View source for Loxodes

{{Short description|Genus of protozoans}}
{{Automatic taxobox 
| image = Loxodes rostrum from page 267 of "American journal of physiology" (1898).jpg
| image_upright = 0.5
| image_caption = Illustration of ''Loxodes rostrum''
| display_parents = 4
| taxon = Loxodes
| authority = Ehrenberg, 1830
| subdivision_ranks = Species
| subdivision = Several, including:<ref name="WoRMS"/>
* ''[[Loxodes magnus]]''
* ''[[Loxodes penardi]]''
* ''[[Loxodes rostrum]]''
* ''[[Loxodes striatus]]''
}}

'''''Loxodes''''' is a genus  of [[karyorelictea]]n [[ciliate]]s, belonging to [[Loxodidae]].<ref name="WoRMS">{{Cite web|url=http://www.marinespecies.org/aphia.php?p=taxdetails&id=415581|title=WoRMS - World Register of Marine Species - Loxodes Ehrenberg, 1830|website=www.marinespecies.org|access-date=2017-02-15}}</ref> It is the only known karyorelictean ciliate that lives in freshwater habitats. The genus is known for its distinctive morphology, including a relatively large, flattened body and unique nuclear structures. It is also known to exhibit fascinating behaviours, such as geotaxis and light sensitivity.<ref name=":0">{{Cite journal |last1=Fenchel |first1=T. |last2=Finlay |first2=B. J. |date=1984 |title=Geotaxis in the ciliated protozoon Loxodes |journal=Journal of Experimental Biology |volume=110 |issue=1 |pages=17–33 |doi=10.1242/jeb.110.1.17 |bibcode=1984JExpB.110...17F }}</ref>

== Etymology ==
The term ''Loxodes'' derives from the [[ancient greek]] {{wikt-lang|grc|λοξός}} ({{grc-transl|λοξός}}), meaning "oblique, tilted".<ref>{{Cite book|title=Abrégé du dictionnaire grec français|last=Bailly|first=Anatole|date=1981-01-01|publisher=Hachette|isbn=978-2010035289|location=Paris|oclc=461974285}}</ref><ref>{{Cite web|url=http://www.tabularium.be/bailly/|title=Greek-french dictionary online|last=Bailly|first=Anatole|website=www.tabularium.be|access-date=2017-01-24}}</ref> According to Ehrenberg, who first described the genus, Loxodes means oblique and refers to the anterior margin of the ciliated lip of the organisms in this genus.<ref name="biodiversitylibrary.org">{{Cite book |last1=Ehrenberg |first1=Christian Gottfried |url=https://www.biodiversitylibrary.org/bibliography/143632 |title=Beiträge zur Kenntniss der Organisation der Infusorien und ihrer geographischen Verbreitung, besonders in Sibirien |last2=Ehrenberg |first2=Christian Gottfried |date=1830 |location=N.p |doi=10.5962/bhl.title.143632}}</ref>

