Evolution and development of evolutionary novelties during anuran ontogenesis

进化的新颖性是一种形态结构，它使生物体具有新的功能或进一步专门化祖先的功能。这些创新是如何进化的，以及是什么机制导致了它们的发展，这是发育生物学领域的基本问题。无尾目蝌蚪的软骨骨骼的组成在脊椎动物中是独一无二的。蝌蚪的下巴由两个额外的软骨组成。肩上软骨是上颌的一部分，而肩下软骨是无尾两栖类幼虫下颌骨的一部分。下软骨位于两个Meckel‘S软骨的前端之间。在下颌下软骨和梅克尔的S软骨之间，存在着独特的下颌内关节。存在几种无尾两栖动物，它们进一步发育出额外的软骨。根据它们各自的位置，这些软骨被称为麦氏下软骨、下颌软骨或肩侧软骨。控制有机体个体发育并确保其以某种方式发展的遗传信号，必须对进化新颖性的进化和发展负责。非洲爪蛙的研究表明，nkx基因bapx1和zax可能参与了上、下软骨的进化。我们将对三种不同蛙的肌肉骨骼发育进行研究，以全面了解无尾两栖动物的个体发生。这篇综述将提供有关肌肉骨骼发育顺序的信息，关于特定摄食习惯对发育的影响，以及关于几种无尾两栖动物新物种的具体发展。此外，我们还将研究选定的NKX基因对这些新事物的进化和发展的影响。我们将使用经典的组织学和现代方法，如免疫组织化学、激光共聚焦扫描显微镜和μ计算机断层扫描技术来研究肌肉骨骼的形态发生。为了研究和操纵各种nkx基因的基因表达，将使用药理物质和CRISPR/Cas9。我们将利用整体原位杂交和定量聚合酶链式反应来研究基因在空间和时间上的表达。这个项目将极大地扩展我们对幼蛙肌肉骨骼发育的了解。此外，它将促进我们对进化新颖性进化的机制的理解。

Evolutionary novelties are morphological structures that enable new functions or further specialize ancestral functions in an organism. How such innovations evolved and which mechanisms led to their development are essential questions in the field of developmental biology.The composition of the cartilaginous skeleton of anuran tadpoles is unique among vertebrates. The jaw of tadpoles consists of two additional cartilages. The suprarostral cartilage is part of the upper jaw, whereas the infrarostral cartilage is part of the lower jaw of larval anurans. The infrarostral cartilage is situated between the anterior tips of the two Meckel´s cartilages. Between the infrarostral and Meckel´s cartilage the unique intramandibular joint is present. Several anurans exist which develop further additional cartilages. Depending on their respective position, these cartilages are called sub-meckelian, admandibular or adrostral cartilage. Genetic signaling, which controls ontogenesis of an organism and ensures that it develops in a certain way, must be responsible for the evolution and development of evolutionary novelties. Investigations in Xenopus laevis have shown that the the nkx-genes bapx1 and zax may have been involved in the evolution of the infrarostral and adrostral cartilage.We will investigate the musculoskeletal development of three different frogs to obtain a comprehensive overview on the ontogenesis of anurans. This overview will provide information about the sequence of the musculoskeletal development, about the influence of the specific feeding habit on the development and about the specific development of several anuran novelties. Additionally, the influence of selected nkx-genes on the evolution and development of these novelties will be investigated.We will study musculoskeletal morphogenesis using classic histology and modern approaches such as immunohistochemistry, confocal laser scanning microscopy and μ-computed tomography. To investigate and manipulate the gene expression of various nkx-genes, pharmacological substances and CRISPR/Cas9 will be used. Spatial and temporal gene expression will be studied using whole mount in situ hybridization and quantitative PCR.This project will significantly expand our knowledge of the musculoskeletal development of larval frogs. Furthermore, it will advance our understanding of the mechanisms responsible for the evolution of evolutionary novelties.