Light and Electron Microscope Study of Urosporidium cannoni N. Sp., a Haplosporidian Parasite of the Polyclad Turbellarian Stylochus sp.

ABSTRACT. Urosporidium cannoni n. sp. was found in most tissues of a polyclad turbellarian associated with commercial oyster farms from eastern Moreton Bay, Australia. Mature spores had 11 to 13 episporal tails at irregular intervals around the spore wall. The spherule, prominent in development, dispersed as the spores matured. Spores were found within cysts that contained up to a few hundred spores at the same stage of development. Mature cysts occurred in groups and their masses of dark, golden spores resulted in black patches on the otherwise red-brown turbellarian. The infection may have commercial importance.