吸鱼粘体虫在异育银鲫心脏中的孢子发生

OBSERVATIONS ON THE SPOROGENESIS OF MYXOSOMA BIBUL LATUM IN THE HEART OF ALLOGYNOGENETIC CRUCIAN CARP

吸鱼粘体虫主要寄生在异育银鲫的心肌纤维间。随着营养体的长大,营养体内的两型生殖细胞相聚,小生殖细胞包围大生殖细胞,形成泛孢子母细胞。大生殖细胞进行连续的核分裂,成为产孢体。核分裂达12核时,产孢体内分化为10个细胞:4个成极囊细胞,4个成壳片细胞和2个双核的孢子质细胞。这些细胞均分为两组,从而形成双生孢子型的泛孢子母细胞。

The allogynogenetic crucian carp is a new breed cultivated with heterologous sperm stimulating the eggs of crucian carp. Myxosoma bibullatum is the most prevalent myxosporidian parasite in this fish. Its sporogenesis occurs among the cardiac muscle cells of the host and causes inflammation and necrosis of the muscle.It was observed that in the cyst there were many vegetative nuclei and two kinds of generative cells which stained deeply with Giemsa's stain and showed condensed sytoplasm. Each smaller generative cell encircled a larger generative cell forming a pansporoblast and, as a result, the enclosed larger generative cell developed into a sporont, the nucleus of which divided to form 12 nuclei. Following successive cell divisions, 10 cells resulted from each sporont. A small vesicle appeared in the cytoplasm of each of the four cells and some filamentogenous substance formed in the vesicle. These four cells are the capsulogenous cells which will become the polar capsules within the spores. Another four cells extended and transformed into valvogenous cells. In the cytoplasm of each of these four cells, there was a small vesicle containing substance which stained green by Giemsa's. The vesicle enlarged and filled nearly the whole inner space of the valvogenous cell and formed the valves of the spore. The remaining two cells were binucleate sporoplasm cells with granular cytoplasm and two pale coloured nuclei. The pansporoblast of M. bibullatum is disporous type.