{"title":"雌雄同体的无尾类 Oikopleura gracilis(鳞目,Oikopleuridae)消化管的超微结构特征","authors":"A. V. Savelieva","doi":"10.1134/s1063074023080084","DOIUrl":null,"url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Appendicularians play an important role in marine food webs, but the alimentary canal of hermaphroditic oikopleurids, which prevalent among urochordates, is little studied ultrastructurally. Serial microtomy revealed that the alimentary canal of <i>Oikopleura gracilis</i> consists of a wide pharynx and a U-shaped gut with typical for oikopleurids anatomy: oesophagus, a bilobed stomach, the vertical, short mid- and voluminous distal or rectal intestines, ending the anal papilla. The mid-intestine leaves under the right gastric lobe. TEM analysis diagnosed the following features in the alimentary canal of <i>Oikopleura gracilis</i>. First, the pharynx is lined with a single layer of highly flattened non-ciliated epithelium. Above the anterior part of the endostyle the pharyngeal epithelium forms a thickening – ciliated ring. It is formed by cells of two types: prismatic, ciliated microvillar cells arranged in several parallel rows, and two rows of narrow parietal cells covering the first cell type. Ciliated ring serves as a kind of first valve, prevents food reflux. Second, in the pharynx of one of the specimens three flagellate protozoans with ultrastructurally similarities of free-living kinetoplastids were found. Third, an additional row of gastric band cells was revealed in the upper part of the right gastric lobe compared to that of the gastric floor. Giant electron-lucent vesicles with homogenous content associated with rough endoplasmic reticulum found in the cytoplasm of the gastric band cell, indicating probable storage the protein digestive secrets in these cells. Large multivesicular bodies diagnosed in gastric band cells ultrastructurally corresponded to autophagosomes. Forth, a new cellular type was found, the osmiophilic enterocytes, scattered throughout the digestive epithelium, that shared ultrastructural signs with apoptotic cells. Fifth, TEM data revealed the peritrophic membrane structure and proposed its formation. The absence of its own microflora in the peritrophic membrane, i.e., the absence of an immunity barrier, may be connected with the short ontogeny of appendicularians. The ultrastructural features revealed in the alimentary canal of <i>O. gracilis</i> expand our knowledge of the functioning of the appendicularians and serve as the basis for further research.</p>","PeriodicalId":49584,"journal":{"name":"Russian Journal of Marine Biology","volume":null,"pages":null},"PeriodicalIF":0.5000,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Ultrastructural Features of the Alimentary Canal in Hermaphroditic Appendicularians Oikopleura gracilis (Tunicata, Oikopleuridae)\",\"authors\":\"A. V. Savelieva\",\"doi\":\"10.1134/s1063074023080084\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<h3 data-test=\\\"abstract-sub-heading\\\">Abstract</h3><p>Appendicularians play an important role in marine food webs, but the alimentary canal of hermaphroditic oikopleurids, which prevalent among urochordates, is little studied ultrastructurally. Serial microtomy revealed that the alimentary canal of <i>Oikopleura gracilis</i> consists of a wide pharynx and a U-shaped gut with typical for oikopleurids anatomy: oesophagus, a bilobed stomach, the vertical, short mid- and voluminous distal or rectal intestines, ending the anal papilla. The mid-intestine leaves under the right gastric lobe. TEM analysis diagnosed the following features in the alimentary canal of <i>Oikopleura gracilis</i>. First, the pharynx is lined with a single layer of highly flattened non-ciliated epithelium. Above the anterior part of the endostyle the pharyngeal epithelium forms a thickening – ciliated ring. It is formed by cells of two types: prismatic, ciliated microvillar cells arranged in several parallel rows, and two rows of narrow parietal cells covering the first cell type. Ciliated ring serves as a kind of first valve, prevents food reflux. Second, in the pharynx of one of the specimens three flagellate protozoans with ultrastructurally similarities of free-living kinetoplastids were found. Third, an additional row of gastric band cells was revealed in the upper part of the right gastric lobe compared to that of the gastric floor. Giant electron-lucent vesicles with homogenous content associated with rough endoplasmic reticulum found in the cytoplasm of the gastric band cell, indicating probable storage the protein digestive secrets in these cells. Large multivesicular bodies diagnosed in gastric band cells ultrastructurally corresponded to autophagosomes. Forth, a new cellular type was found, the osmiophilic enterocytes, scattered throughout the digestive epithelium, that shared ultrastructural signs with apoptotic cells. Fifth, TEM data revealed the peritrophic membrane structure and proposed its formation. The absence of its own microflora in the peritrophic membrane, i.e., the absence of an immunity barrier, may be connected with the short ontogeny of appendicularians. The ultrastructural features revealed in the alimentary canal of <i>O. gracilis</i> expand our knowledge of the functioning of the appendicularians and serve as the basis for further research.