A new microsporidium from the oyster Ostrea lutaria in New Zealand

Microsporidium rapuae n. sp. (Microsporida) forms cysts within the connective tissue surrounding the gut epithelium of the oyster Ostrea lutaria. Except for encapsulation of the cysts by fibroblasts no pathogenic effects were observed. Each cyst contained a large number of spores possessing long well-developed polar filaments. This is the third Microspora recorded from Bivalvia (Mollusca), and the first which does not belong to the family Chytridiopsidae (Minisporida).