Charophyceae

(botany) A class of green algae in the division Chlorophyta.

A group of branched, filamentous green algae, commonly known as the stoneworts, brittleworts, or muskgrasses, that occur mostly in fresh- or brackish-water habitats. They are important as significant components of the aquatic flora in some locales, providing food for waterfowl and protection for fish and other aquatic fauna; as excellent model systems for cell biological research; and as a unique group of green algae thought to be more closely related to the land plants.

Charophytes are multicellular, branched, macroscopic filaments from a few inches to several feet in length. Colorless rhizoidal filaments anchor the plants to lake bottoms and other substrates. The main filaments are organized into short nodes forming whorls of branches, and much longer (up to 6 in. or 15 cm) internodal cells. The general morphology varies with environmental conditions such as depth of the water, light levels, and amount of wave action. Reproductive structures occur at the nodes and consist of egg cell-containing structures, the nucules, and sperm cell-containing structures called globules.

Based on the morphology of the vegetative filaments and the reproductive structures, six extant genera are recognized: Chara, Nitella, Tolypella, Nitellopsis, Lamprothamnium, and Lychnothamnus. There is no agreement on how many valid species exist, but the maximum number of living species is probably fewer than 100. Deoxyribonucleic acid (DNA) sequencing indicates that the charophytes are a distinct natural group that should be recognized at some taxonomic level (for example, as an order, Charales, or as a class, Charophyceae). See also Algae; Chlorophycota.