| Tetrahelia | |
|---|---|
Scientific classification | |
| Phylum: | Cryptista |
| Class: | Endohelea |
| Order: | Axomonadida Cavalier-Smith in Yabuki et al. 2012 emend. 2022 |
| Family: | Tetraheliidae Cavalier-Smith 2022 |
| Genus: | Tetrahelia Cavalier-Smith 2022 |
| Species: | T. pterbica |
| Binomial name | |
| Tetrahelia pterbica (Mikrjukov & Patterson 2000) Cavalier-Smith 2022[1] | |
| Synonyms | |
| |
Tetrahelia (from Latin tetra- 'four' and helio- 'sun') is a genus of four-ciliatedprotists belonging to theEndohelea, a group ofheterotrophiceukaryotes previously consideredheliozoa.[2] It is the only genus in the familyTetraheliidae and orderAxomonadida. It is amonotypic genus, containing the sole speciesTetrahelia pterbica, previously classified asTetradimorpha.[1]
Tetrahelia are unicellularciliates with four standard-lengthcentrioles that are shorter than inHeliomorpha andTetradimorpha, andaxopodia generated by a globularcentrosome with a distinct granular shell and amicrofibrillar core. The centrioles are arranged in two pairs: each pair has two parallel centrioles, and the pairs are positioned at 30° of rotation between each other. They are linked at the base by an amorphous material that connects them to the centrosome. There are lateraldictyosomes on either side of the cellnucleus. The axopodia have several irregularly arrangedmicrotubules and irregularly flattenedextrusomes, instead of thekinetocysts seen inHeliomorpha andTetradimorpha radiata. The cell size is larger than 60 μm, and the centrosome itself measures between 18 and 20 μm. There is a thick pseudopellicle layer beneath thecell membrane.[1]
The life cycle ofTetrahelia contains a lazily swimming, purelyflagellate stage with fully retracted axopodia.[1]