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

形态和分子数据支持后口类群不同的系统发育假说，从而推断出不同的进化特征进化。许多被认为是形态上的“关键特征”还没有得到适当的个体发生或结构细节的充分研究。在本项目中，我们利用基于连续透射电子显微镜的计算机辅助三维重建，结合免疫标记标本的激光共聚焦扫描显微镜，分析了被认为对后口生物进化重要的形态特征的个体发育。到目前为止，我们已经记录了肠腔积液中颈髓的神经形成，并揭示了颈索比迄今认为的要复杂得多。例如，神经元胞体和神经束的区域被清晰地组织成简洁的图案，不对称的鼻孔和颈索之间存在着密切的联系，我们发现在中背线上有一个明显的腺体，它是由整个颈圈周围的腺环发育而来的。我们的数据库允许重建颧骨区的周围神经以及体腔、血管、骨骼元素和肌肉系统。利用电子显微镜固定的连续切片标本，我们首次可以观察到与其他后口动物的右侧原腔相对应的Pericard个体发育原基。基于我们详细的解剖学研究，我们没有发现进一步支持经常被引用的肠息肉肛门后尾巴和脊索尾巴之间的主要同源性假说。在成功采集的两种翼支动物中，我们刚刚开始了我们的形态分析，通过对5-羟色胺能神经系统的激光共聚焦扫描显微镜观察，发现背神经节与中枢神经系统的组织有相似之处。也成功取样的翼鳍鸟发育阶段的透射电子显微镜，计划在今年晚些时候进行分析，对成年结构的研究也是如此。总而言之，这个项目已经取得了重要的成果，成功地完成了生物样本的采集，因此有可能实现最初项目中的所有目标，特别是在为该项目接受过理想培训的博士生Sabrina Kaul加入该项目之后。

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.