Closteriopsis longissima is a green algae characterized by its elongated, cylindrical cells that form extensive filaments or chains. These cells are relatively long and narrow, ranging from several hundred micrometers to several millimeters in length. The cell wall is smooth and firm, supporting the algae’s filamentous structure. Each cell contains one or more chloroplasts, typically located centrally or along the cell wall, facilitating photosynthesis and possibly containing pyrenoids. The nucleus is centrally positioned within each cell. Reproduction occurs through asexual cell division, with new cells forming along the filament. Closteriopsis longissima is often found in freshwater environments such as ponds, lakes, and slow-moving streams, where it may exhibit slow, gliding movements aided by mucilage secretion.