Loricifera

{{Short description|Phylum of tiny marine invertebrates}} {{Technical|date=April 2022}} {{Use dmy dates|date=March 2020}} {{Automatic taxobox | fossil_range = {{Fossil range|Middle Cambrian|Recent|ref=<ref name=Peel-Stein-Kristensen-2013/>}}(total group) | image = Pliciloricus enigmatus.jpg | image_caption = ''Pliciloricus enigmaticus'', illustration by Carolyn Bartlett Gast | display_parents = 7 | taxon = Loricifera | authority = Kristensen, 1983<ref name=Kristensen-1983/> | subdivision_ranks = Families and genera | subdivision = *'''Nanaloricida''' **Nanaloricidae **Pliciloricidae **Urnaloricidae *†''Eolorica'' *''Tenuiloricus'' *†''Sirilorica'' ({{small|stem loriciferan}}) }}

'''Loricifera''' (from Latin, ''lorica'', corselet (armour) + ''ferre'', to bear), also known as '''corset animals''',<ref>[https://www.gbif-north-america.org/dataset/58fc397b-eee4-4138-8a5f-50f9dfb00216 NHMD Invertebrate Zoology Collection - GBIF North America Region]</ref> is a phylum of very small to microscopic marine scalidophoran sediment-dwelling animals with 43 described species<ref name="Neves-Kirstensen-Møbjerg-2021"/> and approximately 100 more that have been collected and not yet described.<ref name=Gad-2005/> Their sizes range from 100 μm to {{circa|1 mm}}.<ref name=Heiner-2005/>

They are characterised by a protective outer case called a lorica and their habitat is in the spaces between marine gravel to which they attach themselves. The phylum was discovered in 1983 by R.M. Kristensen, near Roscoff, France.<ref name=Heiner-Kristensen-2005/> They are among the most recently discovered groups of animals.<ref name=Kristensen-2002/> They attach themselves quite firmly to the substrate, and hence remained undiscovered for so long.<ref name=Ruppert-Fox-Barnes-2004/> The first specimen was collected in the 1970s, and described in 1983.<ref name=Kristensen-2002/> They are found at all depths, in different sediment types, and in all latitudes.<ref name=Ruppert-Fox-Barnes-2004/>

==Morphology== The animals have a head, mouth, and digestive system, as well as the lorica. The head (which contains the mouth and the brain), a trunk region surrounded by six plates that make up the 'lorica' or corselet and – in between these two – the neck region. Loricifera have a well developed brain and each scalid is individually connected to the brain by nerves. The armor-like lorica consists of a protective external shell or case of encircling plicae.<ref name=Heiner-Sorensen-Kristensen-2004/> There is no circulatory system and no endocrine system. Many of the larvae are acoelomate, with some adults being pseudocoelomate, and some remaining acoelomate.<ref name=Kristensen-2002/> Development is generally direct, though there are so-called Higgins larvae, which differ from adults in several respects. As adults, the animals are gonochoric. Very complex and plastic life cycles of pliciloricids include also paedogenetic stages with different forms of parthenogenetic reproduction. Most Loricifera are dioecious, meaning there are males and females. However, there are a few species known to be hermaphroditic, which means they contain both male and female reproductive organs.<ref>{{cite book |editor-last=Schmidt-Rhaesa|editor-first=Andreas|chapter=6. Loricifera|title=Handbook of Zoology: Gastrotricha, Cycloneuralia and Gnathifera|volume=1|last1=Bang-Berthelsen|first1=Iben Heiner|last2=Schmidt-Raesa|first2=Andreas|last3=Kristensen|first3=Reinhardt Møbjerg|date=2013|publisher=De Gruyter|isbn=978-3-11-021938-8|doi=10.1515/9783110272536.349|page=362}}</ref><ref name=Gad-2005/> Fossils have been dated to the late Cambrian.<ref name=SciDaily-2017-01/>

