The glissomonads are a group of bacterivorous gliding flagellated protists that compose the order Glissomonadida, in the amoeboflagellate phylum Cercozoa. They comprise a vast, largely undescribed diversity of

soil Soil, also commonly referred to as earth or dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Debri ...

and freshwater 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 n ...

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

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

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 protoplasmic tail, that unlike most

s doesn't trail along the posterior flagellum. At least two genera, '' Orciraptor'' and '' Viridiraptor'', 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''. 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, deep flagellar groove, or pocket evident. Apart from '' Proleptomonas'', 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 com ...

, 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 Nucl ...

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 v ...

is usually seen in the cell's posterior area. The mitochondria have tubular cristae. There is a microbody attached to the posterior side of the nucleus, except in '' Proleptomonas''. 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 ...

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 e ...

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 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 Aerobics is a form of physical exercise that combines rhythmic aerobic exe ...

s that almost exclusively inhabit

or freshwater, where they feed on

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

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 th ...

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'' **Family Sandonidae ***'' Flectomonas'' ***'' Mollimonas'' ***'' Neoheteromita'' ***'' Sandona'' **Family Proleptomonadidae ***'' Proleptomonas'' *Suborder Pansomonadina **Family Viridiraptoridae ***'' Viridiraptor'' ***'' Orciraptor'' **Family Agitatidae ***'' Agitata'' **Family Acinetactidae ***'' Acinetactis'' **Family Aurigamonadidae ***'' Aurigamonas''

References

External links

{{taxonbar, from=Q21445946 Cercozoa orders