View source for 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 = [[Reinhardt Kristensen|Kristensen]], 1983<ref name=Kristensen-1983/>
| subdivision_ranks = [[Family (biology)|Families]] and [[Genus|genera]]
| subdivision = *'''[[Nanaloricida]]'''
**[[Nanaloricidae]]
**[[Pliciloricidae]]
**[[Urnaloricus|Urnaloricidae]]
*†''[[Eolorica]]''
*''[[Tenuiloricus]]''
*†''[[Sirilorica]]'' ({{small|stem loriciferan}})
}}

'''Loricifera''' (from [[Latin]], ''[[wikt:lorica|lorica]]'', corselet (armour) + ''ferre'', to bear) is a [[phylum]] of very small to microscopic marine [[cycloneuralia]]n sediment-dwelling animals with 43 described species<ref name="Neves-Kirstensen-Møbjerg-2021"/> and approximately 100&nbsp;more that have been collected and not yet described.<ref name=Gad-2005/> Their sizes range from 100&nbsp;μm to {{nowrap|''ca.''{{tsp}}1 mm}}.<ref name=Heiner-2005/>

They are characterised by a protective outer case called a [[Lorica (biology)|lorica]] and their habitat is in the spaces between marine gravel to which they attach themselves. The phylum was discovered in 1983 by [[Reinhardt Kristensen|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 larva]]e, which differ from adults in several respects. As adults, the animals are [[Gonochorism|gonochoric]]. Very complex and plastic [[Biological life cycle|life cycles]] of pliciloricids include also [[paedogenesis|paedogenetic]] stages with different forms of [[parthenogenesis|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 |last1=Schmidt-Rhaesa |first1=Andreas |title=Gastrotricha, Cycloneuralia, and Gnathifera |date=2013 |isbn=978-3-11-021938-8 |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 [[scalid]]s on the introvert, flosculi, and two rings of introvert retracts.<ref name=Heiner-Kristensen-2005/><ref name=Kristensen-2002/> However, despite a 2015 study showing the phylum's closest relatives being the [[Panarthropoda]],<ref name=Yamasaki-Fujimoto-Miyazaki-2015/> a 2022 study again showed that it belonged to the Scalidophora and told that further, more comprehensive genetic tests will be required to find its actual position in [[Ecdysozoa]].<ref name="Howard et al. 2022">Howard, R. J., Giacomelli, M., Lozano-Fernandez, J., Edgecombe, G. D., Fleming, J. F., Kristensen, R. M., Ma, X., Olesen, J., Sørensen, M. V., Thomsen, P. F., Wills, M. A., Donoghue, P. C., &amp; Pisani, D. (2022). The Ediacaran origin of ecdysozoa: Integrating fossil and Phylogenomic Data. ''Journal of the Geological Society'', '''179''' (4). https://doi.org/10.1144/jgs2021-107</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|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&nbsp;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 [[hydrogenosome]]s, 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 (>&nbsp;1.2&nbsp;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&nbsp;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 producer]]s, and a broad diversity of eukaryotic [[heterotroph]]s at the next [[trophic level]].<ref name=Mentel-Martin-2010/>

==Taxa==

{{Nested taxon list
| Nanaloricidae | [[Reinhardt Kristensen|Kristensen]], 1983 |
{{linked genus list
  | Nanaloricus | Kristensen, 1983
  | Armorloricus | Kristensen & Gad, 2004
  | Australoricus | Heiner, Boesgaard & Kristensen, 2009
  | Phoeniciloricus |Gad, 2004
  | Spinoloricus | Heiner, 2007
}}
| Pliciloricidae | Higgins & Kristensen, 1986 |
{{linked genus list
  | Pliciloricus | Higgins & Kristensen 1986
  | Rugiloricus | Higgins & Kristensen, 1986
  | Titaniloricus | Gad, 2005
  | Wataloricus | Fujimoto, Yamasaki, Kimura et al., 2020<ref name=Fujimoto-Yamasaki-etal-2020/>
}}
| Urnaloricidae | Heiner & Møbjerg Kristensen, 2009 |
{{Linked genus list
| Urnaloricus | Heiner & Møbjerg Kristensen, 2009
}}
|Extinct taxa | (unclassified) 
|{{genus list
|†''[[Eolorica]]''|Harvey & Butterfield, 2017
|†''[[Orstenoloricus]]''|Maas et al. 2009
|†''[[Sirilorica]]''?|Peel, 2010
}}

}}

==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 (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=[[Journal of Zoological Systematics and Evolutionary Research]]
 |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>

<!-- unused 
<ref name=Neves-Reichert-etal-2016>
{{cite journal
 |last1=Neves    |first1=Ricardo Cardoso     |last2=Reichert   |first2=Heinrich
 |last3=Sørensen |first3=Martin Vinther      |last4=Kristensen |first4=Reinhardt Møbjerg
 |date=November 2016
 |title=Systematics of phylum Loricifera: Identification keys of families, genera and species
 |journal=[[Zoologischer Anzeiger]]
 |volume=265  |pages=141–170
 |doi=10.1016/j.jcz.2016.06.002
}}
</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>

}} <!-- end "refs=" -->

==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
}}

{{Animalia}}
{{Life on Earth}}
{{Taxonbar|from1=Q5183|from2=Q10594261}}
{{Authority control}}

[[Category:Loricifera| ]]
[[Category:Ecdysozoa phyla]]
[[Category:Extant Cambrian first appearances]]