves in the Zackenberg river, characterized by a rapid discharge increase within a few hours. Our 6 months long seismic dataset comprises the whole fill-and-drain cycle of the ice-dammed lake in 2012 and includes one of the most destructive floods recorded so far for the Zackenberg river. Seismic event detection and localization reveals abundant surface crevassing and correlates with changes of the river discharge. Seismic interferometry suggests the existence of a thin basal sedimentary layer. We show that the ballistic part of the first surface waves can potentially be used to infer medium changes in both the ice body and the basal layer. Interpretation of time-lapse interferograms is challenged by a varying ambient noise source distribution.ISSN:0022-1430ISSN:1727-565

A switch for epitaxial graphene electronics: Utilizing the silicon carbide substrate as transistor channel

Due to the lack of graphene transistors with large on/off ratio, we propose a concept employing both epitaxial graphene and its underlying substrate silicon carbide (SiC) as electronic materials. We demonstrate a simple, robust, and scalable transistor, in which graphene serves as electrodes and SiC as a semiconducting channel. The common interface has to be chosen such that it provides favorable charge injection. The insulator and gate functionality is realized by an ionic liquid gate for convenience but could be taken over by a solid gate stack. On/off ratios exceeding 44000 at room temperature are found

Results of WICOVIR Gargle Pool PCR Testing in German Schools Based on the First 100,000 Tests

Background: Opening schools and keeping children safe from SARS-CoV-2 infections at the same time is urgently needed to protect children from direct and indirect consequences of the COVID-19 pandemic. To achieve this goal, a safe, efficient, and cost-effective SARS-CoV-2 testing system for schools in addition to standard hygiene measures is necessary. Methods: We implemented the screening WICOVIR concept for schools in the southeast of Germany, which is based on gargling at home, pooling of samples in schools, and assessment of SARS-CoV-2 by pool rRT-PCR, performed decentralized in numerous participating laboratories. Depooling was performed if pools were positive, and results were transmitted with software specifically developed for the project within a day. Here, we report the results after the first 13 weeks in the project. Findings: We developed and implemented the proof-of-concept test system within a pilot phase of 7 weeks based on almost 17,000 participants. After 6 weeks in the main phase of the project, we performed >100,000 tests in total, analyzed in 7,896 pools, identifying 19 cases in >100 participating schools. On average, positive children showed an individual CT value of 31 when identified in the pools. Up to 30 samples were pooled (mean 13) in general, based on school classes and attached school staff. All three participating laboratories detected positive samples reliably with their previously established rRT-PCR standard protocols. When self-administered antigen tests were performed concomitantly in positive cases, only one of these eight tests was positive, and when antigen tests performed after positive pool rRT-PCR results were already known were included, 3 out of 11 truly positive tests were also identified by antigen testing. After 3 weeks of repetitive WICOVIR testing twice weekly, the detection rate of positive children in that cohort decreased significantly from 0.042 to 0.012 (p = 0.008). Interpretation: Repeated gargle pool rRT-PCR testing can be implemented quickly in schools. It is an effective, valid, and well-received test system for schools, superior to antigen tests in sensitivity, acceptance, and costs

