1 Record

Mesotaenium is a microscopic, unicellular, freshwater green alga. It is generally pill-shaped and is generally 1.5 to many times longer than broad. It is distinguished from other small, round, green algae by its axial, flat plastid (chloroplast); its central nucleus; pyrenoids; and sexual reproduction by conjugation.

Species of Mesotaenium are distinguished by their size and shape, the presence of lamellated gelatinous sheaths and, most reliably, the ornamentation of their sexual spores.

Mesotaenium species are an infrequent component of most oligotrophic and mesotrophic waters (i.e., habitats with low to moderate nutrients, pH and conductivity). They may form macroscopic, gelatinous masses in subaerial situations such as in seeps or the edges of waterfalls.