Selenastrum Reinsch
	From Greek selene, "moon" + astron, "star"
	Selenastrum has crescent-shaped or sickle-shaped cells that are longer than broad and strongly curved or twisted. The genus can form non-mucilaginous colonies from clusters of 4, 8, or 16 cells that are not intertwined and are instead arranged with their convex sides facing each other. Each cell has a single parietal chloroplast, often with pyrenoids.       The tiny cells of Selenastrum vary in morphology.
Selenastrum inhabits the phytoplankton of ponds, lakes, and swamps. It is commonly found across most of the United States, Canada, and Central America, sometimes in nutrient-rich waters.   Selenastrum, Chlamydomonas and other chlorophyceans are used as a food source for zooplankton that are fed to fish in freshwater aquaculture. Selenastrum capricornutum is the most commonly used biomonitor to assess the levels of nutrients or toxins in freshwater environments. This species is quite sensitive to the presence of toxins and can alert researchers to subtle changes in water conditions before a problem becomes excessive.