== Type species ==
''Loxodes rostrum'' (Müller, 1773) Ehrenberg, 1830

== History of knowledge ==
''Kolpoda rostrum'' was the first loxodid discovered and described.<ref>{{Cite book |last1=Müller |first1=Otto Frederik |url=https://www.biodiversitylibrary.org/bibliography/46299 |title=Vermivm terrestrium et fluviatilium, seu, Animalium infusoriorum, helminthicorum et testaceorum, non marinorum, succincta historia |last2=Müller |first2=Otto Frederik |date=1773 |publisher=apud Heineck et Faber |location=et Lipsiae |doi=10.5962/bhl.title.46299}}</ref> The genus ''Loxodes'' was first proposed in 1830.<ref name="biodiversitylibrary.org"/> Ehrenberg moved ''Kolpoda rostrum'' into the genus ''Loxodes'' and set it as the type species. Research has explored the geotaxis of ''Loxodes'' species, while subsequent work has investigated their photosensitivity.<ref name=":0" /><ref name=":1">{{Cite journal |last1=Finlay |first1=B. J. |last2=Fenchel |first2=T. |date=1986 |title=Photosensitivity in the Ciliated Protozoon Loxodes: Pigment Granules, Absorption and Action Spectra, Blue Light Perception, and Ecological Significance |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1550-7408.1986.tb05658.x |journal=The Journal of Protozoology |language=en |volume=33 |issue=4 |pages=534–542 |doi=10.1111/j.1550-7408.1986.tb05658.x |issn=1550-7408|url-access=subscription }}</ref> Advances in molecular phylogeny have also provided deeper insights into the phylogeny of ''Loxodes'' .<ref name=":2">{{Cite journal |last1=Méndez-Sánchez |first1=Daniel |last2=Mayén-Estrada |first2=Rosaura |last3=Ramírez-Corona |first3=Fabiola |date=2022-02-01 |title=Evolutionary insights and brief review of Loxodes Ehrenberg, 1830 (Ciliophora, Karyorelictea, Loxodidae) with description of a new species from Mexico |url=https://linkinghub.elsevier.com/retrieve/pii/S0932473921000912 |journal=European Journal of Protistology |volume=82 |pages=125856 |doi=10.1016/j.ejop.2021.125856 |pmid=35026702 |issn=0932-4739|url-access=subscription }}</ref><ref name=":6">{{Cite journal |last1=Wang |first1=Lun |last2=Qu |first2=Zhishuai |last3=Li |first3=Song |last4=Hu |first4=Xiaozhong |date=2019-06-01 |title=Morphology and Molecular Phylogeny of Two Little-Known Species of Loxodes, L. kahli Dragesco & Njiné, 1971 and L. rostrum Müller, 1786 (Protist, Ciliophora, Karyorelictea) |url=https://link.springer.com/article/10.1007/s11802-019-3897-3 |journal=Journal of Ocean University of China |language=en |volume=18 |issue=3 |pages=643–653 |doi=10.1007/s11802-019-3897-3 |bibcode=2019JOUC...18..643W |issn=1993-5021|url-access=subscription }}</ref> Over time, new species and subspecies have been described, including the recent discovery of the new species ''L.'' ''tziscaensis'' in Mexico.<ref name=":2" /> Discoveries, such as that of ''L. rex'' in both Florida and Thailand, previously only observed in Africa, have challenged the understanding of the distribution of what were thought to be endemic species.<ref>{{Cite journal |last1=Esteban |first1=Genoveva F. |last2=Finlay |first2=Bland J. |last3=Charubhun |first3=Nuntaporn |last4=Charubhun |first4=Bawpit |date=2001 |title=On the geographic distribution of Loxodes rex (Protozoa, Ciliophora) and other alleged endemic species of ciliates |url=https://zslpublications.onlinelibrary.wiley.com/doi/10.1017/S0952836901001200 |journal=Journal of Zoology |language=en |volume=255 |issue=2 |pages=139–143 |doi=10.1017/S0952836901001200 |issn=1469-7998|url-access=subscription }}</ref><ref name=":7">{{Cite journal |last1=Hines |first1=Hunter N. |last2=McCarthy |first2=Peter J. |last3=Esteban |first3=Genoveva F. |date=2016-01-01 |title=The First Record for the Americas of Loxodes rex, a Flagship Ciliate with an Alleged Restricted Biogeography |journal=Microbial Ecology |language=en |volume=71 |issue=1 |pages=5–8 |doi=10.1007/s00248-015-0656-x |issn=1432-184X |pmc=4686552 |pmid=26687489|bibcode=2016MicEc..71....5H }}</ref>

