Collodictyon

{{Short description|Genus of protists}} {{Automatic taxobox | image = Collodictyon anterior view, showing sulcus, nucleus, blepharoplast, rhizoplast, and four flagella..jpg | image_caption = ''Collodictyon'', with nucleus and four flagella (view from the rear) | taxon = Collodictyon | authority = Carter 1865 | type_species = ''Collodictyon triciliatum'' | type_species_authority = Carter 1865 | subdivision_ranks = Other species | subdivision = * ''C. hongkongense'' Skvortzov 1968 * ''C. indicum'' Iyengar 1981 * ''C. sparsevacuolatum'' Skuja 1956 }}

'''''Collodictyon''''' is a genus of single-celled, omnivorous eukaryotes belonging to the collodictyonids, also known as diphylleids.<ref name="Zhao2012" /><ref name="Rhodes3" /> 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.<ref name=tws2Y24/><ref>Skvortzov, B. V. (1968). ''On a new species of the genus Collodictyon Carter, a colourless flagellata new to the Hongkong flora''. ''22'', 451–454.</ref> Recent research places them in a new "super-group" called CRuMs together with rigifilids and ''Mantamonas.''<ref name="Brown_2018">{{Cite journal|last=Brown|first=Matthew W|last2=Heiss|first2=Aaron A|last3=Kamikawa|first3=Ryoma|last4=Inagaki|first4=Yuji|last5=Yabuki|first5=Akinori|last6=Tice|first6=Alexander K|last7=Shiratori|first7=Takashi|last8=Ishida|first8=Ken-Ichiro|last9=Hashimoto|first9=Tetsuo|last10=Simpson|first10=Alastair|last11=Roger|first11=Andrew|date=2018-01-19|title=Phylogenomics Places Orphan Protistan Lineages in a Novel Eukaryotic Super-Group|journal=Genome Biology and Evolution|language=en|volume=10|issue=2|pages=427–433|doi=10.1093/gbe/evy014|issn=1759-6653|pmc=5793813|pmid=29360967}}</ref>

==Taxonomy and phylogeny== {{cladogram |caption=Phylogenetic position of ''Collodictyon'' relative to a few example organisms<ref name=Zhao2012/> |clades={{clade| style=font-size:75%;line-height:75% |label1=Eukaryotes |1={{clade |label1=Unikonta |1={{clade |label1=Amoebozoa |1=Amoeba 50px |2={{clade |label1=metazoa (Animals) |1=Humans 50px |2=Fungi 50px }} }} |2={{clade |label1="bikonta" |1={{clade |1={{clade |1=plants 50px |2=red algae 50px }} |2=''Paramecium'' 50px }} |2='''''Collodictyon''''' 50px }} }} }} }}

Four species are currently recognised in this genus. The type species is ''Collodictyon triciliatum''. A second species—''Collodictyon sparsevacuolatum''—named by Skuja is also recognised; this species is found in freshwater in the United States and Europe. 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.<ref name=Algaebase>{{cite web | author=MD Guiry in Guiry MD & Guiry GM 2012 | title=Collodictyon HJ Carter, 1865: 289 | work=AlgaeBase. World-wide electronic publication | publisher=National University of Ireland | location=Galway | url=http://www.algaebase.org/search/genus/detail/?genus_id=45305 | accessdate=28 April 2012}}</ref>

* ''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.<ref name=Zhao2012>{{Cite journal | doi = 10.1093/molbev/mss001 | issn = 0737-4038| last = Zhao | first = Sen |author2=Fabien Burki |author3=Jon Bråte |author4=Patrick Keeling | author5-link = Dag Klaveness (limnologist)|author5=Dag Klaveness |author6=Kamran Shalchian-Tabrizi | title = Collodictyon – an Ancient Lineage in the Tree of Eukaryotes | journal = Molecular Biology and Evolution | date = 2012-01-06 |pmid=22319147 | pmc=3351787 | volume=29 | issue=6 | pages=1557–68}}</ref><ref>[https://www.livescience.com/19955-ancient-protist-kingdom.html Live Science Strange, Organism Has Unique Roots in the Tree of Life], by Jennifer Welsh, 29 April 2012</ref> They share some morphological features with the species formerly placed within Excavata 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.<ref name="Brugerolle" /><ref>{{cite journal|vauthors=Heiss AA, Kolisko M, Ekelund F, Brown MW, Roger AJ, ((Simpson AGB)), Al E|date=2018-04-04|title=Combined morphological and phylogenomic re-examination of malawimonads, a critical taxon for inferring the evolutionary history of Eukaryotes|journal=Royal Society Open Science|accessdate=2021-11-01|url=https://royalsocietypublishing.org/doi/full/10.1098/rsos.171707}}</ref> However this latter clade is considered to be polyphyletic 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.<ref>Nishibe, Y., Kawabata, Z., & Nakano, S.-ichi. (2002, September 23). ''Grazing on microcystis aeruginosa by the heterotrophic flagellate Collodictyon Triciliatum in a hypertrophic pond''. Aquatic Microbial Ecology. Retrieved November 1, 2021, from https://www.int-res.com/abstracts/ame/v29/n2/p173-179/ .</ref> The pseudopods in both Amoebozoa and ''Collodictyon'' are used in order to catch prey.