==Taxonomic affinity== {{See also|List of bilateral animal orders}} Morphological studies have traditionally placed the phylum in the Vinctiplicata with the Priapulida; this plus the Kinorhyncha constitutes the taxon Scalidophora. The three phyla share four characters in common – chitinous cuticle, rings of scalids on the introvert, flosculi, and two rings of introvert retracts.<ref name=Heiner-Kristensen-2005/><ref name=Kristensen-2002/> The monophyly of Scalidophora has been questioned: a 2015 study by Yamasaki and co-authors based on 18S and 28S rRNA gene sequences found Loricifera instead to be closely related to Nematoida and Panarthropoda,<ref name=Yamasaki-Fujimoto-Miyazaki-2015/> while a 2019 study by Laumer and co-authors sampling genomes from all animal phyla provisionally recovered Loricifera as the sister group to Nematoda.<ref>{{Cite journal |last1=Laumer |first1=Christopher E. |last2=Fernández |first2=Rosa |last3=Lemer |first3=Sarah |last4=Combosch|first4=David |last5=Kocot |first5=Kevin M. |last6=Riesgo |first6=Ana |last7=Andrade |first7=Sónia C. S. |last8=Sterrer |first8=Wolfgang |last9=Sørensen |first9=Martin V. |last10=Giribet |first10=Gonzalo |date=2019-07-10 |title=Revisiting metazoan phylogeny with genomic sampling of all phyla|journal=Proceedings of the Royal Society B: Biological Sciences |volume=286 |issue=1906 |article-number=20190831 |doi=10.1098/rspb.2019.0831 |issn=0962-8452 |pmc=6650721 |pmid=31288696}}</ref> However, a 2022 study by Howard and co-authors again recovered a monophyletic Scalidophora, but suggested that non-monophyly of Scalidophora should not be ruled out.<ref name="Howard et al. 2022">{{cite journal |last1=Howard |first1=Richard J. |last2=Giacomelli |first2=Mattia |last3=Lozano-Fernandez |first3=Jesus |last4=Edgecombe |first4=Gregory D. |last5=Fleming |first5=James F. |last6=Kristensen |first6=Reinhardt M. |last7=Ma |first7=Xiaoya |last8=Olesen |first8=Jørgen |last9=Sørensen |first9=Martin V. |last10=Thomsen |first10=Philip F. |last11=Wills |first11=Matthew A. |last12=Donoghue |first12=Philip C.J. |last13=Pisani |first13=Davide |display-authors=6 |date=2022-03-10 |df=dmy-all |title=The Ediacaran origin of Ecdysozoa: Integrating fossil and phylogenomic data |journal=Journal of the Geological Society |volume=179 |issue=4 |doi=10.1144/jgs2021-107 |bibcode=2022JGSoc.179..107H |s2cid=246494357 |issn=0016-7649|hdl=2445/186596 |hdl-access=free }}</ref> [[File:Spinoloricus.png|right|thumb|Light microscopy image of ''Spinoloricus cinziae'' adapted to an anoxic environment (stained with Rose Bengal). Scale bar is 50 μm.]]

==Evolutionary history== The loriciferans are believed to be miniaturized descendants of a larger organism, perhaps resembling the Cambrian fossil ''Sirilorica''.<ref name=Peel-2010/> However, the fossil record of the microscopic non-mineralized group is (perhaps unsurprisingly) scarce, so it is difficult to trace out the evolutionary history of the phylum in any detail.

The 2017 discovery of the Cambrian ''Eolorica deadwoodensis'' may shed some light on the group's history.<ref name=Harvey-Butterfield-2017/>

==In anoxic environments== Three species of Loricifera have been found in the oxygen-free sediments at the bottom of the L'Atalante basin in Mediterranean Sea, more than 3,000 meters down, the first multicellular organisms known to spend their entire lives in an anoxic environment. Initially, it was thought that they are able to do this because their mitochondria act like hydrogenosomes, allowing them to respire anaerobically.<ref name=Fang-2010-04-08-Nature/><ref name=Milius-2010-04-09-ScienceNews/> However, by 2021, questions arose as to whether or not they have mitochondria.<ref name=Snyder-2021-05-06-Axios/>

The newly reported animals complete their life cycle in the total absence of light and oxygen, and they are less than a millimetre in size.<ref name=Mentel-Martin-2010/> They were collected from a deep basin at the bottom of the Mediterranean Sea, where they inhabit a nearly salt-saturated brine that, because of its density (> 1.2 g/cm<sup>3</sup>), does not mix with the waters above.<ref name=Mentel-Martin-2010/> As a consequence, this environment is completely anoxic and, due to the activity of sulfate reducers, contains sulphide at a concentration of 2.9 mM.<ref name=Mentel-Martin-2010/> Despite such harsh conditions, this anoxic and sulphidic environment is teeming with microbial life, both chemosynthetic prokaryotes that are primary producers, and a broad diversity of eukaryotic heterotrophs at the next trophic level.<ref name=Mentel-Martin-2010/>

