The evolution of the head appendages in marine bristle worms
Kumulative Dissertation
Datum der mündl. Prüfung:2023-11-17
Erschienen:2023-12-15
Betreuer:Dr. Conrad Helm
Gutachter:Prof. Dr. Christoph Bleidorn
Gutachter:Prof. Dr. Andreas Stumpner
Dateien
Name:Diss_Final-ohne Lebenslauf.pdf
Size:22.8Mb
Format:PDF
Zusammenfassung
Englisch
Annelida can be found in all kind of habitats and thus show a huge diversity in form, size, and colour. A key structure for their evolutionary success and adaptability to their individual lifestyles are the head appendages. The sheer diversity and the baffling distribution of palps, antennae, buccal lips, and tentacular cirri among annelid families have fascinated researchers over decades. Lars Orrhage, a pioneer in the field of annelid comparative morphology, started to unravel the evolutionary history of head appendages in polychaetes by the systematic investigation of the anterior nervous system. However, recent studies question his findings. By using an integrative morphological approach including immunohistochemistry and confocal laser scanning microscopy in combination with Azan-stained serial histology sections, and subsequent 3D-visualization, I comparatively investigated the innervation patterns of head appendages in annelid key taxa in different ontogenetic stages. Chapter II presents an examination concerning a century-old debate regarding the Terebelliformia, a subgroup within the Sedentaria. A proposal is presented regarding the homology of their numerous buccal tentacles with feeding-palps found in other annelid taxa. Chapter III, which is primarily methodological in nature, emphasizes the necessity of employing 3D visualizations through open-source software. This chapter furnishes a modular workflow and a comprehensive, step-by-step guide for conducting morphological research using image stack-based datasets. Chapter IV involves a comparative study of the larval and adult anterior nervous systems of Magelonidae, Amphinomidae, and Spionidae. As a result of this investigation, homologies were identified between the feeding-palps in both distantly related groups, Paleo- and Pleistoannelida. Chapter V centres on the investigation of members of the errant Nereididae, ultimately culminating in the proposition that feeding-palps and short sensorial palps, collectively referred to as "palps," in Annelida exhibit homology across the entirety of their phylogenetic tree. My thesis challenges established knowledge about the evolution of annelid head appendages and answers old questions by using a combination of microscopic methods. I discuss the changes of the understanding about the evolutionary origin and history of head appendages induced by recent research, and show the benefits of open-source software solutions. Additionally, I stress the importance of the integration of different ontogenetic stages into analyses of old morphological traits.
Keywords: Annelida; Polychaeta; cLSM; Histology; 3D-Visualization; larvae; nervous system; development; palps