Taxonomy and Morphology Ofcymbella Stuxbergiifrom Lakes in the Baikal Rift Zone

The morphology and ultrastracture of Cymbella stuxbergii (Cleve in Cleve & Grunow) Cleve were investigated using light and scanning electron microscopy. Cymbella stuxbergii is one characteristic component of a species complex within the nearshore periphyton in large lakes in the Baikal Rift Zone. Its distribution also includes northern mid-Asian continental rivers. Ultrastructure of C. stuxbergii supports the maintenance of this taxon within Cymbella sensu stricto because it has a single bilobed chloroplast, a ventral nucleus, dorsi-ventral valve shape, many ventral stigmata, dorsally deflected distal raphe ends, well-differentiated apical pore fields, and lacks an intermissio. Within Cymbella, C. stuxbergii appears closely allied with C. proxima Reimer because these taxa share similar raphe, stigmatal opening, and areolae configurations.