圆形碘泡虫孢子发生的超微结构研究

寄生于鲫的圆形碘泡虫的孢子发生过程中,最早可认识阶段的营养体是一个单核原初细胞,原初细胞通过分裂直接在细胞内产生生殖细胞,形成一个细胞包围另一个细胞的状态,在以后的过程中,包围细胞不再分裂,生殖细胞进行一系列的分裂,形成双孢子型泛孢子母细胞.生殖细胞分化成10个细胞,形成二个产孢子单元,每个产孢子单元由5个细胞组成,两个壳瓣原细胞位于两边包围着两个极囊原细胞和一个双核孢子质细胞,最后形成两个孢子.  

STUDIES ON THE ULTRASTRUCTURE OF THE SPOROGENESIS OF MYXOBOLUS ROTUNDUS NEMECZCK

This paper dealt with the sporogensis of Myxobolus rotundus Nemeczek, 1911 from Carassius auratus. Sporogensis of M. rotundus was observed by transmission electron microscopy. The earliest stage of the parasite was a primary cell which could give rise to generative cells by fission. Sporogensis was initiated by the envelopment of one generative cell with a enveloping cell. The enveloping cell did not divide anymore, whereas the large, generative cell divided to form a disporous pansporoblast containing 10 cells. Subsequently, the 10 cells began to differentiate and finally formed two 5-cell spore-producing units. Each unit consisted of 2 capsulogenic cells and 1 binucleate sporoplasm, surrounded by 2 valvogenic cells. Each capsular primordium and its connecting external tubule formed a polar capsule which contained 7 helically coiled polar filament. The opening of the polar capsule was plugged by a stopper facing the discharge canal. Two valvogenic cells formed the spore valves. A desmosome-like junction appeared in close contact the suture between two valvogenic cells. There were numerous microtubules at both sides of sutural ridge. The binucleated sporoplasm cell contained numerous sporoplasmosomes and spherical lipid inclusions in different size. Iodinophilous vacuoles, membrane-bounded granules and membrane-bounded vacuoles existed in the sporoplasm cell. In nearly mature spores, there was an unclear zones among sporoplasm cells. Several finger-like extensions of sporoplasm extended to the zones. Other ultrastructural features were the same as those found in other myxosporeans, including absence of centrioles, the structure of mitochondria, distribution patterns of ribosomes and existence of glycogen particles, etc.