Studies On The Differentiation Of The Cell Structure And Cilia During Encystment Of Allotricha Curdsi(Ciliophora:Hypotrichida)

When the environment sudden changes and has bad impact on the life activities of hypotrich ciliates, the process of encystment is common, which takes an important effect on its survival. During the process, the cell structure of hypotrich ciliates happen to significant differentiation, the cells gradually stop the movement and feeding, and then shrink of cells, the cytoplasm organelles and nuclears are also associated with drastic changes. Study on the differentiation of microtubular cytoskeletons has been concerned by biology researchers in different fields. Ciliates are the most advanced heterotrophic protist, especially it has the complicated microtubular cytoskeleton, which plays important role on keeping the cell morphology, the movement and all kinds of functions. Study of the characteristics of microtubules cytoskeleton differentiation in the process of encystment, has become an important aspect to explore the structure and function of eukaryotic cells and regulation of cell. In this study, we used Allotricha curdsi as the experimental material, applying scanning electron microscopy(SEM) and transmission electron microscopy(TEM), to observe the normal cell structure and the formation of encystment and compare the differerntiation of cortex structure and cytoplasm organelles between normal cell and resting cell of Allotricha curdsi, Results are as follows:1. The ultrastructure of normal cell of Allotricha curdsiThe details of the morphology and morphogenesis of the hypotrichous ciliate Allotricha curdsi were observed with SEM in this study:The normal cell has long oval shape, the ventral side is flat and its dorsal side is distinctly vaulted. The tail sharpening and the left upper part micro become warped. The cortex ciliature of the Allotricha curdsi is developed and consists of adoral zone of membranelles(AZM), undulating membranes(UM), front-ventral-transverse cirri(FVTC), left and right marginal cirri(L-and-RMC), caudal cirri(CC) and dorsal kineties(DK). The UM comprises a endoral membrane (EM) and a paroral membrane(PM), which both start at the base of the AZM. A LMC and three RMC are located in the ventral side of the ciliate. The CC consists of three cirris were recognizable and distinct from marginal cirri. Six rows of DK locate in the dorsal side of the ciliate, each unit of DK has a cilia kinetosome and a barren kinetosome. there are exception large individuals occasionally in pure department cell culture, general the volume is the normal2-3times.The internal ultrastructure of Allotricha curdsi was observed by using TEM. We found that the surface membrane was composed of the plasma membrane and the cell membrane. There was dense fiber bundles close to ventral surface membrane to reinforce the structure. We also observed that the cytoplasm is full of the cortical pellicle, cytoplasm beneath pellicle, cortical microtubular organelles and other organelles. The cortical organelles in ciliates have some differentiation and specialization. Extrusomes play an important role in the life activities of ciliates. The study on morphological characteristics, morphogenesis, and the location of extrusomes in hypotrich ciliates can supply the new data for further elucidation of the relationship between function of organelles and cellular activity.2. The differentiation of cilia and cytoplasm during encystment of Allotricha curdsiThe details of the differentiation of cortex and cilia during the encystment of the hypotrichous ciliate Allotricha curdsi was observed with SEM. The result showed that: During the cells transforming from the long oval shape into soccer form, the dedifferentiation of microtubular organelles on ventral side happened, meanwhile, the unit of dorsal bristle started to redifferentiation with a new cilia growing from the previously barren kinetosome. As cells contracted further, the cyst wall began to emerge and the protrusions arranged regularly on the cyst surface simultaneously. After the cyst changing from cactus-like shape to spiral-like shape, the resting cyst formed. Without improving the culturing environment, the resting cysts finally disintegrated and disappeared. The results present in this paper provided new information for better understanding the differentiation of the cilia structure and the formation of the cytoplasm derivatives in special physiological conditions.The details of the differentiation of organelles and nuclear ultrastructure during encystment of hypotrichous ciliate Allotricha curdsi was observed with TEM. During encystment, most of the cortex microtubular is disappeared. The cyst of Allotricha curdsi contains large amounts of mitochondria cyst caterpillars and autophagic vacuoles, which might be related to food digestion and energy storage. Largest nuclear elongated cylindrical, showing wavy. some family reunion into a high electron density of the sizes of the clumps, nucleolus high number of scattered large nucleus; The nuclear pore-like structure made the nuclear membrane into the dotted line. After the formation of cysts, cyst wall became four layers. Cysts have two autophagic vacuoles:organelle autophagic vacuoles, and cytoplasmic autophagic vacuoles. To sum up, the findings in this research are of significantly scientific importance for the further elucidation of the specificity of cytoarchitectures and the relationship between the cytoarchitectures and their functions, the deep of the knowledge about the occurrence of encystment, the changes of cortical structure and the mechanisms of cell regulation in cellular activity of ciliates.