== Habitat and ecology ==
''Loxodes'' lives in [[freshwater habitat]]s such as lakes and ponds, unlike other karyorelictean ciliates such as the other loxodid genus ''[[Remanella]]'', which live in brackish-water or marine habitats.<ref name="Fenchel1986">{{Cite journal |last1=Fenchel |first1=Tom |last2=Finlay |first2=Bland J. |date=1986-02-01 |title=The Structure and Function of Müller Vesicles in Loxodid Ciliates |journal=The Journal of Protozoology |language=en |volume=33 |issue=1 |pages=69–76 |doi=10.1111/j.1550-7408.1986.tb05560.x |issn=1550-7408}}</ref> They feed on bacteria and protists such as [[microalgae]].<ref>{{Cite book |last=H. |first=Lynn, Denis |title=The ciliated protozoa : characterization, classification, and guide to the literature |date=2008 |publisher=Springer |isbn=9781402082382 |location=New York |pages=343 |oclc=272311632}}</ref> It is [[Microaerophile|microaerobic]], preferring low concentrations of oxygen, below 5% atmospheric saturation. It can also survive extended periods in anoxic water, where oxygen is absent. Under such conditions, ''Loxodes'' is able to use [[nitrate]] instead of oxygen as an electron acceptor for [[Cellular respiration|respiration]].<ref>{{Cite book |last1=Fenchel |first1=Tom |url=https://archive.org/details/ecologyevolution00fenc |title=Ecology and evolution in anoxic worlds |last2=Finlay |first2=Bland J. |date=1995 |publisher=Oxford University Press |isbn=978-0198548386 |location=Oxford |pages=[https://archive.org/details/ecologyevolution00fenc/page/n141 129] |oclc=31046101 |url-access=limited}}</ref> [[Denitrification|Nitrate respiration]] is rare among eukaryotes, and ''Loxodes'' was the first eukaryote known to have this capability. ''Loxodes'' is also sensitive to light.

Members of ''Loxodes'' are found in freshwater environments.<ref name=":3">{{Cite journal |last1=Finlay |first1=B. J. |last2=Berninger |first2=U.-G. |date=1984 |title=Coexistence of Congeneric Ciliates (Karyorelictida: Loxodes) in Relation to Food Resources in Two Freshwater Lakes |url=https://www.jstor.org/stable/4668 |journal=Journal of Animal Ecology |volume=53 |issue=3 |pages=929–943 |doi=10.2307/4668 |jstor=4668 |bibcode=1984JAnEc..53..929F |issn=0021-8790|url-access=subscription }}</ref><ref name=":2" /> They typically inhabit aquatic microhabitats, including sediment and water columns, where they feed on small microorganisms. They live in the hypolimnion and range from areas of low O<sub>2</sub> concentration to anoxic conditions.<ref name=":3" /> They will move downwards toward lower O<sub>2</sub> concentrations, where it is hypothesized that there will be less competition for food.<ref name=":1" />

''Loxodes'' have been shown to be able to conduct nitrate reduction, allowing them to switch from aerobic respiration to nitrogen respiration in anoxic conditions.<ref>{{Cite book |last1=Fenchel |first1=Tom |url=https://academic.oup.com/book/54243 |title=Ecology and Evolution in Anoxic Worlds |last2=Finlay |first2=Bland J |date=1995-03-16 |publisher=Oxford University PressOxford |isbn=978-0-19-854838-6 |language=en |doi=10.1093/oso/9780198548386.001.0001}}</ref><ref name=":4">{{Cite journal |last=Finlay |first=B. J. |date=1985 |title=Nitrate respiration by Protozoa (Loxodes spp.) in the hypolimnetic nitrite maximum of a productive freshwater pond |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1365-2427.1985.tb00205.x |journal=Freshwater Biology |language=en |volume=15 |issue=3 |pages=333–346 |doi=10.1111/j.1365-2427.1985.tb00205.x |bibcode=1985FrBio..15..333F |issn=1365-2427|url-access=subscription }}</ref><ref>{{Cite journal |last1=Finlay |first1=B. J. |last2=Span |first2=A. S. W. |last3=Harman |first3=J. M. P. |date=May 1983 |title=Nitrate respiration in primitive eukaryotes |url=https://www.nature.com/articles/303333a0 |journal=Nature |language=en |volume=303 |issue=5915 |pages=333–336 |doi=10.1038/303333a0 |bibcode=1983Natur.303..333F |issn=1476-4687|url-access=subscription }}</ref> Experiments have shown that in oxygen-poor conditions ''Loxodes'' produce nitrate reductase and have increased electron transport chain activity, indicating a switch in terminal electron acceptors from oxygen to nitrate.<ref name=":4" /> Evidence of high nitrite concentration colocalized with ''Loxodes'' further supports this conclusion.<ref name=":4" />