==Taxa==

{{Nested taxon list | Nanaloricidae | Kristensen, 1983 | {{linked genus list | Armorloricus | Kristensen & Gad, 2004 | Australoricus | Heiner, Boesgaard & Kristensen, 2009 | Culexiregiloricus | Gad, 2009 | Fafnirloricus | Fujimoto, 2020 | Nanaloricus | Kristensen, 1983 | Phoeniciloricus |Gad, 2004 | Scutiloricus | Neves, Kristensen & Møbjerg, 2021 | Spinoloricus | Heiner, 2007 }} | Pliciloricidae | Higgins & Kristensen, 1986 | {{linked genus list | Pliciloricus | Higgins & Kristensen 1986 | Rugiloricus | Higgins & Kristensen, 1986 | Scaberiloricus | Sørensen, Herranz, Neves, Kristensen & Garraffoni, 2023 | Titaniloricus | Gad, 2005 | Wataloricus | Fujimoto, Yamasaki, Kimura, Ohtsuka & Kristensen, 2020<ref name=Fujimoto-Yamasaki-etal-2020/> }} | Urnaloricidae | Heiner & Møbjerg Kristensen, 2009 | {{Linked genus list | Urnaloricus | Heiner & Møbjerg Kristensen, 2009 }} | ''incertae sedis''|| {{linked genus list | Patuloricus | Sørensen, Grzelak, Kristensen & Herranz, 2022 | Tenuiloricus | Neves & Kristensen, 2014 }} |Extinct taxa | (unclassified) |{{genus list |†''Eolorica''|Harvey & Butterfield, 2017 |†''Orstenoloricus''|Maas et al. 2009 |†''Sirilorica''?|Peel, 2010 }}

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==References== {{Reflist|25em|refs=

<ref name=Fang-2010-04-08-Nature> {{cite journal |last=Fang |first=Janet |date=8 April 2010 |title=Animals thrive without oxygen at sea bottom |journal=Nature |volume=464 |issue=7290 |page=825 |doi=10.1038/464825b |doi-access= |pmid=20376121 |bibcode=2010Natur.464..825F |s2cid=4340458 }} </ref>

<ref name=Fujimoto-Yamasaki-etal-2020> {{cite journal |last1=Fujimoto |first1=Shinta |last2=Yamasaki |first2=Hiroshi |last3=Kimura |first3=Taeko |last4=Ohtsuka |first4=Susumu |last5=Kristensen |first5=Reinhardt Møbjerg |date=14 November 2020 |title=A new genus and species of Loricifera (Nanaloricida: Pliciloricidae) from the deep waters of Japan |journal=Marine Biodiversity |volume=50 |issue=6 |page=103 |doi=10.1007/s12526-020-01130-3 |bibcode=2020MarBd..50..103F |s2cid=228866331 }} </ref>

<ref name=Gad-2005> {{cite journal |last=Gad |first=Gunnar |date=17 June 2005 |title=Successive reduction of the last instar larva of Loricifera, as evidenced by two new species of Pliciloricus from the Great Meteor Seamount (Atlantic Ocean) |journal=Zoologischer Anzeiger |volume=243 |issue=4 |pages=239–271 |doi=10.1016/j.jcz.2004.09.001 |bibcode=2005ZooAn.243..239G }} </ref>

<ref name=Harvey-Butterfield-2017> {{cite journal |last1=Harvey |first1=Thomas H.P. |last2=Butterfield |first2=Nicholas J. |date=30 January 2017 |title=Exceptionally preserved Cambrian loriciferans and the early animal invasion of the meiobenthos |journal=Nature Ecology and Evolution |volume=1 |issue=3 |page=0022 |pmid=28812727 |s2cid=22874770 |doi=10.1038/s41559-016-0022 |bibcode=2017NatEE...1...22H |hdl=2381/38658 |hdl-access=free |url=http://eprints.esc.cam.ac.uk/3810/2/s41559-016-0022-s1.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://eprints.esc.cam.ac.uk/3810/2/s41559-016-0022-s1.pdf |archive-date=2022-10-09 |url-status=live }} </ref>

<ref name=Heiner-2005> {{cite journal |last=Heiner |first=Iben |year=2005 |title=Preliminary account of the Loriciferan fauna of the Faroe Bank (NE Atlantic) |volume=41 |pages=213–219 |url=http://www.forskningsdatabasen.dk/en/catalog/2185942497 |journal=Annales Societatis Scientiatum Færoensis Supplementum |access-date=26 December 2016 |archive-url=https://web.archive.org/web/20161227055618/http://www.forskningsdatabasen.dk/en/catalog/2185942497 |archive-date=27 December 2016 }} </ref>