</p>\",\"PeriodicalId\":49584,\"journal\":{\"name\":\"Russian Journal of Marine Biology\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.5000,\"publicationDate\":\"2024-01-29\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Russian Journal of Marine Biology\",\"FirstCategoryId\":\"99\",\"ListUrlMain\":\"https://doi.org/10.1134/s1063074023080084\",\"RegionNum\":4,\"RegionCategory\":\"生物学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q4\",\"JCRName\":\"MARINE & FRESHWATER BIOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Russian Journal of Marine Biology","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1134/s1063074023080084","RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MARINE & FRESHWATER BIOLOGY","Score":null,"Total":0}
引用次数: 0
摘要
摘要附肢动物在海洋食物网中发挥着重要作用,但对泌尿纲动物中普遍存在的雌雄同体的食道却很少进行超微结构研究。连续显微解剖发现,Oikopleura gracilis 的消化管由宽阔的咽部和 U 形肠道组成,具有典型的泌尿纲动物解剖结构:食道、双叶胃、垂直的短中肠和体积较大的远端肠或直肠,最后是肛乳头。中肠从右胃叶下方离开。通过 TEM 分析,可以诊断出 Oikopleura gracilis 消化管的以下特征。首先,咽部有一层高度扁平的非纤毛上皮。在内柱前部上方,咽上皮形成一个增厚的纤毛环。纤毛环由两种细胞组成:棱柱状的纤毛微绒毛细胞平行排列成数排,以及覆盖第一种细胞的两排狭窄顶细胞。纤毛环起着第一道瓣膜的作用,防止食物反流。其次,在其中一个标本的咽部发现了三个鞭毛原生动物,其超微结构与自由生活的奇梭子虫相似。第三,与胃底相比,右胃叶上部发现了一排额外的胃带细胞。在胃带细胞的细胞质中发现了与粗面内质网相关的巨型电子透明囊泡,内容物均匀,表明这些细胞中可能贮存着消化蛋白质的秘密。在胃带细胞中发现的大型多囊体在超微结构上与自噬体相对应。第四,发现了一种新的细胞类型--嗜渗肠细胞,散布在整个消化上皮细胞中,与凋亡细胞具有相同的超微结构特征。第五,TEM 数据揭示了营养周膜结构,并提出了其形成原因。营养周膜中没有自己的微生物区系,即没有免疫屏障,这可能与阑尾的本体发育期较短有关。O. gracilis消化管的超微结构特征拓展了我们对附肢动物功能的认识,为进一步的研究奠定了基础。
Ultrastructural Features of the Alimentary Canal in Hermaphroditic Appendicularians Oikopleura gracilis (Tunicata, Oikopleuridae)
Abstract
Appendicularians play an important role in marine food webs, but the alimentary canal of hermaphroditic oikopleurids, which prevalent among urochordates, is little studied ultrastructurally. Serial microtomy revealed that the alimentary canal of Oikopleura gracilis consists of a wide pharynx and a U-shaped gut with typical for oikopleurids anatomy: oesophagus, a bilobed stomach, the vertical, short mid- and voluminous distal or rectal intestines, ending the anal papilla. The mid-intestine leaves under the right gastric lobe. TEM analysis diagnosed the following features in the alimentary canal of Oikopleura gracilis. First, the pharynx is lined with a single layer of highly flattened non-ciliated epithelium. Above the anterior part of the endostyle the pharyngeal epithelium forms a thickening – ciliated ring. It is formed by cells of two types: prismatic, ciliated microvillar cells arranged in several parallel rows, and two rows of narrow parietal cells covering the first cell type. Ciliated ring serves as a kind of first valve, prevents food reflux. Second, in the pharynx of one of the specimens three flagellate protozoans with ultrastructurally similarities of free-living kinetoplastids were found. Third, an additional row of gastric band cells was revealed in the upper part of the right gastric lobe compared to that of the gastric floor. Giant electron-lucent vesicles with homogenous content associated with rough endoplasmic reticulum found in the cytoplasm of the gastric band cell, indicating probable storage the protein digestive secrets in these cells. Large multivesicular bodies diagnosed in gastric band cells ultrastructurally corresponded to autophagosomes. Forth, a new cellular type was found, the osmiophilic enterocytes, scattered throughout the digestive epithelium, that shared ultrastructural signs with apoptotic cells. Fifth, TEM data revealed the peritrophic membrane structure and proposed its formation. The absence of its own microflora in the peritrophic membrane, i.e., the absence of an immunity barrier, may be connected with the short ontogeny of appendicularians. The ultrastructural features revealed in the alimentary canal of O. gracilis expand our knowledge of the functioning of the appendicularians and serve as the basis for further research.
期刊介绍:
The Russian Journal of Marine Biology was founded in 1975 by Alexey V. Zhirmunsky, member of the Russian Academy of Sciences. The Russian Journal of Marine Biology covers a wide range of research and some applied aspects of marine biology as a synthetic science related to various fields of study on marine biota and environment. It presents fundamental research on biological processes at molecular, cellular, organismal, and populational levels in marine organisms. Consideration is given to marine objects as models in life sciences. The journal also publishes papers dedicated to events in Russian and international marine biological science and the history of biology.