It has been suggested that ''L. rostrum'' may form symbiotic relationships with the green algae ''Pediludiella daitoensis'' based on observations of ''L. rostrum'' containing many cells of this algal species.<ref>{{Cite journal |last1=Hoshina |first1=Ryo |last2=Hayakawa |first2=Masashi M. |last3=Kobayashi |first3=Mayumi |last4=Higuchi |first4=Rina |last5=Suzaki |first5=Toshinobu |date=2020-01-20 |title=Pediludiella daitoensis gen. et sp. nov. (Scenedesmaceae, Chlorophyceae), a large coccoid green alga isolated from a Loxodes ciliate |journal=Scientific Reports |language=en |volume=10 |issue=1 |pages=628 |doi=10.1038/s41598-020-57423-x |issn=2045-2322 |pmc=6971069 |pmid=31959793|bibcode=2020NatSR..10..628H }}</ref> Other researchers have reported observing a different unidentified alga within ''L. rostrum''.<ref name=":5">{{Cite journal |last1=Esteban |first1=Genoveva F. |last2=Fenchel |first2=Tom |last3=Finlay |first3=Bland J. |date=2010-12-01 |title=Mixotrophy in Ciliates |url=https://linkinghub.elsevier.com/retrieve/pii/S1434461010000738 |journal=Protist |volume=161 |issue=5 |pages=621–641 |doi=10.1016/j.protis.2010.08.002 |pmid=20970377 |issn=1434-4610|url-access=subscription }}</ref> However, the nature of the relationship with ''P. daitoensis'' has not been resolved, with more recent research questioning if ''L. rostrum'' is merely feeding on this alga or if this is indeed some form of endosymbiosis.<ref name=":2" /> It has been established that many freshwater ciliates can contain as many as hundreds of algae within them, but determining if these organisms are symbiotic or are temporarily retained food has been difficult due to the difficulties in culturing many ciliate species, including ''Loxodes.''<ref>{{Cite journal |last1=Hoshina |first1=Ryo |last2=Kusuoka |first2=Yasushi |date=2016-04-01 |title=DNA Analysis of Algal Endosymbionts of Ciliates Reveals the State of Algal Integration and the Surprising Specificity of the Symbiosis |url=https://linkinghub.elsevier.com/retrieve/pii/S1434461016000158 |journal=Protist |volume=167 |issue=2 |pages=174–184 |doi=10.1016/j.protis.2016.02.004 |pmid=27011222 |issn=1434-4610|url-access=subscription }}</ref> Due to the difficulties in culturing these species, the specimens observed with algal cells within them have solely been collected from the wild already containing algal cells. It is thus not fully understood where they encounter the algae or how long they maintain them. It has been speculated that the alga may be maintained as UV protection or an O<sub>2</sub> source in anoxic conditions.<ref name=":5" />

There is evidence that in some cases, more than one species of ''Loxodes'' coexist in the same habitat where they have the same distribution in the water column.<ref name=":3" /> Observations suggest that they partition food resources by size, where the larger ''Loxodes'' species consume food particles that are too large for the smaller ''Loxodes'' species.

