Acta Protozool Acta Protozool. Motile zoospores appeared a few times in cultures of isolated cysts in vitro . Zoospores may develop from the spores or from sporoblasts without formation of the spore stage.
Zoospores possibly escape from the cysts through pores in the cyst wall.
The cyst wall comprises several strata. During plasmotomy the fibrous stratum of the wall is engulfed to form the walls of different compartments. Cells maturing into zoospores have a prominent inclusion, an eccentric nucleus, a few mitochondria and several membrane-surrounded bodies. The largest body has a quadruple membrane, and the smallest ones have ribosome-like inclusions. The flagellum of the zoospore has a striated rhizoplast penetrating to a ribosome-rich area in the zoospore cytoplasm.