June Feliciano Fronda Ordonez


Neuronal cell type development in the chaetognath Spadella cephaloptera (Busch, 1851)

PhD student
Advisor: Tim Wollesen

Unit for Integrative Zoology, Department of Evolutionary Biology
University of Vienna


The origin and evolution of animal neurons and nervous systems has been a subject of debate fordecades and remains one of the most puzzling topics in the field of animal evolution and development,especially in non-chordate taxa. Chaetognaths (arrow worms) are dart-shaped marine invertebrates thatexhibit a number of unique neuronal organization and developmental features, including anintraepidermal ventral nerve center and a neuro-musculature that lacks specialized junctions of axonalvaricosities. This group is alos often regarded as enigmatic because developmental- and genetic-basedclassification have resulted in their unstable phylogenetic positions. Recently, they have beenphylogenetically placed in the protostome group, as a sister clade to lophotrochozoans, making themparticularly interesting and significant for understanding how neurons and the nervous systems evolvedwithin protostomes. However, knowledge on their neurogenesis and neural patterning, especially themolecular regulatory circuitry that allow these processes, remains incomplete. Thus, the overall goalof the PhD research is to describe the molecular basis of some aspects of neuronal cell-typedevelopment and organization in the chaetognath Spadella cephaloptera, using single-nucleustranscriptomics and in-situ hybridization approaches, in order to infer evolutionary relationships ofnervous system development between this key group and other protostomes. In this talk, I willintroduce my PhD research and present my current progress and future directions.