Brugerolle has proposed a family, Collodictyonidae for this genus and ''Diphylleia''.<ref name="Brugerolle"/>

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.<ref name=tws2Y24/> Scientists from Norway have been studying a particular type of ''Collodictyon'' found living in sludge in Årungen, a lake in the municipality of Ås in Norway.<ref name=tws2Y24/><ref>{{cite web|url=https://www.apollon.uio.no/english/articles/2012/microorganism.html|title=Mankind's remotest relative|author=Yngve Vogt |date=23 April 2012|work=Apollon}} Original Norwegian press release with pictures of researchers.</ref> Kamran Shalchian-Tabrizi, the leader of the Microbial Evolution Research Group (MERG), has claimed that these organisms resemble the basal eukaryote.<ref name=tws2Y24>{{cite web|url=http://phys.org/news/2012-04-scientists-remotest-relative-lake-sludge.html|title=Scientists find 'man's remotest relative' in lake sludge|date=26 April 2012}}</ref>

Collodictyonids were placed by Cavalier-Smith in Varisulca,<ref>{{Cite journal|last=Cavalier-Smith|first=Thomas|last2=Chao|first2=Ema E.|last3=Lewis|first3=Rhodri|date=2016-06-01|title=187-gene phylogeny of protozoan phylum Amoebozoa reveals a new class (Cutosea) of deep-branching, ultrastructurally unique, enveloped marine Lobosa and clarifies amoeba evolution|journal=Molecular Phylogenetics and Evolution|volume=99|pages=275–296|doi=10.1016/j.ympev.2016.03.023|pmid=27001604|doi-access=free}}</ref> but this grouping appears to be paraphyletic.

==Description== The species in this genus range in size from 30 to 50 μm in length,<ref name=tws2Y24/> can grow broad pseudopodia, and have four flagella<ref name=tws2Y24/> and a ventral feeding groove which divides the organism longitudinally called the Sulcus.<ref name=Zhao2012/> They are devoid of cellulosic cell walls, chloroplasts 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. thumb|Joining of the Sulcus during Prophase The mitochondria have tubular cristae.thumb|right|250px|Sketch of ''Collodictyon''.

Organelles called dictyosomes are present and arranged in a horseshoe like shape.<ref name="Brugerolle">{{cite journal | last=Brugerolle | first=Guy |author2=Bricheux G|author3=Philippe H|author4=Coffea G | date=March 2002 | title=''Collodictyon triciliatum'' and ''Diphylleia rotans'' (=''Aulacomonas submarina'') form a new family of flagellates (''Collodictyonidae'') with tubular mitochondrial cristae that is phylogenetically distant from other flagellate groups | journal=Protist | volume=153 | issue=1 | pages=59–70 | pmid=12022276 | doi=10.1078/1434-4610-00083}}</ref>

Members of this genus are known to reproduce asexually through cell division. Whether sexual reproduction 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.<ref name="Rhodes3">{{cite book|last=Rhodes|first=Robert Clinton|title=Binary Fission in Collodictyon tricilliatum | url=https://archive.org/details/binaryfissioninc00rhodrich | quote= number of flagella is four (page 238 of original book; page 50 of the pdf file). Flagella are equal in length, as long as the body or possibly longer...|date=29 October 1917|publisher=University of California|location=Berkeley, California}}</ref> 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 and later in central Europe.<ref name=Carter1865/><ref name="Rhodes">{{cite book|last=Rhodes|first=Robert Clinton|title=Binary Fission in Collodictyon tricilliatum|url=https://archive.org/details/binaryfissioninc00rhodrich|date=29 October 1917|publisher=University of California|location=Berkeley, California}}</ref> In Europe this species is found from Spain<ref name="Sánchez">{{cite web |author1=Cambra Sánchez, J. |author2=Álvarez Cobelas, M. |author3=Aboal Sanjurjo, M. |year=1998 |title=Lista florística y bibliográfica de los clorófitos (Chlorophyta) de la Península Ibérica, Islas Baleares e Islas Canarias |url=https://www.researchgate.net/publication/236623210_Lista_floristica_y_bibliografica_de_los_clorofitos_Chlorophyta_de_la_Peninsula_Iberica_Islas_Baleares_e_Islas_Canarias |accessdate=12 Nov 2025 |publisher=Asociación Española de Limnología |page=9}}</ref> to Norway.<ref name=Zhao2012/> ''Collodictyon'' has also been reported in North America.<ref name=Algaebase/><ref name=Rhodes/><ref>{{Cite journal| doi = 10.2307/2421034| issn = 0003-0031| volume = 27| issue = 1| pages = 191–202| last = Lackey| first = James B.| title = The Plankton Algae and Protozoa of Two Tennessee Rivers| journal = American Midland Naturalist| date = 1942-01-01| jstor = 2421034}}</ref>

