Raphidonema (alga)

Raphidonema
Raphidonema nivale
Scientific classification Edit this classification
Clade: Viridiplantae
Division: Chlorophyta
Class: Trebouxiophyceae
Order: Prasiolales
Family: Koliellaceae
Genus: Raphidonema
Lagerheim, 1892
Type species
Raphidonema nivale
Lagerheim[1]
Species

Raphidonema is a genus of filamentous green alga comprising five species.[1] It is a member of the Trebouxiophyceae.[2][3]

Raphidonema is widely distributed in freshwater habitats, especially snow, where it can impart a green discoloration to the snow.[1]

Description

Raphidonema consists of free-floating filaments of cells, ranging from 2 to 32 cells, which may be straight or slightly curved. Interjacent cells are cylindrical, while cells at the ends taper to a point. The cell membrane is very thin and lacks a mucilaginous sheath. A single chloroplast is present in each cell, girdle- or band-shaped, lacking a pyrenoid. Reproduction occurs asexually via the vegetative division (mitosis) of cells within filaments.[1]

Taxonomy

Raphidonema is similar and closely related to the genus Koliella. Koliella was separated from Raphidonema based on morphology, with Koliella supposedly having cells that separate from each other after division, forming solitary cells. However, some taxonomists do not separate the two taxa, as the difference between the genera is judged to be insufficient for separation.[4] For example, filaments of Raphidonema often separate into single cells akin to Koliella when placed in a liquid medium.[5] Another similar, but poorly studied genus is Raphidonemopsis, which differs from Raphidonema in that its filaments are attached to a substrate.[6]

References

  1. ^ a b c d Guiry, M.D.; Guiry, G.M. (2008). "Raphidonema". AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. Retrieved 2011-01-17.
  2. ^ Eliáš, Marek; Neustupa, Jiří (2009). "Pseudomarvania, gen. nov. (Chlorophyta, Trebouxiophyceae), a new genus for "budding" subaerial green algae Marvania aerophytica Neustupa et Šejnohová and Stichococcus ampulliformis Handa". Fottea. 9 (2): 169–177. doi:10.5507/fot.2009.017.
  3. ^ Lokhorst, Gijsbert M.; Star, Wim; Zuccarello, Giuseppe C. (2004). "New genus Koliellopsis (Trebouxiophyceae, Chlorophyta): its phylogenetic position inferred from ultrastructure and nuclear ribosomal DNA sequences". Phycological Research. 52 (3): 235–243. doi:10.1111/j.1440-183.2004.00350.x. S2CID 86333791.
  4. ^ Bicudo, Carlos E. M.; Menezes, Mariângela (2006). Gêneros de Algas de Águas Continentais do Brasil: chave para identificação e descrições (2 ed.). RiMa Editora. p. 508. ISBN 857656064X.
  5. ^ Yakimovich, Kurt M.; Gauthier, Nick P.G.; Engstrom, Casey B.; Leya, Thomas; Quarmby, Lynne M. (2021). "A Molecular Analysis of Microalgae from Around the Globe to Revise Raphidonema (Trebouxiophyceae, Chlorophyta)". Journal of Phycology. 57 (5): 1419–1432. Bibcode:2021JPcgy..57.1419Y. doi:10.1111/jpy.13183. PMID 33988850.
  6. ^ Shubert, Elliot; Gärtner, Georg (2014). "Chapter 7. Nonmotile Coccoid and Colonial Green Algae". In Wehr, John D.; Sheath, Robert G.; Kociolek, J. Patrick (eds.). Freshwater Algae of North America: Ecology and Classification (2 ed.). Elsevier Inc. ISBN 978-0-12-385876-4.
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