Compare

Achnanthidium rivulare is difficult to distinguish, except under optimal illumination. Achnanthidium crassum has a slightly larger length-to-width ratio and radiate striae at the apices on the raphe valve. Achnanthidium deflexum has a linear-elliptic valves and shortened striae near the central valve. Rossithidium pusillum has strongly curved terminal raphe fissures and parallel striae throughout most of the valve. Achnanthidium convergens has strongly convergent striae near apices of the raphe valve, is larger in size, and has expanded external central raphe ends.

LM scalebar = 10 µm
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 crassum

(Hust.) Potapova and Ponader 2004

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 deflexum

(Reimer) Kingston 2003

Achnanthidium deflexum LM4 Achnanthidium deflexum LM1 Achnanthidium deflexum LM5 Achnanthidium deflexum LM3 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

Rossithidium pusillum

(Grunow) Round and Bukht. 1996

Rossithidium pusillum LM6 Rossithidium pusillum LM8 Rossithidium pusillum LM10 Rossithidium pusillum LM2 Rossithidium pusillum LM4 Rossithidium pusillum LM12
Length Range
10–16 µm
Width Range
3.1-4.1 µm
Striae in 10 µm
20-24

Also compare to

Achnanthidium convergens

(H.Kobayasi) H.Kobayasi