Anostraca: Difference between revisions

| fossil_range = {{fossil range|OrdovicianDevonian|Recent|earliest=Ordovician}}

* [[Brine shrimp|ArtemiidaeTanymastigidae]] <small>GrochowskiWeekers ''et al.'', 18962002</small>

* [[Branchinecta|BranchinectidaeThamnocephalidae]] <small>DadaySimon, 19101886</small>

'''Anostraca''' is one of the four [[order (biology)|orders]] of [[crustacean]]s in the class [[Branchiopoda]]; its members are alsoreferred knownto as '''fairy shrimp'''. They live in [[vernal pool]]s and [[hypersaline lake]]s across the world, and they have even been found in [[desert]]s, ice-covered mountain lakes, and [[Antarctica|Antarctic]] ice. They are usually {{convert|6|-|25|mm|abbr=on}} long (exceptionally up to {{convert|170|mm|abbr=on|disp=or}}). Most species have 20 body segments, bearing 11 pairs of leaf-like ''phyllopodia'' (swimming legs), and the body lacks a [[carapace]]. They live in [[vernal pool]]s and [[hypersaline lake]]s across the world, including pools in [[desert]]s, in ice-covered mountain lakes and in [[Antarctica]]. They swim "upside-down" and [[filter feeder|feed by filtering]] organic particles from the water or by scraping [[algae]] from surfaces, with the exception of ''[[Branchinecta gigas]],'' or "giant fairy shrimp", which is itself a predator of other species of anostracans. They are an important food for many birds and fish, and some are cultured and harvested for use as fish food. There are 300 species spread across 8 [[family (biology)|families]].

The body of a fairy shrimp is elongated and divided into segments.<ref name="Belk"/> The whole animal is typically {{convert|6|-|25|mm}} long, but one species, ''[[Branchinecta gigas]]'' does not reach [[sexual maturity]] until it reaches {{convert|50|mm|abbr=on}} long, and can grow to {{convert|170|mm|abbr=on}} long.<ref name="Belk"/> The [[exoskeleton]] is thin and flexible,<ref name="Belk"/> and lacks any sign of a [[carapace]].<ref name="Australia">{{cite book |author=William David Williams |year=1980 |title=Australian Freshwater Life: the Invertebrates of Australian Inland Waters |edition=2nd |publisher=[[Palgrave Macmillan Australia]] |isbn=978-0-333-29894-7 |chapter=Arachnids and Crustaceans |pages=118–184 |chapter-url=https://books.google.com/books?id=2qqrV5WaJ4sC&pg=PA126}}</ref> The body can be divided into three distinct parts ([[Tagma (biology)|tagmata]]) – head, thorax and abdomen.<ref name="Australia"/>

The thorax of most anostracans has 13 segments (19 in ''[[Polyartemiella]]'' and 21 in ''[[Polyartemia]]'').<ref name="Khanna">{{cite book |author=D. R. Khanna |year=2004 |title=Biology of Arthropoda |publisher=[[Discovery Publishing House]] |isbn=978-81-7141-897-8 |chapter=Segmentation in arthropods |pages=316–394 |chapter-url=https://books.google.com/books?id=Hd4OEDo4gbwC&pg=PA347}}</ref> All but the last two are very similar, with a pair of biramous phyllopods (flattened, leaf-like [[appendage]]s).<ref name="Australia"/> The last two segments are fused together,<ref name="Belk"/> and their appendages are specialised for reproduction.<ref name="Khanna"/> Most anostracans have separate sexes ([[gonochorism]]), but a few reproduce by [[parthenogenesis]].<ref name="Bell">{{Cite book |author=Graham Bell |year=1982 |title=The Masterpiece of Nature: the Evolution and Genetics of Sexuality |publisher=[[Cambridge University Press]] |isbn=978-0-85664-753-6 |chapter=Arthropoda: Crustacea Branchiopoda |pages=239–248 |chapter-url=https://books.google.com/books?id=q5g9AAAAIAAJ&pg=PA239}}</ref> The abdomen comprises 6 segments without appendages, and a [[telson]],<ref name="Khanna"/> which bears two flattened caudal rami or "cercopods".<ref name="Belk"/>