At least one species of ''Loxodes'' has been shown to release toxic compounds from its extrusomes as a defence mechanism to avoid being eaten by predators.<ref>{{Cite journal |last=Buonanno |first=Federico |date=2005-01-01 |title=Variations in the efficiency of ciliate extrusomal toxins against a common ciliate predator, the catenulid Stenostomum Sphagnetorum |url=https://www.tandfonline.com/doi/abs/10.1080/11250000509356688 |journal=Italian Journal of Zoology |volume=72 |issue=4 |pages=293–295 |doi=10.1080/11250000509356688 |issn=1125-0003|url-access=subscription }}</ref> Research has shown that when ''L. stratus'' was consumed by the catenulid flatworm ''Stenostomum sphagnetorum'', it was regurgitated, and when it was extrusome deficient, it was regurgitated far less. Furthermore, extracted toxins from ''L. stratus'' extrusomes were shown to be lethal to ''S. sphagnetorum''.

== Description of organism ==

=== Morphology ===
''Loxodes'' are roughly oval and range in length from 70–657&nbsp;mm and are typically between 20–220&nbsp;mm in width.<ref name=":2" /><ref name=":6" /> They are laterally flattened with the right side ciliated with dikinetids in bipolar kineties in anywhere from 5 to 84 lateral rows depending on species.<ref name=":7" /><ref name=":2" /> There are only two bipolar kineties on their left side. There is an anterior oral aperture on the ventral side leading into a cytostome at the posterior of the aperture. The oral aperture forms a distinctive hook shape at the cell's anterior end, and the cell's posterior end is rounded. The oral aperture contains a single buccal kinety on the right and an inner and outer buccal kinety on the left. Additionally, there is a rectilinear intrabuccal kinety.<ref name=":2" /> ''Loxodes'' are transparent with yellow to brownish pigmentation.<ref name=":8">{{Cite journal |last1=Xu |first1=Yuan |last2=Pan |first2=Hongbo |last3=Miao |first3=Miao |last4=Hu |first4=Xiaozhong |last5=Al-Farraj |first5=Saleh A. |last6=Al-Rasheid |first6=Khaled A. S. |last7=Song |first7=Weibo |date=2015 |title=Morphology and Phylogeny of Two Species of Loxodes (Ciliophora, Karyorelictea), with Description of a New Subspecies, Loxodes striatus orientalis subsp. n. |url=https://onlinelibrary.wiley.com/doi/10.1111/jeu.12162 |journal=Journal of Eukaryotic Microbiology |language=en |volume=62 |issue=2 |pages=206–216 |doi=10.1111/jeu.12162 |pmid=25155338 |issn=1550-7408|url-access=subscription }}</ref>

=== Nuclear and cellular division ===
Like other Ciliates, ''Loxodes'' have macronuclei and micronuclei.<ref name=":9">{{Cite journal |last1=Yan |first1=Ying |last2=Rogers |first2=Anna J. |last3=Gao |first3=Feng |last4=Katz |first4=Laura A. |date=2017-10-01 |title=Unusual features of non-dividing somatic macronuclei in the ciliate class Karyorelictea |journal=European Journal of Protistology |series=Integrating the three dimensions of ciliate diversity: function, taxonomy, and genetics |volume=61 |issue=Pt B |pages=399–408 |doi=10.1016/j.ejop.2017.05.002 |issn=0932-4739 |pmc=5831164 |pmid=28673471}}</ref><ref name=":10">{{Citation |last=Raikov |first=Igor B. |title=Primitive Never-Dividing Macronuclei of Some Lower Ciliates1 |date=1985-01-01 |series=International Review of Cytology |volume=95 |pages=267–325 |editor-last=Bourne |editor-first=G. H. |url=https://linkinghub.elsevier.com/retrieve/pii/S0074769608605847 |access-date=2025-04-18 |publisher=Academic Press |doi=10.1016/s0074-7696(08)60584-7 |pmid=2414246 |isbn=978-0-12-364495-4 |editor2-last=Danielli |editor2-first=J. F. |editor3-last=Jeon |editor3-first=K. W.|url-access=subscription }}</ref> However, in ''Loxodes,'' the fates and transfer of these nuclei during asexual division are unique compared to other Ciliates. In the sister class, Heterotrichea, both the macronucleus and micronucleus divide during asexual cellular division. However, in Karyorelictea, the macronuclei do not divide and are transferred wholly to daughter cells. Different ''Loxodes'' species have different numbers and groupings of the two nuclei types. In species such as ''L. rostrum'', each cell has two macronuclei and one micronucleus. The two macronuclei are separated into the daughter cells when the cell divides. The micronucleus then goes through two rounds of mitosis. The two micronuclei from the second division differentiate into macronuclei. These divisions provide each daughter cell with a micronucleus and a second macronucleus. Similarly, species such as ''L. striatus'' have two pairs of nuclei, each pair made of one macronucleus and one micronucleus. When these cells divide, each micronucleus is divided into one micronucleus and one macronucleus. The remaining micronuclei then divide again to produce another micronucleus, thus providing each daughter cell with two new pairs of nuclei.<ref name=":9" /><ref name=":10" />

