Closterium

Closterium is a genus of desmid, a group of charophyte green algae. It is placed in the family Closteriaceae. Species of Closterium are a common component of freshwater microalgae flora worldwide.

== Description == Closterium is a diverse genus consisting of solitary cells, each made of two identical halves called semicells. Usually they are microscopic, but the largest can become easily visible to the naked eye. Cells are many times longer than broad, and are variously elongate to lunate (crescent-shaped). The poles are rounded, truncated, or pointed. The surface of the cell may be smooth or decorated with various features, such as striations or punctae. The cell wall is transparent, but with age it may become dark brown due to accumulated iron and manganese compounds. The cell nucleus is located in the middle of the cell. Each semicell contains a single axial chloroplast dotted with several pyrenoids.