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Cell with network of ectoplasmic filaments (Aplanochytrium sp.)
Scientific classification e
Phylum: Heterokontophyta
Class: Labyrinthulomycetes
Arx, 1970, Dick, 2001
  • Labyrinthulomycota Whittaker, 1969
  • Labyrinthomorpha Page in Levine et al., 1980
  • Labyrinthulea Olive, 1975
    ex Cavalier-Smith, 1989

The Labyrinthulomycetes (ICBN) or Labyrinthulea[1] (ICZN) are a class of protists that produce a network of filaments or tubes,[2] which serve as tracks for the cells to glide along and absorb nutrients for them. The two main groups are the labyrinthulids (or slime nets) and thraustochytrids. They are mostly marine, commonly found as parasites on algae and seagrasses or as decomposers on dead plant material. They also include some parasites of marine invertebrates.[3]


Although they are outside the cells, the filaments of Labyrinthulomycetes are surrounded by a membrane. They are formed and connected with the cytoplasm by a unique organelle called a sagenogen or bothrosome. The cells are uninucleated and typically ovoid, and move back and forth along the amorphous network at speeds varying from 5-150 μm per minute. Among the labyrinthulids, the cells are enclosed within the tubes, and among the thraustochytrids, they are attached to their sides.


Labyrinthulomycetes/Labyrinthulea used to belong to the defunct fungal phylum Labyrinthulomycota.[4] They were originally considered unusual slime moulds, although they are not very similar to the other sorts. The structure of their zoospores and genetic studies show them to be a primitive group of heterokonts, but their classification and treatment remains somewhat unsettled.

This class has usually two orders, Labyrinthulales and Thraustochytriales (ICBN), or Labyrinthulida and Thraustochytrida (ICZN),[5] but a third has recently been proposed.[6][7][8]

Genetic code[edit]

The labyrinthulomycete Thraustochytrium aureum is notable for the alternative genetic code of its mitochondria which use TTA as a stop codon instead of coding for Leucine.[10] This code is represented by NCBI translation table 23, Thraustochytrium mitochondrial code.[11]

Genetic code Translation
DNA codon RNA codon Translation
with this code
Standard code
(Translation table 1)
Thraustochytrium mitochondrial 23 TTA UUA STOP = Ter (*) Leu (L)



  1. ^ Cavalier-Smith, T. (1997). "Sagenista and bigyra, two phyla of heterotrophic heterokont chromists". Archiv für Protistenkunde. 148 (3): 253–267. doi:10.1016/S0003-9365(97)80006-1.
  2. ^ Tsui CK, Marshall W, Yokoyama R, et al. (January 2009). "Labyrinthulomycetes phylogeny and its implications for the evolutionary loss of chloroplasts and gain of ectoplasmic gliding". Mol. Phylogenet. Evol. 50 (1): 129–40. doi:10.1016/j.ympev.2008.09.027. PMID 18977305.
  3. ^ Schärer, L.; Knoflach, D.; Vizoso, D. B.; Rieger, G.; Peintner, U. (2007). "Thraustochytrids as novel parasitic protists of marine free-living flatworms: Thraustochytrium caudivorum sp. nov. Parasitizes Macrostomum lignano" (PDF). Marine Biology. 152 (5): 1095. doi:10.1007/s00227-007-0755-4.
  4. ^ Bennett, Reuel M; Honda, D; Beakes, Gordon W; Thines, Marco (2017). "Labyrinthulomycota". Bennett RM, Honda D, Beakes GW, Thines M. (2017) Labyrinthulomycota. In Handbook of the Protists. Archibald, Simpson, Slamovits (eds). Springer. 507-542. p. 507. doi:10.1007/978-3-319-28149-0_25. ISBN 978-3-319-28147-6.
  5. ^ "". Retrieved 2009-04-04.
  6. ^ Gomaa; Mitchell; Lara (2013). "Amphitremida (Poche, 1913) Is a New Major, Ubiquitous Labyrinthulomycete Clade". PLoS ONE. 8 (1): e53046. Bibcode:2013PLoSO...853046G. doi:10.1371/journal.pone.0053046. PMC 3544814. PMID 23341921.
  7. ^ ANDERSON; CAVALIER-SMITH (2012). "Ultrastructure of Diplophrys parva, a New Small Freshwater Species, and a Revised Analysis of Labyrinthulea (Heterokonta)". Acta Protozoologica. 8 (1): 291–304. doi:10.4467/16890027AP.12.023.0783. Retrieved 2016-04-04.
  8. ^ FioRito, Rebecca; Leander, Celeste; Leander, Brian (2016). "Characterization of three novel species of Labyrinthulomycota isolated from ochre sea stars (Pisaster ochraceus)". Marine Biology. 163 (8): 170. doi:10.1007/s00227-016-2944-5.
  9. ^ Hassett, Brandon T.; Gradinger, Rolf (2018). "New Species of Saprobic Labyrinthulea (=Labyrinthulomycota) and the Erection of a gen. nov. to Resolve Molecular Polyphyly within the Aplanochytrids". Journal of Eukaryotic Microbiology. 65 (4): 475–483. doi:10.1111/jeu.12494. hdl:10037/13570. ISSN 1550-7408.
  10. ^ Wideman, Jeremy G.; Monier, Adam; Rodríguez-Martínez, Raquel; Leonard, Guy; Cook, Emily; Poirier, Camille; Maguire, Finlay; Milner, David S.; Irwin, Nicholas A. T.; Moore, Karen; Santoro, Alyson E. (2019-11-25). "Unexpected mitochondrial genome diversity revealed by targeted single-cell genomics of heterotrophic flagellated protists". Nature Microbiology. 5 (1): 154–165. doi:10.1038/s41564-019-0605-4. ISSN 2058-5276.
  11. ^ Elzanowski A, Ostell J, Leipe D, Soussov V. "The Genetic Codes". Taxonomy browser. National Center for Biotechnology Information (NCBI), U.S. National Library of Medicine. Retrieved 11 August 2016.
  12. ^ Cienkowski, L. (1867). Ueber den Bau und die Entwicklung der Labyrinthuleen. Arch. mikr. Anat., 3:274, [1].

External links[edit]