Stabilization of a bat-pitcher plant mutualism

Presumably every organism on earth is involved in at least one mutualistic interaction with one or several other species. To interact with each other, the species need traits that provide benefits to the partner species. Surprisingly, the function of traits for the stabilization of mutualisms has rarely been investigated, despite of a general lack of knowledge how mutualisms are maintained. The aim of this work was to find functional traits, which stabilize the mutualism between a bat species and a carnivorous pitcher plant in Northern Borneo. Kerivoula hardwickii is the only bat species known to roost in pitcher-shaped trapping organs of Palaeotropical pitcher plants (Nepenthes). These bats fertilize the pitcher plant Nepenthes hemsleyana with their nutritious nitrogen-rich faeces while roosting inside the pitchers. The plants have outsourced capture and digestion of arthropod prey to the bats on which they strongly rely for nutrient acquisition. The bats in contrast are less dependent on their mutualism partner as they also roost in pitchers of two further Nepenthes species as well as in developing furled leaves of various plant species in the order Zingiberales. In earlier studies, we found that N. hemsleyana outcompetes alternative roosts by providing high-quality roosts for the bats. However, which traits exactly stabilize the mutualism between K. hardwickii and N. hemsleyana was still unclear. I found that both the bats and the pitcher plants show traits, which have the potential to stabilize their interaction. On the level of morphological traits, I found that the pitchers have a low fluid level and a particular shape that provide just enough roosting space for one individual of the solitary K. hardwickii, a mother with juvenile or a mating couple. The bats have enlarged thumb and foot pads that enable them to cling to the smooth surfaces of their roosts without using their claws. This avoids damage to the sensitive N. hemsleyana pitchers. On the level of communicational traits, again N. hemsleyana acquired morphological structures that act as effective ultrasound-reflectors, which guide the echo-orientating bats to the opening of the pitchers and help the bats to identify their mutualism partner. The bats’ calls on the other hand are characterized by extraordinary high starting frequencies and broad bandwidths, which enable K. hardwickii to easily locate pitchers of N. hemsleyana and other Nepenthes species in their dense habitats. Finally, on the level of behavioural traits the bats often but not always prefer their mutualism partner to other roosts when they can select roosts in their natural environment or in behavioural experiments. The reason for this behaviour seems to be a combination of 1) N. hemsleyana’s superior quality compared to alternative roosts and 2) different roosting traditions of the bats. In conclusion, the mutualism between bats and pitcher plants is asymmetric as N. hemsleyana is more dependent on K. hardwickii than vice versa. For the plants bat faeces present their most important nutrient source. In contrast, K. hardwickii can select between alternative roosting plants. This asymmetric dependency is reflected in the specifity and function of the traits that stabilize the mutualism in each of the two involved species. Especially on the morphological level, N. hemsleyana seems to have evolved several traits that perfectly fit to K. hardwickii. In contrast, the bats’ traits more generally facilitate their roosting in funnel-shaped plant structures and their occurrence in cluttered habitats. Thus, they are probably exaptations (i.e. traits that evolved for another reason) that are nevertheless functional and stabilize the mutualism with N. hemsleyana. This plant‘s superior roost quality is likely a consequence of the competition with alternative roosting plants and is a pre-requisite for the bats to prefer N. hemsleyana. Moreover, my study confirms earlier findings that asymmetric dependencies support the stabilization of mutualistic interactions. Finally, my work indicates that the specifity of functional traits can be used as a measure to determine mutual dependencies of mutualistic partners.Buchstäblich jeder Organismus der Erde interagiert mutualistisch mit mindestens einer anderen Art. Dazu benötigen die betroffenen Spezies Merkmale, die für den Partner gewinnbringend sind. Überraschenderweise wurden solche Merkmale auf ihre Funktion für die Stabilisierung von Mutualismen selten untersucht, obwohl noch immer unklar ist, welche Mechanismen Mutualismen erhalten. Ziel dieser Arbeit war es, funktionelle Merkmale zu finden, die den Mutualismus zwischen einer Fledermausart und einer fleischfressenden Kannenpflanze auf Nord-Borneo stabilisieren. Als einzig bekannte Fledermausart übertagt Kerivoula hardwickii in den kannenförmigen Fangorganen paläotropischer Kannenpflanzen (Nepenthes). Dabei düngen die Fledermäuse die Kannenpflanzenart Nepenthes hemsleyana mit ihrem stickstoffhaltigen, nährstoffreichen Kot. Die Pflanzen haben den Fang und die Verdauung ihrer Beute, die vor allem aus Arthropoden besteht, auf die Fledermäuse ausgelagert. Von diesen sind N. hemsleyana daher stark abhängig, um ihren Nährstoffbedarf decken zu können. Im Gegensatz dazu