Gyrosigma acuminatum is smaller in size and more slender. In addition, G. acuminatum also has longitudinal and transverse striae that are equally spaced. Gyrosigma terryanum is larger, with range in length of 340-450 µm. Gyrosigma balticum reaches larger maximum lengths than G. attenuatum, and the center of the valve has parallel margins.

LM scalebar = 10 µm
Gyrosigma attenuatum LM4 Gyrosigma attenuatum LM10 Gyrosigma attenuatum LM14 Gyrosigma attenuatum LM8 Gyrosigma attenuatum LM2 Gyrosigma attenuatum LM6 Gyrosigma attenuatum LM12
Length Range
130-255 µm
Width Range
20-28 µm
Striae in 10 µm
12-14 transverse; 10-12 longitudinal

Gyrosigma acuminatum

(Kütz.) Rabenh. 1853

Images 3 Images 4 Images 5 Images 1 Images 2
Length Range
77-153 µm
Width Range
11-18 µm
Striae in 10 µm
transverse 18-20; longitudinal 18-22

Also compare to

Gyrosigma terryanum

H.Perag. 1891

Gyrosigma balticum

(Ehrenb.) Rabenh. 1853