Compare

Gomphonema stoermeri valves are smaller in length and more rhombic in outline. Gomphonema christensenii lacks an isolated stigmoid. Gomphonema freesei is very similar in shape, size, stria density and overall appearance to G. amerhombicum under the light microscope. Under critical illumination, Gomphonema freesei has coarse areolae. The ultrastructure of the striae of G. freesei, however, is unknown. Gomphoneis rhombicum has a lower stria density (9.5-12 in 10 µm) and greater length to width ratio, that is, valves are more slender for their size (L = 35-53 µm, W = 4.5-7.5 µm). Note that G. rhombicum has not been verified in North America.

LM scalebar = 10 µm
G Amerhombicum  B Isotype 20170301 06 Cl G Amerhombicum  A Isotype 20170301 08 Cl G Amerhombicum  A Isotype 20170301 18 Cl G Amerhombicum  B Isotype 20170301 05 Cl G Amerhombicum  B Isotype 20170301 14 Cl G Amerhombicum  B Isotype 20170301 09 Cl G Amerhombicum  B Isotype 20170301 21 Cl
Length Range
22.5-60 µm
Width Range
5.6-7.7 µm
Striae in 10 µm
13-15 at mid-valve, up to 17 at headpole

Gomphonema freesei

R.L.Lowe and Kociolek 1984

Gc53921  Gomphonema Freesei 1 Gc53921  Gomphonema Freesei 2 Gc53921  Gomphonema Freesei 3 Gc53921  Gomphonema Freesei 4 Holotype Gc53921  Gomphonema Freesei 4B Holotype Gc53921  Gomphonema Freesei 5
Length Range
35.0-53.9 µm
Width Range
6.5-7.5 µm
Striae in 10 µm
12.1-14.5 at valve center, 14.2-16.2 at headpole, 11.7-15.4 at footpole

Gomphonema christenseni

R.L.Lowe and Kociolek 1984

Gomphonema christenseni LM2 Gomphonema christenseni LM5 Gomphonema christenseni LM6 4 53920  Gchristenseni Holo 5 53920  Gchristenseni2 6 53920  Gchristenseni2 7 53920  Gchristenseni2
Length Range
32.8-57.4 µm
Width Range
6.1-7.8 µm
Striae in 10 µm
13-16

Also compare to

Gomphonema stoermeri

Kociolek and Kingston

Gomphoneis rhombicum

(Fricke) Merino, García, Hern.-Mar. and Fernández 1994