Ultrastructural Observations On The Ciliature And Organelle Of Diaxonella Trimarginata (Ciliaphora: Hypotrichida)

At present, studies on the morphology and morphogenesis of the ciliate cortical cytoskeleton have already been the hot issue in exploring the eukaryotic genetic and cell regulation in the field of the cell biology. The observation of some special organelles in the cytoplasm to show the unique biological functions of the ciliate have also been the main topic of revealing the diversity of the eukaryotic structure and functions. Diaxonella trimarginata has the special cell structure, including the common organelles like the other ciliates and the special organelles like the pigment and the extrusome. The methods nowadays are mainly confined to the light microscopy level, at the same time, some related taxonomic problems are on the air all the time. In my research, Scanning Electron Microscopy(SEM) was used to systematically observe the cortex ciliature morphology and morphogenesis of hypotrichous ciliate Diaxonella trimarginata during the asexual reproduction. Meantime, Transmission Electron Microscopy(TEM) was used to reveal the morphologic characteristics of cortical mircrotubular organelles and the cytoplasmic ultrastructure. The research was mainly studied from three aspects:cortical ultrastructure, cytoskeleton systems and cytoplasmic ultrastructure. The results are as follows:1 The morphology and morphogenesis of cortex ciliatures(SEM)The results of the research investigated by SEM show that lateral membranellar cilia(LMC) and unique buccal seal exist at the area of AZM, paroral membrane(PM) and relative cortex. Diaxonella trimarginata is assigned to Holostichidae because it has three frontal cirri and the midventral complex is composed of cirral pairs.10-13 transverse cirri arranged in J-shape pattern. There are 3-4 left marginal rows which shorten incrementally from right to left and 1 right marginal row, one of the left ones lies beside the dorsal kinety. Usually 3 dorsal kineties extend entire length of cell and the unit of the dorsal kinety is composed of one cilia kinetosome. During the process of morphogenesis, the oral primordium of the proter is generated on the inner margin of the old AZM, the old AZM is finally resorbed completely. The formation of the oral primordium of the opisthe commences from the left field of the midventral pairs, with the process of proliferation and differentiation, the oral primordium is finally developed into new AZM of opisthe. Left marginal cirri primordium originates in the rightmost parental left marginal row, forming the 3 streak-like anlagen later and finally the newly structure replaced the parental rows. During the morphogenesis of ciliature, the old cilia experienced the process of gradual degeneration and at the same time provide the necessary nutrition for the new structure. In a word, the results above show the morphology and morphogenesis characteristics on cortex ciliature of Diaxonella trimarginata from the ultrastructure level, and also provide new references for a better understanding of the cell development as well as the formation mechanism of the cirri mode and the cell differentiation.2 The ultrastructure of the cortical cytoskeleton and cytoplasm(TEM)Morphology and morphogenesis characteristics of the cortex ciliature are usually revealed by SEM. However, There are few records on the ultrastructure of Diaxonella trimarginata. Therefore, it is quite necessary to do some research on the ultrastructure of Diaxonella trimarginata. The results are as follows:(1) There are micro tubule layers and fiber bundles underneath the cell pellicle.(2) Some kinds of microtubule cytoskeleton structure lies beside food vacuole.(3) Near to the microtubule cytoskeleton structure exist a bacteria-like structure.(4) There are plenty of mitochondrion surrounding food vacuole and mucocyst.(5) The nuclear apparatus is consisted of macronuclei and micronuclei. There are usually at least one nucleoli in the macronuclei, some macronuclei have circle nucleoli, all the micronuclei have no nucleoli. The chromation distributed evenly in the macronuclei, some chromation connected tightly with the inner nuclear membrane. The chromation in the micronuclei distributed as evenly as that in the macronuclei. (6) Among the adroal zone of membranelles, each membranelle consists of 3 rows cirri, membranellar bolster lies between the neighboring membranelles. This is also observed by SEM. (7) Each kind of cirri has a specific shape at its base, some basal bodies and some cirri are incorporated into the fibrillar cirral basket, the ultrastructural characteristic of them in transverse section is almost the same, many microtubules bundles around the fibrillar cirral basket play a very important role in keeping the stability of the cytoskeleton. (8) The unit of the dorsal kinety is composed of the cilia kinetosome and the naked kinetosome, the latter one can't be observed in the SEM specimen.The results above not only enrich the cytological references, but provide corresponding data for the construction of the three-dimensional graphics.