Editing Triops

{{Short description|Genus of small crustaceans}}
{{Lead too short|date=June 2024}}
{{Automatic taxobox
| name = ''Triops''
| fossil_range = {{fossilrange|Early Miocene|Present}}
| image = Triops longicaudatus2.jpg
| image_caption = ''[[Triops longicaudatus]]''
| taxon = Triops
| authority = [[Franz von Paula Schrank|Schrank]], 1803
| subdivision_ranks = [[Species]]
| subdivision = * ''[[Triops australiensis]]''
* ''[[Triops baeticus]]''
* ''[[Triops cancriformis]]''
* ''[[Triops emeritensis]]''
* ''[[Triops gadensis]]''
* ''[[Triops granarius]]''
* ''[[Triops longicaudatus]]''
* ''[[Triops mauritanicus]]''
* ''[[Triops newberryi]]''
* ''[[Triops vicentinus]]''
}}

'''''Triops''''', from [[Ancient Greek]] τρία (''tría''), meaning "three", and ὄψ (''óps''), meaning "face" or "eye", is a [[genus]] of small [[crustacean]]s in the order [[Notostraca]] (tadpole shrimp). The long-lasting resting eggs of several species of ''Triops'' are commonly sold in kits as pets. The animals hatch upon contact with fresh water. Most adult-stage ''Triops'' have a life expectancy of up to 90 days and can tolerate a [[pH]] range of 6 to 10. In nature, they often inhabit temporary pools.<ref name="Denton Belk 2007 414–417">{{cite book |editor1=Sol Felty Light |editor2=James T. Carlton |year=2007 |title=The Light and Smith manual: intertidal invertebrates from central California to Oregon |edition=4th |publisher=[[University of California Press]] |isbn=978-0-520-23939-5 |chapter=Branchiopoda |author=Denton Belk |pages=414–417 |chapter-url=https://books.google.com/books?id=64jgZ1CfmB8C&pg=PA417}}</ref>

== Relatives and fossil record ==
The genus ''Triops'' can be distinguished from the only other living genus of Notostraca, ''[[Lepidurus]]'', by the form of the [[telson]] (the end of its 'tail'), which bears only a pair of long, thin [[Caudal (anatomical term)|caudal]] extensions in ''Triops'', while ''Lepidurus'' also bears a central platelike process. Only 24 hours after hatching they already resemble miniature versions of the adult form.<ref name="Denton Belk 2007 414–417"/>

''Triops'' are sometimes called "[[living fossil]]s", since [[fossil]]s that have been attributed to this genus have been found in rocks hundreds of millions of years old.<ref>{{cite web |title=An Introduction to ''Triops'' |author1=Chip Hannum |author2=Stuart Halliday |name-list-style=amp |url=http://mytriops.com/articles/triops_intro.stm |publisher=MyTriops.com |access-date=October 4, 2010 |url-status=dead |archiveurl=https://web.archive.org/web/20100805092533/http://mytriops.com/articles/triops_intro.stm |archivedate=August 5, 2010 }}</ref> [[Molecular clock]] estimates suggest that ''Triops'' split from ''Lepidurus'' during the [[Triassic]] or [[Jurassic]], between 152.3–233.5 million years ago. The earliest diverging lineages of living ''Triops'' are found in areas that are part of the former supercontinent [[Gondwana]], suggesting ''Triops'' originated in Gondwana.<ref>{{Cite journal|last1=Korn|first1=Michael|last2=Rabet|first2=Nicolas|last3=Ghate|first3=Hemant V.|last4=Marrone|first4=Federico|last5=Hundsdoerfer|first5=Anna K.|date=December 2013|title=Molecular phylogeny of the Notostraca|url=https://linkinghub.elsevier.com/retrieve/pii/S105579031300314X|journal=Molecular Phylogenetics and Evolution|language=en|volume=69|issue=3|pages=1159–1171|doi=10.1016/j.ympev.2013.08.006|pmid=23973879|bibcode=2013MolPE..69.1159K |hdl=10447/83883|hdl-access=free}}</ref> However, the earliest known definitive fossil attributed to ''Triops'' is known from the [[Early Miocene]] of [[Japan]],<ref>{{cite journal|author1=Gengo, T.|author2=Yuji, T.|author3=Katsuhiko, I.|year=2010|title=Three-dimensionally preserved ''Triops'' sp. (Crustacea, Branchiopoda) from a Miocene volcaniclastic sediment in Ota City, Gunma Prefecture, central Japan|journal=Bulletin of the Gunma Museum of Natural History|volume=14|pages=95–98|url=https://www.gmnh.pref.gunma.jp/wp-content/uploads/bulletin14_11.pdf}}</ref> and careful analysis of the pre-[[Cenozoic]] fossils suggest that they do not belong to ''Triops'', with some not even belonging to [[notostraca]]ns.<ref>{{Cite journal|last1=Wagner|first1=Philipp|last2=Haug|first2=Joachim T.|last3=Sell|first3=Jürgen|last4=Haug|first4=Carolin|date=December 2017|title=Ontogenetic sequence comparison of extant and fossil tadpole shrimps: no support for the "living fossil" concept|url=http://link.springer.com/10.1007/s12542-017-0370-8|journal=PalZ|language=en|volume=91|issue=4|pages=463–472|doi=10.1007/s12542-017-0370-8|bibcode=2017PalZ...91..463W |s2cid=90922613|issn=0031-0220|url-access=subscription}}</ref><ref name=Geyer2024/>