''Loxodes'' species may have as many as 181 macronuclei and 138 micronuclei in similar arrangements, all following similar patterns of nuclear division.<ref name=":2" /> The nuclei can be found in groups containing at least one macronucleus and one micronucleus but often include many more of each.<ref name=":10" /> The macronuclei can range from being equal in number to micronuclei to being twice as numerous. As in other Ciliates, the micronuclei are diploid; however, the macronuclei are paradiploid instead of the usual ampliploid state in other Ciliates.<ref name=":2" /> The macronuclei degrade over time and are lost after relatively few rounds of cellular division.<ref name=":9" /> For example, in ''L. magnus'', the macronucleus only lasts 3-7 divisions. It has been suggested that maintaining multiple macronuclei allows ''Loxodes'' to have higher numbers of transcripts that may be needed to have larger cells.<ref name=":9" />

''Loxode'' cells divide transversally, with the nuclei roughly evenly distributed between the daughter cells.<ref name=":10" /> Division timing is correlated with the number of macronuclei reaching a certain quantity within the cell.<ref name=":10" />

=== Geotaxis ===
Both genera in the family Loxodidae have organelles known as [[Müllerian vesicle|Müller]] (or Müllerian) vesicles, which are involved in the sensing of gravity. They are about 7&nbsp;μm across, and contain a membrane-covered mineral body known as a statolith. In ''Loxodes'', the statolith is mostly composed of [[barium]] salts, compared to ''Remanella'', where they are mostly strontium. Its structure and function resembles the [[statocyst]] of some animals.<ref name="Fenchel1986" /><ref>{{Cite journal |last1=Fenchel |first1=Tom |last2=Finlay |first2=Bland J. |date=1986 |title=The Structure and Function of Müller Vesicles in Loxodid Ciliates |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1550-7408.1986.tb05560.x |journal=The Journal of Protozoology |language=en |volume=33 |issue=1 |pages=69–76 |doi=10.1111/j.1550-7408.1986.tb05560.x |issn=1550-7408|url-access=subscription }}</ref> These vesicles are located on the dorsal rim on the left side of the cell in the cytoplasm and range in number from 2 to as many as 60.<ref name=":2" /> The vesicle is associated with basal granules, with one granule attached by cilia to the Müller vesicle like a stalk. It is thought that movement of the barium grain inside the vesicle is perceived by the cilia, allowing ''Loxodes'' to distinguish between up and down ([[geotaxis]] or [[gravitaxis]]), which it uses as a stimulus in addition to the oxygen concentration to orient itself in the water column. When oxygen concentrations are high, ''Loxodes'' tends to swim downwards, and vice versa.<ref>{{Cite journal|last1=Fenchel|first1=T.|last2=Finlay|first2=B. J.|date=1984-05-01|title=Geotaxis in the Ciliated Protozoon Loxodes|url=http://jeb.biologists.org/node/1054932.full|journal=Journal of Experimental Biology|language=en|volume=110|issue=1|pages=17–33|doi=10.1242/jeb.110.1.17|issn=0022-0949|doi-access=free|bibcode=1984JExpB.110...17F }}</ref>

=== Pigmentocysts ===
''Loxodes'' have also been shown to contain yellow-brown pigment granules that are thought to act as photoreceptors that perceive increased light.<ref name=":1" /> Research has linked light perception in ''Loxodes'' with the partial pressure of O<sub>2</sub>. ''Loxodes'' are thought to integrate light perception with geotaxis to position themselves in the water column.