The head contains two digestive glands and the small lobate [[stomach]] thatinto which they empty into. This is connected to a long [[intestine]], which terminates in a short [[rectum]], with the [[anus]] located on the [[telson]].<ref name="Pennak"/> The [[haemocoel]] of anostracans is pumped by a long, tubular [[heart]], which runs through most of the animal's length.<ref name="Pennak"/> A series of slits allow haemocoel into the heart, which is then pumped out of the anterior opening by [[peristalsis]].<ref name="Pennak"/> The nervous system consists of two nerve cords which run the length of the body, with two [[ganglion|ganglia]] and two transverse [[commissure]]s in most of the body segments.<ref name="Pennak"/>

Anostracans inhabit inland waters ranging from [[hypersaline lake]]s to lakes that are almost devoid of dissolved substances;<ref name="Belk">{{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=PA416}}</ref> they are "the most archetypal crustaceans" in ephemeral waters.<ref name="Dumont">{{cite book |year=2009 |editor=Henri J. Dumont |title=The Nile: Origins, Environments, Limnology and Human Use |series=Volume 89 of Monographiae Biologicae |publisher=[[Springer Science+Business Media|Springer]] |isbn=978-1-4020-9725-6 |chapter=The crustacean zooplankton (Copepoda, Branchiopoda), atyid Decapoda, and Syncarida of the Nile Basin |author=Henri J. Dumont |pages=521–546 |chapter-url=https://books.google.com/books?id=iF_U1NoknHoC&pg=PA536}}</ref> The relatively large size of fairy shrimp, together with their slow means of locomotion, makes them an easy target for [[predator]]y [[fish]] and [[water bird|waterfowl]].<ref name="Dumont"/> This has led to their distribution being restricted to environments with fewer predators, such as [[vernal pool]]s, [[salt lake]]s and lakes at high altitudes or latitudes.<ref name="Dumont"/> The southernmost recorded fairy shrimp is ''[[Branchinecta gaini]]'' from the [[Antarctic Peninsula]],<ref>{{cite journal |author=T.C. Hawes |date=October 2009 |title=Origins and dispersal of the Antarctic fairy shrimp |journal=[[Antarctic Science]] |volume=21 |issue=5 |pages=477–482 |doi=10.1017/S095410200900203X|bibcode=2009AntSc..21..477H |s2cid=84382536 }}</ref> while the altitude record is held by ''[[Branchinecta brushi|B. brushi]]'', which lives at {{convert|5930|m}} in the [[Chile]]an [[Andes]].<ref name="Hegna">{{cite journal|author1=Thomas A. Hegna |author2=Eric A. Lazo-Wasem |date=1 July 2010 |title=''Branchinecta brushi'' n. sp. (Branchiopoda: Anostraca: Branchinectidae) from a volcanic crater in northern Chile (Antofagasta Province): a new altitude record for crustaceans |journal=[[Journal of Crustacean Biology]] |volume=30 |issue=3 |pages=445–464 |doi=10.1651/09-3236.1 |urls2cid=https://yale.academia.edu/documents/0068/6445/Hegna___Lazo-Wasem.pdf85961054 }}{{dead link|date=July 2017 |bot=InternetArchiveBot |fixdoi-attemptedaccess=yesfree }}</ref> Other genera, such as ''[[Streptocephalus]]'', occur in [[desert]]s throughout the world.<ref>{{cite book |author=David Ward |year=2009 |title=The Biology of Deserts |publisher=[[Oxford University Press]] |isbn=978-0-19-921147-0 |chapter=Biodiversity and biogeography of deserts |pages=192–216 |chapter-url=https://books.google.com/books?id=3ixJ5GwT5R4C&pg=PA204}}</ref>

