Tantulocarida#Body length

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In the Tantulocarida, animals do not ever present eyes.{{cite journal | pmc=122207 | year=2002 | last1=Oakley | first1=T. H. | last2=Cunningham | first2=C. W. | title=Molecular phylogenetic evidence for the independent evolutionary origin of an arthropod compound eye | journal=Proceedings of the National Academy of Sciences of the United States of America | volume=99 | issue=3 | pages=1426–1430 | doi=10.1073/pnas.032483599 | pmid=11818548 | bibcode=2002PNAS...99.1426O | doi-access=free }}

The tantulus larvae has a head with a ventral oral disc but no appendages, a six-segmented thorax with six pairs of legs, and a limbless abdomen consisting of one to six segments in addition to a telson.[https://books.google.com/books?id=x7vtCAAAQBAJ&dq=Tantulocarida+tantulus+larva+appendageless+abdomen+telson&pg=PA188 Multicellular Animals: Volume II: The Phylogenetic System of the Metazoa] The larvae also possesses a cuticular stylet on the cephalon through which they can push a rootlet system for extraction of nutrients from a host. The rootlet system itself is a direct extension of the gut.{{Cite journal |last=Petrunina |first=Alexandra S. |last2=Høeg |first2=Jens T. |last3=Kolbasov |first3=Gregory A. |date=December 2018 |title=Anatomy of the Tantulocarida: first results obtained using TEM and CLSM. Part I: tantulus larva |url=http://link.springer.com/10.1007/s13127-018-0376-4 |journal=Organisms Diversity & Evolution |language=en |volume=18 |issue=4 |pages=459–477 |doi=10.1007/s13127-018-0376-4 |issn=1439-6092|url-access=subscription }}

==={{anchor|Body size}}Body length===

Members of this subclass are minute – less than {{convert|0.3|mm|in}} in length and have a dramatic reduction in body form compared to other crustaceans, with an unsegmented, sac-like thorax and a much reduced abdomen.{{cite encyclopedia |url=http://www.accessscience.com/abstract.aspx?id=677750 |title=Tantulocarida |encyclopedia=AccessScience Encyclopedia |publisher=McGraw-Hill |accessdate=2016-09-10 |archive-url=https://web.archive.org/web/20110617082235/http://www.accessscience.com/abstract.aspx?id=677750 |archive-date=2011-06-17 |url-status=dead }} One tantulocarid species, Tantulacus dieteri, is the world's smallest arthropod, with a total body length of only {{convert|85|um}}.{{cite journal |title=Tantulocarida (Crustacea) from the Southern Ocean deep sea, and the description of three new species of Tantulacus Huys, Andersen & Kristensen, 1992|author=Inga Mohrbeck, Pedro Martínez Arbizu & Thomas Glatzel |journal=Systematic Parasitology |volume=77 |issue=2 |date=October 2010 |pages=131–151 |doi=10.1007/s11230-010-9260-0|pmid=20852984 |s2cid=7325858 }}

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The tantulocarid life cycle is unique among crustaceans. The tantulus larva transforms directly from a non-feeding (lecithotrophic) and free-swimming organism into a parasite without any instars. When entering the parasitic stage much of the body, such as the muscles, degenerates, even if the body itself becomes bigger. As a parasite it is permanently attached to its host, and after piercing its host's cuticle with an unpaired stylet, a rootlet system used to absorb nutrients enters through the hole and grow into the host’s tissue. The adult form develops inside the larva, and can become either a sac-like parthenogenetic female, or a fully developed free-living, non-feeding and sexually-reproducing male or female.{{cite journal |author=G. A. Boxshall & R. J. Lincoln |date=June 11, 1987 |title=The life cycle of the Tantulocrida (Crustacea) |journal=Philosophical Transactions of the Royal Society B |volume=315 |issue=1173 |pages=267–303 |jstor=2396610 |doi=10.1098/rstb.1987.0009|doi-access=free |bibcode=1987RSPTB.315..267B }}{{cite journal | url=https://www.sciencedirect.com/science/article/abs/pii/S0079661119301910 | doi=10.1016/j.pocean.2019.102190 | bibcode=2019PrOce.17802190P | title=Anatomy of the free tantulus larva (Crustacea: Tantulocarida) studied with confocal laser scanning microscopy: An extreme case of miniatuarisation in the Arthropoda | last1=Petrunina | first1=Alexandra S. | last2=Kolbasov | first2=Gregory A. | last3=Martinez Arbizu | first3=Pedro | journal=Progress in Oceanography | date=2019 | volume=178 | url-access=subscription }}[https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/108632/3/i0289-0003-9-4-875.pdf Itoitantulus misophricola gen. et sp. nov.: First Record of Tantulocarida (Crustacea: Maxillopoda) in the North Pacific Region]{{Cite journal |last1=Huys |first1=Rony |last2=Boxshall |first2=Geoffrey A. |last3=Lincoln |first3=Roger J. |date=1993 |title=The Tantulocaridan Life Cycle: the Circle Closed? |url=https://academic.oup.com/jcb/article/2328367/The |journal=Journal of Crustacean Biology |language=en |volume=13 |issue=3 |pages=432–442 |doi=10.2307/1548786 |jstor=1548786 |issn=0278-0372|url-access=subscription }}[https://www.gfbs-home.de/fileadmin/user_upload/ode2mods/ode/ode18/ode18_0459/article.pdf Anatomy of the Tantulocarida: first results obtained using TEM and CLSM. Part I: tantulus larva - GfBS] The eggs inside the parthenogenetic female are eventually released as fully developed tantulus larvae. The finding of what appears to be a benthic non-feeding nauplius larva suggests that eggs produced by sexual females hatch as nauplii instead of tantulus larvae. Both the parthenogenetic and sexual females are semelparous.[https://books.google.com/books?id=PPnZAwAAQBAJ&dq=%22The+sexual+cycle+involves+a+unique+type+of+metamorphosis%22&pg=PA122 Atlas of Crustacean Larvae]