The [[Upper Carboniferous]] genus ''Lynceites'' was once thought to represent ''Triops'',<ref>{{Cite journal|last1=Van Damme|first1=Kay|last2=Kotov|first2=Alexey A.|date=December 2016|title=The fossil record of the Cladocera (Crustacea: Branchiopoda): Evidence and hypotheses|url=https://linkinghub.elsevier.com/retrieve/pii/S0012825216303701|journal=Earth-Science Reviews|language=en|volume=163|pages=162–189|doi=10.1016/j.earscirev.2016.10.009|bibcode=2016ESRv..163..162V|url-access=subscription}}</ref> but subsequent analysis consider it as a separate genus.<ref name=Geyer2024/> Fossils from the [[Lower Triassic]] of [[France]] and [[Upper Triassic]] of [[Germany]] have been previously attributed to ''[[Triops cancriformis]]'', with some even described as specimens of the subspecies ''T. c. minor'', but later research reassigned all of these Triassic specimens to different extinct taxa of uncertain [[Family (biology)|taxonomic family]]: the [[notostraca]]n ''Apudites antiquus'' and the [[diplostraca]]ns ''Olesenocaris galli'' and ''Grauvogelocaris alsatica''.<ref name=Geyer2024>{{Cite journal |last=Geyer |first=Gerd |last2=Hegna |first2=Thomas A. |last3=Kelber |first3=Klaus-Peter |date=2024 |title=The end of the ‘living fossil’ tale? A new look at Triassic specimens assigned to the tadpole shrimp Triops cancriformis (Notostraca) and associated phyllopods from the Vosges region (eastern France) |url=https://onlinelibrary.wiley.com/doi/full/10.1002/spp2.1589 |journal=Papers in Palaeontology |volume=10 |issue=5 |at=e1589 |doi=10.1002/spp2.1589 |doi-access=free |url-access=subscription }}</ref> The putative [[Lower Permian]] subspecies of ''Triops cancriformis'' from France has also been redescribed as a separate [[notostraca]]n taxon, ''Heidiops permiensis''.<ref>{{Cite journal |last=Werneburg |first=R. |last2=Schneider |first2=J. W. |date=2023 |title=New branchiopod crustaceans from the late Carboniferous and early Permian of the Thuringian Forest Basin, Germany, with a review of Permian notostracans from the Lodève basin, France |url=https://www.researchgate.net/publication/365839036_New_branchiopod_crustaceans_from_the_late_Carboniferous_and_early_Permian_of_the_Thuringian_Forest_Basin_Germany_with_a_review_of_Permian_notostracans_from_the_Lodeve_basin_France |journal=Semana |volume=37 |pages=57–103}}</ref> Two putative fossil species of ''Triops'', ''T. hanshanensis'' and ''T. bashuensis'', known from the [[Middle Jurassic]] of [[China]] likely belong to separate genera with features unknown in any extant or extinct species of [[notostraca]]ns.<ref name=Geyer2024/>

''Triops'' can be found in Africa, Australia, Asia, South America, Europe (including Great Britain<ref>{{cite episode| series=Autumnwatch | series-link=Autumnwatch | station=[[BBC Two]] | date=5 November 2015 }}</ref>), and in some parts of North America where the climate is right. Some eggs stay unhatched from the previous group and hatch when rain soaks the area. ''Triops'' are often found in [[vernal pool]]s.

