The diatom genus sellaphora: Separation from navicula

Abstract

The genus Sellaphora Mereschkowsky is resurrected to include those naviculoid diatoms with an H-shaped plastid containing an invaginated pyrenoid; a particular, characteristic series of conformational and positional changes in the plastid and nucleus during the cell cycle; gametangia that produce one gamete apiece and which remain closely associated throughout meiosis and plasmogamy, without any obvious mucilage envelope around them; physiological anisogamy, the single auxospore being formed within one gametangium and expanding parallel to its apical axis; small round poroids; and internal central raphe endings that are deflected towards the primary side of the valve. Light microscopical identification of Sellaphora is fairly straightforward if live cells are examined; cleaned valves require SEM observation. Many small “Navicula” species probably belong to Sellaphora’, for the moment the species included are S. papula (the type), S. amerkana, S. bacillum, S. disjunctu, S. laevissima, S. nyassensis, S. seminulum and S. vitabunda. © 1989 The British Phycological Society.