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Pedinellales

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Pedinellales (ICN) or Pedinellida (ICZN) is a group of single-celled algae found in both marine environments and freshwater.[3]

Pedinellales
Light micrograph of Pteridomonas danica
Scientific classification Edit this classification
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Stramenopiles
Phylum: Gyrista
Subphylum: Ochrophytina
Class: Dictyochophyceae
Order: Pedinellales
Zimmermann, Moestrup & Hallfors 1985
Family: Actinomonadaceae
Kent 1880
Genera
Synonyms
As class
  • Pedinellea (ICZN) Cavalier-Smith, 1986
  • Pedinellophyceae (ICN) Cavalier-Smith, 1986
As subclass
  • Pedinellidae Cavalier-Smith, 1995
As order
  • Ciliophryida (ICZN) Febvre-Chevalier 1985
  • Ciliophryales (ICN) Cavalier-Smith, 1995
As suborder
  • Actinomonadineae Cavalier-Smith 2006[1]
  • Ciliophryineae Febvre-Chevalier ex Cavalier-Smith, 2006[1]
As family
  • Apedinellaceae Cavalier-Smith, 1995[2]
  • Cyrtophoraceae Pascher, 1911
  • Pedinellidae (ICZN) Pascher, 1910
  • Pedinellaceae (ICN) Pascher, 1910 orthog. emend. Cavalier-Sith, 1995[2]
  • Ciliophryidae (ICZN) Poche, 1913
  • Ciliophryaceae (ICN) Poche, 1913 orthog. emend. Cavalier-Smith, 1995[2]

These are found in both freshwater and marine environments, and most genera are sessile, attached by posterior stalks. The flagellum is at the anterior of the cell, and the tentacles surround it, often capturing small prey drawn in by its current. The colored genera are Pedinella, Apedinella, Pseudopedinella, and Mesopedinella. Several more genera have lost their chloroplasts and feed entirely by phagocytosis. These are Parapedinella, Actinomonas, and Pteridomonas.

It also appears that certain heliozoa are actually derived pedinellids. Ciliophrys alternates between a mobile flagellate stage and a heliozoan feeding stage, where the body is contracted with extended axopods all over its surface, and the flagellum is curled up into a tight figure eight. The actinophryids, Actinophrys and Actinosphaerium, exist only in a heliozoan form with no flagellum and with more elaborate bundles of microtubules supporting their axopods. Their inclusion was argued by Mikrjukov and Patterson, who coined the term actinodine to refer specifically to this extended group.

Pedinellids were classified as heliozoans by some authors. The colored pedinellids were originally treated as a family of golden algae in the order Ochromonadales, promoted to an order Pedinellales by Zimmerman in 1984. Their relationship to the silicoflagellates became apparent some time later, and Patterson defined this rankless group for the two in 1994. Moestrup treated it as the class Dictyochophyceae, previously restricted to the silicoflagellates, while Cavalier-Smith defined a new class Actinochrysophyceae for them.

Systematics

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Taxonomic history

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Pedinellids have been known since the 19th century, but were classified as either algae or heliozoan protozoa due to the absence of chloroplasts in some species.[4] Before the taxonomic revisions that took place in the late 20th century, pedinellids were treated as a single family Pedinellaceae, described in 1910 by Pascher. Some authors classified pedinellids within the order Ochromonadales, together with a variety of unrelated heterokonts such as Synuraceae and Bicosoecaceae, as part of the class Chrysophyceae or golden algae.[5] In 1985, phycologists Birthe Zimmermann, Øjvind Moestrup and Guy Hällfors classified them as an independent order, Pedinellales.[6] The same year, John J. Lee and coauthors segregated the phagotrophic (i.e. without chloroplasts) pedinellids as a different order Ciliophryida under the polyphyletic class Heliozoea. Other authors, such as Thomas Cavalier-Smith, went a step further and proposed treating pedinellids as a separate class, under the name of Pedinellea (spelt Pedinellophyceae under botanical nomenclature).[7]