<ref name=Heiner-Kristensen-2005> {{cite journal |last1=Heiner |first1=Iben |last2=Kristensen |first2=R.M. |author2-link=Reinhardt Kristensen |date=18 March 2005 |title=Two new species of the genus ''Pliciloricus'' (Loricifera, Pliciloricidae) from the Faroe Bank, North Atlantic |journal=Zoologischer Anzeiger |volume=243 |issue=3 |pages=121–138 |doi=10.1016/j.jcz.2004.05.002 |bibcode=2005ZooAn.243..121H }} </ref>

<ref name=Heiner-Sorensen-Kristensen-2004> {{cite book |last1=Heiner |first1=Iben |last2=Sorensen |first2=Martin Vinther |last3=Kristensen |first3=Reinhardt Mobjerg |date=2004 |section=Loricifera (Girdle Wearers) |title=Grzimek's Animal Life Encyclopedia |volume=1 |pages=343–350 |publisher=Van Nostrand Reinhold Company |location=New York, NY }} </ref>

<ref name=Kristensen-1983> {{cite journal |last=Kristensen |first=R.M. |author-link=Reinhardt Kristensen |date=2009-04-27 |orig-date=September 1983 |title=Loricifera, a new phylum with Aschelminthes characters from the meiobenthos |journal=Zeitschrift für zoologische Systematik und Evolutionsforschung |volume=21 |issue=3 |pages=163–180 |doi=10.1111/j.1439-0469.1983.tb00285.x |issn=0947-5745 |language=en }} </ref>

<ref name=Kristensen-2002> {{cite journal |last=Kristensen |first=R.M. |author-link=Reinhardt Kristensen |date=July 2002 |title=An introduction to Loricifera, Cycliophora, and Micrognathozoa |journal=Integrative and Comparative Biology |volume=42 |issue=3 |pages=641–651 |doi=10.1093/icb/42.3.641 |doi-access=free |pmid=21708760 }} </ref>

<ref name=Mentel-Martin-2010> {{Cite journal |last1=Mentel |first1=Marek |last2=Martin |first2=William |date=6 April 2010 |title=Anaerobic animals from an ancient, anoxic ecological niche |journal=BMC Biology |volume=8 |page=32 |doi=10.1186/1741-7007-8-32 |pmc=2859860 |pmid=20370917 |doi-access=free }} </ref>

<ref name=Milius-2010-04-09-ScienceNews> {{cite news |last=Milius |first=Susan |date=9 April 2010 |title=Briny deep basin may be home to animals thriving without oxygen |website=Science News |url=https://www.sciencenews.org/article/briny-deep-basin-may-be-home-animals-thriving-without-oxygen }} </ref>

<ref name="Neves-Kirstensen-Møbjerg-2021"> {{cite journal |last1=Cardoso Neves |first1=Ricardo |last2=Kristensen |first2=Reinhardt Møbjerg |last3=Møbjerg |first3=Nadja |date=5 May 2021 |title=New records on the rich loriciferan fauna of Trezen ar Skoden (Roscoff, France): Description of two new species of Nanaloricus and the new genus Scutiloricus |journal=PLOS ONE |volume=16 |issue=5 |article-number=e0250403 |doi=10.1371/journal.pone.0250403 |pmid=33951070 |pmc=8099068 |bibcode=2021PLoSO..1650403N |id=id 10.1371 |doi-access=free }} </ref>

<ref name=Peel-2010> {{cite journal |last=Peel |first=John S. |date=March 2010 |title=A corset-like fossil from the Cambrian Sirius Passet lagerstätte of North Greenland and its implications for cycloneuralian evolution |journal=Journal of Paleontology |volume=84 |issue=2 |pages=332–340 |doi=10.1666/09-102R.1 |jstor=40605520 |bibcode=2010JPal...84..332P |s2cid=86256781 }} </ref>

<ref name=Peel-Stein-Kristensen-2013> {{cite journal |last1=Peel |first1=John S. |last2=Stein |first2=Martin |last3=Kristensen |first3=Reinhardt Møbjerg |date=9 August 2013 |title=Life Cycle and Morphology of a Cambrian Stem-Lineage Loriciferan |journal=PLoS ONE |volume=8 |issue=8 |article-number=e73583 |doi=10.1371/journal.pone.0073583 |doi-access=free |bibcode=2013PLoSO...873583P |pmc=3749095 |pmid=23991198 }} </ref>

