Prof. Dr. Thomas Bartolomaeus

The focus of our long-term studies is the radiation of the Bilateria. In a combined approach to uncover the kinship relations within this group we use comparative morphological and molecular methods. The molecular work has been carried out since 2000 in collaboration with Christoph Bleidorn and Lars Podsiadlowski. Together with Lars Vogt, we address the linguistic problem of morphology and develop a resource descriptive framework (RDF) ontology for metazoans. The position of the Nemertea in the system of Bilateria and the evolution of the annelids are currently the focus of my work. Current projects include comparative anatomical studies of nemertines, which, in collaboration with Jörn von Döhren, should help to clarify their phylogeny. The ultrastructure of chaetogenesis and larval kidneys in annelids belongs to another set of current projects, which were originally performed in collaboration with Björn Quast and Harald Hausen and now continued with Ekin Tilic. Within the DFG priority programme "Deep Metazoan Phylogeny" we also analyzed the fate of embryonic coeloms and the formation of nephridia in arthropods in collaboration with Markus Koch. The evolution of the nervous system in the spiralian animals forms another focus of my studies jointly with Pat Beckers.

 

Polychaetes are a highly diverse group of annelids, whose relationships are not sufficiently known. The majority of the previous analyses lack comparative morphological data of as many subgroups of polychaetes as possible. Since 1996 we have been working on the ultrastructure and formation of chaetae and larval nephridia.

Despite their high taxon specificity, chaetae show a high structural diversity among polychaetes, so that they play an important role in taxonomy. Chaetae shape and orientation are determined by a single cell, the chaetoblast, the microvilli of which pattern changes during chaetogenesis. Changes in the superficial microvilli patttern "frozen in time" determine the specific state of a chaeta. Due to the taxon specificity of chaetae, it can be assumed that chaetogenesis is subject to strict regulation to ensure that chaetae develop identically in individuals, populations and species. Therefore, the regulation of chaetogenesis should be conserved in such a way that it could be passed on within parentage communities. An identical structure and formation of chaetae should therefore represent a strong phylogenetic signal indicating larger communities of descent. Studies on chaetogenesis are currently performed in collaboration with Ekin Tilic.

Larval protonephridia are generally called "head kidneys" and are the first renal organs that are differentiated in the course of ontogenesis in polychaetes. The head kidneyes indeed are restricted to the larval stage. They consist of a limited number of cells but show a high variability between groups. So far, it has been shown that a corresponding ultrastructure of these organs indicates monophyletic units among annelids. In addition, head kidneys are very well suited for RDF coding. This work is done in collaboration with Björn Quast, Peter Grobe and Lars Vogt.

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