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Achnanthidium kranzii is similar to A. minutissimum in valve shape and size, but can be distinguished from A. minutissimum by the curved terminal raphe fissures that are usually visible in LM. In addition, A. kranzii has wider valves (on average), a large rectangular central area on the raphe valve and a distinct rhomboid, or apically elliptical, central area on the rapheless valve.

LM scalebar = 10 µm
Achnanthidium kranzii LM7 Achnanthidium kranzii LM3 Achnanthidium kranzii LM5 Achnanthidium kranzii LM6 Achnanthidium kranzii LM1 Achnanthidium kranzii LM2 Achnanthidium kranzii LM4
Length Range
8-20 µm
Width Range
2.8-3.8 µm
Striae in 10 µm
24-30 in the center valve, up to 40 at the ends

Achnanthidium minutissimum

(Kütz.) Czarn. 1994

Achnanthidium minutissimum LM4 Achnanthidium minutissimum LM3 Achnanthidium minutissimum LM7 Achnanthidium minutissimum LM2 Achnanthidium minutissimum LM6 Achnanthidium minutissimum LM1 Achnanthidium minutissimum LM5
Length Range
5.6-20.8 µm
Width Range
1.5-3.3 µm
Striae in 10 µm
25-35

Achnanthidium atomus

(Hust.) Monnier, Lange-Bert. and Ector 2004

Achnanthidium atomus LM3 Achnanthidium atomus LM2 Achnanthidium atomus LM1 Achnanthidium atomus LM4
Length Range
9.9-21 µm
Width Range
3-3.5 µm
Striae in 10 µm
28-30 in raphe valve, 22-25 in rapheless valve