Aulacoseira crassipunctata

Frustules cylindrial, linked into short straight or curved chains; valves 6-10 μm in diameter, mantle height 10-17 μm, ratio height/diameter 0,8-1,5, varies not only throughout the division cycle, but also between sibling valves and even between valves of a single frustule (fig. 72). Outer and inner mantle lines straight and parallel; discus distinctly convex (fig. 76) or concave (fig. 79, in sibling valves, convex and concave disci fit into each another); pseudosulcus a broad but flat furrow. Cell wall thick; linking spines short; separating spines not observed, the broad collum bears on its inside a very broad Ringleiste (figs. 73, 74). The disci have varied patterns of medium-seized areolae, sometimes being dispersed and irregularly distributed (figs. 75, 79), in completely areolated disci the areolae sometimes arranged in tangential rows. Nearly every pervalvar mantle rib bears a very small, somewhat irregularly shaped linking spine with bifid anchors (figs. 76-78). The mantle areolae vary in size (fig. 76), are very large and appear pearl-like in the LM (figs. 71, 72). SEM reveals very irregular areolae foramina (figs. 76-78). The pervalvar rows (6-9/10 μm) run parallel or slightly oblique to the pervalvar axis. The areola arrangement here is somewhat irregular with the consequence that transverse rows are either absent (figs. 71, 78) or indistinct (figs. 72, 76).

• Author
  Krammer 1991
• Length Range
  6-10 µm
• Width
  10-17 µm
• Striae in 10µm
  6-9