<ref name=Ruppert-Fox-Barnes-2004> {{cite book |editor1-last=Ruppert |editor1-first=Edward E. |editor2-last=Fox |editor2-first=Richard S. |editor3-last=Barnes |editor3-first=Robert D. |year=2004 |title=Invertebrate Zoology |edition=7th |page=[https://archive.org/details/isbn_9780030259821/page/776 776] |isbn=978-0-03-025982-1 |url-access=registration |url=https://archive.org/details/isbn_9780030259821/page/776 }} </ref>

<ref name=SciDaily-2017-01> {{cite press release |title = Discovery of new fossil from half billion years ago sheds light on life on Earth: Scientists find 'unfossilizable' creature |date=January 2017 |website=Science Daily |url=https://www.sciencedaily.com/releases/2017/01/170130133409.htm }} </ref>

<ref name=Snyder-2021-05-06-Axios> {{cite news |last=Snyder |first=Alison |title=Something wondrous |date=6 May 2021 |website=Axios Science |url=https://www.axios.com/newsletters/axios-science-94589196-83ae-496f-b201-4948648402e0.html }} </ref>

<ref name=Yamasaki-Fujimoto-Miyazaki-2015> {{cite journal |last1=Yamasaki |first1=Hiroshi |last2=Fujimoto |first2=Shinta |last3=Miyazaki |first3=Katsumi |date=2015-06-30 |title=Phylogenetic position of Loricifera inferred from nearly complete 18S and 28S rRNA gene sequences |journal=Zoological Letters |volume=1 |page=18 |doi=10.1186/s40851-015-0017-0 |issn=2056-306X |pmc=4657359 |pmid=26605063 |doi-access=free }} </ref>

}}

==Further reading== *{{Wikispecies-inline|Loricifera}} * {{cite journal |last1=Bernhard |first1=Joan M. |last2=Morrison |first2=Colin R. |last3=Pape |first3=Ellen |last4=Beaudoin |first4=David J. |last5=Todaro |first5=M. Antonio |last6=Pachiadaki |first6=Maria G. |last7=Kormas |first7=Konstantinos Ar. |last8=Edgcomb |first8=Virginia P. |year=2015 |title=Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins |journal=BMC Biology |volume=13 |page=105 |doi=10.1186/s12915-015-0213-6 |pmid=26652623 |pmc=4676161 |doi-access=free }}

* {{cite journal |last1=Danovaro |first1=Roberto |last2=Dell'Anno |first2=Antonio |last3=Pusceddu |first3=Antonio |last4=Gambi |first4=Cristina |last5=Heiner |first5=Iben |last6=Kristensen |first6=Reinhardt Mobjerg |year=2010 |title=The first metazoa living in permanently anoxic conditions |journal=BMC Biology |volume=8 |page=30 |doi=10.1186/1741-7007-8-30 |pmid=20370908 |pmc=2907586 |doi-access=free }}

*{{cite news |last=Fox-Skelly |first=Jasmin |date=25 January 2017 |title=There is one animal that seems to survive without oxygen |department=BBC Earth |publisher=BBC |url=http://www.bbc.com/earth/story/20170125-there-is-one-animal-that-seems-to-survive-without-oxygen }}

*{{cite journal |last1=Heiner |first1=Iben |year=2008 |title=''Rugiloricus bacatus'' sp. nov. (Loricifera -Pliciloricidae) and a ghost-larva with paedogenetic reproduction |journal=Systematics and Biodiversity |volume=6 |issue=2 |pages=225–47 |doi=10.1017/S147720000800265X |bibcode=2008SyBio...6..225H |s2cid=85855659 }}

*{{cite web |last=Ramel |first=Gordon |title=The Brush Heads (Phylum Loricifera) |date=2 March 2020 |url=http://www.earthlife.net/inverts/loricifera.html }}{{self-published inline |date=December 2016}}

*{{cite press release |title=Can animals thrive without oxygen? |date=28 January 2016 |publisher=Woods Hole Oceanographic Institution |url=http://www.whoi.edu/news-release/can-animals-thrive-without-oxygen }}

*{{cite web |title=Discovery of new fossil from half billion years ago sheds light on life on Earth |website=Science News |url=https://www.sciencedaily.com/releases/2017/01/170130133409.htm |access-date=19 April 2017 }}

Category:Loricifera Category:Ecdysozoa phyla Category:Extant Cambrian first appearances Category:Taxa named by Reinhardt Møbjerg Kristensen