== Life cycle ==
Most species [[sexual reproduction|reproduce sexually]], but some populations are dominated by [[hermaphrodite]]s which produce [[internal fertilisation|internally fertilised]] eggs. Reproduction in ''T. cancriformis'' varies with [[latitude]], with sexual reproduction dominating in the south of its range, and [[parthenogenesis]] dominating in the north.<ref>{{cite book |author=Graham Bell |year=1982 |title=The masterpiece of nature: the evolution and genetics of sexuality |series=Croom Helm applied biology series |publisher=[[Cambridge University Press]] |isbn=978-0-85664-753-6 |page=243 |url=https://books.google.com/books?id=q5g9AAAAIAAJ&pg=PA243}}</ref>

''Triops'' eggs enter a state of extended [[diapause]] when dry, and will tolerate temperatures of up to {{convert|98|C|F}} for 16 hours, whereas the adult cannot survive temperatures above {{convert|34|C|F}} for 24&nbsp;hours or {{convert|40|C|F}} for 2&nbsp;hours.<ref name="Osborne">{{cite book |author=Patrick L. Osborne |year=2000 |title=Tropical ecosystems and ecological concepts |publisher=[[Cambridge University Press]] |isbn=978-0-521-64523-2 |chapter=Hot deserts and environmental factors |pages=18–49 |chapter-url=https://books.google.com/books?id=gA2xfP8hHlEC&pg=PA21}}</ref> The diapause also prevents the eggs from hatching too soon after rain; the pool must fill with enough water for the dormancy to be broken.<ref name="Osborne" />

== Taxonomy ==
[[File:Triops closeup.jpg|thumb|left|Closeup of adult ''Triops'' showing naupliar ocellus]]

The name ''Triops'' comes from [[Ancient Greek]] τρία (''tría''), meaning "three", and ὄψ (''óps''), meaning "face" or "eye".<ref>{{cite book |author=John Scarborough |year=1992 |title=Medical and biological terminologies: classical origins |series=Volume 13 of Oklahoma Series in Classical Culture |publisher=[[University of Oklahoma Press]] |isbn=978-0-8061-3029-3 |chapter=Crustacea |pages=75–81 |chapter-url=https://books.google.com/books?id=hjwN65nZBE0C&pg=PA75}}</ref> The head of ''T. longicaudatus'' bears a pair of [[Dorsum (biology)|dorsal]] [[compound eye]]s that lie close to each other and are nearly fused together. The compound eyes are generally sessile (not stalked). In addition, there is a [[Nauplius (larva)|naupliar]] [[ocellus]] (the "third eye") between them. The compound eyes are on the surface of the head, but the ocellus is deep within the head. All the eyes, however, are easily visible through the shell covering of the head.

[[File:Kian-triops.jpg|thumb|350px|Upper and underside ''Triops''. '''1''' eyes, '''2''' antennae, '''3''' tail, '''4''' torso, '''5''' antenne, '''6''' 1st torso appendix, '''7''' legs with gill, '''8''' middelline, '''9''' tail, '''10''' anus]]

[[Franz von Paula Schrank]] was the first author to use the [[genus]] name ''Triops'',<ref name="Møller" /> coining it in his 1803 work on the fauna of [[Bavaria]]. Their [[German language|German]] name was ''{{lang|de|Dreyauge}}'', which means 'three-eye'. He collected and described specimens from the same locality in [[Regensburg]] from which [[Jacob Christian Schäffer|Schäffer]], another naturalist who had studied the Notostraca, obtained his specimens in the 1750s. However, other authors, starting with [[Louis Augustin Guillaume Bosc]], had adopted the genus name ''Apus'' for the organisms Schrank had named ''Triops''

[[Ludwig Keilhack]] used the genus name ''Triops'' in his 1909 field identification key of the freshwater fauna of [[Germany]]. He suggested that the genus name ''Apus'' be replaced by ''Triops'' Schrank since an avian genus had already been described by [[Giovanni Antonio Scopoli]] under the name ''[[Apus (genus)|Apus]]''.<ref name="Møller">{{cite journal |author=Ole S. Møller |author2=Jørgen Olesen |author3=Jens T. Høeg |name-list-style=amp |year=2003 |title=SEM studies on the early larval development of ''Triops cancriformis'' (Bosc) (Crustacea: Branchiopoda, Notostraca) |journal=[[Acta Zoologica: Morphology and Evolution|Acta Zoologica]] |volume=84 |issue=4 |pages=267–284 |doi=10.1046/j.1463-6395.2003.00146.x |url=http://www.zmuc.dk/inverweb/staff/Ole_S_M%F8ller/PDF/M%F8ller_et_al(2003).pdf }}</ref> However, [[Robert Gurney]] preferred the name ''Apus'' Schäffer. He suggested that the name '…''Triops'' Schrank, may be returned to the obscurity from which it was unearthed'.<ref name="Møller" /> This controversy continued and was not resolved until the 1950s.

