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Loricifera
Loricifera
(from Latin, lorica, corselet (armour) + ferre, to bear) is a phylum of very small to microscopic marine cycloneuralian sediment-dwelling animals with 37 described species, in nine genera.[3][4][5] Aside from these described species, there are approximately 100 more that have been collected and not yet described.[4] Their sizes range from 100 µm to ca. 1 mm.[6] They are characterised by a protective outer case called a lorica and their habitat, which is in the spaces between marine gravel to which they attach themselves. The phylum was discovered in 1983 by Roberto Ramos, in Roscoff, France.[7] They are among the most recently discovered groups of Metazoans.[8] They attach themselves quite firmly to the substrate, and hence remained undiscovered for so long.[5] The first specimen was collected in the 1970s, and later described in 1983.[8] They are found at all depths, in different sediment types, and in all latitudes.[5]

Contents

1 Morphology 2 Taxonomic affinity 3 Evolutionary history 4 In anoxic environment 5 Species 6 References 7 Further reading

Morphology[edit] The animals have a head, mouth and digestive system as well as a lorica. The armor-like lorica consists of a protective external shell or case of encircling plicae. There is no circulatory system and no endocrine system. Many of the larvae are acoelomate, with some adults being pseudocoelomate, and some remaining acoelomate.[8] Development is generally direct, though there are so-called Higgins larvae, which differ from adults in several respects. The animals have two sexes as adults. Very complex and plastic life cycles of pliciloricids include also paedogenetic stages with different forms of parthenogenetic reproduction.[4] They are not known to be present in the fossil record. Taxonomic affinity[edit] 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.[7][8] However, mounting molecular evidence indicates a closer relationship with the Panarthropoda.[9]

Light microscopy image of Spinoloricus cinziae
Spinoloricus cinziae
adapted to an anoxic environment (stained with Rose Bengal). Scale bar is 50 μm.

Evolutionary history[edit] The loriciferans are believed to be miniaturized descendants of a larger organism perhaps resembling the Cambrian
Cambrian
fossil Sirilorica.[10] However, the fossil record of the microscopic non-mineralized group is (perhaps unsurprisingly) scarce, so it is difficult to trace out the phylum's evolutionary history in any detail. The 2017 discovery of Cambrian-era Eolorica deadwoodensis may shed some light on the group's history.[11] In anoxic environment[edit] Three species of Loricifera
Loricifera
have been found in the 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 oxygen-free environment. They are able to do this because they rely on hydrogenosomes (or similar organelles) instead of on mitochondria for energy.[12][13] 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.[14] 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/cm3), does not mix with the waters above.[14] 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.[14] 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.[14] Species[edit]

Nanaloricidae
Nanaloricidae
Kristensen, 1983

Nanaloricus Kristensen, 1983 Armorloricus Kristensen & Gad, 2004 Australoricus Heiner, Boesgaard & Kristensen, 2009 Phoeniciloricus Gad, 2004 Spinoloricus Heiner, 2007

Pliciloricidae
Pliciloricidae
Higgins & Kristensen, 1986

Pliciloricus
Pliciloricus
Higgins & Kristensen 1986 Rugiloricus Higgins & Kristensen, 1986 Titaniloricus
Titaniloricus
Gad, 2005

Urnaloricidae Heiner & Møbjerg Kristensen, 2009

Urnaloricus Heiner & Møbjerg Kristensen, 2009

Extinct taxa (unclassified)

Eolorica Harvey & Butterfield, 2017

References[edit]

