Nitzschia clausii is comparatively narrower than N. brevissima and has finer striae than both N. filiformis and N. sigma. The valves of N. clausii are more sigmoid in shape and have narrower, more constricted apices than N. filiformis. Nitzschia clausii has a curved keel at the valve center, while that of N. sigma is straight at the valve center. N. clausii is narrower and has more narrowly rounded apices than N. scalpelliformis. Nitzschia clausii has apices that are more constricted than those of N. nana.

LM scalebar = 10 µm
Clausii 009 Clausii 004 Clausii 014 Clausii 011 Clausii 010 Clausii 007 Clausii 013
Length Range
20.0-68.0 µm
Width Range
3.0-5.0 µm

Nitzschia brevissima

Grunow in Van Heurck 1881

Brevissima Gc109965H006 Brevissima Gc109965H005 Brevissima Gc109965H002 Brevissima Gc109965H004 Brevissima Gc109965H003 Brevissima Gc109965H001
Length Range
20-55 µm
Width Range
3.5-5.5, as measured in the middle of the valve µm
Striae in 10 µm

Nitzschia filiformis

(W.Sm.) F.Schütt 1896

Filiformis Gc106965H009 Filiformis Gc106965H001 Filiformis Gc106965H008 Filiformis Gc106965H004 Filiformis Gc106965H010 Filiformis Gc106965H006 Filiformis Gc106965H005
Length Range
27.0-150.0 µm
Width Range
4.0-5.0 µm
Striae in 10 µm

Nitzschia sigma

(Kütz.) W.Sm. 1853

Nitzschia sigma LM3 Nitzschia sigma LM2 Nitzschia sigma LM4 Nitzschia sigma LM5 Nitzschia sigma LM1
Length Range
30.0-200.0 µm
Width Range
4.0-13.0 µm
Striae in 10 µm

Also compare to

Nitzschia scalpelliformis


Nitzschia nana

Grunow in Van Heurck