Collodictyon | |
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Collodictyon, with nucleus and four flagella (view from the rear) | |
Scientific classification (incertae sedis within Eukaryota) | |
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Genus: | Collodictyon Carter 1865 |
Type species | |
Collodictyon triciliatum Carter 1865 | |
Species | |
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Collodictyon is a genus of single-celled, omnivorous eukaryotes belonging to the collodictyonids, also known as diphylleids. [1] [2] 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. [3] [4] Recent research places them in a new 'supergroup' together with rigifilids and Mantamonas, with the so-far informal name 'CRuMs'. [5]
Phylogenetic position of Collodictyon relative to a few example organisms [1] |
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 but this description is considered inadequate and this species is regarded as being of dubious validity. [6]
Along with the genus Diphylleia , this organism appears to be only distantly related to the other eukaryotes. [1] [7] They share some morphological features with the species currently 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. [8] [9] However this latter clade is considered to be polyphyletic 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. [10] 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. [8]
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. [3] 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. [3] [11] Kamran Shalchian-Tabrizi, the leader of the Microbial Evolution Research Group (MERG), has claimed that these organisms resemble the basal eukaryote. [3]
Collodictyonids were placed by Cavalier-Smith in Varisulca, [12] but this grouping appears to be paraphyletic.
The species in this genus range in size from 30 to 50 μm in length, [3] can grow broad pseudopodia, and have four flagella [3] and a ventral feeding groove which divides the organism longitudinally called the Sulcus. [1] 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.
The mitochondria have tubular cristae.
Organelles called dictyosomes are present and arranged in a horseshoe like shape. [8]
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. [2] 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.
Originally Collodictyon triciliatum was described from the island of Bombay and later in central Europe. [13] [14] In Europe this species is found from Spain [15] to Norway. [1] Collodictyon has also been reported in North America. [6] [14] [16]
The feeding habits of this organism have rarely been studied.
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 [17]
Dag Klaveness reported that the creatures are "not sociable" and will cannibalize each other when food is scarce. [3] 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". [17]
Collodictyon triciliatum was originally named by H. J. Carter in 1865. [13] Carter's original species description is as follows:
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 [14]
In 1917, it was classified as being one of the "simplest and most primitive" type of Polymastigina . [18]
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word flagellate also describes a particular construction characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, several derivations of the term "flagellate" are more formally characterized.
A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and eukaryotic organisms. Most prokaryotes are unicellular and are classified into bacteria and archaea. Many eukaryotes are multicellular, but some are unicellular such as protozoa, unicellular algae, and unicellular fungi. Unicellular organisms are thought to be the oldest form of life, with early protocells possibly emerging 3.5–4.1 billion years ago.
Cryptomonas is the name-giving genus of the Cryptomonads established by German biologist Christian Gottfried Ehrenberg in 1831. The algae are common in freshwater habitats and brackish water worldwide and often form blooms in greater depths of lakes. The cells are usually brownish or greenish in color and are characteristic of having a slit-like furrow at the anterior. They are not known to produce any toxins. They are used to feed small zooplankton, which is the food source for small fish in fish farms. Many species of Cryptomonas can only be identified by DNA sequencing. Cryptomonas can be found in several marine ecosystems in Australia and South Korea.
Amoebozoa is a major taxonomic group containing about 2,400 described species of amoeboid protists, often possessing blunt, fingerlike, lobose pseudopods and tubular mitochondrial cristae. In traditional classification schemes, Amoebozoa is usually ranked as a phylum within either the kingdom Protista or the kingdom Protozoa. In the classification favored by the International Society of Protistologists, it is retained as an unranked "supergroup" within Eukaryota. Molecular genetic analysis supports Amoebozoa as a monophyletic clade. Modern studies of eukaryotic phylogenetic trees identify it as the sister group to Opisthokonta, another major clade which contains both fungi and animals as well as several other clades comprising some 300 species of unicellular eukaryotes. Amoebozoa and Opisthokonta are sometimes grouped together in a high-level taxon, named Amorphea. Amoebozoa includes many of the best-known amoeboid organisms, such as Chaos, Entamoeba, Pelomyxa and the genus Amoeba itself. Species of Amoebozoa may be either shelled (testate) or naked, and cells may possess flagella. Free-living species are common in both salt and freshwater as well as soil, moss and leaf litter. Some live as parasites or symbionts of other organisms, and some are known to cause disease in humans and other organisms.
Pelomyxa is a genus of giant flagellar amoebae, usually 500–800 μm but occasionally up to 5 mm in length, found in anaerobic or microaerobic bottom sediments of stagnant freshwater ponds or slow-moving streams.
