Temereva Elena N
Biological Faculty, Department of Invertebrate Zoology, Moscow State University, Vorobievi Gory 1-12, Moscow, 119991, Russia.
J Morphol. 2017 Jul;278(7):997-1011. doi: 10.1002/jmor.20693. Epub 2017 May 2.
The organization of the coelomic system and the ultrastructure of the coelomic lining are used in phylogenetic analysis to establish the relationships between major taxa. Investigation of the anatomy and ultrastructure of the coelomic system in brachiopods, which are poorly studied, can provide answers to fundamental questions about the evolution of the coelom in coelomic bilaterians. In the current study, the organization of the coelom of the lophophore in the brachiopod Lingula anatina was investigated using semithin sectioning, 3D reconstruction, and transmission electron microscopy. The lophophore of L. anatina contains two main compartments: the preoral coelom and the lophophoral coelom. The lining of the preoral coelom consists of ciliated cells. The lophophoral coelom is subdivided into paired coelomic sacs: the large and small sinuses (= canals). The lining of the lophophoral coelom varies in structure and includes monociliate myoepithelium, alternating epithelial and myoepithelial cells, specialized peritoneum and muscle cells, and podocyte-like cells. Connections between cells of the coelomic lining are provided by adherens junctions, tight-like junctions, septate junctions, adhesive junctions, and direct cytoplasmic bridges. The structure of the coelomic lining varies greatly in both of the main stems of the Bilateria, that is, in the Protostomia and Deuterostomia. Because of this great variety, the structure of the coelomic lining cannot by itself be used in phylogenetic analysis. At the same time, the ciliated myoepithelium can be considered as the ancestral type of coelomic lining. The many different kinds of junctions between cells of the coelomic lining may help coordinate the functioning of epithelial cells and muscle cells.
体腔系统的组织和体腔衬里的超微结构被用于系统发育分析，以建立主要类群之间的关系。对研究较少的腕足动物体腔系统的解剖结构和超微结构进行研究，可以为有关体腔两侧对称动物体腔进化的基本问题提供答案。在本研究中，使用半薄切片、三维重建和透射电子显微镜对鸭嘴舌形贝腕足动物的触手冠体腔组织进行了研究。鸭嘴舌形贝的触手冠包含两个主要腔室：口前腔和触手冠腔。口前腔的衬里由纤毛细胞组成。触手冠腔被细分为成对的体腔囊：大窦和小窦（=管道）。触手冠腔的衬里结构各异，包括单纤毛肌上皮、交替的上皮细胞和肌上皮细胞、特化的腹膜和肌肉细胞以及足细胞样细胞。体腔衬里细胞之间的连接由黏着连接、紧密样连接、分隔连接、黏附连接和直接的细胞质桥提供。在两侧对称动物的两个主要分支中，即原口动物和后口动物中，体腔衬里的结构差异很大。由于这种多样性，体腔衬里的结构本身不能用于系统发育分析。同时，纤毛肌上皮可被视为体腔衬里的原始类型。体腔衬里细胞之间许多不同类型的连接可能有助于协调上皮细胞和肌肉细胞的功能。
