Ochrophyte

Ochrophytes, also known as heterokontophytes or stramenochromes, are a phylum of algae. They are the photosynthetic stramenopiles, a group of eukaryotes, organisms with a cell nucleus, characterized by the presence of two unequal flagella, one of which has tripartite hairs called mastigonemes. In particular, they are characterized by photosynthetic organelles or plastids enclosed by four membranes, with membrane-bound compartments called thylakoids organized in piles of three, chlorophyll a and c as their photosynthetic pigments, and additional pigments such as β-carotene and xanthophylls. Ochrophytes are one of the most diverse lineages of eukaryotes, containing ecologically important algae such as brown algae and diatoms. They are classified either as phylum Ochrophyta, Heterokontophyta or as subphylum Ochrophytina within phylum Gyrista. Their plastids are of red algal origin.

Etymology

Throughout history, different names have been used to describe photosynthetic stramenopiles. The more widely used name is the phylum —or division, in botanical nomenclature— Ochrophyta, based on the golden alga Ochromonas. This name was first coined by evolutionary biologist Thomas Cavalier-Smith in 1986 as Ochrista, later renamed to Ochrophyta to comply with the recommendations of the International Code of Botanical Nomenclature. In 2018, the same author lowered it to a subphylum inside phylum Gyrista, and modified the name to Ochrophytina to match the -phytina suffix used for botanical subdivisions.