hängen die Fledermäuse weniger von N. hemsleyana ab, da sie zusätzlich die Kannen anderer Nepenthes-Arten sowie sich entwickelnde gedrehte Blätter einer Reihe unterschiedlicher Pflanzenarten der Ordnung Zingiberales als Tagesquartier nutzen. In früheren Studien konnten wir zeigen, dass N. hemsleyana aufgrund ihrer Qualität als Fledermausquartier wettbewerbsstärker ist als diese (unfreiwillig) konkurrierenden Pflanzenquartiere. Welche funktionellen Merkmale jedoch den Mutualismus zwischen N. hemsleyana und K. hardwickii stabilisieren, war bisher weitgehend unklar. Sowohl für die Pflanzen wie für die Fledermäuse konnte ich Merkmale bestimmen, die potentiell stabilisierend auf die Interaktion der beiden Partner wirken. Auf morphologischer Merkmalsebene fand ich heraus, dass die Pflanzen einen niedrigen Flüssigkeitsstand und eine spezielle Form haben, die gerade genügend Platz für ein einzelnes Individuum, eine Mutter mit Jungtier oder ein sich fortpflanzendes K. hardwickii-Pärchen bereitstellt. Die Fledermäuse haben vergrößerte Daumen- und Fußflächen, die es ihnen erlauben, sich an die glatten Oberflächen ihrer Tagesquartiere zu hängen, ohne ihre Krallen einsetzen zu müssen. Dadurch vermeiden sie Beschädigungen an der sensiblen Oberfläche der N. hemsleyana-Kannen. Auf der kommunikativen Merkmalsebene konnte ich zeigen, dass N. hemsleyana morphologische Strukturen aufweist, die als effektive Ultraschallreflektoren wirken. Diese weisen den echoortenden Fledermäusen den Weg zur Kannenöffnung und helfen den Tieren, ihren Mutualismuspartner zu erkennen. Die Ultraschallrufe der Fledermäuse wiederum sind gekennzeichnet durch ungewöhnlich hohe Startfrequenzen und enorme Bandbreiten, die es K. hardwickii erlauben, die Kannen von N. hemsleyana und anderer Nepenthes-Arten in ihren dichtbewachsenen Habitaten aufzufinden. Auf Ebene der Verhaltensmerkmale schließlich bevorzugen die Fledermäuse häufig, jedoch nicht ausschließlich, die Kannen ihres Mutualismuspartners gegenüber alternativen Tagesquartieren und zwar sowohl im Freiland als auch bei Verhaltensexperimenten. Der Grund für dieses Verhalten ist vermutlich eine Kombination aus 1) der überragenden Qualität als Tagesquartier verglichen zu anderen Pflanzen seitens N. hemsleyana und 2) unterschiedlichen Traditionen bezüglich der Tagesquartierwahl seitens der Fledermäuse. Zusammenfassend lässt sich feststellen, dass der Mutualismus zwischen Fledermäusen und Kannenpflanzen asymmetrisch ist, wobei N. hemsleyana stärker von K. hardwickii abhängig ist als umgekehrt. Dagegen können die Fledermäuse zwischen unterschiedlichen Tagesquartieren wählen. Bei beiden Partnern spiegelt sich diese asymmetrische Abhängigkeit in den Merkmalen wider, welche den Mutualismus stabilisieren, und zwar sowohl bezüglich ihrer Spezifität auf den Partner hin als auch in ihrer Funktion. Besonders auf morphologischer Ebene scheint N. hemsleyana Merkmale entwickelt zu haben, die perfekt auf K. hardwickii angepasst sind. Die Merkmale der Fledermäuse dagegen sind unspezifischer und unterstützen generell das Übertagen in tunnelförmigen Pflanzenstrukturen und ihr Vorkommen in dichtbewachsenen Habitaten. Daher sind die Fledermausmerkmale vermutlich als Präadaptionen zu sehen, als Merkmale also, die zu einem anderen Zweck evolvierten, aber dennoch funktionell sind und den Mutualismus mit N. hemsleyana stabilisieren. Die überragende Tagesquartierqualität von N. hemsleyana resultiert vermutlich aus dem Wettbewerb mit alternativen quartierbietenden Pflanzen und hilft N. hemsleyana, die Fledermäuse stärker an sich zu binden. Darüber hinaus bestätigt meine Studie frühere Erkenntnisse, dass asymmetrische Abhängigkeiten die Stabilisierung mutualistischer Interaktionen unterstützen. Letztendlich gibt meine Arbeit Hinweise darauf, dass die Spezifität der funktionellen Merkmale als Maß für die gegenseitige Abhängigkeit mutualistischer Partner verwendet werden kann

Stabilization of a bat-pitcher plant mutualism

International audienceDespite the long persistence of many mutualisms, it is largely unknown which mechanisms stabilize these interactions. This is especially true if only one mutualism partner can choose alternative partners while the other cannot, resulting in a power asymmetry. According to biological market theory the choosing partner should prefer the more dependent partner if the latter offers commodities of higher quality than its competitors. We tested this prediction using Bornean carnivorous pitcher plants (Nepenthes hemsleyana) that strongly rely on faecal nitrogen of bats (Kerivoula hardwickii) which roost inside the pitchers. The bats also roost in furled leaves of various plants. Surprisingly, during field observations the bats did not always choose N. hemsleyana pitchers despite their superior quality but were generally faithful either to pitchers or to furled leaves. In behavioural experiments 21% of the leaf-roosting bats switched to pitchers, while the majority of these bats and all pitcher-roosting individuals were faithful to the roost type in which we had found them. Genetic differentiation cannot explain this faithfulness, which likely results from different roosting traditions. Such traditions could have stabilizing or destabilizing effects on various mutualisms and should be investigated in more detai