Raphidophyte

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Raphidophytes
Gonyostomum-cells.JPG
Gonyostomum semen
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Clade: Sar
Clade: Stramenopiles
Phylum: Ochrophyta
Clade: Chrysista
Class: Raphidophyceae
Chadefaud 1950 emend. Silva 1980 [1]
Order: Chattonellales
Throndsen in Tomas 1993 emend. Yamaguchi, Nakayama, Murakami & Inouye 2010 [2]
Families [3]
Synonyms
  • Chloromonadina Klebs 1892
  • Raphidomonadida Heywood & Leedale 1983
  • Chloromonadophyceae Rothmaler 1951; Fott 1968
  • Raphidomonadida Heywood & Leedale 1983
  • Raphidophycidae Cavalier-Smith in Cavalier-Smith & Chao 2013
  • Vacuolariales Shameel 2001

The raphidophytes, previously known as chloromonads, [4] [5] are a small but widespread group of single-celled eukaryotic algae, found in both marine and freshwater environments. [6] [7] They are formally known as class Raphidophyceae and order Chattonellales.

Contents

Characteristics

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.

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.

Classification

The position of this group varied in former classifications. Some protozoologists treated chloromonads as an order within the phytoflagellates. [4] Some phycologists classified them with the Xanthophyceae and the Eustigmatophyceae in the division Xanthophyta. [8] Others considered them as related to the Chrysophyceae, Dinophyceae, or Cryptophyceae. [9] Cavalier-Smith proposed them as a subclass of algae within the class Raphidomonadea, which also included the heliozoan group Actinophryida and the enigmatic flagellate Commation . [10] [2]

Currently, raphidophytes consist of the class Raphidophyceae, [7] which contains only one order Chattonellales composed of four families. [3]

Several genera have been proposed as raphidophytes but their position remains uncertain. The genus Oltmannsia Schiller 1925 was tentatively placed in the order Chattonellales by Jahn Throndsen in 1993, [12] : 30  [13] : 511  but it is not included in later studies. Similarly, the genus Swirenkoiamonas Skvortzov 1968 was described as a member of the Chloromonadales, [14] was later regarded as a euglenid in 1991, [15] : 428  and is not mentioned by subsequent studies. [7] The genus Olisthodiscus was originally proposed as a raphidophyte, [12] : 30  but it currently composes a separate class, Olisthodiscophyceae. [16]

References

  1. ↑ Adl, Sina M.; Bass, David; Lane, Christopher E.; Lukeš, Julius; Schoch, Conrad L.; et al. (26 September 2018). "Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes". The Journal of Eukaryotic Microbiology. 66 (1): 4–119. doi:10.1111/JEU.12691. PMC   6492006 . PMID   30257078.
  2. 1 2 Yamaguchi, Haruyo; Nakayama, Takeshi; Murakami, Akio; Inouye, Isao (2010). "Phylogeny and taxonomy of the Raphidophyceae (Heterokontophyta) and Chlorinimonas sublosa gen. et sp. nov., a new marine sand-dwelling raphidophyte". Journal of Plant Research. 123 (3): 333–342. doi:10.1007/s10265-009-0281-1. ISSN   0918-9440.
  3. 1 2 Engesmo, Anette; Eikrem, Wenche; Seoane, Sergio; Smith, Kirsty; Edvardsen, Bente; et al. (2016). "New insights into the morphology and phylogeny of Heterosigma akashiwo (Raphidophyceae), with the description of Heterosigma minor sp. nov " (PDF). Phycologia. 55 (3): 279–294. doi:10.2216/15-115.1. ISSN   0031-8884 . Retrieved 27 October 2025.
  4. 1 2 Levine, N. D.; Corliss, J. O.; Cox, F. E. G.; Deroux, G.; Grain, J.; et al. (1980). "A newly revised classification of the Protozoa". Journal of Protozoology. 27 (1): 37–58. doi: 10.1111/j.1550-7408.1980.tb04228.x . PMID   6989987.
  5. ↑ 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.
  6. ↑ Hoek, C. van den; Mann, D. G.; Jahns, H. M. (1995). Algae: An introduction to phycology. UK: Cambridge University Press. ISBN   978-0-521-31687-3.
  7. 1 2 3 Graf, Louis (2024). "Heterokontophyta—Photosynthetic Stramenopiles". In Büdel, Burkhard; Friedl, Thomas; Beyschlag, Wolfram (eds.). Biology of Algae, Lichens and Bryophytes. Springer Spektrum. pp. 220–279. doi:10.1007/978-3-662-65712-6_5. ISBN   978-3-662-65712-6.
  8. ↑ American Water Works Association (2010). Algae: Source to Treatment. p. 281. ISBN   978-1-61300-116-5.
  9. ↑ 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.
  10. ↑ Cavalier-Smith, Thomas; Scoble, Josephine Margaret (August 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.
  11. ↑ Demir‐Hilton, Elif; Hutchins, David A.; Czymmek, Kirk J.; Coyne, Kathryn J. (2012). "Description of Viridilobus marinus (gen. et sp. nov.), a new raphidophyte from Delaware's inland bays". Journal of Phycology. 48 (5): 1220–1231. doi:10.1111/j.1529-8817.2012.01212.x. ISSN   0022-3646.
  12. 1 2 Throndsen, Jahn (1993). "The Planktonic Marine Flagellates". In Tomas, Carmelo R. (ed.). Marine Phytoplankton: A Guide to Naked Flagellates and Coccolithophorids. San Diego: Academic Press. pp. 7–145. ISBN   0-12-693010-4.
  13. ↑ Hallegraeff, G. M.; Hara, Y. (2004). "Taxonomy of harmful marine raphidophytes". In Hallegraeff, G.M.; Anderson, D.M.; Cembella, A.D. (eds.). Manual on Harmful Marine Microalgae. Monographs on Oceanographic Methodology. Vol. 11 (2nd ed.). Paris: UNESCO Publishing. pp. 511–522. ISBN   92-3-103948-2.
  14. ↑ Skvortzov, B. V. (1972). "A list of new genera and type species of flagellates and algae published in 1966?1968". Hydrobiologia. 39 (1): 1–7. doi:10.1007/BF00047593. ISSN   0018-8158 . Retrieved 27 October 2025.
  15. ↑ Patterson, David J; Zölffel, Michael (30 January 1992). "Heterotrophic flagellates of uncertain taxonomic position". The Biology of Free-Living Heterotrophic Flagellates. Oxford: Oxford University Press. pp. 427–476. doi:10.1093/oso/9780198577478.003.0026. ISBN   978-0-19-857747-8.
  16. ↑ Dovilė Barcytė; Wenche Eikrem; Anette Engesmo; Sergio Seoane; Jens Wohlmann; Aleš Horák; Tatiana Yurchenko; Marek Eliáš (2 March 2021). "Olisthodiscus represents a new class of Ochrophyta". Journal of Phycology. 57 (4): 1094–1118. Bibcode:2021JPcgy..57.1094B. doi: 10.1111/jpy.13155 . hdl: 10852/86515 . PMID   33655496.
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