Corynoplastis japonica gen. et sp. nov. and Dixoniellales ord. nov. (Rhodellophyceae, Rhodophyta) based on morphological and molecular evidence

SUMMARY A new unicellular red alga, Corynoplastis japonica gen. et sp. nov., is described from Tobishima, Japan. Cells are spherical, 18–33 µm in diameter, pale purple to brownish red and surrounded by a mucilaginous sheath. A single chloroplast with many lobes extends from the cell periphery to the cell center. A peripheral thylakoid is present. A pyrenoid occurs at each innermost chloroplast lobe end and one or two thylakoids are present in the pyrenoid matrix. The nucleus is eccentric to peripheral and Golgi bodies are scattered throughout the cell and associated with endoplasmic reticulum. Cells have a slow random gliding motility. The low molecular weight carbohydrate mannitol is present in the cells. Molecular phylogenetic analysis indicates that this alga is closely related to members of the genus Rhodella. A new order, Dixoniellales, is established for Dixoniella, Neorhodella and Glaucosphaera based on molecular and ultrastructural evidence (Golgi bodies associated only with the nucleus). The redefined order Rhodellales in which Rhodella and Corynoplastis are placed is characterized ultrastructurally by Golgi bodies scattered throughout the cytoplasm and associated with endoplasmic reticulum.