Studies on spore dimorphism of the microsporidia

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The purpose of present research was to make sure the development of two types of spores of Nosema bombycis in cells of the silkworm larvae, and examine other microsporidia whether they produce the two types of spores or not. Those spores were discovered first in cultured cells after N . bombycis was inoculated. One type of those spors is characterized by 3 to 5 coils of the polar tube, early development (36 h postinoculation), and the spontaneous discharge of a short polar tube. The other is characterized by 10 to 12 coils of the polar tube and the late development (54 h postinoculation).The results are summerized as below, 1) The two types of spores were confirmed to develop in midgut epithelial cells of the silkworm larvae after peroral inoculation. 2) A new Nosema sp. was isolated from the lawn grass cutworm, Spodoptera deprauata. This microsporidium produced two types of spores exactly the same ones as found in N.bombycis, while it did not infect the silkworm by oral administration of spores, and its spores did not react with latex particles whic had been sensitized with a monoclonal antibody against spores of N.bombycis. This microsporidium had two nuclei in diplokaryotic arrangement throughout its development. A meront gave rise to two spores, and there was no sporophorous vesicle. Hence it is another Nosema sp. isolated from S.deprauata. 3) We also identified the two types of spores in N.furnacalis developing in cultured cells. Furthermore, one of spore, early developing one, was isolated and successfully inoculated onto cultured cells, giving high rate of infection.These results indicate that this spore dimorphism is a character shared by microsporidia belonging to the genus Nosema.