In 1995, Charles J. O'Kelly and Daniel E. Wujek classified the Dictyochophyceae in three orders: Rhizochromulinales (containing the sole genus Rhizochromulina), Pedinellales (containing all pedinellids) and Dictyochales (silicoflagellates), separating them from golden algae.[8] Simultaneously, Cavalier-Smith proposed a slightly different classification where he created a new class Actinochrysea to embrace these three groups, avoiding the usage of Dictyochophyceae as a name. He considered pedinellids as subclass Pedinellidae, with two orders: Pedinellales (with chloroplasts), containing the families Pedinellaceae and Apedinellaceae; and Ciliophryales (without chloroplasts), containing Actinomonadaceae and Ciliophryaceae. The remaining two groups, Rhizochromulinales and Dictyochales, were transferred to a separate subclass Dictyochidae.[2] The next year, Cavalier-Smith and Ema E. Chao recognized that the chloroplast losses were polyphyletic, and the family Actinomonadaceae was transferred to Pedinellales on the basis of a molecular phylogenetic analysis.[9]

In 2006, Cavalier-Smith once again rearranged the classification. He lowered Actinochrysea to a subclass Actinochrysia within a new class Hypogyristea, which also included pelagophytes as subclass Pelagophycia. He lumped together all pedinellid genera in the family Actinomonadaceae and new suborder Actinomonadineae, with the exception of Ciliophrys, which he included with the non-pedinellid Rhizochromulina in two families of a new suborder Ciliophryineae.[1] He maintained this classification in later years.[10] In 2018, he finally recognized class Dictyochophyceae, and created the subclass Pedinellia or Pedinellophycidae (equivalent to his earlier Actinochrysea/Actinochrysia) to lump together pedinellids and silicoflagellates. Pelagophytes remained under the subclass Pelagophycidae, and two genera of more uncertain placement under a third subclass Sulcophycidae: Olisthodiscus and Sulcochrysis.[11]

Cavalier-Smith's taxonomic scheme is not accepted by the scientific community. Instead, Moestrup's 1995 classification is more commonly supported, where pedinellids are all contained in the order Pedinellales, rendering Ciliophryales a junior synonym. They are considered part of Dictyochophyceae, along with orders Dictyochales (silicoflagellates), Rhizochromulinales (Rhizochromulina),[12] and a more recent fourth order Florenciellales.[13] In addition, pelagophytes are rejected as members of Dictyochophyceae, and instead form an independent class Pelagophyceae.[14] Within pedinellids, there have been several attempts to establish different families according to morphological data such as the presence or absence of stalks and chloroplasts. However, molecular analyses do not support these internal divisions.[12] Consequently, all pedinellids have been grouped into a single family, Actinomonadaceae, which has taxonomic preference due to being the earliest described, and all other proposed families (Pedinellaceae, Apedinellaceae, etc.) have become junior synonyms.[15]

History of pedinellid classification
Cavalier-Smith (1995)[2] Cavalier-Smith (2006)[1] Current[14] Includes
Pedinellidae Pedinellales Pedinellaceae Pedinellales Actinomonadineae Actinomonadaceae Pedinellales Actinomonadaceae Pedinella
Pseudopedinella
Apedinellaceae Apedinella
Ciliophryales Actinomonadaceae Actinomonas
Pteridomonas
Ciliophryaceae Ciliophryineae Ciliophryaceae Ciliophrys
excluded Rhizochromulinaceae excluded Rhizochromulina

Classification

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Pedinellids currently sum the following genera:[16][10]

