Raphidophyte

The Raphidophyceae (raphidophytes, formerly referred to as Chloromonadophyceae and Chloromonadineae)[1] are a small group of eukaryotic algae that includes both marine and freshwater species.[2] All raphidophytes are unicellular, with large cells (50 to 100 μm), but no cell walls. Raphidophytes possess a pair of flagella, organised such that both originate from the same invagination (or gullet). One flagellum points forwards,and is covered in hair-like mastigonemes, while the other points backwards across the cell surface, lying within a ventral groove. Raphidophytes contain numerous ellipsoid chloroplasts, which contain chlorophylls a, c1 and c2. They also make use of accessory pigments including β-carotene and diadinoxanthin. Unlike other heterokontophytes, raphidophytes do not possess the photoreceptive organelle (or eyespot) typical of this group.

Raphidophytes
Gonyostomum semen
Scientific classification
Kingdom: Chromista
Phylum: Ochrophyta
Class: Raphidophyceae
Chadefaud 1950 ex Silva 1980
Orders
Synonyms
  • Chloromonadina Klebs 1892
  • Raphidomonadida Heywood & Leedale, 1983
  • Chloromonadophyceae Rothmaler, 1951; Fott, 1968
  • Raphidophyta
  • Chloromonadida

In terms of ecology, raphidophytes occur as photosynthetic autotrophs across a range of aquatic systems. Freshwater species are more common in acidic waters, such as pools in bogs. Marine species often produce large blooms in summer, particularly in coastal waters. Off the Japanese coast, the resulting red tides often cause disruption to fish farms, although raphidophytes are not usually responsible for toxic blooms.

The position of this group varied in former classifications. Some protozoologists treated the chloromonads as an order within the phytoflagellates.[3] Some phycologists classified them with the Xanthophyceae and the Eustigmatophyceae in the division Xanthophyta.[4] Others considered them as related to the Chrysophyceae, Dinophyceae, or Cryptophyceae [5]

Recently, the heliozoan Actinophyrida was moved to the group.

Taxonomy

Classification based on Cavalier-Smith and Scoble 2013[6][7]

  • Class Raphidomonadea Silva 1980 emend. Cavalier-Smith 2013 [Raphidophyceae Chadefaud 1950 emend. Silva 1980 s.l.]
    • [unplaced genera]
      • Genus Psammamonas Grant et al. 2013
      • Genus Chloromorum Tomas et al.
    • Subclass Raphopoda Cavalier-Smith 2013
      • Order Commatiida Cavalier-Smith 1997
        • Family Commatiidae Cavalier-Smith 2013
          • Genus Commation Thomsen & Larsen 1993
      • Order Actinophyrida Hartmann 1913 [Actinophrydia Kühn 1926; Actinophrydea Hartmann 1913]
        • Family Actinosphaeriidae Cavalier-Smith 2013
          • Genus Actinosphaerium Ritter von Stein 1857 [Camptonema Schaudinn 1894; Echinosphaerium Hovasse 1965]
        • Family Helioraphidae Cavalier-Smith 2013
          • Genus Heliorapha Cavalier-Smith 2013
        • Family Actinophryidae Dujardin 1841
          • Genus Actinophrys Ehrenberg 1830 [Trichoda Müller 1773 nomen oblitum; Peritricha Bory de St.Vincent 1824 nomen dubium non Stein 1859]
    • Subclass Raphidophycidae Cavalier-Smith 2013 [Raphidophyceae Chadefaud 1950 emend. Silva 1980 s.s.; Chloromonadophyceae Rothmaler 1951; Raphidophyta]
      • Order Raphidomonadales [Chattonellales Throndsen 1993; Chloromonadida; Chloromonadales; Raphidomonadida Heywood & Leedale 1983; Chloromonadina Klebs 1892]
        • Genus Viridilobus Demir-Hilton et al. 2012
        • Family Fibrocapsaceae Cavalier-Smith 2013
          • Genus Fibrocapsa Toriumi & Takano 1973
        • Family Haramonadaceae Cavalier-Smith 2013
          • Genus Haramonas Horiguchi 1996
        • Family Chattonellaceae Throndsen
          • Genus Oltmannsia Schiller 1925
          • Genus Chlorinimonas Yamaguchi et al. 2010
          • Genus Heterosigma Hada 1967 ex Hara & Chihara 1987
          • Genus Chattonella Biecheler 1936 [Hornellia Subrahmanyan 1954; Hemieutreptia Hada 1974]
        • Family Vacuolariaceae
          • Genus Swirenkoiamonas Skvortzov 1968
          • Genus Vacuolaria Cienkowski 1870
          • Genus Merotricha Mereschkowsky 1877
          • Genus Gonyostomum Diesing 1866

References
  1. Herbert Graffius, J. (1966). "Additions to Our Knowledge of Michigan Pyrrhophyta and Chloromonadophyta". Transactions of the American Microscopical Society. 85 (2): 260–270. doi:10.2307/3224637. JSTOR 3224637.
  2. Hoek, C. van den, Mann, D. G. and Jahns, H. M. (1995). Algae : An introduction to phycology. UK: Cambridge University Press. ISBN 978-0-521-31687-3.CS1 maint: uses authors parameter (link)
  3. "RAPHIDIOPHYTA". susqu.edu.
  4. American Water Works Association (2010). Algae: Source to Treatment. p. 281. ISBN 978-1-61300-116-5.
  5. Potter, D; Saunders, G; Andersen, R (1997). "Phylogenetic relationships of the Raphidophyceae and Xanthophyceae as inferred from nucleotide sequences of the 18S ribosomal RNA gene". American Journal of Botany. 84 (7): 966. doi:10.2307/2446287. JSTOR 2446287. PMID 21708651.
  6. Cavalier-Smith, T; Scoble, J. M. (2013). "Phylogeny of Heterokonta: Incisomonas marina, a uniciliate gliding opalozoan related to Solenicola (Nanomonadea), and evidence that Actinophryida evolved from raphidophytes". European Journal of Protistology. 49 (3): 328–353. doi:10.1016/j.ejop.2012.09.002. PMID 23219323.
  7. Guiry, M.D.; Guiry, G.M. (2016). "Raphidophyceae". AlgaeBase (3). Retrieved 2016-08-26.
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