Developmental and gene expression patterns during neurogenesis in basal branching Annelida

• Applicant: Dr. Conrad Helm
• Subject Area: Evolutionary Cell and Developmental Biology (Zoology) ; Systematics and Morphology (Zoology)
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 264906995

The Annelida are represented by various taxa possessing a huge variety of ecological and morphological features. Nevertheless, most annelids exhibit true segmentation, which is represented by the serial repetition of different organ systems and detectable over the whole body. Notably, former discussions about characteristics of the last common annelid ancestor were difficult due to the lack of a well-supported annelid phylogeny. Recently, transcriptomic data and the placement of several annelid families at the base of the annelid radiation provide a solid framework for further investigations concerning the evolution of different annelid organ systems and developmental patterns.Therefore, goal of the project will be the investigation of the larval development in the basal branching annelid Magelona johnstoni (Magelonidae) to uncover general developmental patterns. Interestingly, preliminary results dealing with larval and adult nervous system characters indicate characters that strongly differ from the conditions known for derived annelid taxa like, e.g., Platynereis or Capitella. Thus, adult magelonids exhibit a non-segmented, intra-epidermal nervous system instead of the ladder-like, sub-epidermal arrangement described for most other annelids. Focusing on nervous system development, immunocytochemical investigations along with gene expression studies (in situ hybridization) will be used to investigate the neurogenesis in this member of the basal branching Magelonidae. With emphasis on the larval development of M. johnstoni and the expression pattern of the neurogenesis genes Pax6, Pax3/7, msx, nk2.1, nk6, engrailed, and the neuroectoderm markers synaptotagmin and elav, along with immunohistochemical methods, the intended project will provide comparable developmental and gene expression patterns of the sparsely investigated basal branching annelids. The investigations therefore will shed light on the evolution of the annelid nervous system and the annelid body plan in general. Comparisons of the generated data of Magelona johnstoni with existing investigations in so-called annelid model organisms like, e.g, Platynereis or Capitella, will substantially broaden the scarce knowledge concerning the evolution of body plans and organ systems within the Annelida. Furthermore, investigations of the basal branching annelid Magelona johnstoni provide fundamental and comparable insights into the evolution of lophotrochozoan nervous systems and into the evolution of metazoan neuronal patterns in general.

• DFG Programme: Research Fellowships
• International Connection: Norway
• Host: Dr. Harald Hausen