龟壳为研究发育机制的进化修饰提供了一个引人入胜的模型。对其发展提出了不同的结论,有人认为,分歧的原因之一可能是使用的海龟种类的差异-硬壳海龟和软壳海龟之间的差异。为了阐明差异的原因,我们比较了两组龟的龟壳发育情况。在背壳发育中,这两个乌龟群共享形成所需的基因表达谱,并在开发过程中共享相似的解剖元素空间组织。因此,两只海龟都通过侧面体壁的折叠形成背壳,Wnt信号通路似乎参与了发育过程。外壳的腹侧部分,另一方面,含有大量的真皮骨骼。尽管HNK-1表位的表达表明躯干神经c有助于硬壳龟的真皮骨,在两种海龟的骨骼的最初分析中都没有表达。因此,没有证据支持神经脊起源。
The turtle shell provides a fascinating model for the investigation of the evolutionary modifications of developmental mechanisms. Different conclusions have been put forth for its development, and it is suggested that one of the causes of the disagreement could be the differences in the species of the turtles used - the differences between hard-shelled turtles and soft-shelled turtles. To elucidate the cause of the difference, we compared the turtle shell development in the two groups of turtle. In the dorsal shell development, these two turtle groups shared the gene expression profile that is required for formation, and shared similar spatial organization of the anatomical elements during development. Thus, both turtles formed the dorsal shell through a folding of the lateral body wall, and the Wnt signaling pathway appears to have been involved in the development. The ventral portion of the shell, on the other hand, contains massive dermal bones. Although expression of HNK-1 epitope has suggested that the trunk neural crest contributed to the dermal bones in the hard-shelled turtles, it was not expressed in the initial anlage of the skeletons in either of the types of turtle. Hence, no evidence was found that would support a neural crest origin.