Chlamydomonadales


Chlamydomonadales, also known as Volvocales, are an order of flagellated or pseudociliated green algae, specifically of the Chlorophyceae. Chlamydomonadales can form planar or spherical colonies. These vary from Gonium up to Volvox. Each cell has two flagella, and is similar in appearance to Chlamydomonas, with the flagella throughout the colony moving in coordination.
Both asexual and sexual reproduction occur. In the former, cells divide until they form new colonies, which are then released. In the smaller forms, typically all cells are involved, but larger forms have anterior vegetative and posterior reproductive cells. Sexual reproduction varies from isogamy to oogamy.
The classification of the Chlamydomonadales varies. Very often they are taken to include the orders Volvocales and Dunallielales, which contain closely related unicellular flagellates, as suborders. Colony inversion is believed to have arisen twice in this order. Spheroidal colony formation differs between the two lineages: rotation of daughter protoplasts during successive cell divisions in Astrephomene, and inversion after cell divisions in the Volvocaceae.
to Volvox, and the other in the genus Astrephomene. The phylogeny is based on previous reports. All drawings and photographs represent side views of individuals with anterior ends orienting toward the top of this figure.