Epithemia: Difference between revisions – Wikipedia

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| synonyms =

| synonyms =

* ”Rhopalodia” O. Müller, 1895

* ”Rhopalodia” O. Müller, 1895

* ”Tetralunata” Hamsher, Graeff, Stepanek & Kociolek, 2014

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Latest revision as of 11:17, 14 January 2026

Genus of algae

Epithemia is a genus of diatoms belonging to the family Rhopalodiaceae.[1] The genus has cosmopolitan distribution and are found in freshwater and marine ecosystems.[2][1] Recent studies have proposed that the genus Rhopalodia should be recategorized to join Epithemia based on phylogenetic evidence,[3] although this change in nomenclature has been disputed.[4]

Members of this genus have endosymbionts that fix nitrogen called spheroid bodies, that are derived from cyanobacteria.[5][6] Because of their nitrogen fixing endosymbionts, they can be a possible indicator of eutrophication, because Epithemia abundance decreased with increased ambient inorganic N concentrations.[7]

Epithemia and Rhopalodia, two (or one) genera of rhopalodiacean diatoms, have nitrogen-fixing endosymbioants called spheroid bodies (SBs). They are cyanobacteria that have undergone various degrees of gene loss in adaptation to their new dependent lifestyle. The SB of E. turgida has undergone faster evolution and more gene loss compared to the SB of E. gibberula.[8]

The closest relatives of the SBs are various members of the (overly broad, since divided)[9] genus Cyanothece, especially strain ATCC 51142. Based on fossil records, the symbiosis happened in a common ancestor of species that carry it about 12 million years ago.[6] The SBs are closely related to the nitroplasts,[10] which had separately entered into an endosymbiosis with Braarudosphaera bigelowii about 90 million years ago.[11]

GTDB annotates the SB of E. gibberula as Rippkaea sp003574135, a species-level cluster bearing a placeholder name.[12] Additional assignments include Rippkaea sp000829235 for the E. turgida SB and Rippkaea sp029919255 for the E. clementina SB.[13]

Those marked with a * were previously in the genus Rhopalodia.[1]

