State Key Laboratory of Crop Stress Biology for Arid Areas, Key Laboratory of Plant Protection Resources and Pest Management of the Education Ministry, Entomological Museum, Northwest A&F University, Yangling, Shaanxi, China.
Microsc Res Tech. 2013 May;76(5):457-66. doi: 10.1002/jemt.22187. Epub 2013 Feb 11.
The embryonic origin of the alimentary canal, especially the midgut, is a controversial problem in insects, and it has not been satisfactorily resolved to date. The organogenesis of the digestive system in the embryonic development was observed in the scorpionfly Panorpa obtusa Cheng using light, transmission, and scanning electron microscopy. The embryonic development lasts about 150-160 h at 24°C. The stomodaeum is formed from an invagination in the medioposterior portion of the protocephalon mid-ventrally posterior to the labral segment at 76 h after oviposition. The proctodaeum arises as an invagination from the caudal end of the abdomen at 78 h. Four anal forks are formed from within the opening of proctodaeum. Three pairs of proctodaeal evaginations are formed from the anterior part of the proctodaeum, and eventually developing into Malpighian tubules, thus are of ectodermal origin. The cardiac and pyloric valves develop from stomodaeum and proctodaeum, respectively, and also of ectodermal origin. The midgut epithelium originates from anterior and posterior midgut rudiments in blind ends of the stomodaeum and proctodaeum, and it is of endodermal origin. The two cell-bands (rudiments) cover the yolk ventrally and then dorsally, elongate to each other, and eventually fuse to form the midgut. The midgut formation pattern is briefly discussed in different insects.
消化系统的胚胎起源，尤其是中肠，在昆虫中是一个有争议的问题，至今尚未得到令人满意的解决。使用光学显微镜、透射电子显微镜和扫描电子显微镜观察了蝎子蛉 Panorpa obtusa Cheng 胚胎发育过程中消化系统的器官发生。在 24°C 下，胚胎发育大约需要 150-160 小时。口道是在产卵后 76 小时，位于头部中后段的基板段后腹中线处的原头区背中线处的内陷形成的。直肠是在 78 小时时从腹部的后端以内陷的方式形成的。四个肛叉是从直肠的开口内形成的。三对直肠突出物从前部的直肠形成，最终发育成马氏管，因此具有外胚层起源。心脏瓣和幽门瓣分别由口道和直肠发育而来，也具有外胚层起源。中肠上皮来源于口道和直肠盲端的前、后中肠原基，具有内胚层起源。两个细胞带（原基）先覆盖卵黄的腹侧，然后覆盖背侧，彼此伸长，最终融合形成中肠。简要讨论了不同昆虫中的中肠形成模式。
