Stigeoclonium
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| Stigeoclonium | |
|---|---|
 | |
| Stigeoclonium sp. | |
Scientific classification  | |
| Kingdom: | Plantae |
| Division: | Chlorophyta |
| Class: | Chlorophyceae |
| Order: | Chaetophorales |
| Family: | Chaetophoraceae |
| Genus: | Stigeoclonium Kützing, 1843 |
| Type species | |
| Stigeoclonium tenue Kützing 1843 | |
| Species[1] | |
|
See text | |
Stigeoclonium is a genus of green algae in the family Chaetophoraceae. It is a common freshwater genus, found growing attached to various substrates; it has a cosmopolitan distribution.[1]
There are currently 53 accepted species within this group. However, recent phylogenetics have identified that this group is polyphyletic and will need reassessment.[2][3]
The holotype for this genus is S. tenue, described in 1843 by F.T. Kützing. It was first described in 1814 by Carl Agardh under the basionym Draparnaldia tenuis.[4] The name Stigeoclonium has been conserved against the genus Myxonema named by Elias Magnus Fries; Myxonema is a heterogeneous assemblage of various algae.[5]
Stigeoclonium consists of two systems of filaments, prostrate and erect filaments. Prostrate filaments are attached to the substrate and are creeping or rhizoidal, occasionally forming a pseudoparenchymatous mass. Erect filaments emerge from the prostrate filaments, and are variously branched. The erect filaments terminate in an obtuse or acutely pointed tip, or a long multicellular hair.[1] Under unfavorable conditions, a "stunted" form develops with predominantly prostrate filaments.[5] Cells are uninucleate, cylindrical or swollen, with a single parietal chloroplast and one to several pyrenoids.[1] The whole thallus is commonly surrounded by a layer of mucilage.[5]
Reproduction occurs asexually and sexual reproduction. Asexual reproduction occurs by zoospores of two sizes, large and small (macrozoospores and microzoospores), both of which have four flagella. Sexual reproduction is isogamous and involves biflagellate or quadriflagellate gametes.[1] Both zoospores and gametes are termed "swarmers", and are formed mostly in the erect filaments. They escape through a lateral pore in the cell wall. Zoospores swim for some time, then attach to a substrate via their anterior (flagellar) end, withdraw their flagella, and germinate. Mature zygotes are orange to red in color.[5]