Another important aspect of the fairy shrimp’s life cycle is their universal ability to enter diapause,<ref name=":0">{{Cite journal|lastlast1=Hairston|firstfirst1=Nelson G.|last2=Cáceres|first2=Carla E.|date=1996-03-01|title=Distribution of crustacean diapause: micro- and macroevolutionary pattern and process|journal=Hydrobiologia|language=en|volume=320|issue=1–3|pages=27–44|doi=10.1007/bf00016802|s2cid=44914111|issn=0018-8158}}</ref><ref name=":1">{{Cite journal|last=Fryer|first=Geoffrey|date=1996-03-01|title=Diapause, a potent force in the evolution of freshwater crustaceans|journal=Hydrobiologia|language=en|volume=320|issue=1–3|pages=1–14|doi=10.1007/bf00016800|s2cid=24128518|issn=0018-8158|doi-access=free}}</ref> a state of biological dormancy where growth and metabolism are arrested,<ref name=":2">{{Cite journal|lastlast1=Alekseev|firstfirst1=Victor R.|last2=Starobogatov|first2=Yaroslav I.|date=1996-03-01|title=Types of diapause in Crustacea: definitions, distribution, evolution|journal=Hydrobiologia|language=en|volume=320|issue=1–3|pages=15–26|doi=10.1007/bf00016801|s2cid=253609|issn=0018-8158}}</ref> as an egg (or cyst). This trait assists in both species' dispersal and in overcoming adverse environmental conditions.<ref name=":1" /><ref name=":2" /> Once dormant, these cysts can withstand conditions as harsh and diverse as droughts, frosts, hypersalinity, complete desiccation, exposure to UV radiation and the vacuum of space.<ref>{{Cite journal|lastlast1=Czyż|firstfirst1=M.|last2=Woliński|first2=P.|last3=Gołdyn|first3=B.|date=2016|title=Cyst morphology of large branchiopod crustaceans (Anostraca, Notostraca, Laevicaudata, Spinicaudata) in western Poland|url=|journal=Biological Letters|volume=53|issue=2|pages=79–88|via=|doi=10.1515/biolet-2017-0006|doi-access=free}}</ref><ref name="Belk" /><ref name=":2" /> It is also the only way for the fairy shrimps to colonize new habitats—facilitated by a variety of conditions including wind, predators, currents<ref name=":3">{{Cite journal|lastlast1=Parnov|firstfirst1=V.|last2=Krylov|first2=P.|last3=Riccardi|first3=N.|date=2004|title=Role of diapause in dispersal and invasion success by aquatic invertebrates|url=|journal=Journal of Limnology|volume=63|pages=59–69|via=}}</ref><ref name=":4">{{Cite journal|last=Rogers|first=C.|date=2015|title=A conceptual model for Anostracan biogeography|url=|journal=Journal of Crustacean Biology|volume=35|issue=5|pages=686–699|via=|doi=10.1163/1937240x-00002369|doi-access=free}}</ref><ref>{{Cite journal|lastlast1=Brendonck|firstfirst1=Luc|last2=Riddoch|first2=Bruce J.|date=1999-05-01|title=Wind-borne short-range egg dispersal in anostracans (Crustacea: Branchiopoda)|journal=Biological Journal of the Linnean Society|volume=67|issue=1|pages=87–95|doi=10.1111/j.1095-8312.1999.tb01931.x|issn=0024-4066|doi-access=free}}</ref>—as the soft-bodied adults are unable to leave the freshwater system.<ref name=":4" /> Once in diapause, these cysts can remain viable for centuries,<ref name=":3" /> and the mixing of system sediment results in the hatching of different aged cysts in each generation.<ref name=":5">{{Cite journal|lastlast1=Remigio|firstfirst1=E. A.|last2=Hebert|first2=P. D. N.|last3=Savage|first3=A.|date=2001-09-01|title=Phylogenetic relationships and remarkable radiation in Parartemia (Crustacea: Anostraca), the endemic brine shrimp of Australia: evidence from mitochondrial DNA sequences|journal=Biological Journal of the Linnean Society|volume=74|issue=1|pages=59–71|doi=10.1006/bijl.2001.0567|issn=0024-4066|doi-access=free|bibcode=2001BJLS...74...59R }}</ref><ref name=":4" /><ref>{{Cite journal|lastlast1=Kraus|firstfirst1=Holger|last2=Eder|first2=Erich|last3=Sten Møller|first3=Ole|last4=Werding|first4=Bernd|date=2004-07-01|title=Cyst Deposition Behaviour and the Functional Morphology of the Brood Pouch in Streptocephalus Torvicornis (Branchiopoda: Anostraca)|journal=Journal of Crustacean Biology|volume=24|issue=3|pages=393–397|doi=10.1651/c-2470|issn=0278-0372|doi-access=free}}</ref> This inbreeding slows the rate of selection by resisting gene flow and minimizing phenotypic variation, in turn promoting the stability of the existing, successful phenotype.<ref name=":4" />

