''Neocercomonas'' is a protist genus of the order Cercomonadida. It consists of single-celled bacteriophagous organisms that usually live on or nearby terrestrial

plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...

s, both above and belowground. Species are biflagellate and may grow up to 60 micrometers long, with a trailing tail-like mass of protoplasm at their posterior end and a pair of roots connecting their posterior flagellum to the cytoskeleton.

Etymology

The genus was named by Ekelund ''et al.'' in 2004. The first three letters of the genus name are directly lifted from the Greek '' neo'', meaning 'new', whereas the second part refers to the closely related genus ''Cercomonas'', from which ''Neocercomonas'' was originally distinguished when the former was discovered not to be a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

group. Hence, ''Neocercomonas'' can be interpreted as 'new ''Cercomonas. Higher classifications such as the phylum

Cercozoa Cercozoa (now synonymised with Filosa) is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead united by phylogeny, molecular phylogenies of rRNA and actin or Ubiqu ...

and the order Cercomonadida also bear similar names, though ''Cercomonas'' was identified first (in 1841).

History of knowledge

The genus was discovered in 2004 by Flemming Ekelund, Niels Daugbjerg, and Line Fredslund, whose phylogenetic analysis of rDNA sequences led them to conclude that the genus ''Cercomonas'' should be separated into two taxa, with the new one being named ''Neocercomonas''. In 2006 Karpov ''et al.'' determined that there was insufficient evidence for its status as a separate genus and reclassified it as part of ''Cercomonas'', but study of differences in microtubule nucleation by Karpov and Cavalier-Smith in 2012 re-established it as a genus, and more recent genetic analysis seems to support ''Neocercomonas'' being a monophyletic group.

Habitat and ecology

Organisms belonging to this genus occur in terrestrial systems, most often in forested, agricultural, or otherwise plant-rich areas. Some may be found aboveground on leaf surfaces, while others live amongst soil particles. In the former case, their ability to quickly reproduce while resisting desiccation is key to their ability to survive in an exposed environment.

Description

Morphologically, ''Neocercomonas'' is similar to the genus ''Cercomonas'', though genetic analysis has indicated that they are separate

taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

. Cells are 13-60 micrometers long, feed on

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

, and are usually flattened in shape. They have a ragged 'tail' formed from the

protoplasm Protoplasm (; ) is the part of a cell that is surrounded by a plasma membrane. It is a mixture of small molecules such as ions, monosaccharides, amino acids, and macromolecules such as proteins, polysaccharides, lipids, etc. In some definitions ...

at their posterior end, as well as two

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

near the front end of the cell, each being around one and a half times the cell's length. The anterior flagellum beats rapidly in front of the cell to propel its movement; the posterior flagellum remains attached to both the body and the substrate to provide stability while the organism glides. Two

cytoskeletal The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all Cell (biology), cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane ...

'roots' are attached to different points along the posterior flagellum's length, adding further support. After having settled on a substrate for some time, ''Neocercomonas'' may also deploy

pseudopodia A pseudopod or pseudopodium (: pseudopods or pseudopodia) is a temporary arm-like projection of a eukaryotic cell membrane that is emerged in the direction of movement. Filled with cytoplasm, pseudopodia primarily consist of actin filaments and ...

from the posterior end of the cell. The anterior flagellum will continue to move after pseudopodia have been extended, though usually in a more erratic manner. Within the cell there is an anterior nucleus, accompanied by numerous contractile

vacuole A vacuole () is a membrane-bound organelle which is present in Plant cell, plant and Fungus, fungal Cell (biology), cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water ...

s spread throughout the cell. The cytoplasm tends to be filled with small granules, some of which are refractive, making it difficult to observe the organelles. As part of their life cycle, cells may form round

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubb ...

s 5-13 micrometers in diameter. Some species (''N. dactyloptera'' and ''N. braziliensis'') have been noted as having a particularly strong anterior cytoskeleton, though it is unknown whether this is the case for all ''Neocercomona'' species. The species ''Neocercomonas grandis'' is the largest known member of the order Cercomonadida.

List of species

Source: * '' Neocercomonas braziliensis'' (Howe & Cavalier-Smith 2009) Cavalier-Smith & Karpov 2012 * '' Neocercomonas celer'' (Bass, Mylnikov & Cavalier-Smith 2009) Cavalier-Smith & Karpov 2012 * '' Neocercomonas clavideferens'' (Vickerman 2009) Cavalier-Smith & Karpov 2012 * '' Neocercomonas dactyloptera'' (Skuja 1939) Cavalier-Smith & Karpov 2012 * '' Neocercomonas effusa'' (Vickerman 2009) Cavalier-Smith & Karpov 2012 * '' Neocercomonas epiphylla'' Flues et al. 2018 * '' Neocercomonas gigantica'' (Mylnikov 2002) Cavalier-Smith & Karpov 2012 * '' Neocercomonas grandis'' (Maskell 1886) Cavalier-Smith & Karpov 2012 * '' Neocercomonas incurva'' (Skuja 1939) Cavalier-Smith & Karpov 2012 * '' Neocercomonas jendrali'' * '' Neocercomonas jutlandica'' Ekelund, Fredslund & Daugbjerg 2004 * '' Neocercomonas lata'' (Bass, Mylnikov & Cavalier-Smith 2009) Cavalier-Smith & Karpov 2012 * '' Neocercomonas magna'' (Howe & Cavalier-Smith 2009) Cavalier-Smith & Karpov 2012 * '' Neocercomonas nitschei'' Flues et al. 2018 * '' Neocercomonas parincurva'' (Howe & Cavalier-Smith 2009) Cavalier-Smith & Karpov 2012 * '' Neocercomonas pigra'' (Vickerman 2009) Cavalier-Smith & Karpov 2012 * '' Neocercomonas sphagnicola'' (Vickerman 2009) Cavalier-Smith & Karpov 2012 * '' Neocercomonas tuberculata'' Flues et al. 2018 * '' Neocercomonas vacuolata'' (Howe & Cavalier-Smith 2009) Cavalier-Smith & Karpov 2012

References

{{Taxonbar, from=Q25368011 Cercomonadida