Guide to Synedra

Currently, species in Synedra are considered to be primarily marine, typified by S. balthica, which is synonymous with Synedra gaillonii (Bory) Ehrenberg. The taxon shown here is S. gaillonii. Following recent changes in the literature, elongate, needle-like freshwater species on the Diatoms of the United States site are treated in Fragilaria and Ulnaria.

Araphid genera, including Synedra, Fragilaria, Ulnaria and others, have been subject to a longstanding debate concerning nomenclature (Williams 2011). Historically, Fragilaria and Synedra were distinguished based on their growth form. Synedra included taxa that produced stellate colonies that attached to subtrates by a mucilage pad. Those taxa are now largely included in Ulnaria, but many have yet to be transferred. Compare also with the genus Fragilaria, which also includes linear, elongate valves that form ribbon-like colonies.