The glissomonads are a group of

bacterivorous A bacterivore is an organism which obtains energy and nutrients primarily or entirely from the consumption of bacteria. The term is most commonly used to describe free-living, heterotrophic, microscopic organisms such as nematodes as well as many s ...

gliding Gliding is a recreational activity and competitive air sport in which pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. The word ''soaring'' is al ...

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their ...

d protists that compose the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Glissomonadida, in the amoeboflagellate phylum

Cercozoa Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major eu ...

. They comprise a vast, largely undescribed diversity of

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

and

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

organisms. They are the sister group to

cercomonad 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 ...

s; the two orders form a solid clade of gliding soil-dwelling flagellates called

Pediglissa Pediglissa () is a subclass of phagotrophic protists that inhabit soil or freshwater habitats. They were defined in 2018 according to phylogenetic analyses that showed a clade containing the orders Cercomonadida and Glissomonadida. They're the sis ...

Morphology

External appearance

Glissomonads are zooflagellates that aren't strongly

amoeboid An amoeba (; less commonly spelled ameba or amœba; plural ''am(o)ebas'' or ''am(o)ebae'' ), often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopo ...

, and are only covered by a

plasma membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (t ...

. Their common ancestor is thought to be a biflagellate, with a short

anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

flagellum A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

and a long posterior flagellum, that

glided Gliding is a recreational activity and competitive air sport in which pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. The word ''soaring'' is a ...

on the substrate by moving their posterior flagellum. In gliding descendants, the cell's posterior zone is usually rounded, giving the cell an ovoid shape. Some species may temporarily extend a

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

ic tail, that unlike most

s doesn't trail along the posterior flagellum. At least two genera, ''

Orciraptor ''Orciraptor'' is a genus of heterotrophic protists, containing the single species ''Orciraptor agilis''. It belongs to the family Viridiraptoridae, in the phylum Cercozoa. Morphology ''Orciraptor'' are unicellular organisms with two flagella: a ...

'' and ''

Viridiraptor ''Viridiraptor'' is a genus of heterotrophic protists, containing the single species ''Viridiraptor invadens''. It belongs to the family Viridiraptoridae, in the phylum Cercozoa. Morphology ''Viridiraptor'' are unicellular biflagellated organism ...

'', are capable of transforming into a distinctly amoeboid state attached to the surface. The group also includes descendants that have lost their gliding, mainly ''

Proleptomonas Monadofilosa is a grouping of Cercozoa. (It is sometimes considered one of three, the other two being Phytomyxa and Reticulofilosa.) These organisms are single-celled amoeboid protists. Classification Monadofilosa includes the testaceans, whi ...

''. This genus has another exception to the group: an anterior flagellum that is longer than the posterior, while the posterior is adherent to the cell and not used for gliding.

Internal structure

Most species lack obvious morphological specializations: there is no

cytopharynx A cytostome (from ''cyto-'', cell and ''stome-'', mouth) or cell mouth is a part of a cell specialized for phagocytosis, usually in the form of a microtubule-supported funnel or groove. Food is directed into the cytostome, and sealed into vacuole ...

, deep flagellar groove, or pocket evident. Apart from ''

'', which is exceptionally elongated and has a modified

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

, the

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucle ...

is usually anterior and attached to the kinetid (= flagellar apparatus) through well-developed fibrous roots. There are typically two posterior and one anterior microtubular centriolar roots. A

contractile vacuole A contractile vacuole (CV) is a sub-cellular structure (organelle) involved in osmoregulation. It is found predominantly in protists and in unicellular algae. It was previously known as pulsatile or pulsating vacuole. Overview The contractile va ...

is usually seen in the cell's posterior area. The

mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...

have tubular cristae. There is a microbody attached to the posterior side of the nucleus, except in ''

''. The

Golgi apparatus The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles ins ...

is usually seen associated with the nucleus, which doesn't happen in all

cercozoan Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead defined by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major euk ...

s. Both flagella have the same thickness and are simple, without a paraxonemal rod, hairs or scales, sometimes acronematic (= with an acroneme). Unlike in cercomonads, the ciliary transition zone has a dense transverse plate at the

distal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

end. The anterior flagellum beats like a cilium towards the left, as seen in cercomonads, and is sometimes reduced to a short stub without an axoneme.

Ecology and behavior

Glissomonads are

heterotrophic A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...

aerobic organism Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cell ...

s that almost exclusively inhabit

, where they feed on

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

Sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...

is unknown.

Cysts 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 bubble) ...

are present in the group, and have smooth walls.

Classification

The current classification is: *Suborder Allapsina **Family Allapsidae ***'' Allapsa'' ***'' Allantion'' ***'' Teretomonas'' *Suborder Sandonina **Family Bodomorphidae ***''

Bodomorpha Monadofilosa is a grouping of Cercozoa. (It is sometimes considered one of three, the other two being Phytomyxa and Reticulofilosa.) These organisms are single-celled amoeboid protists. Classification Monadofilosa includes the testaceans, whi ...

'' **Family Sandonidae ***'' Flectomonas'' ***'' Mollimonas'' ***'' Neoheteromita'' ***'' Sandona'' **Family

Proleptomonadidae Monadofilosa is a grouping of Cercozoa. (It is sometimes considered one of three, the other two being Phytomyxa and Reticulofilosa.) These organisms are single-celled amoeboid protists. Classification Monadofilosa includes the testaceans, which ...

***''

'' *Suborder Pansomonadina **Family

Viridiraptoridae Viridiraptoridae, previously known as clade X, is a clade of heterotrophic protists in the phylum Cercozoa. They're a family of glissomonads, a group containing a vast, mostly undescribed diversity of soil and freshwater organisms. Morphology and ...

***''

'' ***''

'' **Family Agitatidae ***'' Agitata'' **Family Acinetactidae ***'' Acinetactis'' **Family

Aurigamonadidae ''Aurigamonas'' is a genus of predatory protists of an unusual cell structure, with two flagella and numerous haptopodia. It is a monotypic genus containing the single species ''Aurigamonas solis''. It is the only genus of the family Aurigamonad ...

***'' Aurigamonas''

References

External links

{{taxonbar, from=Q21445946 Cercozoa orders