Lobosa is a taxonomic group of amoebae in the phylum Amoebozoa. Most lobosans possess broad, bluntly rounded pseudopods, although one genus in the group, the recently discovered Sapocribrum, has slender and threadlike (filose) pseudopodia. In current classification schemes, Lobosa is a subphylum, composed mainly of amoebae that have lobose pseudopods but lack cilia or flagella.
Amorphea is a taxonomic supergroup that includes the basal Amoebozoa and Obazoa. That latter contains the Opisthokonta, which includes the Fungi, Animals and the Choanomonada, or Choanoflagellates. The taxonomic affinities of the members of this clade were originally described and proposed by Thomas Cavalier-Smith in 2002.
Chaos is a genus of single-celled amoeboid organisms in the family Amoebidae. The largest and most-known species, the so-called "giant amoeba", can reach lengths up to 5 mm, although most specimens fall between 1 and 3 mm.
Amoeba proteus is a large species of amoeba closely related to another genus of giant amoebae, Chaos. As such, the species is sometimes given the alternative scientific name Chaos diffluens.
Cafeteria roenbergensis is a small bacterivorous marine flagellate. It was discovered by Danish marine ecologist Tom Fenchel and named by him and taxonomist David J. Patterson in 1988. It is in one of three genera of bicosoecids, and the first discovered of two known Cafeteria species. Bicosoecids belong to a broad group, the stramenopiles, also known as heterokonts (Heterokonta) that includes photosynthetic groups such as diatoms, brown, and golden algae, and non-photosynthetic groups such as opalinids, actinophryid "heliozoans", and oomycetes. The species is found primarily in coastal waters where there are high concentrations of bacteria on which it grazes. Its voracious appetite plays a significant role in regulating bacteria populations.
Polychaos dubium is a freshwater amoeboid and one of the larger species of single-celled eukaryote. Like other amoebozoans, P. dubium moves by means of temporary projections called pseudopods. P. dubium reportedly has one of the largest genome size of any organism known, though the authors of a 2004 study suggest treating that measurement with caution.
Protozoan infections are parasitic diseases caused by organisms formerly classified in the kingdom Protozoa. These organisms are now classified in the supergroups Excavata, Amoebozoa, Harosa, and Archaeplastida. They are usually contracted by either an insect vector or by contact with an infected substance or surface.
Protozoa are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically, protozoans were regarded as "one-celled animals".
Phalansterium is a genus of single-celled flagellated organisms comprising several species, which form colonies. Phalansterium produces tetraspores.
The kathablepharids or katablepharids are a group of heterotrophic flagellates closely related to cryptomonads. First described by Heinrich Leonhards Skuja in 1939, kathablepharids were named after the genus Kathablepharis. This genus is corrected to Katablepharis under botanical nomenclature, but the original spelling is maintained under zoological nomenclature. They are single-celled protists with two anteriorly directed flagella, an anterior cytostome for ingesting eukaryotic prey, and a sheath that covers the cell membrane. They have extrusomes known as ejectisomes, as well as tubular mitochondrial cristae.
Gyromitus, is a biflagellated thaumatomonas cercozoan found in fresh water. Gyromitus was first discovered in 1939, but, there is still, to this day, very little research done on this organism. The body of the organism is covered in small siliceous oval scales. The two flagella extend from an anterior depression and are used for swimming, not gliding. On occasion this organism can form pseudopods where there are breaks in the silliceous armor, on the ventral side. There are two common species: Gyromitus cordiformis and Gyromitus disomatus.
Collodictyonidae 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 of this clade is its uncertain position in the tree of life.
An amoeba, often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopods. Amoebae do not form a single taxonomic group; instead, they are found in every major lineage of eukaryotic organisms. Amoeboid cells occur not only among the protozoa, but also in fungi, algae, and animals.
Varisulca was a proposed basal Podiate taxon. It encompassed several lineages of heterotrophic protists, most notably the ancyromonads (planomonads), collodictyonids (diphylleids), rigifilids and mantamonadids. Recent evidence suggests that the latter three are closely related to each other, forming a clade called CRuMs, but that this is unlikely to be specifically related to ancyromonads.
An amoeboflagellate is any eukaryotic organism capable of behaving as an amoeba and as a flagellate at some point during their life cycle. Amoeboflagellates present both pseudopodia and at least one flagellum, often simultaneously.
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...
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: CS1 maint: numeric names: authors list (link)(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 ...
(page 239 of original book; page 51 of pdf file) ... Collodictyon is "one of the simplest and most primitive of the Polymastigina"...