^ Peel, John S.; Stein, Martin; Kristensen, Reinhardt Møbjerg (9 August 2013). "Life Cycle and Morphology of a Cambrian
Cambrian
Stem-Lineage Loriciferan". PLoS ONE. 8 (8): e73583. Bibcode:2013PLoSO...873583P. doi:10.1371/journal.pone.0073583. PMC 3749095 . PMID 23991198.  ^ Kristensen, R. M. (2009). "Loricifera, a new phylum with Aschelminthes characters from the meiobenthos". Journal of Zoological Systematics and Evolutionary Research. 21 (3): 163–80. doi:10.1111/j.1439-0469.1983.tb00285.x.  ^ Neves, Ricardo Cardoso; Reichert, Heinrich; Sørensen, Martin Vinther; Kristensen, Reinhardt Møbjerg (November 2016). "Systematics of phylum Loricifera: Identification keys of families, genera and species". Zoologischer Anzeiger. 265: 141–70. doi:10.1016/j.jcz.2016.06.002.  ^ a b c Gad, Gunnar (17 June 2005). "Successive reduction of the last instar larva of Loricifera, as evidenced by two new species of Pliciloricus
Pliciloricus
from the Great Meteor Seamount (Atlantic Ocean)". Zoologischer Anzeiger. 243 (4): 239–71. doi:10.1016/j.jcz.2004.09.001.  ^ a b c Ruppert, Edward E.; Fox, Richard S.; Barnes, Robert D., eds. (2004). Invertebrate Zoology (7th ed.). p. 776. ISBN 978-0-03-025982-1.  ^ Heiner, Iben. "Preliminary account of the Loriciferan fauna of the Faroe Bank (NE Atlantic)". Annales Societatis Scientiatum Færoensis Supplementum. 41: 213–9.  ^ a b Heiner, Iben; Kristensen, Reinhardt Møbjerg (18 March 2005). "Two new species of the genus Pliciloricus
Pliciloricus
(Loricifera, Pliciloricidae) from the Faroe Bank, North Atlantic". Zoologischer Anzeiger. 243 (3): 121–38. doi:10.1016/j.jcz.2004.05.002.  ^ a b c d Kristensen, R. M. (July 2002). "An Introduction to Loricifera, Cycliophora, and Micrognathozoa". Integrative and Comparative Biology. 42 (3): 641–51. doi:10.1093/icb/42.3.641. PMID 21708760.  ^ Yamasaki, Hiroshi; Fujimoto, Shinta; Miyazaki, Katsumi (2015-06-30). "Phylogenetic position of Loricifera
Loricifera
inferred from nearly complete 18S and 28S rRNA gene sequences". Zoological Letters. 1: 18. doi:10.1186/s40851-015-0017-0. ISSN 2056-306X.  ^ Peel, John S. (March 2010). "A Corset-Like Fossil from the Cambrian Sirius Passet Lagerstätte of North Greenland and Its Implications for Cycloneuralian Evolution". Journal of Paleontology. 84 (2): 332–40. doi:10.1666/09-102R.1. JSTOR 40605520.  ^ Harvey, Thomas H. P.; Butterfield, Nicholas J. (30 January 2017). "Exceptionally preserved Cambrian
Cambrian
loriciferans and the early animal invasion of the meiobenthos". Nature Ecology & Evolution. 1 (3): 0022. doi:10.1038/s41559-016-0022.  ^ Fang, Janet (8 April 2010). "Animals thrive without oxygen at sea bottom". Nature. 464 (7290): 825. doi:10.1038/464825b. PMID 20376121.  ^ Milius, Susan (April 9, 2010). "Briny deep basin may be home to animals thriving without oxygen". Science News.  ^ a b c d Mentel, Marek; Martin, William (6 April 2010). "Anaerobic animals from an ancient, anoxic ecological niche". BMC Biology. 8: 32. doi:10.1186/1741-7007-8-32. PMC 2859860 . PMID 20370917. 

Further reading[edit]

Wikispecies
Wikispecies
has information related to Loricifera

Bernhard, Joan M.; Morrison, Colin R.; Pape, Ellen; Beaudoin, David J.; Todaro, M. Antonio; Pachiadaki, Maria G.; Kormas, Konstantinos Ar.; Edgcomb, Virginia P. (2015). "Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins". BMC Biology. 13: 105. doi:10.1186/s12915-015-0213-6. PMC 4676161 . PMID 26652623.  Danovaro, Roberto; Dell'Anno, Antonio; Pusceddu, Antonio; Gambi, Cristina; Heiner, Iben; Kristensen, Reinhardt Mobjerg (2010). "The first metazoa living in permanently anoxic conditions". BMC Biology. 8: 30. doi:10.1186/1741-7007-8-30. PMC 2907586 . PMID 20370908.  Fox-Skelly, Jasmin (25 January 2017). "BBC Earth: There is one animal that seems to survive without oxygen". BBC News.  Heiner, Iben (2008). " Rugiloricus bacatus sp. nov. (Loricifera ‐Pliciloricidae) and a ghost‐larva with paedogenetic reproduction". Systematics and Biodiversity. 6 (2): 225–47. doi:10.1017/S147720000800265X.  Ramel, Gordon. "The Brush Heads (Phylum Loricifera)". [self-published source?] "Can animals thrive without oxygen?". Woods Hole Oceanographic Institution. January 28, 2016.  "Discovery of new fossil from half billion years ago sheds light on life on Earth". Science News. Retrieved 19 April 2017. 