[[File:Artemia breeding ponds.jpg|thumb|Salt evaporation ponds at [[Redwood City, California|Redwood City]] on [[San Francisco Bay Salt Ponds]]: the orange colour is produced by the presence of ''[[brine shrimp|Artemia]]''.]]

Fairy shrimp are believed to have diverged from the main line of Branchiopoda during the Ordovician period,<ref name=":6">{{Cite journal|last=Olesen|first=Jørgen|date=2007-04-01|title=Monophyly and Phylogeny of Branchiopoda, with Focus on Morphology and Homologies of Branchiopod Phyllopodous Limbs|journal=Journal of Crustacean Biology|volume=27|issue=2|pages=165–183|doi=10.1651/s-2727.1|issn=0278-0372|doi-access=free}}</ref><ref name=":7">{{Cite journal|lastlast1=Daniels|firstfirst1=Savel R.|last2=Hamer|first2=Michelle|last3=Rogers|first3=Christopher|date=2004-07-01|title=Molecular evidence suggests an ancient radiation for the fairy shrimp genus Streptocephalus (Branchiopoda: Anostraca)|journal=Biological Journal of the Linnean Society|volume=82|issue=3|pages=313–327|doi=10.1111/j.1095-8312.2004.00359.x|issn=0024-4066|doi-access=free}}</ref> around the same time it is thought they colonized freshwater and estuarine ecosystems.<ref name=":2" /> This transition is believed to have been the result of selection pressure to escape predation in the Early Paleozoic seas.<ref name="Diversity" /><ref name="Belk" /><ref name=":1" /> ''[[Lepidocaris]]'' from the early [[Devonian]] [[Rhynie chert]] is likely a close relative of Anostraca. The oldest known modern-looking ansotracan is ''[[Haltinnaias]]'' from the late Devonian ([[Famennian]]) Strud locality of Belgium, around 365 million years old.<ref>{{Cite journal|last1=Gueriau|first1=Pierre|last2=Rabet|first2=Nicolas|last3=Clément|first3=Gaël|last4=Lagebro|first4=Linda|last5=Vannier|first5=Jean|last6=Briggs|first6=Derek E.G. |last7=Charbonnier|first7=Sylvain|last8=Olive|first8=Sébastien|last9=Béthoux|first9=Olivier|date=February 2016|title=A 365-Million-Year-Old Freshwater Community Reveals Morphological and Ecological Stasis in Branchiopod Crustaceans|journal=Current Biology|language=en|volume=26|issue=3|pages=383–390|doi=10.1016/j.cub.2015.12.039|pmid=26776738 |doi-access=free|bibcode=2016CBio...26..383G }}</ref><ref>{{Cite journal|last1=Luo|first1=Cihang|last2=Jarzembowski|first2=Edmund A.|last3=Fang|first3=Yan|last4=Wang|first4=Bo|last5=Xiao|first5=Chuantao|date=February 2020|title=First Anostraca (Crustacea: Branchiopoda) from the Middle Jurassic of Daohugou, China|url=https://linkinghub.elsevier.com/retrieve/pii/S0016787819301300|journal=Proceedings of the Geologists' Association|language=en|volume=131|issue=1|pages=67–72|doi=10.1016/j.pgeola.2019.11.004|bibcode=2020PrGA..131...67L |s2cid=214226902 }}</ref>

