Morphology And Morphogenesis Of Cortical Silver-line Systems In Three Euplotes Species

As a complete organism, the single-cell protozoa have a variety of functions, behaviors and adaptability to the environment which are owned by the higher animals. Any cells in multi-cellular organisms could not compare with the protozoa in the complexity of cell structure. Hypotrichous ciliates belong to the groups which have the most complex cell structure in the protozoa. The cells contain a specialized cortex, which is one of the most complex structures of all cells. The developed cytoskeleton within the complex is a hot topic in the current research of cellular biology. The main components of cortical cytoskeleton are microtubules in hypotrichous ciliates. The microtubules include two microtubule systems of cortical ciliary microtubules and non-ciliary microtubules. Cortical cytoskeleton is a structure to maintain cell shape, ontogenesis and movement etc. Non-ciliary microtubules are structures to maintain cell shape and to ensure normal cell movement. At present, the research on the cortical ciliary microtubules has achieved abundant data, but it is not known that the relationship between the ciliary microtubules and the non-ciliary microtubules in the morphogenesis of cells. Using hypotrichous ciliates as the material to study the microtubular cytoskeleton has important theoretical significance for further study of the structure and function of eukaryotic cells and the exploration on the regulation of the structure pattern formation in cells.Based on the application of silver nitrate impregnation and scanning electron microscopy, and using E. vannus, E. harpa and E. encysticus as the representatives, the morphogenesis of three types of cortical silver-line systems in the genus Euplotes are examined in this study. It is shown the relationship of the cortical cytoskeleton in different life cycle and revealed the law between ciliary organelle and silver-line system in morphogenesis, differentiation and positioning. The main results and conclusions are as follows:1. The morphogenesis of three types of cortical silver-line systems and ciliary organelle are accompanied in the genus Euplotes (E. vannus, E. harpa and E. encysticus). The ventral silver-line system occurs around the new membranelles and the segmented frontoventral-transverse anlagen. The dorsal silver-line system occurs around the basal bodies of the dorsal bristle primordia. Thus, it is speculated that the composite element of basal bodies is not only microtubule organizing center, but also the center of the silver-line system.2. The ventral side of E. vannus contains neatly arranged and sparse silver-line system, but the ventral side of E. harpa and E. encysticus contains irregular and close silver-line system. This different arrangement is similar with the arrangement of dorsal silver-line system, especially in the close degree of silver-line system. But the close degree of the silver-line system is closely related to the number of basal bodies in the dorsal kineties. Thus, it is speculated that even though the ventral silver-line system could not be specifically divided, the consistency of the morphological characteristics and the dorsal silver-line system has a certain degree. This shows the integrated control of the cells in the morphogenesis of ventral and dorsal silver-line system.3. The new meshwork on the left of the basal bodies develops before the meshwork on the right, thus, it is speculated that the silver-line system shows similar orientation with ciliary organelles during their morphogenesis. In addition, the old meshwork near new silver-line first disintegrate, which leads to the new silver-line system constantly develop. It is assumed that the old silver-line system may play a role of induction and orientation on the formation of new structure. The old silver-line system which is located in the first half of the proter and in the latter part of the opisthe is reserved to form the dorsal silver-line system in new cells. It is supposed that the old silver-line system participates in the form of new structure and also has a material contribution to it.