A complex system of ligaments and a muscle keep the crystalline lens in place in the eyes of bony fishes (teleosts)

AbstractThe suspension of the crystalline lens in the eye was studied in 11 species of teleost (bony fish) from 10 families and 7 orders by light and electron microscopy. In all species there were 4–5 ligaments in about the equatorial plane of the eye, in which also the tendon of the retractor lentis muscle attaches to the lens. In two cichlid species two additional ligaments were found running from the mid-posterior surface of the lens to the optic nerve head, where they attach to the falciform process. Lens suspension in teleosts is more complex than previously described and well-suited to firmly keep the heavy spherical lens in position for well-focused vision

Ein trans-synaptischer Mechanismus reguliert das Clustern von Glutamat- Rezeptoren an der neuromuskulären Synapse von Drosophila

Chemical synapses are cell-cell contacts, which play a central role in neuronal communication. These cell-cell contacts rely on a precise alignment of pre- and postsynaptic domains. The formation and maturation of synapses requires therefore bidirectional communication across the synaptic cleft. Recent in vitro studies suggest that the transsynaptic Neurexin-Neuroligin (Nrx-Nlg) complex is a key component in this process. The data presented in this work derive from studies that aimed at untangling the function of the Nrx-Nlg complex at the Drosophila neuromuscular junction (NMJ). In a genetic screen several mutant alleles of Drosophila neuroligin 1 (dnlg1) were recovered causing severe assembly defects at NMJs. In situ hybridization experiments showed that DNlg1 is exclusively expressed in muscle fibres, and subsequent immunohistological labeling revealed that DNlg1 forms discrete clusters adjacent to postsynaptic densities (PSDs). Formation of these clusters depends on presynaptic Drosophila Neurexin (DNrx). A second study showed that sufficient localization of DNlg1 depends further on Drosophila synapse defective 1 (DSyd-1), as DSyd-1 interacts with DNrx to control synapse formation at the NMJ. Mutants of dsyd-1, dnrx, and dnlg1 share active zone- cytomatrix defects, which behave non-additive in double mutant combinations. DSyd-1 and DNrx form a complex in vivo, and the PDZ domain-binding motif of DSyd-1 is important for synaptic clustering and immobilization of DNrx. Consequently, glutamate receptor (GluR) incorporation into newly forming PSDs is altered in dsyd-1, dnrx, and dnlg1 mutants. Thus, cooperation between DSyd-1 and DNrx-DNlg1 seems to orchestrate early assembly processes between pre- and postsynaptic membranes, promoting seed-points for newly forming synaptic scaffolds. Finally, a novel mechanism for regulating synaptic GluR clustering is discussed. Unpublished results from a mutated GluR show that altered bio-physical properties of GluRs result in increased mobility and changes in the distinct localization pattern at PSDs. These findings could shed new light on mechanisms which regulate GluR trafficking depending on their physiological properties.Chemische Synapsen sind Zell-Zell-Kontakte, welche eine zentrale Rolles in neuronalen Netzen spielen. Diese Zell-Zell Kontakte sind auf eine präzise Anordnung von prä- und postsynaptischen Strukturen angewiesen sind. Daher ist für die Entstehung und Entwicklung von Synapsen eine bidirektionale Kommunikation über den synaptischen Spalt unerlässlich. Frühere in vitro Experimente ließen vermuten, dass der trans-synaptische Neurexin-Neuroligin (Nrx-Nlg) Komplex eine zentrale Rolle bei diesem Prozess spielt. Die hier präsentierte Arbeit befasst sich mit der Funktion des Nrx-Nlg Komplexes an der neuromuskulären junction (NMJs) von Drosophila melanogaster. Bei einem genetischen Screen wurden mehrere Fliegen mit Mutationen im Drosophila neuroligin 1 (dnlg1) Gen gefunden, welche starke Assemblierungsdefekte an den NMJs aufwiesen. In anschließenden In-situ-Hybridisierungs- und immunohistochemischen Markierungsexperimenten konnte gezeigt werden,dass DNlg1 ausschließlich in Muskelzellen exprimiert wird und in der Nähe von postsynaptic densities (PSDs) clustert. Zur Bildung dieser Cluster benötigt es die Präsenz von präsynaptischem Drosophila Neurexin (DNrx). In einer weiteren Studie stellte sich heraus, dass Drosophila synapse defective 1 (DSyd-1) ebenfalls einen Einfluss auf die Lokalisierung von DNlg1 hat. Darüber hinaus zeigten weitere Experimente, dass DSyd-1 über die Interaktion mit DNrx die Bildung von Synapsen an der NMJ kontrollieren kann: Einzelmutanten für dsyd-1, dnrx und dnlg1 weisen Defekte in der Morphologie ihrer Aktiven Zonen- Cytomatrix auf, welche sich in den Doppelmutanten nicht verstärkten. DSyd-1 und DNrx bilden einen Komplex in vivo, wobei das PDZ-Bindungsmotiv von DSyd-1 eine wichtige Rolle für das synaptische Clustern von DNrx spielt. Desweiteren ist die postsynaptische Anreicherung von Glutamatrezeptoren (GluRs) an neu entstandenen PSDs in dsyd-1, dnrx und dnlg1 Mutanten stark verändert. Somit kann geschlußfolgert werden, dass das Zusammenspiel von DSyd-1 mit dem DNrx- DNlg1 Komplex die frühen Anlagerungsprozesse an der prä- und postsynaptischen Membran dirigiert und hierdurch die Neuentstehung des synaptischen Gerüsts unterstützt. Der letzte Abschnitt dieser Arbeit befasst sich mit einem bisher unbekannten Mechanismus, der das Clustern von GluRs an Synapsen reguliert. Untersucht wurde ein mutierter GluR, der veränderte bio-physikalischen Eigenschaften aufweist, welche sich auf seine synaptische Mobilität und Lokalisierung auswirken. Diese Befunde könnten zu neuen Hypothesen führen, die erklären, warum GluRs mit unterschiedlichen physiologischen Eigenschaften sich in Ihrem synaptischen targeting unterscheiden

