Editing Protura

{{short description|Order of arthropods}}
{{Automatic taxobox
| image = Protura (Acerentomon species) micrograph.jpg
| image_caption = ''[[Acerentomon]]'' sp. under stereomicroscope
| display_parents = 2
| taxon = Protura
| authority = [[Filippo Silvestri|Silvestri]], 1907
| subdivision_ranks = Families
| subdivision_ref = <ref name="szeptycki"/>
| subdivision = 
Acerentomata
* [[Hesperentomidae]]
* [[Protentomidae]]
* [[Acerentomidae]]
Eosentomata
* [[Antelientomidae]]
* [[Eosentomidae]]
Sinentomata
* [[Fujientomidae]]
* [[Sinentomidae]]
}}

The '''Protura''', or '''proturans''', and sometimes nicknamed '''coneheads''',<ref name="NCSU_General_Entomology">{{cite web|url=http://www.cals.ncsu.edu/course/ent425/compendium/protura.html|title=Proturans / Coneheads|publisher=North Carolina State University College of Agriculture and Life Sciences|url-status=dead|archive-url=https://web.archive.org/web/20080515145323/http://www.cals.ncsu.edu/course/ent425/compendium/protura.html|archive-date=May 15, 2008|access-date=July 30, 2008}}</ref><ref name="BugGuide_Iowa_State_Protura">{{cite web|url=https://bugguide.net/node/view/258495|title=Order Protura - Coneheads|publisher=Iowa State University Department of Entomology|access-date=December 13, 2021}}</ref> are very small (0.6–1.5mm long), soil-dwelling animals, so inconspicuous they were not noticed until the 20th century. The Protura constitute an [[Order (biology)|order]] of [[Hexapoda|hexapods]] that were previously regarded as insects, and sometimes treated as a [[Class (biology)|class]] in their own right.<ref name="szeptycki"/><ref>{{cite web |url=http://www.eeb.uconn.edu/Courses/Eeb477/ |title=Insect phylogeny |author=Charles S. Henry |publisher=[[University of Connecticut]] |year=2005 |url-status=dead |archive-url=https://web.archive.org/web/20060905053555/http://www.eeb.uconn.edu/Courses/Eeb477/ |archive-date=2006-09-05 }}</ref><ref name=galli/>

Some evidence indicates the Protura are [[basal (phylogenetics)|basal]] to all other hexapods,<ref name="machida">{{cite web |year=2006 |title=Evidence from embryology for reconstructing the relationships of hexapod basal clades |author=Ryuichiro Machida |url=http://globiz.sachsen.de/snsd/publikationen/ArthropodSystematicsPhylogeny/ASP_64_1/ASP_64_1_Machida_95-104.pdf |url-status=dead |archive-url=https://web.archive.org/web/20070720033500/http://globiz.sachsen.de/snsd/publikationen/ArthropodSystematicsPhylogeny/ASP_64_1/ASP_64_1_Machida_95-104.pdf |archive-date=2007-07-20 }}</ref> although not all researchers consider them [[Hexapoda]], rendering the [[monophyly]] of Hexapoda unsettled.<ref>{{cite journal |title=Mitochondrial genomes suggest that hexapods and crustaceans are mutually paraphyletic |author=Charles E Cook, Qiaoyun Yue & Michael Akam |doi=10.1098/rspb.2004.3042 |journal=[[Proceedings of the Royal Society B]] |year=2005 |volume=272 |issue=1569 |pages=1295–1304 |pmid=16024395 |pmc=1564108}}</ref> Uniquely among hexapods, proturans show [[anamorphosis (biology)|anamorphic]] development, whereby [[body segment]]s are added during [[ecdysis|moults]].<ref name="Gullan">{{cite book |title=The insects: an outline of entomology |url=https://archive.org/details/the-insects-an-outline-of-entomology |author=P. J. Gullan & P. S. Cranston |publisher=[[Chapman and Hall]] |isbn=978-0-412-49360-7 |year=1994}}</ref>{{page number needed|date=January 2025}}

There are close to 800 species, described in seven [[family (biology)|families]]. Nearly 300 species are contained in a single [[genus]], ''[[Eosentomon]]''.<ref name="szeptycki">{{cite web |year=2007 |title=Catalogue of the World Protura |author=Andrzej Szeptycki |url=http://www.isez.pan.krakow.pl/journals/azc_i/pdf/50B(1)/01.pdf |archive-url=https://web.archive.org/web/20090205062910/http://www.isez.pan.krakow.pl/journals/azc_i/pdf/50B(1)/01.pdf |archive-date=5 February 2009}}</ref><ref name="pass">{{cite web |year=2011 |title=100 years of research on the Protura: many secrets still retained |author=G Pass & NU Szucsich |url=http://evolutionsbiologie.univie.ac.at/fileadmin/user_upload/dep_evolutionsbiologie/Pass/Pass_Szucsich_100_years_protura.pdf |access-date=2016-06-08 |archive-date=2020-06-18 |archive-url=https://web.archive.org/web/20200618023620/https://evolutionsbiologie.univie.ac.at/fileadmin/user_upload/dep_evolutionsbiologie/Pass/Pass_Szucsich_100_years_protura.pdf |url-status=dead }}</ref>