The pigment granules have also been demonstrated to act as extrusomes that contain defence toxins.<ref name=":11">{{Cite journal |last1=Buonanno |first1=Federico |last2=Saltalamacchia |first2=Piero |last3=Miyake |first3=Akio |date=2005-04-29 |title=Defence function of pigmentocysts in the karyorelictid ciliate Loxodes striatus |url=https://linkinghub.elsevier.com/retrieve/pii/S093247390500012X |journal=European Journal of Protistology |volume=41 |issue=2 |pages=151–158 |doi=10.1016/j.ejop.2005.01.001 |issn=0932-4739|url-access=subscription }}</ref> In addition to the experiments with ''S. sphagnetorum'' discussed above, ''Loxodes'' have been shown to release the contents of the pigment granules when they are attacked by the predatory ciliate ''Dileptus''. Furthermore, it has been experimentally demonstrated that the contents of the granules damage the proboscis of ''Dileptus'' and can even be fatal.<ref name=":11" />

=== Genetic code ===
Recent research has shown that members of the Loxodidae family, of which ''Loxodes'' is one of two genera, use a variation of the standard genetic code where the stop codons have alternate uses.<ref>{{Cite journal |last1=Seah |first1=Brandon Kwee Boon |last2=Singh |first2=Aditi |last3=Swart |first3=Estienne Carl |date=2022 |title=Karyorelict ciliates use an ambiguous genetic code with context-dependent stop/sense codons |url=https://peercommunityjournal.org/articles/10.24072/pcjournal.141/ |journal=Peer Community Journal |language=fr |volume=2 |doi=10.24072/pcjournal.141 |issn=2804-3871}}</ref> UAA and UAG incorporate glutamine, and UGA is assigned to tryptophan or as a stop codon. This [[Ciliate, dasycladacean and hexamita nuclear code|variant code]] is also used by other ciliates.<ref>{{Cite journal |last1=Bezerra |first1=Ana R. |last2=Guimarães |first2=Ana R. |last3=Santos |first3=Manuel A. S. |date=2015-11-12 |title=Non-Standard Genetic Codes Define New Concepts for Protein Engineering |journal=Life |language=en |volume=5 |issue=4 |pages=1610–1628 |doi=10.3390/life5041610 |pmc=4695839 |pmid=26569314 |doi-access=free|bibcode=2015Life....5.1610B }}</ref>

