''Monas'' is a genus of

Chrysophyceae The Chrysophyceae, usually called chrysophytes, chrysomonads, golden-brown algae or golden algae are a large group of algae, found mostly in freshwater. Golden algae is also commonly used to refer to a single species, ''Prymnesium parvum'', which ...

, described by

Otto Friedrich Müller Otto Friedrich Müller, also known as Otto Friedrich Mueller (2 November 1730 – 26 December 1784) was a Danish naturalist and scientific illustrator. Biography Müller was born in Copenhagen. He was educated for the church, became tutor to a ...

1773 Events January–March * January 1 – The hymn that becomes known as ''Amazing Grace'', at this time titled "1 Chronicles 17:16–17", is first used to accompany a sermon led by curate John Newton in the town of Olney, Buckin ...

as a group of

Infusoria Infusoria are minute freshwater life forms including ciliates, euglenoids, protozoa, unicellular algae and small invertebrates. Some authors (e.g., Bütschli) used the term as a synonym for Ciliophora. In modern formal classifications, the term ...

. Throughout time, it represented an aggregate genus.

Taxonomic history

Many organisms were transferred to this genus, and most ''Monas'' spp. have later been synonymised with or integrated in other genera. The organisms once affiliated with ''Monas'' spp. truly belong to all major eukaryotic lineages ( Opisthokonta,

Amoebozoa Amoebozoa is a major taxonomic group containing about 2,400 described species of amoeboid protists, often possessing blunt, fingerlike, lobose pseudopods and tubular mitochondrial cristae. In traditional and currently no longer supported class ...

Rhizaria The Rhizaria are an ill-defined but species-rich supergroup of mostly unicellular eukaryotes. Except for the Chlorarachniophytes and three species in the genus Paulinella in the phylum Cercozoa, they are all non-photosynthethic, but many foramin ...

Archaeplastida The Archaeplastida (or kingdom Plantae ''sensu lato'' "in a broad sense"; pronounced /ɑːrkɪ'plastɪdə/) are a major group of eukaryotes, comprising the photoautotrophic red algae (Rhodophyta), green algae, land plants, and the minor group ...

Stramenopiles Stramenopile is a clade of organisms distinguished by the presence of stiff tripartite external hairs. In most species, the hairs are attached to flagella, in some they are attached to other areas of the cellular surface, and in some they have be ...

, Alveolata,

Cryptophyta The cryptophyceae are a class of algae, most of which have plastids. About 220 species are known, and they are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, ...

Excavata Excavata is a major supergroup of unicellular organisms belonging to the domain Eukaryota. It was first suggested by Simpson and Patterson in 1999 and introduced by Thomas Cavalier-Smith in 2002 as a formal taxon. It contains a variety of free- ...

), and even to prokaryotic lineages. The genus was also included in other groups, as in Mastigophora or Flagellata. The current practice is the (questionable) synonymous use, based on morphological similarity, of the generic names ''Monas'' (mostly used in the east-Asian literature) and ''Spumella'' (synonymously used in the European and American literature) as unpigmented biflagellates in

. However, there is a conflict between the morphological and molecular investigations. The present-day taxon ''Monas''/''Spumella'' is still

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...

, comprising at least three to five lineages, and evidence about the identity of the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

of ''Monas'' is missing. This problem in the circumscription of groups, using the practical morphological (or taxonomic) species concept or the

biological species concept The species problem is the set of questions that arises when biologists attempt to define what a species is. Such a definition is called a species concept; there are at least 26 recognized species concepts. A species concept that works well for se ...

(based on the degree of molecular similarity), is also faced in the taxonomy of other microorganisms, like other flagellates (e.g., '' Bodo'', ''

Cercomonas Cercomonads are small flagellates, widespread in aqueous habitats and common in soils. Characteristics The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do no ...

'') and

microalgae Microalgae or microphytes are microscopic algae invisible to the naked eye. They are phytoplankton typically found in freshwater and marine systems, living in both the water column and sediment. They are unicellular species which exist indiv ...

(e.g.,

Chlorococcales Chlorococcales is a formerly recognized order of green algae in the class Chlorophyceae. , the type family Chlorococcaceae was placed in the order Chlamydomonadales. Conventionally, many groups of coccoid green algae were lumped in the order ...

References

{{Taxonbar, from=Q18180890 Heterokont genera Algae genera Chrysophyceae Taxa named by Otto Friedrich Müller