Closterium subulatum is a freshwater desmid characterized by its elongated, spindle-shaped cells ranging from 100 to 400 micrometers in length. Each cell has a firm cellulose cell wall and contains ribbon-like chloroplasts responsible for photosynthesis. The nucleus is centrally located. Reproduction occurs mainly through binary fission, with occasional sexual reproduction. Closterium subulatum is commonly found in ponds, lakes, and slow-moving streams, typically attached to submerged vegetation or sediment. It plays a crucial role as a primary producer in freshwater ecosystems.