Evolution and development of evolutionary novelties during anuran ontogenesis

进化上的新颖性是指使生物体具有新功能或进一步特化祖先功能的形态结构。这些创新是如何进化的，哪些机制导致了它们的发展，这是发育生物学领域的基本问题。无尾蝌蚪的软骨骨骼组成在脊椎动物中是独一无二的。蝌蚪的下颚由两个额外的软骨组成。喙上软骨是上颚的一部分，而喙下软骨是无尾目动物幼虫下颌的一部分。鼻下软骨位于两个梅克尔软骨的前尖端之间。在鼻下软骨和梅克尔软骨之间存在独特的下颌内关节。有几种无尾目动物发育了额外的软骨。根据它们各自的位置，这些软骨被称为下颌下软骨、下颌软骨或下颌前软骨。遗传信号控制着生物体的个体发生，并确保其以某种方式发育，必然对进化新事物的进化和发展负责。对非洲爪蟾的研究表明，nkx基因bapx1和zax可能参与了鼻下和鼻前软骨的进化。我们将研究三种不同青蛙的肌肉骨骼发育，以获得对无尾动物个体发生的全面概述。本综述将提供有关肌肉骨骼发育的顺序、特定摄食习惯对发育的影响以及几种无脊椎动物的特定发育的信息。此外，还将研究选定的nkx基因对这些新颖性的进化和发展的影响。我们将使用经典组织学和现代方法，如免疫组织化学，共聚焦激光扫描显微镜和μ计算机断层扫描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，将使用药物和CRISPR/Cas9。利用全株原位杂交和定量PCR技术研究基因的时空表达。这个项目将大大扩展我们对幼虫蛙肌肉骨骼发育的认识。此外，它将促进我们对进化新颖性进化机制的理解。

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.