v t e

Extant Animal
Animal
phyla

Domain Archaea Bacteria Eukaryota (Supergroup Plant Hacrobia Heterokont Alveolata Rhizaria Excavata Amoebozoa Opisthokonta

Animal Fungi)

A n i m a l i a

Porifera (sponges)

Diploblasts (Eumetazoa)

Ctenophora
Ctenophora
(comb jellies)

ParaHoxozoa

Placozoa
Placozoa
(Trichoplax)

Planulozoa

Cnidaria
Cnidaria
(jellyfish and relatives)

Bilateria (Triploblasts)

(see below↓)

Bilateria

Xenacoelomorpha

Xenoturbellida (Xenoturbella) Acoelomorpha

acoels nemertodermatids

N e p h r o z o a

Deuterostomia

Chordata

lancelets tunicates craniates / vertebrates

Ambulacraria

Echinodermata (starfish and relatives) Hemichordata

acorn worms pterobranchs

P r o t o s t o m i a

Ecdysozoa

Scalidophora

Kinorhyncha
Kinorhyncha
(mud dragons) Priapulida
Priapulida
(penis worms)

N+L+P

Nematoida

Nematoda (roundworms) Nematomorpha
Nematomorpha
(horsehair worms)

L+P

Loricifera

Panarthropoda

Arthropoda (arthropods) Tardigrada (waterbears) Onychophora
Onychophora
(velvet worms)

S p i r a l i a

Gnathifera¹

Chaetognatha
Chaetognatha
(arrow worms) Gnathostomulida (jaw worms) Micrognathozoa (Limnognathia) Syndermata

Rotifera Acanthocephala

Platytrochozoa

R+M

Mesozoa

Orthonectida Dicyemida
Dicyemida
or Rhombozoa

Rouphozoa¹

Platyhelminthes (flatworms) Gastrotricha (hairybacks)

Lophotrochozoa

Cycliophora (Symbion) Mollusca
Mollusca
(molluscs)

A+N

Annelida (ringed worms) Nemertea
Nemertea
(ribbon worms)

Lophophorata

Bryozoa

Entoprocta
Entoprocta
or Kamptozoa Ectoprocta (moss animals)

Brachiozoa

Brachiopoda (lamp shells) Phoronida (horseshoe worms)

Major groups within phyla

Sponges

Calcareous Hexactinellid Demosponge Homoscleromorpha

Cnidarians

Anthozoa
Anthozoa
inc. corals Medusozoa
Medusozoa
inc. jellyfish Myxozoa

Vertebrates

Jawless fish Cartilaginous fish Bony fish Amphibians Reptiles/Birds Mammals

Echinoderms

Sea lilies Asterozoa
Asterozoa
inc. starfish Echinozoa

Nematodes

Chromadorea Enoplea Secernentea

Arthropods

Chelicerates/Arachnids Myriapods Crustaceans Hexapods/Insects

Platyhelminths

Turbellaria Trematoda Monogenea Cestoda

Bryozoans

Phylactolaemata Stenolaemata Gymnolaemata

Annelids

Polychaetes Clitellata Echiura

Molluscs

Gastropods Cephalopods Bivalves Chitons Tusk shells

Phyla with ≥5000 extant species bolded See also Diploblasts Monoblastozoa (nomen dubium)

¹Platyzoa

Taxon identifiers

Wd: Q5183 ADW: Loricifera EoL: 1537 Fossilworks: 67129 iNaturalist: 151833 ITIS: 202425 NCBI: 310840 WoRMS: 101061

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