Diatoms of North AmericaDiatoms of North America
Return to overview

Guide to Aulacoseira ambigua

(Grunow) Simonsen 1979

Aulacoseira Ambigua Guide
Credit: Marina Potapova
  1. Ratio of mantle height to valve diameter > 1
  2. Rows of mantle areolae curved to right
  3. Ringleiste hollow
  4. Separation valve with short, pointed spines
  5. Spines originate from every pervalvar costa

Valves are 3-12 µm in diameter, with a mantle height of 5-15 µm. The ratio of the mantle height to valve diameter is greater than 1. The spiral rows of mantle areolae are curved to the right (dextrorse) and number 17-22 in 10 µm. Spines are located at the end of each pervalvar costa. Linking spines are short, triangular or bifurcated. Separation spines are small and pointed. In some separation valves, rows of areolae coalesce near the valve face, giving the appearance of spines originating from two pervalvar costae. The ringleiste is hollow, described by some authors as a 'U-shaped sulcus'.