Desmid

Desmids are an order (Desmidiales) of green algae, comprising around 40 genera and 5,000 to 6,000 species, found mostly but not exclusively in fresh water. Most are unicellular, and are divided into two compartments separated by a narrow bridge or isthmus. Desmids assume a variety of highly symmetrical and generally attractive shapes, which provide the basis for their classification. Each compartment has one chloroplast, and no flagella. Sexual reproduction occurs through a process of conjugation, also found among the Zygnematales. These two groups are closely related, and may be united as the division Gamophyta. The desmids are sometimes treated as members of the Zygnematales, but more often given the separate order Desmidiales.