== Morphology ==
Proturans have no eyes, wings, or antennae, and, lacking [[pigment]]ation, are usually whitish or pale brown. The sensory function of the absent antennae is fulfilled by the first pair of the three pairs of five-segmented [[arthropod leg|legs]], which are held up, pointing forward, and bearing numerous tarsal [[sensillum|sensilla]] and sensory hairs. They ambulate using the four rear legs.<ref name="Florida">{{cite web |url=http://entomology.ifas.ufl.edu/creatures/misc/proturans.htm |title=Proturans |author=Christopher Tipping |year=2004 |publisher=[[University of Florida]]}}</ref> The head is conical, and bears two [[pseudoculus|pseudoculi]] with unknown function. The body is elongated and cylindrical,<ref name="CSIRO">{{cite web |url=http://www.ento.csiro.au/education/hexapods/protura.html |title=Protura |publisher=[[Commonwealth Scientific and Industrial Research Organisation|CSIRO]]}}</ref> with a post-anal [[telson]] at the end. The [[Insect mouthparts|mouthparts]] are [[Entognatha|entognathous]] (enclosed within the head capsule) and consist of narrow [[Mandible (insect)|mandibles]] and maxillae.<ref name="Gullan" /> There are no [[cercus|cerci]] at the end of the abdomen, which gives the group their name, from the [[Greek language|Greek]] ''proto-'' (meaning "first", in this case implying primitive), and ''ura'', meaning "tail".<ref name="Carolina">{{cite web |url=http://www.cals.ncsu.edu/course/ent425/compendium/protura.html |title=Protura |date=March 5, 2005 |author=John R. Meyer |publisher=[[North Carolina State University]] |url-status=dead |archive-url=https://web.archive.org/web/20080515145323/http://www.cals.ncsu.edu/course/ent425/compendium/protura.html |archive-date=May 15, 2008 }}</ref> The first three abdominal segments bear short limb-like [[appendage]]s,<ref name="Florida" /> called "styli".<ref name="Carolina" /> The first pair of styli is two-segmented, while the second and third pair are either two-segmented or unsegmented.<ref name="galli" /> The [[Sex organ|genitalia]] are internal and the genital opening lies between the eleventh segment and the telson of the adult.<ref name="Florida" /> During mating, the genitalia of both sexes are everted from an abdominal chamber.<ref>{{cite book|page=184|title=Insect Morphology and Phylogeny |url=https://archive.org/details/insectmorphology0000beut |first1=Rolf G. |last1=Beutel|first2= Frank |last2=Friedrich|first3= Si-Qin|last3=Ge|first4=Xing-Ke|last4=Yang|isbn= 978-3-11-026263-6|publisher=De Gruyter|year=2014}}</ref> Only the two families [[Eosentomidae]] and [[Sinentomidae]] possess a simple [[Invertebrate trachea|tracheal]] system with a pair of [[Spiracle (arthropods)|spiracle]]s on both the [[mesothorax]] and the [[metathorax]], while proturans in the remaining families lack these structures and perform [[gas exchange]] by [[diffusion]].<ref name="Florida" /><ref>{{cite journal | pmc=6523364 | year=2019 | last1=Carapelli | first1=A. | last2=Bu | first2=Y. | last3=Chen | first3=W. J. | last4=Nardi | first4=F. | last5=Leo | first5=C. | last6=Frati | first6=F. | last7=Luan | first7=Y. X. | title=Going Deeper into High and Low Phylogenetic Relationships of Protura | journal=Genes | volume=10 | issue=4 | page=292 | doi=10.3390/genes10040292 | pmid=30974866 | doi-access=free }}</ref><ref>{{Cite book |last1=Resh |first1=Vincent H. |url=https://books.google.com/books?id=Jk0Hym1yF0cC&dq=Meso-+and+metathorax+are+the+only+body+segments+that+primarily+have+one+pair+of+spiracles+each&pg=PA857 |title=Encyclopedia of Insects |last2=Cardé |first2=Ring T. |date=2009-07-22 |publisher=Academic Press |isbn=978-0-08-092090-0 |language=en}}</ref>

== Ecology ==
[[File:Protura from Durham, NC, USA..jpg|left|thumb|Proturan found in [[Durham, NC|Durham, United States]]]]

