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

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

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 and this makes them distinctive from other families. Recent research places them in a new " super-group" called

CRuMs CRuMs is a clade of microbial eukaryotes, whose name is an acronym of the following constituent groups: i) Diphylleids, ii) rigifilids and iii) mantamonads as sister of the Amorphea. A new CRuMs order Glissandrida was proposed in 2025 to pla ...

together with rigifilids and '' Mantamonas.''

Taxonomy and phylogeny

Four

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

are currently recognised in this

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

. The type species is '' Collodictyon triciliatum''. 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. The term excludes seawater and brackish water, but it does include non-salty mi ...

in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

and

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

. A third species ''Collodictyon sphaericum'' has been described but its description is in doubt and reclassified as ''Quadricilia rotundata'' (Skuja 1948) Vørs 1992. 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. * ''C. hongkongense'' Skvortzov 1968 * ''C. indicum'' Iyengar 1981 * ''C. sparsevacuolatum'' Skuja 1956 * ''C. triciliatum'' Carter 1865 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 formerly placed within

Excavata Excavata is an obsolete, extensive and diverse paraphyletic group of unicellular Eukaryota. The group was first suggested by Simpson and Patterson in 1999 and the name latinized and assigned a rank by Thomas Cavalier-Smith in 2002. It contains ...

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 In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

is considered to be

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

and in need of resolution (reorganisation into different groups). 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 Bacteria (; : bac ...

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 located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

have been studying a particular type of ''Collodictyon'' found living in sludge in Årungen, 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 Varisulca was a proposed basal Podiate taxon. It encompassed several lineages of heterotrophic protists, most notably the ancyromonads (planomonads), collodictyonids (diphylleids), rigifilids (''Rigifila'', ''Micronuclearia'') and mantamona ...

, but this grouping appears to be paraphyletic.

Description

The species in this genus range in size from 30 to 50 μm in length, can grow broad

pseudopod 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 ...

ia, and have four

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 ...

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, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

s or stigmata. There are two to several contractile vacuoles. 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 us ...

have tubular

cristae A crista (; : 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 for che ...

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

s called dictyosomes are present and arranged in a

horseshoe A horseshoe is a 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 toenail, altho ...

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

cell division Cell division is the process by which a parent cell (biology), 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 eukar ...

. 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 tha ...

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 ( ; its official name until 1995), is the capital city of the Indian States and union territories of India, state of Maharashtra. Mumbai is the financial centre, financial capital and the list of cities i ...

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

Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...

. ''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