diplostraca

File:Leptodora.png is an unusually large diplostracan, at up to 18 mm long.]]

They are mostly {{convert|0.2|-|6.0|mm|2|abbr=on}} long, with the exception of Leptodora, which can be up to {{convert|18|mm|abbr=on}} long. The body is not obviously segmented and bears a folded carapace which covers the thorax and abdomen.

The head is angled downwards, and may be separated from the rest of the body by a "cervical sinus" or notch. It bears a single black compound eye, located on the animal's midline, in all but two genera, and often, a single ocellus is present. The head also bears two pairs of antennae – the first antennae are small, unsegmented appendages, while the second antennae are large, segmented, and branched, with powerful muscles. The first antennae bear olfactory setae, while the second are used for swimming by most species. The pattern of setae on the second antennae is useful for identification. The part of the head which projects in front of the first antennae is known as the rostrum or "beak".

The mouthparts are small, and consist of an unpaired labrum, a pair of mandibles, a pair of maxillae, and an unpaired labium. They are used to eat "organic detritus of all kinds" and bacteria.

The thorax bears five or six pairs of lobed, leaf-like appendages, each with numerous hairs or setae. Carbon dioxide is lost, and oxygen taken up, through the body surface.

File:Rodząca dafnia.jpg

With the exception of a few purely asexual species, the lifecycle of diplostracans is dominated by asexual reproduction, with occasional periods of sexual reproduction; this is known as cyclical parthenogenesis.{{cite book |editor1=Isa Schön |editor2=Koen Martens |editor3=Peter van Dijk |year=2009 |title=Lost Sex: The Evolutionary Biology of Parthenogenesis |publisher=Springer |isbn=978-90-481-2769-6 |chapter=Cyclical parthenogeness in Daphnia: sexual versus asexual reproduction |author1=Ellen Decaestecker |author2=Luc De Meester |author3=Joachim Mergaey |pages=295–316 |chapter-url=https://lirias.kuleuven.be/handle/123456789/208129 |doi=10.1007/978-90-481-2770-2_15|s2cid=82949264 }} When conditions are favourable, reproduction occurs by parthenogenesis for several generations, producing only female clones. As the conditions deteriorate, males are produced, and sexual reproduction occurs. This results in the production of long-lasting dormant eggs. These ephippial eggs can be transported over land by wind, and hatch when they reach favourable conditions, allowing many species to have very wide – even cosmopolitan – distributions.{{cite book |editor=Douglas Grant Smith |chapter=Cladoceran Branchiopoda (water fleas) |pages=453–488 |author1=Douglas Grant Smith |author2=Kirstern Work |year=2001 |title=Pennak's Freshwater Invertebrates of the United States: Porifera to Crustacea |edition=4th |publisher=John Wiley and Sons |isbn=978-0-471-35837-4 |chapter-url=https://books.google.com/books?id=GqIctb8IqPoC&pg=PA468}} Except for the genus Leptodora, which has a metanauplius stage, a nauplius larval stage is absent in Diplostraca.[https://books.google.com/books?id=2U8CBAAAQBAJ&dq=A+naupliar+stage+is+absent+in+Cladocera%2C+except+Leptodora%2C+which+has+a+metanauplius+stage&pg=PA438 Thorp and Covich's Freshwater Invertebrates: Keys to Nearctic Fauna]

Diplostraca are nested within the clam shrimp, being most closely related to the order Cyclestherida, the only living genus of which is Cyclestheria. Though several fossils from the Paleozoic have been claimed to represent fossils of diplostracans, none of these records can be confirmed. The oldest confirmed records of diplostracans are from the Early Jurassic of Asia. Fossils from the Jurassic are assignable to modern as well as extinct groups, indicating that the initial radiation of the group occurred prior to the beginning of the Jurassic, likely during the late Paleozoic.{{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}} A Devonian to Carboniferous genus, Ebullitiocaris, is tentatively placed as a diplostracan, however since it is only known from carapaces this is uncertain.

