Fairweather I, Threadgold L T
Parasitology. 1981 Jun;82(Pt 3):429-43. doi: 10.1017/s0031182000066968.
The fine structure of the envelopes surrounding hatched and unhatched oncospheres of Hymenolepis nana has been investigated by transmission and scanning electron microscopy (SEM), together with light microscope histochemical observations of JB-4 embedded material. The oncosphere is surrounded by 3 layers--the capsule, the outer envelope and the inner envelope, the latter giving rise to the embryophore and the 'oncospheral membrane'. An additional layer--the polar filament layer--lies between the 'oncospheral membrane' and the oncosphere. Shell material is deposited on the capsule as a thin layer. It is secreted by the outer envelope, which degenerates once shell formation is complete. The uterus may also contribute to shell formation. The embryophore forms a thin incomplete and peripheral layer within the inner envelope. In the basal region of this envelope, partial development of an 'oncospheral membrane' takes place, but it does not become detached as a separate layer. The polar filaments, which are characteristic of the oncosphere of H. nana, are derived from the epithelial covering of the oncosphere itself, which delaminates to form a separate polar filament layer. The filaments arise from knob-like projections at opposite poles of this layer. The design of the embryonic envelopes in H. nana show a number of modifications from the basic cyclophyllidean pattern, and these can be related to the demands of its 'direct' life-cycle.
利用透射电子显微镜和扫描电子显微镜（SEM），并结合对JB - 4包埋材料的光学显微镜组织化学观察，研究了微小膜壳绦虫已孵化和未孵化六钩蚴周围包膜的精细结构。六钩蚴被三层结构包围——囊膜、外层包膜和内层包膜，内层包膜产生胚膜和“六钩蚴膜”。在“六钩蚴膜”和六钩蚴之间还有一层——极丝层。壳物质以薄层形式沉积在囊膜上。它由外层包膜分泌，一旦壳形成完成，外层包膜就会退化。子宫也可能参与壳的形成。胚膜在内层包膜内形成一层薄的、不完整的外周层。在该包膜的基部区域，会发生“六钩蚴膜”的部分发育，但它不会作为一个单独的层分离出来。微小膜壳绦虫六钩蚴特有的极丝，源自六钩蚴自身的上皮覆盖物，该上皮覆盖物分层形成一个单独的极丝层。极丝从该层相对两极的瘤状突起处产生。微小膜壳绦虫胚胎包膜的结构与基本圆叶目模式有许多不同之处，这些不同之处与其“直接”生命周期的需求有关。
