Ultrastructural and immunohistochemical studies of the ontogeny of the nervous system and the mesoderm in Enteropneusta and Pterobranchia in order to elucidate deuterostome evolution.

形态学和分子数据支持不同的后口动物分类群的系统发育假说，从而推断出不同的进化特征进化。许多被认为是形态学上的“关键特征”并没有在个体发生或结构细节上得到充分的研究。在本项目中，我们利用基于免疫标记标本的串行透射电子显微图结合共聚焦激光扫描显微镜的计算机辅助3d重建，分析了被认为对后口动物进化重要的形态特征的个体发生。到目前为止，我们已经记录了企业颈索的神经系统，并揭示了颈索比迄今为止认为的要复杂得多。例如，神经元体和神经细胞的区域清晰地以简洁的模式组织，不对称的吻孔和颈索之间存在密切的关系，我们在中背线上发现了一个独特的腺体，它是从整个颈索周围的腺环发育而来的。我们的数据库可以重建鳃区周围神经以及体腔、血管、骨骼和肌肉组织。利用连续切片的标本固定在电镜下，我们首次观察到包皮虫的个体发生原基，与其他后口动物的正确模式相对应。根据我们详细的解剖学研究，我们找不到进一步的证据来支持经常被引用的肠动物后肛尾和脊索动物尾巴之间的初级同源性假设。在成功采集到的两种翼枝中，我们刚刚开始形态学分析，通过共聚焦激光扫描显微镜对血清素能神经系统的观察，发现背神经节与脊索动物中枢神经系统的组织结构有相似之处。对翼枝发育阶段的透射电子显微镜也已成功取样，计划在今年晚些时候进行分析，对成虫结构的研究也是如此。综上所述，这个项目已经取得了重要的成果，已经成功地完成了生物样本的采集，因此有可能实现原项目的所有目标，特别是在Sabrina Kaul博士候选人加入这个项目之后。

Morphological and molecular data support different phylogenetic hypotheses of deuterostome taxa and therefore infer contrasting evolutionary character evolution. Many of the supposedly morphological “key characters” have not been adequately studied in proper ontogenetic or structural detail. In the present project, we analyze the ontogeny of morphological characters that have been considered important for deuterostome evolution utilizing computer assisted 3D-reconstruction based on serial transmission electron micrographs in combination with confocal laser scanning microscopy of immunolabeled specimens. We have so far documented the neurulation of the collar cord in an enteropneust and revealed that the collar cord is much more complex than was hitherto believed. E.g., areas of neuronal somata and neuropil are clearly organized in concise patterns, a intimate relation between the asymmetric proboscis pore and the collar cord exists, and we discovered a distinct gland in the mid-dorsal line that develops from a glandular ring around the entire collar. Our database allows the reconstruction of peripheral nerves in the branchial region along with coelomic cavities, blood vessels, skeletal elements, and musculature. Using serially sectioned specimens fixed for electron microscopy, we could for the first time observe the ontogenetic primordium of the pericard, corresponding to the right protocoel of other deuterostomes. Based on our detailed anatomical studies, we could find no further support for the often-quoted primary homology hypothesis between the post-anal tail of enteropneusts and the chordate tail. In the successfully collected two species of pterobranchs, we just started our morphological analyses and found similarities in the dorsal ganglion to the organization of chordate central nervous systems based on confocal laser scanning microscopical investigation of the serotonergic nervous system. Transmission electron microscopy of developmental stages of pterobranchs that were also successfully sampled, are scheduled for analysis later this year, as are studies of adult structures. In summary, this project has already yielded important results, has successfully completed acquisition of biological samples, and has therefore the potential to fulfill all goals aimed for in the original project, especially after Sabrina Kaul a PhD candidate ideally trained for this project joined the project.