Fine structure of Minchinia sp., a haplosporidan infecting the mussel Mytilus galloprovincialis L.

The fine structure of the mature spore of a haplosporidan found in the mussel Mytilus galloprovincialis L. is described. The mature spore (10 × 5 µm) is operculate and characterised by the presence of epispore cytoplasm that is prolongated into two bipolar extensions or 'tails' of 80–100 µm in length. The extensions are supported by bundles of microtubule-like structures which are not found in continuity with the wall. Due to the presence of episporal extensions and because the present species differs in some morphological characters from other haplosporidans assigned to the genus Minchinia Labbé, the parasite of the mussel has been placed in this genus as Minchinia sp.