The Labyrinthulomycetes (ICBN) 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 algae 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. 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 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), 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] Family Labyrinthulidae Cienkowski 1867 Genus Labyrinthomyxa Duboscq 1921 Genus Pseudoplasmodium Molisch 1925 Genus Labyrinthula Cienkowski 1864 [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