[7] The body plan of Zygnematophyceae is simple, and the group appears to have gone through a secondary loss of morphological complexity.

The shape of the chloroplast may be star-shaped (in Zygnema), ribbon-shaped (in Spirogyra), or elaborately lobed and dissected.

[11][12] A new subclass called Spirogloeophycidae, represented by the species Spirogloea muscicola, was established after the unicellular subaerial algae, resembling a "gelatinous blob", was rediscovered on a rock close to a river bank near Cologne in 2006, after first being discovered in France in 1845.

Asexual reproduction takes place via fragmentation, cell division, akinete formation, or parthenospores.

[7] Sexual reproduction in the Zygnematophyceae takes place through a process called conjugation.

As of 2023[update], five orders and two subclasses are recognized: the Spirogloeales in Spirogloeophycidae, and the Serritaeniales, the Zygnematales, the Spirogyrales, and the Desmidiales in Zygnematophycidae.

[18] Vegetative cells of the Zygnematophyceae are fragile and usually not preserved, but the zygospores are resistant to decay and can become fossilized.

Fossils of zygospores are indicators of warming spring conditions and shallow, stagnant mesotrophic habitats.