Opportunities and limitations: A comparative analysis of citizen science and expert recordings for bioacoustic research

Citizen science is an approach that has become increasingly popular in recent years. Despite this growing popularity, there still is widespread scepticism in the academic world about the validity and quality of data from citizen science projects. And although there might be great potential, citizen science is a rarely used approach in the field of bioacoustics. To better understand the possibilities, but also the limitations, we here evaluated data generated in a citizen science project on nightingale song as a case study. We analysed the quantity and quality of song recordings made in a non-standardized way with a smartphone app by citizen scientists and the standardized recordings made with professional equipment by academic researchers. We made comparisons between the recordings of the two approaches and among the user types of the app to gain insights into the temporal recording patterns, the quantity and quality of the data. To compare the deviation of the acoustic parameters in the recordings with smartphones and professional devices from the original song recordings, we conducted a playback test. Our results showed that depending on the user group, citizen scientists produced many to a lot of recordings of valid quality for further bioacoustic research. Differences between the recordings provided by the citizen and the expert group were mainly caused by the technical quality of the devices used—and to a lesser extent by the citizen scientists themselves. Especially when differences in spectral parameters are to be investigated, our results demonstrate that the use of the same high-quality recording devices and calibrated external microphones would most likely improve data quality. We conclude that many bioacoustic research questions may be carried out with the recordings of citizen scientists. We want to encourage academic researchers to get more involved in participatory projects to harness the potential of citizen science—and to share scientific curiosity and discoveries more directly with society

Discovering Nature in the City with a Citizen Science Mobile App

In the project "Stadtnatur entdecken" (discovering nature in the city) a multidisciplinary team of specialists in biology, informatics, urban ecology and social sciences is looking into how to effectively communicate educational content on environmental topics to young adults and to allow them to contribute as citizen scientists. The mobile app "Naturblick" presents on experience of nature in an urban setting. Several tools are combined in the app that allows users to identify species. The team developed auditory and visual pattern recognition tools that will automatically identify sound recordings and photographs and multi-access identification keys for flora and fauna. There is a map function that will help explore nature in the users’ immediate vicinity in Berlin, Germany, highlighting the diversity of species to be found. Users are able to share their observations and records. The project is designed to involve user participation and continuous improvement based on user feedback of both the content and technology.

Cooperation of Syd-1 with Neurexin synchronizes pre- with postsynaptic assembly

Synapse formation and maturation requires bidirectional communication across the synaptic cleft. The trans-synaptic Neurexin-Neuroligin complex can bridge this cleft, and severe synapse assembly deficits are found in Drosophila melanogaster neuroligin (Nlg1, dnlg1) and neurexin (Nrx-1, dnrx) mutants. We show that the presynaptic active zone protein Syd-1 interacts with Nrx-1 to control synapse formation at the Drosophila neuromuscular junction. Mutants in Syd-1 (RhoGAP100F, dsyd-1), Nrx-1 and Nlg1 shared active zone cytomatrix defects, which were nonadditive. Syd-1 and Nrx-1 formed a complex in vivo, and Syd-1 was important for synaptic clustering and immobilization of Nrx-1. Consequently, postsynaptic clustering of Nlg1 was affected in Syd-1 mutants, and in vivo glutamate receptor incorporation was changed in Syd-1, Nrx-1 and Nlg1 mutants. Stabilization of nascent Syd-1-Liprin-α (DLiprin-α) clusters, important to initialize active zone formation, was Nlg1 dependent. Thus, cooperation between Syd-1 and Nrx-1-Nlg1 seems to orchestrate early assembly processes between pre- and postsynaptic membranes, promoting avidity of newly forming synaptic scaffolds.status: publishe