File:Evadne_spinifera.jpg, one of very few marine diplostracan species]]

Most diplostracan species live in fresh water and other inland water bodies, with only eight species being truly oceanic.{{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}} The marine species are all in the family Podonidae, except for the genus Penilia. Some diplostracans inhabit leaf litter.{{Cite journal|last1=Rubbo |first1=Michael J. |last2=Kiesecker |first2=Joseph M. |date=2004 |title=Leaf litter composition and community structure: translating regional species changes into local dynamics |journal=Ecology |volume=85 |issue=9 |pages=2519–2525 |doi=10.1890/03-0653|bibcode=2004Ecol...85.2519R |doi-access=free }}

File:Daphnia magna.png]]

According to the World Registry of Marine Species, Cladocera is a synonym of the superorder Diplostraca, which is included in the class Branchiopoda. Both names are currently in use. The superorder forms a monophyletic group of 7 orders, about 24 families, and more than 11,000 species. Many more species remain undescribed.{{cite journal |author1=L. Forró |author2=N. M. Korovchinsky |author3=A. A. Kotov |author4=A. Petrusek |year=2008 |title=Global diversity of cladocerans (Cladocera; Crustacea) in freshwater |journal=Hydrobiologia |volume=595 |issue=1 |pages=177–184 |doi=10.1007/s10750-007-9013-5 |s2cid=45363782 |url=http://decapoda.nhm.org/pdfs/27704/27704.pdf }} {{doi|10.1007/978-1-4020-8259-7_19}} The genus Daphnia alone contains around 150 species. Many groups of the water fleas are cryptic species or species flocks.{{Cite journal |last1=Kotov |first1=Alexey A. |last2=Garibian |first2=Petr G. |last3=Bekker |first3=Eugeniya I. |last4=Taylor |first4=Derek J. |last5=Karabanov |first5=Dmitry P. |date=2020-06-17 |title=A new species group from the Daphnia curvirostris species complex (Cladocera: Anomopoda) from the eastern Palaearctic: taxonomy, phylogeny and phylogeography |journal=Zoological Journal of the Linnean Society |volume=191 |issue=3 |pages=772–822 |doi=10.1093/zoolinnean/zlaa046 |issn=0024-4082 |doi-access=}}

The following families are recognised:

Superorder Diplostraca Gerstaecker, 1866 (=Cladocera)