Some studies point to fossils resembling fairy shrimp in the Upper Cambrian,<ref name=":8">{{Cite journal|lastlast1=Richter|firstfirst1=Stefan|last2=Olesen|first2=Jørgen|last3=Wheeler|first3=Ward C.|date=2007-08-01|title=Phylogeny of Branchiopoda (Crustacea) based on a combined analysis of morphological data and six molecular loci|journal=Cladistics|language=en|volume=23|issue=4|pages=301–336|doi=10.1111/j.1096-0031.2007.00148.x|pmid=34905837 |s2cid=55997584|issn=1096-0031|doi-access=free}}</ref><ref>{{Cite journal|last=Brendonck|first=L.|date=1996|title=Diapause, quiescence, hatching requirements: what we can learn from large freshwater branchiopods (Crustacea Branciopoda: Anostraca, Notostraca, Conchostraca)|doi=10.1007/bf00016809|journal=Hydrobiologia|volume=320|issue=1–3|pages=85–97|vias2cid=26327230}}</ref> specifically the oldest known branchiopod fossil, ''Rebachiella[[Rehbachiella|Rehbachiella kinnekullensis]]'', from Orsten marine deposits.<ref>{{cite journal|author1=Joel W. Martin|author2=Michael S. Laverack|date=December 1992|title=On the distribution of the crustacean dorsal organ|url=http://crustacea.nhm.org/people/martin/publications/pdf/59.pdf|url-status=dead|journal=[[Acta Zoologica: Morphology and Evolution|Acta Zoologica]]|volume=73|issue=5|pages=357–368|doi=10.1111/j.1463-6395.1992.tb01108.x|archiveurlarchive-url=https://web.archive.org/web/20110719085139/http://crustacea.nhm.org/people/martin/publications/pdf/59.pdf|archivedatearchive-date=2011-07-19}}</ref> Despite its seeming resemblance to modern fairy shrimp, this fossil is still considered by most to be an outlying member of the ancestral marine Branchiopoda rather than a true fairy shrimp.<ref name=":6" />

The monophyly of this order is well supported,<ref name="Diversity" /><ref>{{Cite book|title=Arthropod Relationships|lastlast1=Fortey|firstfirst1=R.|last2=Thomas|first2=H.|publisher=Springer Science & Business Media|year=2012|isbn=|location=Berlin|pages=104–105}}</ref><ref>{{Cite book|title=Perspectives in Animal Phylogeny and Evolution|url=https://archive.org/details/perspectivesanim00mine|url-access=limited|last=Minelli|first=A.|publisher=Oxford University Press|year=2009|isbn=|location=Oxford|pages=98–100[https://archive.org/details/perspectivesanim00mine/page/n57 98]–100}}</ref><ref name=":6" /><ref name=":8" /><ref>{{Cite journal|last=Weekers|first=P|title=Phylogenetic analysis of anostracans (Branchiopoda: Anostraca) inferred from nuclear 18S ribosomal DNA (18S rDNA) sequences|journal=Molecular Phylogenetics and Evolution|volume=25|issue=3|pages=535–544|doi=10.1016/s1055-7903(02)00289-0|year=2002|pmid=12450757}}</ref><ref name=":9">{{Cite journal|lastlast1=Regier|firstfirst1=Jerome C.|last2=Shultz|first2=Jeffrey W.|last3=Zwick|first3=Andreas|last4=Hussey|first4=April|last5=Ball|first5=Bernard|last6=Wetzer|first6=Regina|last7=Martin|first7=Joel W.|last8=Cunningham|first8=Clifford W.|date=2010-02-10|title=Arthropod relationships revealed by phylogenomic analysis of nuclear protein-coding sequences|journal=Nature|language=en|volume=463|issue=7284|pages=1079–1083|doi=10.1038/nature08742|pmid=20147900|bibcode=2010Natur.463.1079R|s2cid=4427443|issn=1476-4687}}</ref> and the scientific community has reached consensus that Anostraca was the first group to branch off from the Branchiopoda.<ref name=":0" /><ref name=":8" /><ref name=":1" /><ref name=":9" /><ref name=":7" />

