扩张莫尼茨绦虫(绦虫纲:圆叶目)的原肾管及原肾管概念的评述(英文)

The protonephridium of Moniezia expansa (Cestoda: Cyclophyllidea), with comments on the protonephridium concept

本研究应用透射电子显微镜研究了扩张莫尼茨绦虫原肾管的细胞学特征 ,莫尼茨绦虫原肾管的焰茎球为一个过滤器结构 ,类似于“挡河坝”样构造 ,此构造由端细胞和近管细胞外突形成的肋条 (或称杆 )相互交错排列而成。肋条之间由细胞外物质构成的“膜”结构连接 ,过滤作用通过该“膜”发生。焰细胞与近管细胞交界处有裂缝或孔与细胞外的结缔组织 (实质组织 )相通 ;原肾管的毛细排泄管细胞质索之间没有隔状联结 ;毛细排泄管及排泄管的管腔内有大量珠状微绒毛突起以增加表面积。从扩张莫尼茨绦虫及其它一些无脊椎动物原肾管的研究结果表明 ,原原肾管概念将焰细胞作为封闭的盲端已不再合适 ,需要进行修订 ,建议修订为 :原肾管是一种焰细胞系统 ,通常由焰细胞、管细胞和肾孔细胞组成 ,焰茎球作为过滤装置与周围的结缔组织 (实质组织 )有或没有裂缝 (孔 )

Transmission electron microscopic observations have been made on the protonephridium of the cestode Moniezia expansa. The flame bulb of M expansa has a filtration apparatus constructed as a “weir”and consisting of ribs (rods) which are outgrowths of the terminal cell as well as the proximal canal cells. The ribs are connected by a “membrane” of extracellular substance through which filtration is believed to occur. Pores connect the protonephridial lumen to the intercellular space of connective tissue (parenchyma) and are located at the junction of a flame cell and a proximal canal cell. The cytoplasmic cords of protonephridial capillaries do not contain a septate junction. The surface area of the capillaries and other protonephridial ducts lining the lumen is enlarged by many small bead like microvilli. From the present study of M expansa and from those of protonephridia in other invertebrates, it is suggested that the concept of defining a protonephridium as having a closed inner end is improper. We suggest its definition should be modified as follows: a protonephridium is a flame cell system consisting of flame cells, canal cells and nephropore cells and that the flame bulb functions as a filtration apparatus with or without slits (pores) opening to the intercellular space of connective tissue (parenchyma) .