Volvulina
Volvulina is a genus of colonial green algae in the family Volvocaceae. It is cosmopolitan, but rare.
Description
Volvulina is a multicellular organism. The colony, termed a coenobium, is broadly ellipsoidal or spherical and consists of a fixed number of cells, usually 16 in mature individuals. The cells are located at periphery of the coenobium and separated from each other by being embedded in a gelatinous matrix. The cell body is lens-shaped or hemispherical when mature, with two equal flagella. The chloroplast is dish- or bowl-shaped. Pyrenoids may be absent or present ; eyespots are present, with eyespots in anterior cells larger than those in posterior cells. The nucleus is centrally located and there may be two contractile vacuoles at the base of each flagella, or several scattered contractile vacuoles.Volvulina reproduces both asexually and sexually. In asexual reproduction, each cell of the colony develops into a daughter colony through successive cell divisions, and then subsequent colony inversion. Sexual reproduction is isogamous.