References

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  1. ^ a b c d Thomas Cavalier-Smith; Ema E-Y Chao (April 2006). "Phylogeny and megasystematics of phagotrophic heterokonts (kingdom Chromista)". Journal of Molecular Evolution. 62 (4): 388–420. doi:10.1007/S00239-004-0353-8. ISSN 0022-2844. PMID 16557340. Wikidata Q28303534.
  2. ^ a b c d e Cavalier-Smith T, Chao EE, Allsopp MTEP (1995). "Ribosomal RNA Evidence for Chloroplast Loss within Heterokonta: Pedinellid Relationships and a Revised Classification of Ochristan Algae". Archiv für Protistenkunde. 145 (3–4): 209–220. doi:10.1016/S0003-9365(11)80316-7.
  3. ^ Lee RE (March 2018). "Heterokontophyta - Dictyochochyceae". Phycology (5 ed.). Cambridge University Press. p. 345. ISBN 9781107555655. Retrieved 28 August 2018.
  4. ^ R. Mck. Smith; D. J. Patterson (22 April 1986). "Analyses of heliozoan interrelationships: an example of the potentials and limitations of ultrastructural approaches to the study of protistan phylogeny". Proceedings of the Royal Society of London. Series B, Biological sciences. 227 (1248): 325–366. doi:10.1098/RSPB.1986.0026. ISSN 0950-1193. JSTOR 36115. Wikidata Q125959734.
  5. ^ Christensen, Tyge (1980). Algae: a taxonomic survey. Vol. 1. Odense: AiO Tryk as. p. 116.
  6. ^ Zimmermann, B.; Moestrup, Ø.; Hällfors, G. (1985). "Chrysophyte or heliozoon: ultrastructural studies on a cultured species of Pseudopedinella (Pedinellales ord. nov.), with comments on species taxonomy". Protistologica. 20: 591–612.
  7. ^ Moestrup, Øjvind (1995). "Current status of chrysophyte 'splinter groups': synurophytes, pedinellids, silicoflagellates". In Sandgren, Craig D.; Smol, John P.; Kristiansen, Jørgen (eds.). Chrysophyte algae: ecology, phylogeny, and development. Cambridge University Press. pp. 75–92. ISBN 0521462606.
  8. ^ O'Kelly, Charles J.; Wujek, Daniel E. (1995). "Staus of the Chrysamoebales (Chrysophyceae): observations on Chrysamoeba pyrenoidifera, Rhizochromulina marina and Lagynion delicatum". In Sandgren, Craig D.; Smol, John P.; Kristiansen, Jørgen (eds.). Chrysophyte algae: ecology, phylogeny, and development. Cambridge University Press. pp. 361–372. ISBN 0521462606.
  9. ^ Cavalier-Smith, T.; Chao, E.E. (1996). "18S rRNA sequence of Heterosigma carterae (Raphidophyceae), and the phylogeny of heterokont algae (Ochrophyta)". Phycologia. 35 (6): 500–510. doi:10.2216/i0031-8884-35-6-500.1.
  10. ^ a b Cavalier-Smith, Thomas; Scoble, Josephine Margaret (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. ^ Thomas Cavalier-Smith (5 September 2017). "Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences". Protoplasma. 255 (1): 297–357. doi:10.1007/S00709-017-1147-3. ISSN 0033-183X. PMC 5756292. PMID 28875267. Wikidata Q47194626.
  12. ^ a b Preisig, Hans R. (1999). "Systematics and Evolution of the Algae: Phylogenetic Relationships of Taxa Within the Different Groups of Algae". In Esser, K.; Kadereit, J.W.; Lüttge, U.; Runge, M. (eds.). Progress in Botany. Vol. 60. Berlin: Springer. pp. 369–412. doi:10.1007/978-3-642-59940-8_14.
  13. ^ Edvardsen, Bente; Eikrem, Wenche (2007). "Verrucophora farcimen gen. et sp. nov. (Dictyochophyceae, Heterokonta)—a bloom-forming ichthyotoxic flagellate form the Skagerrak, Norway". Journal of Phycology. 43: 1054–1070. doi:10.1111/j.1529-8817.2007.00390.x. hdl:10852/11590.
  14. ^ a b Sina M. Adl; David Bass; Christopher E. Lane; et al. (1 January 2019). "Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes". Journal of Eukaryotic Microbiology. 66 (1): 4–119. doi:10.1111/JEU.12691. ISSN 1066-5234. PMC 6492006. PMID 30257078. Wikidata Q57086550.
  15. ^ Moestrup, Øjvind; O'Kelly, Charles J. (2000). "Class Silicoflagellata Lemmermann, 1901" (PDF). In Lee, John J.; Leedale, Gordon F.; Bradbury, Phyllis (eds.). An Illustrated Guide to the Protozoa. Vol. II (2nd ed.). Lawrence, Kansas: Society of Protozoologists. pp. 775–782.
  16. ^ Guiry, M.D. & Guiry, G.M. (2016). "Dictyochophyceae". AlgaeBase. National University of Ireland, Galway.
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