Proturans live chiefly in [[soil]], [[moss]]es, and [[leaf litter]]<ref name="Gullan"/> of moist temperate forests<ref name="Carolina"/> that are not too acidic.<ref name="Gordon">{{cite web |url=http://www.earthlife.net/insects/protura.html |title=Gordon's Protura Page |date=November 11, 2005}}</ref> They have also been found beneath rocks or under the [[Bark (botany)|bark]] of trees,<ref name="CSIRO"/> as well as in animal burrows.<ref name="Florida"/> They are generally restricted to the uppermost {{convert|0.1|m|abbr=on}},<ref name="Gordon"/> but have been found as deep as {{convert|0.25|m|abbr=on}}.<ref name="tolweb">{{cite web |publisher=Tree of Life Web Project |title=Protura |date=January 1, 2002 |url=http://tolweb.org/Protura/8203/2002.01.01 |archive-url=https://web.archive.org/web/20071001031740/http://tolweb.org/Protura/8203/2002.01.01 |archive-date=1 October 2007}}</ref> Although they are sometimes regarded as uncommon,<ref name="Carolina"/> proturans are most likely overlooked because of their small size,<ref name="CSIRO"/> as densities of over 90,000 individuals per square metre have been recorded.<ref>{{cite journal |author=J. Krauß & W. Funke |year=1999 |title=Extraordinary high density of Protura in a windfall area of young spruce plants |journal=[[Pedobiologia]] |volume=43 |pages=44–46|doi=10.1016/S0031-4056(24)00489-X |doi-access=free }}</ref>

The diet of proturans has not yet been sufficiently observed to be characterised. In laboratory culture, they may be fed [[Mycorrhiza|mycorrhizal fungi]], dead [[Acari|mites]] and pulverized, dried mushrooms;<ref name="Florida"/> they are believed to feed on decaying vegetable matter and fungi in the wild.<ref name="CSIRO"/><ref name="Carolina"/> The styliform mouthparts suggest the Protura may be fluid feeders, based on evidence that some species suck out the liquid contents of [[hypha|fungal hyphae]].<ref name="Gordon"/>

Proturan species which spend their lives near the soil surface generally produce one new generation of offspring each year; they also possess longer legs. Species living at deeper soil levels have shorter legs and tend to reproduce less seasonally. Some [[Insect migration|migratory]] proturan species move to deeper soil layers for the winter and ascend to shallower soil layers for the summer.<ref name="Gordon"/>

Proturans play a role in [[soil formation]] and composition by speeding decomposition, helping in the breakdown of leaf litter and recycling nutrients into the soil.<ref>{{Cite book|year= 1993| chapter=Diversity of soil arthropods in Canada: systematic and ecological problems |chapter-url=https://www.researchgate.net/publication/272335529 |pages=11–50|editor1=G.E. Ball |editor2=H.V. Danks |title= Systematics and Entomology: Diversity, Distribution, Adaptation and Application. Memoirs of the Entomological Society of Canada. 165|publisher = Entomological Society of Canada|author=Behan-Pelletier, V.M. }}</ref>

== Development ==
The [[Nymph (biology)|nymph]] has 8 abdominal segments plus the telson; the number of abdominal segments increases through [[ecdysis|moulting]] until the full adult complement of 12 abdominal segments is achieved. Further moults may occur, but do not add additional body segments;<ref name="Carolina"/> it is still not known whether the adults continue to moult throughout their lives.<ref name="Florida"/> [[Egg (biology)|Eggs]] have been observed in only a few species.<ref name="Florida"/>

In most proturan families, five [[Instar|developmental stages]] follow the egg stage: the prenymph hatches from the egg and has only weakly developed mouthparts and 8 abdominal segments; nymph I follows and has fully developed mouthparts; nymph II has 9 abdominal segments; "maturus junior" has 11 abdominal segments, and moults into the sexually mature adult.<ref name="Florida"/> Male individuals of the family [[Acerentomidae]] differ from this five-stage scheme, having an additional developmental stage, the [[Imago|preimago]], which has partially developed genitalia and appears between the "maturus junior" and the adult stage.<ref name="Florida"/>

== History ==
Proturans were first discovered in the early 20th century, when [[Filippo Silvestri]] and [[Antonio Berlese]] independently described the animals.<ref name="Gordon"/> The first species to be described was ''[[Acerentomon doderoi]]'', published in 1907 by Silvestri,<ref name="Florida"/> based on material found near [[Syracuse, New York]].<ref name="Carolina"/>

== References ==
{{Reflist|2|refs =
<ref name="galli">
{{Cite journal
| title = Genera of the Protura of the World: diagnosis, distribution, and key
| first1 = Loris| last1 = Galli
| first2 = Julia| last2 = Shrubovych
| first3 = Yun| last3 = Bu
| first4 = Matteo| last4 = Zinni
| journal = ZooKeys
| issue = 772
| pages = 1–45| doi = 10.3897/zookeys.772.24410
|pmc=6045683
| year = 2018
| pmid = 30018507| doi-access = free
}}</ref>
}}

== External links ==
{{Portal|Arthropods}}

* {{Wikispecies-inline|Protura}}
* {{Commons category-inline}}
* [http://entomology.ifas.ufl.edu/creatures/misc/proturans.htm Proturans] on the [[University of Florida]] / [[Institute of Food and Agricultural Sciences]] ''Featured Creatures'' website

{{Arthropods}}
{{Taxonbar|from=Q271631}}
{{Authority control}}

[[Category:Protura| ]]
[[Category:Arthropod orders]]
[[Category:Taxa described in 1907]]
[[Category:Taxa named by Filippo Silvestri]]