Labyrinthulomycetes


The Labyrinthulomycetes or Labyrinthulea are a class of protists that produce a network of or tubes, which serve as tracks for the cells to glide along and absorb nutrients for them. The two main groups are the labyrinthulids 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, or Labyrinthulida and Thraustochytrida, but a third has recently been proposed.
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. This code is represented by NCBI translation table 23, Thraustochytrium mitochondrial code.

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