Mouth formation involves the processes of mouth opening, formation of the oral cavity, and the development of associated sensory organs. In deuterostomes, the surface ectoderm and the anterior part of the archenteron are reconfigured and reconnected to make a mouth opening. This study of the larval development of the larvacean, Oikopleura dioica, investigates the cellular organization of the oral region, the developmental processes of the mouth, and the formation of associated sensory cells. O. dioica is a simple chordate whose larvae are transparent and have a small number of constituent cells. It completes organ morphogenesis in 7 h, between hatching 3 h after fertilization and the juvenile stage at 10 h, when it attains adult form and starts to feed. It has two types of mechanosensory cell embedded in the oral epithelium, which is a single layer of cells. There are twenty coronal sensory cells in the circumoral nerve ring and two dorsal sensory organ cells. Two bilateral lip precursor cells (LPCs), facing the anterior surface, divide dorsoventrally and make a wedge-shaped cleft between the two daughter cells named the dorsal lip cell (DLC) and the ventral lip cell (VLC). Eventually, the DLC and VLC become detached and separated into dorsal and ventral lips, triggering mouth opening. This is an intriguing example of cell division itself contributing to morphogenesis. The boundary between the ectoderm and endoderm is present between the lip cells and coronal sensory cells. All oral sensory cells, including dorsal sensory organ cells, were of endodermal origin and were not derived from the ectodermal placode. These observations on mouth formation provide a cellular basis for further studies at a molecular level, in this simple chordate.

嘴的形成涉及张口，口腔形成以及相关的感觉器官发育的过程。在氘骨口，表面外胚层和弓肠的前部被重新配置并重新连接以张口。这项关于幼虫卵幼虫发育的研究（Oikopleura dioica）研究了口腔区域的细胞组织，口腔的发育过程以及相关的感觉细胞的形成。O.dioica是一种简单的碳酸盐，其幼虫是透明的，并具有少量的组成细胞。它在受精后3 h孵化到10 h幼体阶段（成年并开始觅食）后的7 h内完成器官形态发生。它在口腔上皮细胞中嵌入了两种类型的机械感觉细胞，它是单层细胞。周围神经环中有二十个冠状感觉细胞和两个背侧感觉器官细胞。面对前表面的两个双侧唇前体细胞（LPC）背腹分开，在两个称为背唇细胞（DLC）和腹唇细胞（VLC）的子细胞之间形成楔形裂口。最终，DLC和VLC分离并分成背唇和腹唇，触发张口。这是细胞分裂本身促成形态发生的一个有趣例子。外胚层和内胚层之间的边界存在于唇细胞和冠状感觉细胞之间。所有的口腔感觉细胞，包括背侧感觉器官细胞，都是内胚层来源的，而不是来自外胚层斑块。这些关于口腔形成的观察结果为在这种简单的cho酸盐中进行分子水平的进一步研究提供了细胞基础。