Development of head and trunk mesoderm in the dogfish, Scyliorhinus torazame: I. Embryology and morphology of the head cavities and related structures
Development of head and trunk mesoderm in the dogfish, Scyliorhinus torazame: I. Embryology and morphology of the head cavities and related structures
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DOI：
10.1111/j.1525-142x.2012.00542.x
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发表时间：
2012-05-01
影响因子：
2.9
通讯作者：
Kuratani, Shigeru
中科院分区：
文献类型：
--
作者：
Adachi, Noritaka;Kuratani, Shigeru
几个世纪以来，脊椎动物的头部分割引起了比较和进化形态学家的注意，因为它对于理解脊椎动物的发育身体计划及其进化起源非常重要。特别是中胚层的分割是问题的核心。鲨鱼胚胎提供了一个典型的头部形态图，其上皮化的体腔（头腔），通常被认为是头部体节。为了了解头腔的进化意义，在形态学和组织学水平上研究了中胚层的胚胎发育在鲨鱼，Scyliorhinus torazame。与其他脊椎动物体节和肠腔中胚层成分不同，S.托拉沙梅在最初未分割的间充质头部中胚层中表现为不规则的囊肿，而不是通过未分割体腔的分割。下颌腔最早出现在下颌中胚层的近轴部，其次是舌骨腔，最后是下颌前腔。索前板被认为是口前肠的菱形屋顶，与吻侧脊索连续，并被下丘脑原基的生长前后分为两部分。其中，后部可能分化为下颌前腔，前部随后消失。躯干中的头腔和体节在组织学外观和分化时间方面表现出显着差异。下颌腔发达的喙过程其次，其同源性的前腔报道在一些板鳃类胚胎进行了讨论。
Vertebrate head segmentation has attracted the attention of comparative and evolutionary morphologists for centuries, given its importance for understanding the developmental body plan of vertebrates and its evolutionary origin. In particular, the segmentation of the mesoderm is central to the problem. The shark embryo has provided a canonical morphological scheme of the head, with its epithelialized coelomic cavities (head cavities), which have often been regarded as head somites. To understand the evolutionary significance of the head cavities, the embryonic development of the mesoderm was investigated at the morphological and histological levels in the shark, Scyliorhinus torazame. Unlike somites and some enterocoelic mesodermal components in other vertebrates, the head cavities in S. torazame appeared as irregular cyst(s) in the originally unsegmented mesenchymal head mesoderm, and not via segmentation of an undivided coelom. The mandibular cavity appeared first in the paraxial part of the mandibular mesoderm, followed by the hyoid cavity, and the premandibular cavity was the last to form. The prechordal plate was recognized as a rhomboid roof of the preoral gut, continuous with the rostral notochord, and was divided anteroposteriorly into two parts by the growth of the hypothalamic primordium. Of those, the posterior part was likely to differentiate into the premandibular cavity, and the anterior part disappeared later. The head cavities and somites in the trunk exhibited significant differences, in terms of histological appearance and timing of differentiation. The mandibular cavity developed a rostral process secondarily; its homology to the anterior cavity reported in some elasmobranch embryos is discussed.