Taxonomic studies of marine Ascomycotina: ultrastructure of the asci, ascospores, and appendages of Savoryella species

Abstract

The asci, ascospores, and appendages of Savoryella longispora, Savoryella paucispora, and Savoryella appendiculata were examined at the transmission electron microscope level. Asci of S. longispora and S. appendiculata have a well-developed apical apparatus that consists of a thickened electron-dense ring with a central pore. In S. appendiculata the pore is occluded by a plug of electron-lucent material. The ascus wall comprises an outer narrow electron-opaque layer and an inner electron-lucent layer that are continuous over the apical apparatus. Ascospore walls possess an inner electron-lucent mesosporium and an outer electron-opaque episporium. The episporium of the central cells of all three species is covered with a layer of fibrillar mucilage. Granular strand-like outgrowths of the ascospore wall are present on the polar cells of S. appendiculata and S. paucispora. In all three species the hyaline polar cells of the ascospore contain organelles and in S. appendiculata the polar cells are verrucose. Ascospore appendages are only found in S. appendiculata and these arise endogenously by outgrowth of the endosporium of the polar cell. The differences between the three species are not considered significant at the generic level and therefore all are assigned to the genus Savoryella. Key words: appendages, Ascomycotina, ascospores, marine, taxonomy, ultrastructure.