The radiation hypothesis championing rapid spread and colonization during the Gondwana fragmentation closely echoes the current distribution of the order.<ref name=":7" /><ref name=":4" /> Presently, Anostraca are found on all seven continents.<ref name="Diversity" /> Most of the extant genera have restricted geographical distributions. Only three genera are widespread across the remnants of the former supercontinent [[Pangaea]]: ''[[Artemia]]'', ''[[Branchinella]]'' and ''[[Branchinecta]]'', while the remaining genera are found only throughout former Laurasia.<ref name="Williams">{{cite book|chapter-url=https://books.google.com/books?id=gKgOAAAAQAAJ&pg=PA25|title=The Ecology of Temporary Waters|author=D. Dudley Williams|publisher=[[Taylor & Francis]]|year=1987|isbn=978-0-7099-5211-4|pages=21–67|chapter=The Biota}}</ref> This suggests that much of the potential habitat in this supercontinent, now occupied by Anostraca, to have been unoccupied by ecologically similar species, or to have been inhabited by species with less adaptive ability.<ref name=":4" /> Studies have found Anostraca capable of rapid colonization<ref>{{Cite journal|lastlast1=Kappas|firstfirst1=Ilias|last2=Mura|first2=Graziella|last3=Synefiaridou|first3=Dimitra|last4=Marrone|first4=Federico|last5=Alfonso|first5=Giuseppe|last6=Alonso|first6=Miguel|last7=Abatzopoulos|first7=Theodore J.|date=2017-10-01|title=Molecular and morphological data suggest weak phylogeographic structure in the fairy shrimp Streptocephalus torvicornis (Branchiopoda, Anostraca)|journal=Hydrobiologia|language=en|volume=801|issue=1|pages=21–32|doi=10.1007/s10750-017-3203-6|s2cid=25271723|issn=0018-8158|url=https://research.rug.nl/en/publications/11d3e994-3461-4015-9a3a-6d1f80d5c321 }}</ref> and speciation.<ref name=":5" />

Anostraca is the most diverse of the four orders of Branchiopoda. It comprises around 300313 species, grouped into 26 genera in eight families:<ref name="Diversity">{{cite book |author1=Luc Brendonck |author2=D. Christopher Rogers |author3=Jorgen Olesen |author4=Stephen Weeks |author5=Walter R. Hoch |year=2008 |chapter=Global diversity of large branchiopods (Crustacea: Branchiopoda) in freshwater |id=Reprinted from [[Hydrobiologia]], Volume 595 |pages=167–176 |doi=10.1007/s10750-007-9119-9 |title=Freshwater Animal Diversity Assessment |editor1=Estelle V. Balian |editor2=Christian Lévêque |editor3=Hendrik Segers |editor4=Koen Martens |series=Developments in Hydrobiology 198 |isbn=978-1-4020-8258-0 |s2cid=46608816 |chapter-url=https://books.google.com/books?id=Dw4H6DBHnAgC&pg=PA167}}</ref>

* [[Brine shrimp|Artemiidae]] – 1 genus, 98 species

* [[Branchinecta|Branchinectidae]] – 1 genus, 45 species

* [[Branchipodidae]] – 5 genera, 35 species

* [[Chirocephalidae]] – 9 genera, 81 species

* [[Parartemia|Parartemiidae]] – 1 genus, 1318 species

* [[Streptocephalus|Streptocephalidae]] – 1 genus, 56 species

* [[Tanymastigidae]] – 2 genera, 8 species

* [[Thamnocephalidae]] – 6 genera, 62 species

{{Reflist|30em}}

* {{Wikispecies-inline|Anostraca}}

* {{commonsCommons category-inline|Anostraca}}