''Pseudoblepharisma'' is a genus of

heterotrich The heterotrichs are a class of ciliates. They typically have a prominent adoral zone of membranelles circling the mouth, used in locomotion and feeding, and shorter cilia on the rest of the body. Many species are highly contractile, and are ...

ciliates inhabiting oxygen depleted freshwater habitats. Most sources report that it contains one species, ''Pseudoblepharisma tenue'', but at least four have been seen in literature. ''P. tenue'' was originally described in Germany as ''Blepharisma tenuis''. Starting in 2006, it was recognized that the German strain may have two bacterial symbionts, one pink, one green. In 2021, both symbionts were confirmed to be photosynthetic: a '' Chlorella'' sp. K10 (

green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...

), discovered earlier as a symbiont of ''

Hydra viridissima ''Hydra viridissima'' is a species of cnidarian which is commonly found in still or slow-moving freshwater in the Northern temperate zone. ''Hydra viridissima'' is commonly called green hydra due to its coloration, which is due to the symbiotic ...

''; and Ca. ''

Thiodictyon ''Thiodictyon'' is a genus of gram-negative bacterium classified within purple sulfur bacteria (PSB). * ''T. elegans'' forms "netlike aggregates under certain culture conditions." It is obligately phototrophic and strictly anaerobic. * ''T. baci ...

intracellulare'' ( Chromatiaceae), a purple sulfur bacterium that has lost its sulfur-metabolizing genes. The complexity of such a

tripartite symbiosis Tripartite symbiosis is a type of symbiosis involving three species. This can include any combination of plants, animals, fungi, bacteria, or archaea, often in interkingdom symbiosis. Ants Fungus-growing ants Ants of Attini cultivate fung ...

is novel to science. European reports also mentioned a variant ''P. tenue'' var. ''viride'', which only has green symbionts. In 2022, one strain matching these descriptions was found in tropical freshwaters of Florida, North America. Unlike its the bicolor European counterpart, it builds a lorica (shell) around itself. The current taxonomy is inconsistent with molecular phylogeny using SSU rRNA; the latter places the genus sister to ''

Spirostomum ''Spirostomum'' is a genus of ciliated protists that belongs to the class Heterotrichea. It is known for being very contractile.Fernandes, N.M.; da Silva Neto, I.D. (2013). “Morphology and 18S rDNA gene sequence of ''Spirostomum minus'' and ''S ...

''.

References

{{reflist Heterotrichea Alveolata genera