Biology subjects

Arndt, H.

Publications and source records attributed to Arndt, H..

4 recordsLinked to original sources

bioRxiv2025

The morphology and small subunit rDNA gene phylogeny of the novel goniomonad genus Ebisugoniomonas and two novel Poseidogoniomonas species

Goniomonads are heterotrophic representatives of Cryptista, sister lineage to the phototrophic Cryptists. Goniomonads are morphologically and genetically diverse, comprising nine genera described so far. Besides morphologically described genera, SSU rDNA sequencing data has revealed the existence of at least one more monophyletic genus-level lineage within goniomonads, as well as more novel species within the described genera. Furthermore, the diversity of SSU rDNA sequences within goniomonads is not fully investigated, and addition of novel sequences can be crucial for understanding the evolution and diversity of goniomonads and for providing a basis for taxonomic descriptions. The morphological data record available for goniomonads is relatively limited: many cellular features remain undescribed, or described only for a few isolates. In this study, we describe the new genus and species Ebisugoniomonas hispanica n. gen. n. sp., and two novel species within Poseidogoniomonas: P. posteriocircus n. sp. and P. zopfkaesiformis n. sp. We report a range of observations on the cellular features of goniomonads: periplast plate arrangement pattern and intracellular structures. We also update the SSU rDNA phylogeny of goniomonads by adding sequences from novel isolates and environmental DNA studies. Several sequences recovered from novel isolates and environmental DNA datasets likely represent highly divergent lineages of goniomonads in the SSU rDNA phylogeny.

microbiology↗

bioRxiv2024

Cryptic Cryptophytes-revision of the genus Goniomonas

Cryptomonad protists are ubiquitously distributed over marine and freshwater habitats. As an exception to the coloured cryptomonads, the heterotrophic cryptomonads of the genus Goniomonas have an ancestral phylogenetic position. They lack any kind of chloroplast and most likely represent a basal group to those cryptomonad groups having obtained their chloroplast by secondary endosymbiosis. Earlier studies have shown a deep divergence between freshwater and marine clades of goniomonads that comprise large genetic distances between members within the group and also between the two groups of marine and freshwater taxa. Still, marine and freshwater species carry the same genus name, and until up to date only few species have been described. We therefore restructured goniomonad systematics based not only on a separation of marine and freshwater taxa, but, taking the large genetic distances into account, also several new genera are described. Based on morphological as well as phylogenetic data (18S rDNA sequences), this leads to the formation of the freshwater genera Limnogoniomonas n. g., Goniomonas and Aquagoniomonas n. g. and the marine genera Neptunogoniomonas n. g., Baltigoniomonas n. g., Marigoniomonas n. g., Thalassogoniomonas n. g., Poseidogoniomonas n. g. and Cosmogoniomonas n. g. To give the restructuring process a stable basis, we additionally propose a neotype for Goniomonas truncata.

molecular biology↗

bioRxiv2024

The dilemma of underestimating freshwater biodiversity: morphological and molecular approaches

BackgroundThe Lower Rhine ecosystem has been extensively shaped by human activities, destroying, modifying, and even creating novel water bodies as habitats. Freshwater systems are hotspots of biodiversity and highly complex ecosystems. However, knowledge and description of its biodiversity across all trophic levels is still incomplete and the complexity of interactions remains unresolved, especially below the micro scale. This is even true for important international inland waterways such as the River Rhine. We here document the biodiversity of the Lower Rhine and associated water bodies, spanning from the level of protists up to the level of larger invertebrate predators and herbivores organized in faunal size classes (nano-, micro, meio- and macrofauna). This study is part of a long-term ecological research project (LTER-D REES). Our study includes two riprap sections of the rivers main channel, two oxbows and two gravel-pit lakes in the rivers flood plain. Diversity was assessed through morphotype richness and metabarcoding, as well as accounting for sediment composition. ResultsWe found high discrepancies between amplicon sequencing variants (ASVs) and morphotype richness in all size classes, as well as a problematic limitation of reference sequences from freshwater organisms in public databases. Irrespective of the size class, we observed habitat specific zoobenthos communities in each of the three investigated habitat types, with few taxa or taxonomic groups overlapping. ConclusionsOur results demonstrate the importance to integrate different methodologies and extend freshwater sequencing efforts for the assessment of biodiversity across all trophic levels, as particularly relevant for long term projects.

ecology↗

bioRxiv2020

Dynamic patterns of YAP1 expression and cellular localization in the developing and injured utricle

The Hippo pathway is an evolutionarily conserved signaling pathway involved in regulating organ size, development, homeostasis and regeneration1-4. YAP1 is a transcriptional coactivator and the primary effector of Hippo signaling. Upstream activation of the Hippo pathway leads to nuclear translocation of YAP1, which then evokes changes in gene expression and cell cycle entry5. A prior study has demonstrated nuclear translocation of YAP1 in the supporting cells of the developing utricle6, but the possible role of YAP1 in hair cell regeneration is unclear. The present study characterizes the cellular localization of YAP1 in the utricles of mice and chicks, both under normal conditions and after hair cell injury. During neonatal development of the mouse utricle, YAP1 expression was observed in the cytoplasm of supporting cells, and was also transiently expressed in the cytoplasm of hair cells. We also observed temporary nuclear translocation of YAP1 in supporting cells of the mouse utricle at short time periods after placement in organotypic culture. However, little or no nuclear translocation of YAP1 was observed after injury to the utricles of neonatal or mature mice. In contrast, a significant degree of YAP1 nuclear translocation was observed in the chicken utricle after streptomycin-induced hair cell damage in vitro and in vivo. Together, these data suggest that differences in YAP1 signaling may be partly responsible for the distinct regenerative abilities of the avian vs. mammalian inner ear.

cell biology↗