Ultrastructure of asci and ascospores of Massarina velatospora from intertidal mangrove wood

A transmission electron microscope investigation of the asci and ascospores of Massarina velatospora was undertaken using material collected from Boracay, Philippines. Our collection agrees with the type material although the ascospores were predominantly 1-septate. It was collected on wood of Sonneraita sp. that had been heavily attacked by molluscan borers. The asci are bitunicate with a thick (2-4 μm), fibrillar endoascus and a narrow ectoascus (100-300 nm) that is thickened at the apex with an ocular chamber in mature asci. Ascospore walls comprise a mesosporium, an electron-dense episporium surrounded by an exosporial mucilaginous sheath and bounded by a delimiting membrane that ruptures in water. A comparison of the ultrastructure of M. velatospora and other aquatic Massarina species is made.