Centrophyceae

Centrophyceae 

a class of diatoms. The cells are single or form filamentous and chainlike colonies. The chromatophores are usually in the form of small, numerous grains, occasionally of one or more small plates. Reproduction consists in the asexual division of the cell into two halves; however, oogamy, a type of sexual reproduction, also occurs. The shells may be cylindrical, disklike, lenticular, ellipsoid, spherical, dolioform, or occasionally prismatic; the two halves of the shell overlap. The valves of the shell have a radial structure and always lack a raphe.

The Centrophyceae consist of 100 genera and approximately 4,000 species, including fossil species from as far back as the Cretaceous and extant species widely distributed in fresh and salt waters. Since they develop in phytoplankton, the Centrophyceae serve as food for many invertebrates and young fish. The shells of the algae form thick layers of diatomite, which is used in industry.