Oedogonium is a genus of filamentous, free-living green algae. It was first discovered in the fresh waters of Poland in 1860 by W. Hilse, and later given its name by German scientist K. E. Hirn.

The morphology of Oedogonium is unique, with an interior and exterior that function differently from one another and change throughout its life cycle. These algae reside in freshwater ecosystems in both hemispheres and are both benthic and planktonic in nature. They form algal patches on the water's surface and so interact closely with a multitude of other algae. These filamentous cells' life cycles include both sexual and asexual reproduction, depending on the life cycle stage.

Although quite common, Oedogonium is difficult to identify since key definitive markers are only present during reproduction, which is an uncommon life stage among this genus. Oedogonium has been found to be important in the fixation of heavy metals in freshwater ecosystems.

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