Volvulina
Genus of algae
From Wikipedia, the free encyclopedia
Volvulina is a genus of colonial green algae in the family Volvocaceae.[2] It is cosmopolitan, but rare.[1]
| Volvulina | |
|---|---|
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| Volvulina steinii | |
Scientific classification  | |
| Kingdom: | Plantae |
| Division: | Chlorophyta |
| Class: | Chlorophyceae |
| Order: | Chlamydomonadales |
| Family: | Volvocaceae |
| Genus: | Volvulina Playfair |
| Type species | |
| Volvulina steinii Playfair[1] | |
| Species[1] | |
| |
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 (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]
Species
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]
Phylogeny
Molecular phylogenetic studies show that Volvulina is paraphyletic with respect to Pandorina:[6][7][8]
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