  1. ^ a b c “Epithemia F.T.Kützing, 1844”. www.gbif.org. Retrieved 23 April 2021.
  2. ^ a b c Schvarcz, Christopher R.; Wilson, Samuel T.; Caffin, Mathieu; Stancheva, Rosalina; Li, Qian; Turk-Kubo, Kendra A.; White, Angelicque E.; Karl, David M.; Zehr, Jonathan P.; Steward, Grieg F. (2022-02-10). “Overlooked and widespread pennate diatom-diazotroph symbioses in the sea”. Nature Communications. 13 (1): 799. Bibcode:2022NatCo..13..799S. doi:10.1038/s41467-022-28065-6. ISSN 2041-1723. PMC 8831587. PMID 35145076.
  3. ^ Ruck, Elizabeth C.; Nakov, Teofil; Alverson, Andrew J.; Theriot, Edward C. (2016-10-01). “Phylogeny, ecology, morphological evolution, and reclassification of the diatom orders Surirellales and Rhopalodiales”. Molecular Phylogenetics and Evolution. 103: 155–171. Bibcode:2016MolPE.103..155R. doi:10.1016/j.ympev.2016.07.023. ISSN 1055-7903. PMID 27456747.
  4. ^ Kociolek, J.P.; Greenwood, M.; Hamsher, S.E.; Miller, S.; Li, J. (2024-04-02). “Valve ultrastructure of Rhopalodia constricta (W.Smith) Krammer (Rhopalodiales, Bacillariophyceae) and a consideration of its systematic placement”. Diatom Research. 39 (2): 51–60. Bibcode:2024DiaRe..39…51K. doi:10.1080/0269249X.2024.2378769. ISSN 0269-249X.
  5. ^ Nakayama, Takuro; Kamikawa, Ryoma; Tanifuji, Goro; Kashiyama, Yuichiro; Ohkouchi, Naohiko; Archibald, John M.; Inagaki, Yuji (2014-08-05). “Complete genome of a nonphotosynthetic cyanobacterium in a diatom reveals recent adaptations to an intracellular lifestyle”. Proceedings of the National Academy of Sciences. 111 (31): 11407–11412. Bibcode:2014PNAS..11111407N. doi:10.1073/pnas.1405222111. ISSN 0027-8424. PMC 4128115. PMID 25049384.
  6. ^ a b Nakayama, Takuro; Ikegami, Yuko; Nakayama, Takeshi; Ishida, Ken-ichiro; Inagaki, Yuji; Inouye, Isao (2011-01-01). “Spheroid bodies in rhopalodiacean diatoms were derived from a single endosymbiotic cyanobacterium”. Journal of Plant Research. 124 (1): 93–97. Bibcode:2011JPlR..124…93N. doi:10.1007/s10265-010-0355-0. ISSN 1618-0860. PMID 20512519.
  7. ^ Stancheva, Rosalina; Sheath, Robert G.; Read, Betsy A.; McArthur, Kimberly D.; Schroepfer, Chrystal; Kociolek, J. Patrick; Fetscher, A. Elizabeth (2013-12-01). “Nitrogen-fixing cyanobacteria (free-living and diatom endosymbionts): their use in southern California stream bioassessment”. Hydrobiologia. 720 (1): 111–127. Bibcode:2013HyBio.720..111S. doi:10.1007/s10750-013-1630-6. ISSN 1573-5117. S2CID 254550477.
  8. ^ Nakayama, Takuro; Inagaki, Yuji (12 October 2017). “Genomic divergence within non-photosynthetic cyanobacterial endosymbionts in rhopalodiacean diatoms”. Scientific Reports. 7 (1). doi:10.1038/s41598-017-13578-8.
  9. ^ Mareš, J; Johansen, JR; Hauer, T; Zima J, Jr; Ventura, S; Cuzman, O; Tiribilli, B; Kaštovský, J (June 2019). “Taxonomic resolution of the genus Cyanothece (Chroococcales, Cyanobacteria), with a treatment on Gloeothece and three new genera, Crocosphaera, Rippkaea, and Zehria”. Journal of phycology. 55 (3): 578–610. doi:10.1111/jpy.12853. PMID 30830691.
  10. ^ Cornejo‐Castillo, Francisco M.; Muñoz‐Marín, Maria del Carmen; Turk‐Kubo, Kendra A.; Royo‐Llonch, Marta; Farnelid, Hanna; Acinas, Silvia G.; Zehr, Jonathan P. (January 2019). “UCYN‐A3, a newly characterized open ocean sublineage of the symbiotic N 2 ‐fixing cyanobacterium Candidatus Atelocyanobacterium thalassa”. Environmental Microbiology. 21 (1): 111–124. doi:10.1111/1462-2920.14429. PMID 30255541.
  11. ^ Cornejo-Castillo, Francisco M.; Cabello, Ana M.; Salazar, Guillem; Sánchez-Baracaldo, Patricia; Lima-Mendez, Gipsi; Hingamp, Pascal; Alberti, Adriana; Sunagawa, Shinichi; Bork, Peer; de Vargas, Colomban; Raes, Jeroen; Bowler, Chris; Wincker, Patrick; Zehr, Jonathan P.; Gasol, Josep M.; Massana, Ramon; Acinas, Silvia G. (22 March 2016). “Cyanobacterial symbionts diverged in the late Cretaceous towards lineage-specific nitrogen fixation factories in single-celled phytoplankton”. Nature Communications. 7 (1). doi:10.1038/ncomms11071.
  12. ^ “GTDB – GCF_003574135.1”. gtdb.ecogenomic.org.
  13. ^ “GTDB – Search “cyanobacterium endosymbiont”“. gtdb.ecogenomic.org.
  14. ^ Kociolek, J.P.; Greenwood, M.; Hamsher, S.E.; Miller, S.; Li, J. (2024-04-02). “Valve ultrastructure of Rhopalodia constricta (W.Smith) Krammer (Rhopalodiales, Bacillariophyceae) and a consideration of its systematic placement”. Diatom Research. 39 (2): 51–60. Bibcode:2024DiaRe..39…51K. doi:10.1080/0269249X.2024.2378769. ISSN 0269-249X.

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