Kurtkrammeria, a new genus of freshwater diatoms (Bacillariophyta, Cymbellaceae) separated from Encyonopsis

Abstract

The new genus Kurtkrammeria is erected to include 13 species assigned to Encyonopsis that have (1) slit-like or crescent-shaped areolae aligned lengthwise along the apical axis, (2) striae convergent at the apices, and (3) internal proximal raphe ends hooked strongly towards the dorsal side of the valve. Some species of Kurtkrammeria also have dorsal stigmata, apical pore fields and internal anastomosing costae at both poles, and lateral papilla-like projections from intercostae into internal areola openings. Species of Kurtkrammeria are reported infrequently from fossil deposits and from recent diatom assemblages. Kurtkrammeria is a genus of remote and undeveloped regions from the Arctic to the Tropics, in both the Old World and New World. Most species are local or regional endemics and only four species - K. aequalis, K. neoamphioxys, K. recta, and K. subspicula - appear to be widely distributed. Kurtkrammeria species consistently occur in oligotrophic or dystrophic waters with very low specific conductance and circumneutral pH. An extant population of the very rare Kurtkrammeria stodderi is described from Montana, USA. Living cells of K. stodderi were observed to be motile and to have plastids similar to those of Encyonema species. Examination under SEM reveals that K. stodderi also has apical pore fields at both poles.