Five families are recognised:{{BioRef|WoRMS|id=1083 |title=Tantulocarida |access-date=13 December 2022}}

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Basipodellidae Boxshall & Lincoln, 1983:{{cite web |author=Geoff Boxshall |title=Basipodellidae |editor=T. Chad Walter & Geoff Boxshall |work=World Copepoda database |publisher=World Register of Marine Species |url=http://www.marinespecies.org/aphia.php?p=taxdetails&id=136591 |accessdate=2016-09-10 |date=August 20, 2008}}

• Basipodella Becker, 1975
• Hypertantulus Ohtsuka & Boxshall, 1998
• Nipponotantulus Huys, Ohtsuka & Boxshall, 1994
• Polynyapodella Huys, Møberg & Kristensen, 1997
• Rimitantulus Huys & Conroy-Dalton, 1997
• Serratotantulus Savchenko & Kolbasov, 2009
• Stygotantulus Boxshall & Huys, 1989

Doryphallophoridae Huys, 1991:{{cite web |author=Geoff Boxshall |title=Doryphallophoridae |editor=T. Chad Walter & Geoff Boxshall |work=World Copepoda database |publisher=World Register of Marine Species |url=http://www.marinespecies.org/aphia.php?p=taxdetails&id=136593 |accessdate=2016-09-10 |date=August 20, 2008}}

• Doryphallophora Huys, 1990
• Paradoryphallophora Ohtsuka & Boxshall, 1998

Microdajidae Boxshall & Lincoln, 1987:{{cite web |author=Geoff Boxshall |title=Microdajidae |editor=T. Chad Walter & Geoff Boxshall |work=World Copepoda database |publisher=World Register of Marine Species |url=http://www.marinespecies.org/aphia.php?p=taxdetails&id=136594 |accessdate=2016-09-10 |date=August 20, 2008}}

• Microdajus Greve, 1965
• Xenalytus Huys, 1991

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Cumoniscidae Nierstrasz & Brender à Brandis, 1923 (formerly family Deoterthridae:{{BioRef|WoRMS|id=1063847 |title=Cumoniscidae Nierstrasz & Brender à Brandis, 1923 |access-date=13 December 2022}}

• Amphitantulus Boxshall & Vader, 1993
• Aphotocentor Huys, 1991
• Arcticotantulus Kornev, Tchesunov & Rybnikov, 2004
• Boreotantulus Huys & Boxshall, 1988
• Campyloxiphos Huys, 1991
• Coralliotantulus Huys, 1991
• Cumoniscus Bonnier, 1903
• Deoterthron Bradford & Hewitt, 1980
• Dicrotrichura Huys, 1989
• Itoitantulus Huys, Ohtsuka Boxshall & Itô, 1992
• Tantulacus Huys, Andersen & Kristensen, 1992

Onceroxenidae Huys, 1991:{{cite WoRMS |author=Geoff Boxshall |year=2012 |title=Onceroxenidae |db=Copepoda |id=136595 |accessdate=2016-09-10}}

• Onceroxenus Boxshall & Lincoln, 1987

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{{Arthropods}}

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Category:Maxillopoda

Category:Parasitic crustaceans

Category:Arthropod subclasses