{{div col|colwidth=24em}}

: Order Anomopoda G.O. Sars, 1865

:: Family Acantholeberidae Smirnov, 1976

:: Family Bosminidae Baird, 1845

:: Family Chydoridae Dybowski & Grochowski, 1894

:: Family Daphniidae Straus, 1820

:: Family Dumontiidae Santos-Flores & Dodson, 2003

:: Family Eurycercidae Kurz, 1875

:: Family Gondwanothrichidae Van Damme, Shiel & Dumont, 2007

:: Family Ilyocryptidae Smirnov, 1976

:: Family Macrothricidae Norman & Brady, 1867

:: Family Moinidae Goulden, 1968

:: Family Ophryoxidae Smirnov, 1976

: Order Ctenopoda G.O. Sars, 1865

:: Family Holopediidae G.O. Sars, 1865

:: Family Pseudopenilidae Korovchinsky & Sergeeva, 2008

:: Family Sididae Baird, 1850

: Order Cyclestherida Sars G.O., 1899

:: Family Cyclestheriidae Sars G.O., 1899

: Order Haplopoda G.O. Sars, 1865

:: Family Leptodoridae Lilljeborg, 1861

: Order Laevicaudata Linder, 1945

:: Family Lynceidae Stebbing, 1902

: Order Onychopoda G.O. Sars, 1865

:: Family Cercopagididae Mordukhai-Boltovskoi, 1968

:: Family Podonidae Mordukhai-Boltovskoi, 1968

:: Family Polyphemidae Baird, 1845

: Order Spinicaudata Linder, 1945

:: Family Cyzicidae Stebbing, 1910

:: Family Eocyzicidae Schwentner, et al., 2020

:: Family Leptestheriidae Daday, 1913: 44

:: Family Limnadiidae Burmeister, 1843

{{div col end}}

File:Daphnia Ephippia.jpg

The word "Cladocera" derives via Neo-Latin from the Ancient Greek {{lang|el|κλάδος}} ({{lang|el|kládos}}, "branch") and {{lang|el|κέρας}} ({{lang|el|kéras}}, "horn").{{cite dictionary |title=Webster's II New College Dictionary |chapter=Cladoceran |page=211 |edition=3rd |publisher=Houghton Mifflin Harcourt |year=2005 |isbn=978-0-618-39601-6 |chapter-url=https://books.google.com/books?id=OL60E3r2yiYC&pg=PA211}}

File:Daphnia.sp.jpg

{{Portal|Crustaceans|Arthropods}}

• Bythotrephes longimanus (invasive species) [formerly known as Bythotrephes cederstroemiUSGS Nonindigenous Aquatic Species: [https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=162 Bythotrephes longimanus]] - Spiny Water Flea(April 16, 2013) [https://www.youtube.com/watch?v=7yDuwqkTu6Q NorthAmericanFishing - "Silent Invaders" Spiny Water Flea PT 1 2013 ]
• Cercopagis pengoi (invasive species)
• Daphnia lumholtzi (invasive species)
• Moina (smallest)
• Zooplankton

{{Reflist|32em|refs=

WoRMS (2021). Diplostraca. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=155670 on 2021-11-23

{{Cite journal|last1=Norambuena|first1=Juan-Alejandro|last2=Farías|first2=Jorge|last3=De los Ríos|first3=Patricio|date=2019-12-05|title=The water flea Daphnia pulex (Cladocera, Daphniidae), a possible model organism to evaluate aspects of freshwater ecosystems|url=https://doi.org/10.1163/15685403-00003948|journal=Crustaceana|volume=92|issue=11–12|pages=1415–1426|doi=10.1163/15685403-00003948|s2cid=213266769|issn=0011-216X}}

{{cite journal |author1=K. Van Damme |author2=R. J. Shiel |author3=H. J. Dumont |year=2007 |title=Notothrix halsei gen. n., sp. n., representative of a new family of freshwater cladocerans (Branchiopoda, Anomopoda) from SW Australia, with a discussion of ancestral traits and a preliminary molecular phylogeny of the order |journal=Zoologica Scripta |volume=36 |issue=5 |pages=465–487 |doi=10.1111/j.1463-6409.2007.00292.x|s2cid=83893469 }}

{{cite journal |author1=K. Van Damme |author2=R. J. Shiel |author3=H. J. Dumont |year=2007 |title=Gondwanotrichidae nom. nov. pro Nototrichidae Van Damme, Shiel & Dumont, 2007 |journal=Zoologica Scripta |volume=36 |issue=5 |pages=623 |doi=10.1111/j.1463-6409.2007.00304.x|s2cid=222187102 |doi-access=free }}

}}

{{refbegin}}

• Brusca, R.C.; Brusca, G.J. (1990). Invertebrates. Sinauer Associates: Sunderland, MA (USA). ISBN 0-87893-098-1. 922 pp
• Martin, J.W., & Davis, G.E. (2001). An updated classification of the recent Crustacea. Science Series, 39. Natural History Museum of Los Angeles County. Los Angeles, CA (USA). 124 pp.
• Norambuena, J., J. Farías & P. De los Ríos. (2019). he water flea Daphnia pulex (Cladocera, Daphniidae), a possible model organism to evaluate aspects of freshwater ecosystems. Crustaceana, (11-12): 1415-1426.

{{refend}}

• [https://web.archive.org/web/20080530091637/http://www.tafi.org.au/zooplankton/imagekey/cladocera/index.html Cladocera] – Guide to the Marine Zooplankton of South Eastern Australia
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{{Branchiopoda}}

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Category:Freshwater crustaceans

Category:Crustacean orders