Comparison of life-long neurogenic processes in sea spiders and crustaceans - indications for an ancestral adult neurogenic system in Arthropoda?

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Adult neurogenesis, i.e., the production and integration of neural cells into adult nervous systems, is well known in vertebrates. By comparison, however, this phenomenon remains incompletely documented in numerous invertebrate groups. This holds also for the most diverse animal lineage Arthropoda, for which detailed data are only available in decapod crustaceans and to a lesser degree for some insects.In this project, adult neurogenic processes in sea spiders (Pycnogonida) and crayfish as representatives of decapod crustaceans will be investigated at the cell genealogical level. A combination of in-vitro and in-vivo techniques will be applied in conjunction with (time-lapse) confocal imaging and 3D reconstruction.A major goal of the investigations on crayfish is to clarify whether first-generation neural precursors are recruited from specific blood cells, which represent a component of the innate immune system and are descendents from hematopoietic stem cells. This would highlight a remarkable trans-differentiation from cells of mesodermal origin into neural cell types that are classical textbook examples for an ectodermal cell fate.The studies on sea spiders, on the other hand, will first of all seek to unequivocally prove that neurogenic processes - as strongly indicated by recent findings - do continue throughout adult life of these animals. Subsequent experiments will then aim to provide a better characterization of the neural precursors, their cell division and cell migration dynamics, and of the differentiating neural cell types.Moreover, potential similarities between the adult neurogenic systems of sea spiders and crayfish will be critically assessed and evaluated against an evolutionary background. It will be determined whether the involved structures and processes can be considered as being homologous, i.e., to have a common evolutionary origin. Since the sea spider lineage is a relatively early offshoot during arthropod evolution, this promises to reveal important insights into an ancestral life-long neurogenic system in the arthropod stem species.