An ultrastructural study of Marsupiomonas pelliculata gen. et sp. nov., a new member of the Pedinophyceae

A new species, Marsupiomonas pelliculata gen. et sp. nov. (Pedinophyceae), is described. A single flagellum emerges from a deep pit with a distinctive thickened margin. The flagellum has rigid fibrillar hairs which are probably formed in the perinuclear space. A short second flagellar basal body lies within the cell close to the basal body of the emergent flagellum and the flagellar root system consists of striated and microtubular roots. There is a distinctive theca covering all but the anterior end of the cell and also a single large bright green chloroplast with an immersed pyrenoid surrounded by a starch shell. The wide salinity tolerance of the species is discussed in relation to its distribution in estuarine and salt marsh habitats. The salient features of the new species—the insertion of the emergent flagellum into a deep pit and the possession of a theca—are also seen in Pedinomonas tenuis, and it is suggested that P. tenuis could be transferred to the new genus Marsupiomonas. The class Pedinophyceae now includes three genera (Pedinomonas, Resultor and Marsupiomonas) and the distinguishing features are discussed.