Euglenophyceae

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title: "Euglenophyceae" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["euglenozoa-classes", "algae", "taxa-described-in-1925", "euglenozoa"] description: "Unicellular algae" topic_path: "general/euglenozoa-classes" source: "https://en.wikipedia.org/wiki/Euglenophyceae" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Unicellular algae ::

| taxon = Euglenophyceae | authority = Schoenichen, 1925 emend. Marin & Melkonian, 2003 | image = Ehrenberg euglena viridis.jpg | image_caption = Euglena viridis, by Ehrenberg | subdivision_ranks = Orders | subdivision = * Rapazida

• Eutreptiales
• Euglenales | synonyms = Euglenea | type_genus = Euglena | type_genus_authority = Ehrenberg, 1830

Euglenophyceae (ICNafp, proposed as a class) or Euglenea (ICZN, proposed as a class) is an unranked clade of single-celled algae belonging to the phylum Euglenozoa. They have chloroplasts originated from an event of secondary endosymbiosis with a green alga. They are distinguished from other algae by the presence of paramylon as a storage product and three membranes surrounding each chloroplast.

Description

Euglenophyceae are unicellular algae, protists that contain chloroplasts. Their chloroplasts originated from a secondary endosymbiosis with a green alga, particularly from the order Pyramimonadales, and contain chlorophylls a and b. Some have secondarily lost this ability and evolved toward osmotrophy. In addition to photosynthetic plastids, most species have a photosensitive eyespot.

Ecology

Euglenophyceae are mainly present in the water column of freshwater habitats. They are abundant in small eutrophic water bodies of temperate climates, where they are capable of forming blooms, including toxic blooms such as those caused by Euglena sanguinea. In tropical climate, blooms are common in ponds. In marine environments they have been reported in a lower amount. Some species are capable of migrating vertically through the sand along with the cycles of ocean tides. Two lineages of Euglenophyceae are part of the marine plankton: Rapazida and Eutreptiales. Eutreptiales can amount up to 46% of the total phytoplankton biomass when blooming in eutrophic coastal waters.

Classification

|{{clade|style=font-size:80%;line-height=80%; |1={{clade |label1=Euglenales|1={{clade |1={{clade |1={{clade |2=Euglenaria|1={{clade |2=Discoplastis|1={{clade |2=Phacus limnophila|1={{clade |1="Phacus" |2=Lepocinclis |2={{clade |1={{clade |1=Cryptoglena|2=Monomorphina |2= |2={{clade |1= |2=Euglena |label2=Eutreptiales|2={{clade|1=Eutreptia|2=Eutreptiella |2= |caption=Cladogram of Euglenophyceae genera, based on a 18S rDNA phylogenetic analysis published in 2022.

Euglenophyceae encompasses three taxonomic groups: the mixotrophic Rapaza viridis and two mainly phototrophic orders, Euglenales and Eutreptiales. The classification is as follows (species numbers based on AlgaeBase):

• Order Euglenales
  • Family Euglenaceae [Euglenidae]
    • Colacium – 17 spp.
    • Cryptoglena – 11 spp.
    • Euglena – 174 spp.
    • Euglenaformis – 3 spp.
    • Euglenaria – 4 spp.
    • Monomorphina – 17 spp.
    • Strombomonas – 99 spp.
    • Trachelomonas – 410 spp.
  • Family Phacaceae [Phacidae]
    • Discoplastis – 6 spp.
    • Flexiglena – 1 sp.
    • Lepocinclis – 90 spp.
    • Phacus – 188 spp.
• Order Eutreptiales
  • Family Eutreptiaceae [Eutreptiidae]
    • Eutreptia – 11 spp.
    • Eutreptiella – 9 spp.
• Order Rapazida
  • Family Rapazidae
    • Rapaza – 1 sp.

Several genera assigned to Euglenophyceae are considered incertae sedis, because the lack of genetic data makes their phylogenetic position unresolved:

• Ascoglena – 4 spp.
• Euglenamorpha – 2 spp.
• Euglenopsis – 11 spp.
• Glenoclosterium – 1 sp.
• Hegneria – 1 sp.
• Klebsina – 1 sp.
• Euglenocapsa – 1 sp.
• Menoidium – 28 spp.
• Parmidium – 10 spp.

References

References

1. (1 April 2003). "Phylogeny and taxonomic revision of plastid-containing euglenophytes based on SSU rDNA sequence comparisons and synapomorphic signatures in the SSU rRNA secondary structure". [[Protist (journal).
2. (1 January 2019). "Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes". [[Journal of Eukaryotic Microbiology]].
3. (10 March 2021). "Euglenozoa: taxonomy, diversity and ecology, symbioses and viruses". [[Open Biology]].
4. (16 August 2020). "The Molecular Diversity of Phagotrophic Euglenids Examined Using Single-cell Methods". [[Protist (journal).
5. (2023). "18S rDNA sequence–structure phylogeny of the Euglenophyceae (Euglenozoa, Euglenida)". Journal of Eukaryotic Microbiology.
6. (16 March 2016). "Phylogeny and Classification of Euglenophyceae: A Brief Review". Frontiers in Ecology and Evolution.
7. (25 May 2020). "AlgaeBase".
8. (2018). "Phycology". Cambridge University Press.

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