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Pyramimonas sp color.jpg
Pyramimonas sp.
Scientific classification
Domain: Eukaryota
Kingdom: Viridiplantae
Class: Prasinophyceae
T.Christensen ex P.C.Silva 1980

The Prasinophytes are a paraphyletic class of unicellular green algae.[2] Prasinophytes mainly include marine planktonic species, as well as some freshwater representatives.[2][3] The prasinophytes are morphologically diverse, including flagellates with one to eight flagella and non-motile (coccoid) unicells. The cells of many species are covered with organic body scales; others are naked.[3] Well studied genera include Ostreococcus, considered to be the smallest (ca. 0.95 μm) free-living eukaryote,[4] and Micromonas, both of which are found in marine waters worldwide. Prasinophytes have simple cellular structures, containing a single chloroplast and a single mitochondrion. The genomes are relatively small compared to other eukaryotes (about 12 Mbp for Ostreococcus[5][6] and 21 Mbp for Micromonas[7]).

Recent studies agree that the prasinophytes are a non-evolutionary grouping (paraphyletic) of green algae from different clades. Alternative classifications of the chlorophytes have been proposed in which this class is replaced by at least six separate taxa.[8]


A study of photosynthetic gene-sequence diversity (rbcL) in the Gulf of Mexico indicated that Prasinophytes are particularly prevalent at the Subsurface Chlorophyll Maximum (SCM)[9] and several different ecotypes of Ostreococcus have been detected in the environment.[10] These ecotypes were thought to be distinguished in the environment by their adaptation to light intensities. O. lucimarinus was isolated from a high-light environment[11] and observed year-round in the coastal North Pacific Ocean.[12] RCC141 was considered low-light, because it was isolated from the lower euphotic zone. These strains, or ecotypes, were later shown to live in different habitats (open-ocean or mesotrophic) and their distributions do not appear to be connected to light availability.[13] O. tauri was isolated from a coastal lagoon and appears to be light-polyvalent. Genetic data indicates that distinct molecular differences exist between the different ecotypes that have been detected.[14]

Prasinophytes are subject to infection by large double-stranded DNA viruses belonging to the family Phycodnaviridae [15] [16] [17], as well as a Reovirus. [18] It has been estimated that from 2 to 10% of the Micromonas pusilla population is lysed per day by viruses. [19]


Recent studies agree that the prasinophytes are not a natural group, being highly paraphyletic.[3][8][20][21] Relationships among the groups making up the Chlorophyta are not fully resolved. The cladogram produced by Leliaert et al. 2011[3] and some modification according to Silar 2016[22] and Leliaert 2016[23] is shown below. The blue shaded groups are or have traditionally been placed in the Prasinophyceae[2]). The species Mesostigma viride has been shown to be a member of the Streptophyta. The others are member of the Chlorophyta.

Green Algae




Chlorodendrophyceae ("prasinophyte clade IV")


"CCMP1205 clade"

Picocystis clade ("prasinophyte clade VII")

Pyramimonadales ("prasinophyte clade I")

Mamiellophyceae ("prasinophyte clade II")




Pycnococcaceae ("prasinophyte clade V")

Nephroselmidophyceae ("prasinophyte clade III")

Prasinococcales ("prasinophyte clade VI")









