Nitzschia radicula is very similar to N. incognita, and further work may show them to be the same species.

Nitzschia alpina and N. perminuta have fibulae that are continuous through the median.

Nitzschia acidoclinata has linear valves.

Nitzschia fonticola, N. frustulum, N. hantzschiana and N. liebetruthii have wider valves and lower stria densities.

LM scalebar = 10 µm
Nitzschia incognita LM7 Nitzschia incognita LM6 Nitzschia incognita LM5 Nitzschia incognita LM4 Nitzschia incognita LM3 Nitzschia incognita LM2 Nitzschia incognita LM1
Length Range
18.8-47.7 µm
Width Range
2.2-3.0 µm
Striae in 10 µm

Nitzschia alpina

Hust. 1943

Nitzschia alpina LM7 Nitzschia alpina LM6 Nitzschia alpina LM5 Nitzschia alpina LM4 Nitzschia alpina LM3 Nitzschia alpina LM2 Nitzschia alpina LM1
Length Range
13-21 µm
Width Range
3.3-4.2 µm
Striae in 10 µm

Nitzschia acidoclinata

Lange-Bert. 1977

Nitzschia acidoclinata LM5 Nitzschia acidoclinata LM4 Nitzschia acidoclinata LM3 Nitzschia acidoclinata LM7 Nitzschia acidoclinata LM2 Nitzschia acidoclinata LM1 Nitzschia acidoclinata LM6
Length Range
18.4-32.8 µm
Width Range
2.2-2.9 µm
Striae in 10 µm

Nitzschia fonticola

(Grunow) Grunow in Van Heurck 1881

Fonticola 001 Fonticola 004 Fonticola 002 Fonticola 011 Fonticola 005 Fonticola 003 Fonticola 007
Length Range
10-55 µm
Width Range
2.5-4.5 µm
Striae in 10 µm

Nitzschia liebethruthii

Rabenh. 1864

Liebetruthii Gc106965H005 Liebetruthii Gc106965H003 Liebetruthii Gc106965H001 Liebetruthii Gc108446A005 Liebetruthii Gc106965H002 Liebetruthii Gc108446A004 Liebetruthii Gc108446A002
Length Range
9.0-21.0 µm
Width Range
3.0-6.0 µm
Striae in 10 µm

Nitzschia perminuta

(Grunow in Van Heurck) H.Perag. 1903

Nitzschia perminuta LM1 Nitzschia perminuta LM5 Nitzschia perminuta LM4 Nitzschia perminuta LM3 Nitzschia perminuta LM2
Length Range
8-20 µm
Width Range
3-4 µm
Striae in 10 µm

Also compare to

Nitzschia frustulum

(Kütz.) Grunow in Cleve and Grunow

BioData Reference
Krammer and Lange-Bertalot 2/2 Pl 68 Fig 1-8

Nitzschia hantzschiana

Rabenh. 1860

Nitzschia radicula

Hust. 1942