The central gibbous valve margin of A. tumescens is much smaller than that of A inflata, while the central valve margin of A. coarctata. Achnanthes tumescens is coarser and more robust than A. mauiensis. The striae of A. tumescens are finer than those of A. elata.

LM scalebar = 10 µm
Achnanthes tumescens LM4 Achnanthes tumescens LM5 Achnanthes tumescens LM7 Achnanthes tumescens LM3 Achnanthes tumescens LM2 Achnanthes tumescens LM6 Achnanthes tumescens LM1
Length Range
29-37 µm
Width Range
8.0-9.5 µm
Striae in 10 µm
14-15 on raphe valve, 12-13 on rapheless valve

Achnanthes coarctata

(Bréb. ex W.Sm.) Grunow in Cleve and Grunow 1880

Achnanthes coarctata LM4 Achnanthes coarctata LM2 Achnanthes coarctata LM1 Achnanthes coarctata LM5 Achnanthes coarctata LM3
Length Range
32-70 µm
Width Range
9.4-15 µm
Striae in 10 µm
11 on the raphe valve, 9-10 on the rapheless valve

Achnanthes inflata

(Kütz.) Grunow 1867

Achnanthes inflata LM7 Achnanthes inflata LM1 Achnanthes inflata LM2 Achnanthes inflata LM3 Achnanthes inflata LM4 Achnanthes inflata LM5 Achnanthes inflata LM6
Length Range
32-59 µm
Width Range
13.5–21.1 µm
Striae in 10 µm

Achnanthes mauiensis

R.L.Lowe and A.R.Sherwood 2009

Achnanthes mauiensis LM1 Achnanthes mauiensis LM3 Achnanthes mauiensis LM5 Achnanthes mauiensis LM7 Achnanthes mauiensis LM4 Achnanthes mauiensis LM2 Achnanthes mauiensis LM6
Length Range
22.4-27.1 µm
Width Range
5-7.5 µm
Striae in 10 µm
15-19 on both valves

Also compare to

Achnanthes elata

(Leud.-Fortm.) Gandi