Land plants


  1. ^ Guiry, M.D. & Guiry, G.M. (2007). "Class: Prasinophyceae taxonomy browser". AlgaeBase version 4.2 Worldwide electronic publication, National University of Ireland, Galway. Retrieved 2007-09-23. 
  2. ^ a b c Sym, S. D. and Pienaar, R. N. 1993. The class Prasinophyceae. In Round, F. E. and Chapman, D. J. (eds) Progress in Phycological Research, Vol. 9. Biopress Ltd., Bristol, pp. 281-376.
  3. ^ a b c d Leliaert, Frederik; Verbruggen, Heroen; Zechman, Frederick W. (2011). "Into the deep: New discoveries at the base of the green plant phylogeny". BioEssays. 33 (9): 683–692. doi:10.1002/bies.201100035. ISSN 0265-9247. PMID 21744372. 
  4. ^ Courties C, Vaquer A, Troussellier M, Lautier J, Chrétiennot-Dinet MJ, Neveux J, Machado C, Claustre H (1994). "Smallest eukaryotic organism". Nature. 370 (6487): 255. doi:10.1038/370255a0. 
  5. ^ Derelle E, et al. (2006). "Genome analysis of the smallest free-living eukaryote Ostreococcus tauri unveils many unique features". PNAS. 103 (31): 11647–52. doi:10.1073/pnas.0604795103. PMC 1544224Freely accessible. PMID 16868079. 
  6. ^ Palenik, Brian; et al. (2007). "The tiny eukaryote Ostreococcus provides genomic insights into the paradox of plankton speciation". PNAS. 104 (18): 7705–7710. doi:10.1073/pnas.0611046104. PMC 1863510Freely accessible. PMID 17460045. 
  7. ^ Worden AZ, et al. (2009). "Green evolution and dynamic adaptations revealed by genomes of the marine picoeukaryotes Micromonas". Science. 324 (5924): 268–272. doi:10.1126/science.1167222. PMID 19359590. 
  8. ^ a b Lewis, Louise A. & McCourt, R.M. (2004). "Green algae and the origin of land plants". Am. J. Bot. 91 (10): 1535–1556. doi:10.3732/ajb.91.10.1535. PMID 21652308. 
  9. ^ Wawrik B, Paul JH, Campbell L, Griffin D, Houchin L, Fuentes-Ortega A, Müller-Karger F (2003). "Vertical Structure of the Phytoplankton Community Associated with a Coastal Plume in the Gulf of Mexico". Marine Ecology Progress Series. 251: 87–101. doi:10.3354/meps251087. 
  10. ^ Guillou L, Eikrem W, Chrétiennot-Dinnet MJ, Le Gall F, Massana R, Romari K, Pedros-Alio C, Vaulot D (2004). "Diversity of picoplanktonic Prasinophyceae assessed by direct SSU rDNA sequencing of environmental samples and novel isolates retrieved from oceanic and coastal marine ecosystems". Protist. 155 (2): 193–214. doi:10.1078/143446104774199592. PMID 15305796. 
  11. ^ Worden AZ, Nolan JK, Palenik B (2004). "Assessing the dynamics and ecology of marine picophytoplankton: The importance of the eukaryotic component". Limnology and Oceanography. 49 (1): 168–179. doi:10.4319/lo.2004.49.1.0168. 
  12. ^ Worden AZ (2006). "Picoeukaryote diversity in coastal waters of the Pacific Ocean". Aquatic Microbial Ecology. 43 (2): 165–175. doi:10.3354/ame043165. 
  13. ^ Demir-Hilton E, Sudek S, Cuvelier ML, Gentemann CL, Zehr JP, Worden AZ (2011). "Global distribution patterns of distinct clades of the photosynthetic picoeukaryote Ostreococcus". ISME Journal. 5 (7): 1095–1107. doi:10.1038/ismej.2010.209. PMC 3146286Freely accessible. PMID 21289652. 
  14. ^ Rodríguez F, Derelle E, Guillou L, Le Gall F, Vaulot D, Moreau H (2005). "Ecotype diversity in the marine picoeukaryote Ostreococcus (Chlorophyta, Prasinophyceae)". Environmental Microbiology. 7 (6): 853–859. doi:10.1111/j.1462-2920.2005.00758.x. PMID 15892704. 
  15. ^ Mayer, J.A.; Taylor, F.J.R. (1979). "A virus which lyses the marine nanoflagellate, "Micromonas pusilla"". Nature. 281: 299–301. doi:10.1038/281299a0. 
  16. ^ Cottrell, Matthew T.; Suttle, Curtis A. (1991). "Wide-spread occurrence and clonal variation in viruses which cause lysis of a cosmopolitan, eukaryotic marine phytoplankter, "Micromonas pusilla"" (PDF). Marine Ecology Progress Series. 78: 1–9. ISSN 1616-1599. 
  17. ^ Bellec, Laure; Grimsley, Nigel; Derelle, Evelyn; Moreau, Herve; Desdevises, Yves (2010). "Abundance, spatial distribution and genetic diversity of Ostreococcus tauri viruses in two different environments". Environmental Microbiology Reports. 2: 313–321. doi:10.1111/j.1758-2229.2010.00138.x. 
  18. ^ Attoui, H; Jaafar, F.M.; Belhouchet, M.; de Micco, P.; Lamballerie, X.; Brussaard, C.P.D. (2006). "Micromonas pusilla reovirus: a new member of the family Reoviridae assigned to a novel proposed genus (Mimoreovirus)". Journal of General Virology. 87: 1375–1383. doi:10.1099/vir.0.81584-0. 
  19. ^ Cottrell, Matthew T.; Suttle, Curtis A. (1995-06-01). "Dynamics of lytic virus infecting the photosynthetic marine picoflagellate "Micromonas pusilla"". Limnology and Oceanography. 40 (4): 730–739. doi:10.4319/lo.1995.40.4.0730. ISSN 1939-5590. 
  20. ^ Becker, B. & Marin, B. (2009). "Streptophyte algae and the origin of embryophytes". Annals of Botany. 103 (7): 999–1004. doi:10.1093/aob/mcp044. PMC 2707909Freely accessible. PMID 19273476. 
  21. ^ Marin, Birger (2012). "Nested in the Chlorellales or Independent Class? Phylogeny and Classification of the Pedinophyceae (Viridiplantae) Revealed by Molecular Phylogenetic Analyses of Complete Nuclear and Plastid-encoded rRNA Operons". Protist. 163: 778–805. doi:10.1016/j.protis.2011.11.004. PMID 22192529. 
  22. ^ Silar, Philippe (2016), "Protistes Eucaryotes: Origine, Evolution et Biologie des Microbes Eucaryotes", HAL archives-ouvertes: 1–462 
  23. ^ Leliaert, Frederik; Tronholm, Ana; Lemieux, Claude; Turmel, Monique; DePriest, Michael S.; Bhattacharya, Debashish; Karol, Kenneth G.; Fredericq, Suzanne; Zechman, Frederick W. (2016-05-09). "Chloroplast phylogenomic analyses reveal the deepest-branching lineage of the Chlorophyta, Palmophyllophyceae class. nov". Scientific Reports. 6 (1). doi:10.1038/srep25367. ISSN 2045-2322. 

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