''Collodictyon'' is a genus of single-celled, omnivorous

eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacter ...

s belonging to the collodictyonids, also known as diphylleids. Due to their mix of cellular components, Collodictyonids do not belong to any well-known kingdom-level grouping of that

domain Domain may refer to: Mathematics *Domain of a function, the set of input values for which the (total) function is defined ** Domain of definition of a partial function ** Natural domain of a partial function **Domain of holomorphy of a function * ...

and this makes them distinctive from other families. Recent research places them in a new 'supergroup' together with rigifilids and ''Mantamonas'', with the so-far informal name '

CRuMs CRuMs is a proposed clade of microbial eukaryotes, whose name is an acronym of the following constituent groups: i) collodictyonids also known as diphylleids, ii) rigifilids Rigifilida is a clade of non- ciliate phagotrophic eukaryotes. It ...

Taxonomy and phylogeny

Three species are currently recognised in this

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

. The type species is ''

Collodictyon triciliatum ''Collodictyon'' is a genus of single-celled, omnivorous eukaryotes belonging to the collodictyonids, also known as diphylleids. Due to their mix of cellular components, Collodictyonids do not belong to any well-known kingdom-level grouping of th ...

''. A second species—''Collodictyon sparsevacuolatum''—named by Skuja is also recognised; this species is found in

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 incl ...

in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

and

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

. A third species ''Collodictyon sphaericum'' has been described but its description is in doubt. A fourth species—''Collodictyon hongkongense''—has been described by Skvortzow but this description is considered inadequate and this species is regarded as being of dubious validity. Along with the genus '' Diphylleia'', this organism appears to be only distantly related to the other eukaryotes. They share some morphological features with the species currently placed within

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- ...

due to the fact that the Collodictyon sulcus is similar because it also contains a supporting structure from left and right microtubular roots that line the entirety of the lips of the Sulcus. However this latter

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

is considered to be

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 ...

and in need of resolution (reorganisation into different groups). For this reason inclusion of this genus within the excavates may not assist in understanding its phylogenetic position. They also share similar features as Amoebozoa because the feeding groove of ''Collodictyon'' also form pseudopods at the base which have a related function to the pseudopods in Amoebozoa. The pseudopods in both Amoebozoa and ''Collodictyon'' are used in order to catch prey. Brugerolle has proposed a family, ''

Collodictyonidae Collodictyonidae (also Diphylleidae) is a group of aquatic, unicellular eukaryotic organisms with two to four terminal flagella. They feed by phagocytosis, ingesting other unicellular organisms like algae and bacteria. The most remarkable fact ...

'' for this genus and ''Diphylleia''. Another genus that is related to ''Collodictyon'' is '' Sulcomonas''. Scientists speculate that further study of ''Collodictyon'' may yield insights into the prehistoric beginnings of life hundreds of millions of years ago. Scientists from

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of ...

have been studying a particular type of ''Collodictyon'' found living in sludge in

Årungen Årungen is a lake in Norway in the municipality of Ås about south of Oslo which is notable for being an environment containing microscopic creatures called collodictyons. Norwegian scientists have been studying the creatures for two decades and ...

, a lake in the municipality of Ås in

. Kamran Shalchian-Tabrizi, the leader of the Microbial Evolution Research Group (MERG), has claimed that these organisms resemble the basal eukaryote. Collodictyonids were placed by Cavalier-Smith in Varisulca, but this grouping appears to be paraphyletic.

Description

The species in this genus range in size from 30 to 50

µm The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer ( American spelling), also commonly known as a micron, is a unit of length in the International System of Uni ...

in length, can grow broad

pseudopod A pseudopod or pseudopodium (plural: 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 filament ...

ia, and have four

flagella 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 fro ...

and a ventral feeding groove which divides the organism longitudinally called the Sulcus. They are devoid of cellulosic cell walls,

chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it i ...

s or stigmata. There are two to several contractile

vacuoles A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic mo ...

. The cell shape is variable but is mostly obovoid to ellipsoid. The lateral cell margins maybe somewhat angular leading to a broad, truncated rounded apex. This posterior margin narrows posteriorly and either bears 1-3 lobes or is simply broadly rounded. This margin is often pseudopodial. The nucleus typically lies in the posterior half of the cell. Collodictyon telophase constrict

The

mitochondria A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...

have tubular

cristae A crista (; plural cristae) is a fold in the inner membrane of a mitochondrion. The name is from the Latin for ''crest'' or ''plume'', and it gives the inner membrane its characteristic wrinkled shape, providing a large amount of surface area fo ...

Organelle In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' th ...

s called

dictyosome 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 insid ...

s are present and arranged in a

horseshoe A horseshoe is a fabricated product designed to protect a horse hoof from wear. Shoes are attached on the palmar surface (ground side) of the hooves, usually nailed through the insensitive hoof wall that is anatomically akin to the human ...

like shape. Members of this genus are known to reproduce asexually through

cell division Cell division is the process by which a parent cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukaryotes, there ...

. Whether

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 ...

occurs is currently unknown. ''Collodictyon triciliatum'' has four flagella connected to basal bodies, generally of equal length, as long as or slightly longer than the body of Collodictyon. Number one flagellum is connected to a dorsal root, while number two flagellum is connected to a ventral root. Number three and four flagella are on either side of these two and have dorsal roots.

Distribution

Originally ''Collodictyon triciliatum'' was described from the island of

Bombay Mumbai (, ; also known as Bombay — List of renamed Indian cities and states#Maharashtra, the official name until 1995) is the capital city of the Indian States and union territories of India, state of Maharashtra and the ''de facto'' fin ...

and later in central Europe. In Europe this species is found from

Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = '' Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , ...

. ''Collodictyon'' has also been reported in North America.

Feeding

The feeding habits of this organism have rarely been studied. Dag Klaveness reported that the creatures are "not sociable" and will cannibalize each other when food is scarce. ''Collodictyon'' will ingest freshwater algae and appears to be unable to survive on a diet of bacteria alone. Curiously the algae remain viable at least for a while after being engulfed. It is possible that the algae are "enslaved".

History

''Collodictyon triciliatum'' was originally named by H. J. Carter in 1865. Carter's original species description is as follows: In 1917, it was classified as being one of the "simplest and most primitive" type of '' Polymastigina''.

References