==Feeding== [[File:Collodictyon meets Pandorina.jpg|thumb|right|250px|Diagram of ''Collodictyon'' failed ingestion of a ''Pandorina''. The ''Pandorina'' escapes and the ''Collodictyon'' dies from water loss. Sketched by researcher Robert Clinton Rhodes; sketch appeared in print in 1917.]]

The feeding habits of this organism have rarely been studied.

{{Quote|In its feeding habits, Collodictyon is most interesting. When hungry, it can be distinguished from moribund stages in which all food is extruded by pseudopial projections from the lateral groove or sulcal region ... these pseudopodia ... function actively whenever the organism is seeking food. At these times when coming in contact with Protozoa or algae which it may use for food, they are wafted to the sulcal region by the flagella, or else Collodictyon aligns itself alongside of its prey with the pseudopodia in contact. ... Both the flagella and the pseudopodia appear sensitive to food stimulus ...|Robert Clinton Rhodes, 1917<ref name="Rhodes2">{{cite book|last=Rhodes|first=Robert Clinton|title=Binary Fission in Collodictyon tricilliatum|url=https://archive.org/details/binaryfissioninc00rhodrich|quote= (page 220 from original book; page 32 from the pdf) ... In its feeding habits, Collodictyon is most interesting. When hungry, it can be distinguished from moribund stages in which all food is extruded by pseudopial projections from the lateral groove or sulcal region ... these pseudopodia ... function actively whenever the organism is seeking food. At these times when coming in contact with Protozoa or algae which it may use for food, they are wafted to the sulcal region by the flagella, or else Collodictyon aligns itself alongside of its prey with the pseudopodia in contact. ... Both the flagella and the pseudopodia appear sensitive to food stimulus ...|date=29 October 1917|publisher=University of California|location=Berkeley, California}}</ref>}}

Dag Klaveness reported that the creatures are "not sociable" and will cannibalize each other when food is scarce.<ref name=tws2Y24/> ''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".<ref name="Rhodes2"/>

==History==

''Collodictyon triciliatum'' was originally named by H. J. Carter in 1865.<ref name=Carter1865>{{Cite journal |url=https://www.biodiversitylibrary.org/page/22251825#page/292/mode/1up |accessdate=11 February 2018 |issn= 0374-5481 |volume= 15 |issue=88 |pages= 277–293 |last= Carter |first= H.J. |title= XXXII.—On the fresh- and salt-water Rhizopoda of England and India |journal= Journal of Natural History |series= Series 3 |year=1865|doi=10.1080/00222936508681805 }}</ref> Carter's original species description is as follows:

{{Quote|Pyriform, straight, or slightly bent upon itself, bifid (two-lobed) at the small extremity, presenting at the larger one an indentation, from which spring three cilia. Structure transparent, cancellated, composed of globular cells, with a strongly marked, greenish granule here and there in the triangular spaces between them. Locomotive, swimming by means of the cilia; subpolymorphic, flexible, yielding, capable of assuming a globular form ... or one more or less modified by the body it may incept . . . ; enclosing crude material for nourishment in stomachal spaces, and ejecting the refuse, like Amoeba. Provided with a nucleus and contracting vesicles.|Carter, 1865<ref name="Rhodes"/>}}

In 1917, it was classified as being one of the "simplest and most primitive" type of ''Polymastigina''.<ref name="Rhodes4">{{cite book|last=Rhodes|first=Robert Clinton|title=Binary Fission in Collodictyon tricilliatum|url=https://archive.org/details/binaryfissioninc00rhodrich|quote= (page 239 of original book; page 51 of pdf file) ... Collodictyon is "one of the simplest and most primitive of the Polymastigina"...|date=29 October 1917|publisher=University of California|location=Berkeley, California}}</ref>

==See also== {{Commons category}} *''Collodictyon triciliatum'' at 400x in phase contrast by microuruguay 25 June 2011 {{youtube|AsY8s-HnTMQ}}

==References== {{Reflist}}

Category:CRuMs genera Category:Origin of life Category:Taxa named by Henry John Carter