| Volvulina | |
|---|---|
 | |
| Volvulina steinii | |
Scientific classification  | |
| Clade: | Viridiplantae |
| Division: | Chlorophyta |
| Class: | Chlorophyceae |
| Order: | Chlamydomonadales |
| Family: | Volvocaceae |
| Genus: | Volvulina Playfair |
| Type species | |
| Volvulina steinii Playfair [1] | |
| Species [1] | |
Volvulina is a genus of colonial green algae in the family Volvocaceae. [2] It is cosmopolitan, but rare. [1]
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 (rarely 4, 8 or 32). 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 (located at the base of the chloroplast); eyespots are present, with eyespots in anterior cells larger than those in posterior cells. [1] The nucleus is centrally located [3] and there may be two contractile vacuoles at the base of each flagella, or several scattered contractile vacuoles. [1]
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. [1]
Three species of Volvulina are well-characterized: Volvulina steinii , Volvulina pringsheimii , and Volvulina compacta . [1] The three species differ from each other in morphology, namely: the shape of the cells and whether they are contiguous, and the presence or location of pyrenoids. [4] In addition to these three species, there is also Volvulina playferiana which is poorly described and may be an immature form of V. steinii, [4] and Volvulina boldii which is a nomen nudum. [5]
Molecular phylogenetic studies show that Volvulina is paraphyletic with respect to Pandorina : [6] [7] [8]
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