Dictyosphaerium Explained

Dictyosphaerium is a genus of green algae, in the family Chlorellaceae. It occurs in freshwater habitats around the world and is planktonic.

Description

Dictyosphaerium consists of irregular colonies of 4 to 64 cells in a common mucilaginous envelope 10–100 μm wide. Cells are roughly spherical to ellipsoidal, 1-10 μm in diameter, with one nucleus and a single pyrenoid-containing chloroplast. Cells are attached to the end of thin stalks; the stalks emerge from the center of the colony and continuously branch out. These stalks are formed from the remnants of the mother cell wall.[1]

Dictyosphaerium cells reproduce asexually by autospores. Two or four autospores are produced per sporangium; after release, the mother cell wall gelatinizes and develops into a thin strand, which are connected to the newly released cells.[1]

Taxonomy

Dictyosphaerium has traditionally been classified in its own family, Dictyosphaeriaceae,[2] or as part of the family Botryococcaceae, characterized by cells connected by gelatinous stalks or strands of mucilage.[3] However, molecular phylogenetic studies have demonstrated that Dictyosphaerium is closely related to the unicellular genus Chlorella, and is now currently placed in the family Chlorellaceae.

Additionally, the morphotype of Dictyosphaerium (consisting of branching strands of mucilage connecting cells) is known to be polyphyletic, having evolved multiple times. Therefore, this morphotype can now be found in many new genera. For example, the genus Mucidosphaerium differs from Dictyosphaerium sensu stricto in having spherical cells, as opposed to Dictyosphaerium with oval cells.[4] The genus Mychonastes (including the former genus Pseudodictyosphaerium) differs in having chloroplasts without pyrenoids, and more irregular mucilaginous strands.[5]

Other similar genera include Compactochlorella, Kalenjinia, Marasphaerium, Masaia,[1] Hindakia, Heynigia,[6] and Xerochlorella.[7] These genera appear to be more or less cryptic, being reliably differentiated only by DNA barcoding.[8] Their biogeographical patterns remain unclear.[9]

Notes and References

  1. Book: Gêneros de Algas de Águas Continentais do Brasil: chave para identificação e descrições . 2 . 2006 . Carlos E. M. . Bicudo . Mariângela . Menezes . RiMa Editora . 508 . 857656064X .
  2. New taxa and reclassifications in the Chlorococcales (Chlorophyceae). Hindák. F.. 1978. Preslia. 50. 97–109.
  3. Book: Chlorophyceae (Grünalgen), Ordnung Chlorococcales . Komárek . J. . Fott . B. . 1983 . E. Schweizerbart'sche Verlagsbuchhandlung . Das Phytoplankton des Süßwassers . German . 1044 .
  4. 10.1111/j.1529-8817.2011.00989.x. Updating the Genus Dictyosphaerium and Description of Mucidosphaerium gen. nov. (Trebouxiophyceae) Based on Morphological and Molecular Data. 2011. Bock. Christina. Pröschold. Thomas. Krienitz. Lothar. Journal of Phycology. 47. 3. 638–652. 27021993. 2011JPcgy..47..638B. 26144724.
  5. 10.2216/10-15.1 . Taxonomic reassessment of the genus Mychonastes (Chlorophyceae, Chlorophyta) including the description of eight new species . 2011 . Krienitz . L. . Bock . C. . Dadheech . P. K. . Pröschold . T. . Phycologia . 50 . 1 . 89–106 . 2011Phyco..50...89K . 86110297 .
  6. 10.1080/09670262.2010.487920 . Two new Dictyosphaerium-morphotype lineages of the Chlorellaceae (Trebouxiophyceae): Heynigia gen. nov. and Hindakia gen. nov. . 2010 . Bock . Christina . Pröschold . Thomas . Krienitz . Lothar . European Journal of Phycology . 45 . 3 . 267–277 . 2010EJPhy..45..267B . 85093080 . free .
  7. 10.1111/jpy.12974 . Dictyosphaerium-like morphotype in terrestrial algae: What is Xerochlorella (Trebouxiophyceae, Chlorophyta). 2020 . Mikhailyuk . Tatiana . Holzinger . Andreas . Tsarenko . Petro . Glaser . Karin . Demchenko . Eduard . Karsten . Ulf . Journal of Phycology . 56 . 3 . 671–686 . 31994728 . 7317402 . 2020JPcgy..56..671M .
  8. 10.5507/fot.2012.017. Genotypic diversity of Dictyosphaerium-morphospecies (Chlorellaceae, Trebouxiophyceae) in African inland waters, including the description of four new genera. 2012. Krienitz. Lothar. Bock. Christina. Kotut. Kiplagat. Pröschold. Thomas. Fottea. 12. 2. 231–253. free.
  9. 10.1111/jeu.12482 . Phylogenic Diversity and Taxonomic Problems of the Dictyosphaerium Morphotype within the Parachlorella Clade (Chlorellaceae, Trebouxiophyceae) . 2018 . Song . Huiyin . Wang . Qinghua . Liu . Xudong . Hu . Yuxin . Long . Jijian . Liu . Guoxiang . Hu . Zhengyu . Journal of Eukaryotic Microbiology . 65 . 3 . 382–391 . 29080384 . 19043002 .

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