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Chlorarachniophyte

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Chlorarachniophytes
Chlorarachnion reptans
Scientific classification
Domain:
Eukaryota
(unranked):
SAR
(unranked):
Rhizaria
Phylum:
Cercozoa
Subphylum:
Filosa
Class:
Chlorarachniophyceae

Hibberd & Norris, 1984
Orders & Families
  • Minorisida
    • Minorisidae
  • Chlorarachniales
    • Chlorarachniaceae
Synonyms
  • Chlorarachnea Cavalier-Smith, 1993, orth. zool.
  • Chlorarachniophyta Hibberd & Norris, 1984[1]
A cultured chlorarachniophyte, Lotharella globosa LEX01 strain [2]

The chlorarachniophytes are a small group of exclusively marine algae widely distributed in tropical and temperate waters.[3] They are typically mixotrophic, ingesting bacteria and smaller protists as well as conducting photosynthesis. Normally they have the form of small amoebae, with branching cytoplasmic extensions that capture prey and connect the cells together, forming a net. They may also form flagellate zoospores, which characteristically have a single subapical flagellum that spirals backwards around the cell body, and walled coccoid cells.

The chloroplasts were presumably acquired by ingesting some green alga.[4] They are surrounded by four membranes, the outermost of which is continuous with the endoplasmic reticulum, and contain a small nucleomorph between the middle two, which is a remnant of the alga's nucleus. This contains a small amount of DNA and divides without forming a mitotic spindle. The origin of the chloroplasts from green algae is supported by their pigmentation, which includes chlorophylls a and b, and by genetic similarities. The only other group of algae that contain nucleomorphs are the cryptomonads, but their chloroplasts seem to be derived from a red alga.

The chlorarachniophytes only include five genera, which show some variation in their life-cycles and may lack one or two of the stages described above. Genetic studies place them among the Cercozoa, a diverse group of amoeboid and amoeboid-like[clarification needed] protozoa.

The chlorarachniophytes were placed before in the order Rhizochloridales, class Xanthophyceae (e.g., Smith, 1938), as algae, or in order Rhizochloridea, class Xanthomonadina (e.g., Deflandre, 1956), as protozoa.

So far sexual reproduction has only been reported in two species; Chlorarachnion reptans and Cryptochlora perforans.[5]

Phylogeny

Based on the work of Hirakawa et al. 2011.[2]

Chlorarachniaceae

Taxonomy

  • Lotharella globosa extending a filopodium (Fp) through a pore of the cell wall (CW) from a walled amoeboid cell. Py: pyrenoid. Scale bar = 10µm
    Lotharella globosa extending a filopodium (Fp) through a pore of the cell wall (CW) from a walled amoeboid cell. Py: pyrenoid.
    Scale bar = 10µm
  • Binary and quaternary cell divisions of Lotharella globosa. Arrowheads indicate the parental cell wall. Scale bar = 10µm
    Binary and quaternary cell divisions of Lotharella globosa. Arrowheads indicate the parental cell wall.
    Scale bar = 10µm
  • Flagellate cell of Lotharella globosa with a single flagellum (Fl) and plastid (P) Scale bar = 10µm
    Flagellate cell of Lotharella globosa with a single flagellum (Fl) and plastid (P)
    Scale bar = 10µm

References

  1. ^ Hibberd, David J.; Norris, Richard E. (1984). "Cytology and ultrastructure of Chlorarachnion reptans (Chlorarchniophyta Divisio nova, Chlorachniophyceae Classis nova)". Journal of Phycology. 20 (2): 310–330. doi:10.1111/j.0022-3646.1984.00310.x.
  2. ^ a b Hirakawa; et al. (2011), "Morphological Diversity between Culture Strains of a Chlorarachniophyte, Lotharella globosa", PLoS ONE, 6 (8): e23193, doi:10.1371/journal.pone.0023193, PMC 3156133, PMID 21858028{{citation}}: CS1 maint: unflagged free DOI (link)
  3. ^ Unravelling the algae: the past, present, and future of algal systematics
  4. ^ Keeling PJ (2009). "Chromalveolates and the evolution of plastids by secondary endosymbiosis". J. Eukaryot. Microbiol. 56 (1): 1–8. doi:10.1111/j.1550-7408.2008.00371.x. PMID 19335769.
  5. ^ Unravelling the algae: the past, present, and future of algal systematics
  6. ^ M.D. Guiry (2016), "Chlorarachniophyceae [Chlorarachnea]", AlgaeBase, World-wide electronic publication, National University of Ireland, Galway, retrieved 25 October 2016
  7. ^ Cavalier-Smith (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, PMC 5756292, PMID 28875267
Wikispecies has information related to Chlorarachniophyta.
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