In his 1955 taxonomic review of the Notostraca, [[Alan R. Longhurst]] supported Keilhack's genus name ''Triops'' over ''Apus''. Longhurst provided historical evidence to support this position.<ref name="Møller" /> The [[International Commission on Zoological Nomenclature]] (ICZN) followed Longhurst in their 1958 ruling on the usage and origin of the genus names ''Triops'' and ''Apus''. They rejected the genus name ''Apus'' and instead recognized the genus name ''Triops'' Schrank, 1803 (ICZN name no. 1246).<ref name="Møller" />

Although the taxonomy of the genus has not been reviewed since 1955, the following species are recognised:<ref>{{cite web |url=http://mytriops.com/articles/triops_species.stm |title=A Brief Overview of the Species |author=Chip Hannum |publisher=MyTriops.com |access-date=October 4, 2010}}</ref><ref>{{cite journal |author=Michael Korn |author2=Andy J. Green |author3=Margarida Machado |author4=Juan García-de-Lomas |author5=Margarida Cristo |author6=Luís Cancela da Fonseca |author7=Dagmar Frisch |author8=José L. Pérez-Bote |author9=Anna K. Hundsdoerfer |name-list-style=amp |year=2010 |title=Phylogeny, molecular ecology and taxonomy of southern Iberian lineages of ''Triops mauritanicus'' (Crustacea: Notostraca) |journal=Organisms Diversity and Evolution |volume=10 |issue=5 |pages=409–440 |doi=10.1007/s13127-010-0026-y |url=http://www.ebd.csic.es/Andy/OrgDivEvo10%20online.pdf |url-status=dead |archiveurl=https://web.archive.org/web/20110908010647/http://www.ebd.csic.es/andy/OrgDivEvo10%20online.pdf |archivedate=2011-09-08 |hdl=10261/38752 |s2cid=14145762 |hdl-access=free }}</ref>
* ''[[Triops australiensis]]'' <small>(Spencer & Hall, 1895)</small>
* ''[[Triops baeticus]]'' <small>Korn, 2010</small>
* ''[[Triops cancriformis]]'' <small>(Bosc, 1801)</small>
* ''[[Triops emeritensis]]'' <small>Korn & Pérez-Bote, 2010</small>
* ''[[Triops gadensis]]'' <small>Korn & García-de-Lomas, 2010</small>
* ''[[Triops granarius]]'' <small>(Lucas, 1864)</small>
* ''[[Triops longicaudatus]]'' <small>(LeConte, 1846)</small>
* ''[[Triops mauritanicus]]'' <small>Ghigi, 1921</small>
* ''[[Triops newberryi]]'' <small>Thomas, 1921</small>
* ''[[Triops vicentinus]]'' <small>Korn, Machado, Cristo & Cancela da Fonseca, 2010</small>

''T. mauritanicus'' was considered a subspecies of ''T. cancriformis'' by Longhurst in 1955, but was given full species status again by Korn ''et al.'' in 2006.<ref name="Korn">{{cite journal |author= Michael Korn |author2= Federico Marrone |author3= Jose L. Pérez-Bote |author4= Margarida Machado |author5= Margarida Cristo |author6= Luís Cancela de Fonseca |author7= Anna K. Hundsdoerfer |name-list-style= amp |year= 2006 |title= Sister species within the Triops cancriformis lineage (Crustacea, Notostraca) |journal= [[Zoologica Scripta]] |volume= 35 |issue= 4 |pages= 301–322 |doi= 10.1111/j.1463-6409.2006.00230.x |s2cid= 84611515 |url= http://www.triops.es/articulos/paper16.pdf |access-date= 2011-12-14 |archive-date= 2017-08-12 |archive-url= https://web.archive.org/web/20170812115417/http://triops.es/articulos/paper16.pdf |url-status= dead }}</ref>

Note that for several of these species there are different varieties, some of which have recently been suggested as subspecies and even separate species. ''T. longicaudatus'', for example, may actually be several species lumped together, and ''[[Triops cancriformis|T. cancriformis]]'' is generally recognized as having three subspecies: ''T. cancriformis cancriformis'',
''T. c. mauretanicus'', and ''T. c. simplex''.<ref>[http://mytriops.com/articles/triops_species2.stm Species list] {{webarchive|url=https://web.archive.org/web/20111006181802/http://mytriops.com/articles/triops_species2.stm |date=2011-10-06 }}. Mytriops.com. Retrieved on 2016-07-23.</ref> Also, the albino form has the special name of ''T. cancriformis'' var. ''Beni-Kabuto Ebi''.

