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Achnanthidium druartii differs from similar species A. deflexum and A. alpestre by the lanceolate shape of the valve and the large difference in stria density in the valve center, as compared to the valve ends. Achnanthidium pyrenaicum and A. eutrophilum can be easily distinguished from A. druartii by their smaller size range. Achnanthidium rivulare is distinguished by its linear-elliptical valve outline.

LM scalebar = 10 µm
Asp 3 Kdow03024042 8 Kdow03024042 12 Kdow03024042 6B Kdow03024042 11 Asp 1 Kdow03024042 7
Length Range
14-25 µm
Width Range
4.1-5.3 µm
Striae in 10 µm
15-20 in 10 µm in the center valve, 40-50 in 10 µm at the ends of raphe valve, 25-35 in 10 µm at the ends of rapheless valve

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

Achnanthidium alpestre

(R.L.Lowe and Kociolek) R.L.Lowe and Kociolek in J.R.Johans. et al. 2004

Achnanthidium alpestre LM2 Ada 2A Ed Ada 2B A Ed Achnanthidium alpestre LM1 Achnanthidium alpestre LM3 Ada 3A A Ed
Length Range
10.3-20.4 µm
Width Range
3.7-4.4 µm
Striae in 10 µm
24-28 in the center of raphe valve, 26-32 in the center of rapheless valve, 35-42 at the ends

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

Achnanthidium eutrophilum

(Lange-Bert.) Lange-Bert. 1999

Gs009181  Rl4 Gs009181  R46 Achnanthidium eutrophilum LM2 Achnanthidium eutrophilum LM1 Gs001021  R25 Gs001021  R20 Gs001021  R1
Length Range
5.4-17.8 µm
Width Range
2.1-4.0 µm
Striae in 10 µm
25-35 in the middle of raphe valve

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