The phytomonadina (syn. Volvocales) possess one single, cup-shaped green plastid and a stigma. Ratio of pigments is similar to that of higher plants suggesting the phytomonadina to be the group in which their common ancestor may be found. 2, 4 or 8 smooth flagellae. There are solitary and colonial phytomonads with the colonies being plate-, sphere- or egg-shaped. In the case of colonies, differentiation into somatic and generative cells is observed. After generation of daughter colonies the somatic cells die. Besides asexual also sexual propagation with equally (isogamy) or unequally sized (anisogamy) gametes. Phytomonadina are haplonts with zygotic meiosis. Almost exclusively limnic distribution. |