== Phylogeny ==
The most recent phylogenetic work using 18S rRNA has confirmed that ''Loxodes'' form a clade separate from the sister genus of ''Remanella'' within the Loxodidae family .<ref name=":2" /> This work has also shown that ''Loxodes'' species cluster in correlation with nuclear organization, with the species that have two macronuclei and a single micronucleus clustered in one group and the rest clustered in another.<ref name=":2" /><gallery mode="packed" style="float:left" heights="180px">
File:Loxodes.png| Species of ''Loxodes'' containing significantly large green-colored algae. Scale bar: 10 μm.<ref name="Hoshina2020">{{cite journal |doi = 10.1038/s41598-020-57423-x|title = Pediludiella daitoensis gen. Et sp. Nov. (Scenedesmaceae, Chlorophyceae), a large coccoid green alga isolated from a Loxodes ciliate|year = 2020|last1 = Hoshina|first1 = Ryo|last2 = Hayakawa|first2 = Masashi M.|last3 = Kobayashi|first3 = Mayumi|last4 = Higuchi|first4 = Rina|last5 = Suzaki|first5 = Toshinobu|journal = Scientific Reports|volume = 10|issue = 1|page = 628|pmid = 31959793|pmc = 6971069|bibcode = 2020NatSR..10..628H}}</ref>
File:Müller vesicle.png| Detail showing a Müller vesicle (top arrow).<ref name="Hoshina2020" />
File:Инфузория Loxodes съедает длинную цианобактерию.webm| ''Loxodes'' ciliate eating a long [[cyanobacteria|cyanobacterium]] 
</gallery>
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== Cell cycle ==
Unlike other ciliates, the macronuclei of [[karyorelictea]]ns do not divide. This was first observed in ''Loxodes'' by [[Otto Bütschli]] in the 1870s.<ref name="Raikov1985">{{Cite book|last=Raikov|first=Igor B.|date=1985|title=Primitive never-dividing nuclei of some lower ciliates|series=International Review of Cytology|volume=95|pages=267–325|pmid=2414246|doi=10.1016/S0074-7696(08)60584-7|isbn=978-0-12-364495-4 }}</ref> It was later shown to be a distinctive feature of the class Karyorelictea in general. Experiments on ''Loxodes'' have shown that little or no [[DNA synthesis]] occurs in their macronuclei, and that the DNA content of a macronucleus is only slightly more than that of a [[diploid]] micronucleus ("paradiploid").<ref name="Raikov1985" />

== List of species ==

* ''Loxodes kahli'' Dragesco and Njiné, 1971
* ''Loxodes magnus'' Stokes, 1887
* ''Loxodes penardi'' Kahl, 1931
* ''Loxodes'' ''rex'' Dragesco, 1970
* ''Loxodes rostrum'' (Müller, 1773) Ehrenberg, 1830
* ''Loxodes striatus'' (Engelman, 1862) Penard, 1917
* ''Loxodes'' ''tziscaensis'' Mendez-Sanchez, Mayen-Estrada and Ramirez-Corona, 2022
* ''Loxodes'' ''vorax'' Stokes 1884

== Practical importance ==
Research into ''Loxodes'' has been important as a model organism for increasing scientific understanding of Karyorelictids.<ref name=":8" /> ''Loxodes''’ adaptation to freshwater makes them easier to culture, thus making them useful for studying the cellular features and behaviours of these Karyorelictids as well as other related Ciliates.<ref name=":6" /> Despite the comparative ease of culturing compared to other karyorelictids, ''Loxodes'' are still quite difficult to culture. Research continues to work to improve culturing, fixation, and staining techniques to aid future research.<ref>{{Cite journal |last1=Munyenyembe |first1=Ketty |last2=Timmons |first2=Caitlin |last3=Weiner |first3=Agnes K. M. |last4=Katz |first4=Laura A. |last5=Yan |first5=Ying |date=2021-10-01 |title=DAPI staining and DNA content estimation of nuclei in uncultivable microbial eukaryotes (Arcellinida and Ciliates) |journal=European Journal of Protistology |volume=81 |pages=125840 |doi=10.1016/j.ejop.2021.125840 |issn=0932-4739 |pmc=8699166 |pmid=34717075}}</ref><ref>{{Cite journal |last1=Seah |first1=Brandon Kwee Boon |last2=Emmerich |first2=Christiane |last3=Singh |first3=Aditi |last4=Swart |first4=Estienne Carl |date=2022-10-01 |title=Improved Methods for Bulk Cultivation and Fixation of Loxodes Ciliates for Fluorescence Microscopy |url=https://linkinghub.elsevier.com/retrieve/pii/S1434461022000505 |journal=Protist |volume=173 |issue=5 |pages=125905 |doi=10.1016/j.protis.2022.125905 |pmid=36027633 |issn=1434-4610|doi-access=free }}</ref> These advancements demonstrate the usefulness of ''Loxodes'' as a model organism for investigating new scientific methods for working with other organisms that are difficult to culture, such as other marine Ciliates.

== References ==
{{Reflist}}

== External links ==
* {{Wikispecies-inline}}

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[[Category:Karyorelictea]]
[[Category:Ciliate genera]]