Oxymonad


The oxymonads are a group of flagellated protists found exclusively in the intestines of animals, mostly termites and other wood-eating insects. Along with the similar parabasalid flagellates, they harbor the symbiotic bacteria that are responsible for breaking down cellulose. There is no evidence for presence of mitochondria in oxymonads and three species have been shown to completely lack any molecular markers of mitochondria.
It includes e.g. Dinenympha, Pyrsonympha, Oxymonas, Streblomastix, Monocercomonoides, and Blattamonas.

Characteristics

Most Oxymonads are around 50 μm in size and have a single nucleus, associated with four flagella. Their basal bodies give rise to several long sheets of microtubules, which form an organelle called an axostyle, but different in structure from the axostyles of parabasalids. The cell may use the axostyle to swim, as the sheets slide past one another and cause it to undulate. An associated fiber called the preaxostyle separates the flagella into two pairs. A few oxymonads have multiple nuclei, flagella, and axostyles.

Relationship to ''Trimastix'' and ''Paratrimastix''

The free-living flagellates Trimastix and Paratrimastix are closely related to the oxymonads. They lack aerobic mitochondria and have four flagella separated by a preaxostyle, but unlike the oxymonads have a feeding groove. This character places the Oxymonads, Trimastix, and Paratrimastix among the Excavata, and in particular they may belong to the metamonads. Molecular phylogenetic studies indeed place Preaxostyla in Metamonada.

Taxonomy