龟足白垩腺的组织学和超微结构

Histology and Ultrastructure of the Cement Apparatus in Capitulum mitella

应用光学显微镜和透射电子显微镜对龟足(Capitulum mitella)白垩腺的组织学和超微结构进行观察。龟足的白垩腺由腺细胞和管道系统组成,外周覆有一层结缔组织膜。腺细胞为单细胞,其发育与个体发育不同步。年幼腺细胞较小,形态为圆形或椭圆形,细胞核也为圆形或椭圆形。随着腺细胞的发育,细胞及细胞核逐渐变大,形状不规则具多态性。成熟腺细胞的细胞质电子密度高,充满大量粗面内质网和游离核糖体;线粒体很丰富,但未见高尔基体。细胞质中含有丰富的颗粒状物质以及大小不一的囊泡,小囊泡的聚集和融合形成了大囊泡即胞内管。管道系统根据位置和功能分为4个层次:胞内管、收集管、次级管和初级管。收集管、次级管和初级管的管壁均由单层上皮细胞组成,初级管较收集管和次级管大且内腔衬有几丁质层。收集管的管壁上皮细胞与腺细胞之间形成隔状连接,各级管壁上皮细胞之间也形成隔状连接,这种结构保证了管道的紧密性。总之,龟足白垩腺的形态结构类似于茗荷(Lepas anatifera)和Dosima fascicularis。

Histology and ultrastructure of the cement apparatus of Capitulum mitella were observed by light microscopy and electron microscopy. The results show that the cement apparatus of Capitulum mitella is composed of gland cells and canal system（Fig. 1）. The cement apparatus is sheathed in a layer of connective tissue membrane（PlateⅠ﹣Ⅲ）. Gland cell is a unicellular gland（PlateⅠ）. Development of gland cells and animal itself is not synchronous. Young gland cells are small, and the shape of cells and nuclei is round or ovoid（PlateⅠ）. With development of cement gland, gland cells and their nuclei enlarge, and their shape becomes irregular with polymorphism（PlateⅠ）. The cytoplasm of mature gland cells, which has high electron density, is full of abundant rough endoplasmic reticulum, free ribosomes, and a few of mitochondria without Golgi body（PlateⅠ,Ⅱ）. The cytoplasm contains rich particulate matters and vacuoles in different sizes（PlateⅠ,Ⅱ）. Formation of intracellular canal in gland cells is via aggregation and fusion of cytoplasmic vacuoles（PlateⅠ,Ⅱ）. The canal system is divided into four levels depending on location and function： intracellular canal, collector canal, secondary canal, principal canal（Fig. 1）. The collector canal, the secondary canal, and the principal canal are composed of monolayer epithelial cells（Plate Ⅲ）. The principal canal is larger than the secondary canal and collector canal（Plate Ⅲ）. The lumen of the principal canal is lined by a dense cuticle layer（Plate Ⅲ）. Septate junction connects gland cells with wall cells of the collector canal. The epithelial cells of canal walls are also connected by septate junction（Plate Ⅲ）. This structure ensures tightness of the canal system. In this paper formation and structural characteristics of the intracellular canal and collector canal are described in detail. In short, morphological structure of the cement apparatus in Capitulum mitella is similar to that of Lepas anatifera and Dosima fascicularis（Plate Ⅲ）.