The Labyrinthulomycetes (
ICBN
The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...
) or Labyrinthulea (
ICZN) are a
class of
protists that produce a network of
filaments or tubes,
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
alga
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
e and
seagrasses or as decomposers on dead plant material. They also include some parasites of marine invertebrates.
Characteristics
Although they are outside the cells, the filaments of Labyrinthulomycetes are surrounded by a
membrane
A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. ...
. 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.
Classification
Labyrinthulomycetes/Labyrinthulea used to belong to the defunct fungal phylum Labyrinthulomycota. They were originally considered unusual
slime mould
Slime mold or slime mould is an informal name given to several kinds of unrelated eukaryotic organisms with a life cycle that includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic mu ...
s, although they are not very similar to the other sorts. The structure of their
zoospores
A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves.
Diversity Flagella types
Zoospores may possess one or mo ...
and genetic studies show them to be a primitive group of
heterokont
Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which a ...
s, but their classification and treatment remains somewhat unsettled.
This class has usually two orders, Labyrinthulales and Thraustochytriales (ICBN), or Labyrinthulida and Thraustochytrida (ICZN),
but a third has recently been proposed.
* Genus ''
Stellarchytrium''
FioRito & Leander 2016
* Family
Oblongichytriidae Cavalier-Smith 2012
** Genus ''
Oblongichytrium''
Yokoyama & Honda 2007
* Order
Labyrinthulida Doflein 1901
** Family
Aplanochytriidae Leander ex Cavalier-Smith 2012
*** Genus ''
Aplanochytrium''
Bahnweg & Sparrow 1972 'Labyrinthuloides''_Perkins_1973.html" ;"title="Labyrinthuloides.html" ;"title="'Labyrinthuloides">'Labyrinthuloides'' Perkins 1973">Labyrinthuloides.html" ;"title="'Labyrinthuloides">'Labyrinthuloides'' Perkins 1973
** Family Labyrinthulidae
Cienkowski 1867
*** Genus ''Labyrinthomyxa''
Duboscq 1921
*** Genus ''Pseudoplasmodium''
Molisch 1925
*** Genus ''
Labyrinthula''
Cienkowski 1864 'Labyrinthodictyon''_
Valkanov_1969;_''Labyrinthorhiza.html" ;"title="Labyrinthodictyon.html" ;"title="'Labyrinthodictyon">'Labyrinthodictyon''
Valkanov 1969; ''Labyrinthorhiza">Labyrinthodictyon.html" ;"title="'Labyrinthodictyon">'Labyrinthodictyon''
Valkanov 1969; ''Labyrinthorhiza''
Chadefaud 1956]
* Order Amphitremida
Gomaa et al. 2013
** Family Diplophryidae
Cavalier-Smith 2012
*** Genus ''Diplophrys''
Barker 1868
** Family Amphitrematidae
Poche 1913
*** Genus ''
Paramphitrema''
Valkanov 1970
*** Genus ''
Archerella''
Loeblich & Tappan 1961
*** Genus ''
Amphitrema''
Archer 1867
* Order
Thraustochytriida Alderman & 1974
** Genus ''
Pyrrhosorus''
Juel 1901
** Genus ''
Thanatostrea''
Franc & Arvy 1969
** Family
Althorniidae Cavalier-Smith 2012
*** Genus ''
Althornia''
Jones & Alderman 1972
** Family
Sorodiplophryidae Cavalier-Smith 2012
*** Genus ''
Sorodiplophrys''
Olive & Dykstra 1975
** Family
Amphifilidae Cavalier-Smith 2012
*** Genus ''
Amphifila''
Cavalier-Smith 2012
*** Genus ''
Fibrophrys columna''
Takahashi et al. 2016
** Family
Thraustochytriidae Sparrow ex Cejp 1959
*** Genus ''
Japonochytrium''
Kobayasi & Ôkubo 1953
*** Genus ''
Monorhizochytrium''
Doi & Honda 2017
*** Genus ''
Sicyoidochytrium''
Yokoy., Salleh & Honda 2007
*** Genus ''
Aurantiochytrium''
Yokoy. & Honda 2007
*** Genus ''
Ulkenia''
Gaertn. 1977
*** Genus ''
Parietichytrium''
Yokoy., Salleh & Honda 2007
*** Genus ''
Botryochytrium''
Yokoy., Salleh & Honda 2007
*** Genus ''
Schizochytrium''
Goldst. & Belsky emend. Booth & Mill.
*** Genus ''
Thraustochytrium''
Sparrow 1936
*** Genus ''
Hondaea''
Amato & Cagnac 2018
*** Genus ''
Labyrinthulochytrium Hassett & Gradinger 2018''
Genetic code
The labyrinthulomycete ''
Thraustochytrium aureum'' is notable for the
alternative genetic code of its
mitochondria which use as a
stop codon
In molecular biology (specifically protein biosynthesis), a stop codon (or termination codon) is a codon (nucleotide triplet within messenger RNA) that signals the termination of the translation process of the current protein. Most codons in mess ...
instead of coding for
Leucine
Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α- amino group (which is in the protonated −NH3+ form under biological conditions), an α- ...
. This code is represented by
NCBI
The National Center for Biotechnology Information (NCBI) is part of the United States National Library of Medicine (NLM), a branch of the National Institutes of Health (NIH). It is approved and funded by the government of the United States. The ...
translation table 23,
''Thraustochytrium'' mitochondrial code.
Gallery
File:Aplanolm.jpg, '' Aplanochytrium'' sp. under light microscope
File:Aplanosem.png, ''Aplanochytrium'' sp. under SEM
File:Aurantiochytrium limacinum SR21.jpg, ''Aurantiochytrium'' sp.
File:Collection Penard MHNG Specimen 48-2-4 Amphitrema stenostoma.tif, Test of '' Amphitrema'', a testate amoeba
Testate amoebae (formerly thecamoebians, Testacea or Thecamoeba) are a polyphyletic group of unicellular amoeboid protists, which differ from naked amoebae in the presence of a test that partially encloses the cell, with an aperture from which the ...
recently included in the group
File:Tsenkovsky Lev Semyonovich.jpg, Leon Cienkowski, Polish botanist who in 1867 described '' Labyrinthula'', the first genus of the group[Cienkowski, L. (1867). Ueber den Bau und die Entwicklung der Labyrinthuleen. ''Arch. mikr. Anat.'', 3:274]
References
External links
Labyrinthulomycota
{{Taxonbar, from1=Q1148791, from2=Q16653009
Heterokont classes
Bigyra