== Relationship with humans ==
[[File:Beni-KabutoEbiAlbino1.jpg|thumb|''Triops cancriformis'' "Beni-Kabuto Ebi Albino" showing translucent carapace. As the animal grows the carapace will become more opaque but will never take on the color pattern normally associated with ''T. cancriformis''.]]
[[File:Triopslongredcanc.jpg|thumb|Captive ''Triops cancriformis'' (left) and ''Triops longicaudatus'' (right) feeding on carrot.]]
''T. longicaudatus'' is considered a human ally against the [[West Nile virus]], as the individuals consume ''[[Culex]]'' mosquito larvae.<ref>Tietze, N. S., & Mulla, M. S. (1989). [https://pubmed.ncbi.nlm.nih.gov/2584973/#:~:text=Abstract,quinquefasciatus%20larvae%20in%20the%20laboratory. Prey-size selection by Triops longicaudatus (Notostraca: Triopsidae) feeding on immature stages of Culex quinquefasciatus.] Journal of the American Mosquito Control Association. Retrieved on 2023-03-03.</ref> They also are used as a [[biological pest control]] in Japan, eating weeds in rice [[Paddy field|paddies]]. The Beni-Kabuto Ebi Albino variant of ''T. cancriformis'' is particularly valued for this purpose. In [[Wyoming]], the presence of ''T. longicaudatus'' usually indicates a good chance of the hatching of [[American spadefoot toads]].

Dried eggs of ''T. longicaudatus'' are sold in kits to be raised as aquarium pets, sold under the name of "aquasaurs", "trigons" or "triops". Among enthusiasts, ''T. cancriformis'' is also common. Other species often encountered in captivity include ''[[Triops australiensis|T. australiensis]]'', ''[[Triops newberryi|T. newberryi]]'' and ''[[Triops granarius|T. granarius]]''.

Captive ''Triops'' are frequently kept in aquaria and fed a diet consisting mainly of carrots, shrimp pellets and dried shrimp.<ref>[https://web.archive.org/web/20140331201144/http://www.triops.com/CMS/html/index.aspx?p32sda=faq&psdge87d=310&tl97abi=90 Frequently Asked Questions]. triops.com</ref> Often they are also given living shrimp and ''[[Daphnia]]'' as live prey.<ref>[http://mytriops.com/articles/triops_food_recipes.stm Triops food] {{Webarchive|url=https://web.archive.org/web/20070529034011/http://mytriops.com/articles/triops_food_recipes.stm |date=2007-05-29 }}. Mytriops.com (2003-10-28). Retrieved on 2016-07-23.</ref> Because they can feed on just about anything they are also fed lunch meat, crackers, potatoes etc.<ref>[http://triops-eggs.com/triops-and-their-food/ "Triops and their food"]. Triops-eggs.com. Retrieved on 2016-07-23.</ref>

In California, ''T. longicaudatus'' has emerged as a significant pest of rice cultivation, due to its digging behaviour uprooting young rice seedlings.<ref>{{Cite journal|last1=Bloese|first1=Joanna B|last2=Goding|first2=Kevin M|last3=Godfrey|first3=Larry D|date=2020-06-06|editor-last=Musser|editor-first=Fred|title=Effect of Rice Winter Cultural Management Practices on the Size of the Hatching Population of Triops longicaudatus (Notostraca: Triopsidae) in California Rice Fields|url=https://academic.oup.com/jee/article/113/3/1243/5714876|journal=Journal of Economic Entomology|language=en|volume=113|issue=3|pages=1243–1247|doi=10.1093/jee/toaa006|pmid=31971596|issn=0022-0493|url-access=subscription}}</ref>

==See also==
* [[Notostraca]]
* [[Lepidurus]]
* [[Xiphosura]]
* [[Synziphosurina]]
* [[Trilobite]]

== References ==
{{Reflist|32em}}

== External links ==
* [https://www.reddit.com/r/triops/ Discussing Triops (r/Triops)]—A [[Reddit]] community devoted to their care and ecology. 
* [http://www.mytriops.com Mytriops.com]—Website with useful information about ''Triops'' and keeping ''Triops'' as pets.
* [https://www.youtube.com/watch?v=VfcEGK-NfhY Triops]—[[YouTube]] video on raising ''Triops''

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[[Category:Notostraca]]
[[Category:Branchiopoda genera]]
[[Category:Extant Miocene first appearances]]
[[Category:Taxa named by Franz von Paula Schrank]]
[[Category:Animals bred for albinism on a large scale]]