Compare

Achnanthidium crassum is difficult to distinguish, except under optimal illumination. Achnanthidium rivulare has a slightly smaller length-to-width ratio and parallel striae at the apices on the raphe valve. Achnanthidium deflexum has subrostrate ends, areolae that are resolvable in LM and shortened marginal striae in the center of the valve. Achnanthidium pyrenaicum has slightly rostrate ends and a fascia on the raphe valve.

LM scalebar = 10 µm
Achnanthidium Crassum Nrsa2361 053116 14 Achnanthidium Crassum Nrsa2361 053116 3 Achnanthidium Crassum Ct10010 A 122017 88 Achnanthidium Crassum Ct10010 A 122017 89 Achnanthidium Crassum Nrsa2361 053116 16 Achnanthidium Crassum Nrsa2361 053116 1
Length Range
7.3-19.6 µm
Width Range
3.1-4.5 µm
Striae in 10 µm
17-24

Achnanthidium rivulare

Potapova and Ponader 2004

Achnanthidium rivulare LM4 Achnanthidium rivulare LM5 Achnanthidium rivulare LM3 Achnanthidium rivulare LM2 Achnanthidium rivulare LM1
Length Range
5.4-23.8 µm
Width Range
2.6-4.4 µm
Striae in 10 µm
19-25 in the middle of raphe valve, 19-28 in the middle of the rapheless valve

Achnanthidium deflexum

(Reimer) Kingston 2003

Achnanthidium deflexum LM4 Achnanthidium deflexum LM1 Achnanthidium deflexum LM3 Achnanthidium deflexum LM5 Achnanthidium deflexum LM2
Length Range
7.4-28.3 µm
Width Range
3.1-5.3 µm
Striae in 10 µm
15-28 in the middle of raphe valve

Achnanthidium pyrenaicum

(Hust.) H.Kobayasi 1997

Achnanthidium pyrenaicum LM5 Achnanthidium pyrenaicum LM3 Achnanthidium pyrenaicum LM1 Achnanthidium pyrenaicum LM4 Achnanthidium pyrenaicum LM2
Length Range
10–16 µm
Width Range
2.5-4.0 µm
Striae in 10 µm
20-25 in the center, 34-40 at the raphe valve ends; 20-28 in the center, 32-38 at the rapheless valve ends

Also compare to

Achnanthidium japonicum

(H.Kobayasi) H.Kobayasi