Cladocera

Cladus: Eukaryota
Supergroup: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Superphylum: Ecdysozoa
Phylum: Arthropoda
Subphylum: Crustacea
Classis: Branchiopoda
Subclassis: Phyllopoda
Ordo: Diplostraca
Subordo: Cladocera
Infraordines: Anomopoda - Ctenopoda - Haplopoda - Onychopoda

Vernacular names
Internationalization
Česky: Perloočky
Dansk: Dafnier
Deutsch: Wasserflöhe
Ελληνικά: Κλαδοκεραιωτά
English: Waterfleas
فارسی: شاخه‌سرونیان
Français: Cladocères
日本語: ミジンコ目
Nederlands: Watervlooien
‪Norsk (bokmål)‬: Vannlopper
Polski: Wioślarki
Português: Cladócera
Русский: Ветвистоусые раки
Svenska: Hinnkräfter
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Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. They are ubiquitous in inland aquatic habitats, but rare in the oceans. Most are 0.2–6.0 mm (0.0079–0.24 in) long, with a down-turned head, and a carapace covering the apparently unsegmented thorax and abdomen. There is a single median compound eye. Most species show cyclical parthenogenesis, where asexual reproduction is occasionally supplemented by sexual reproduction, which produces resting eggs that allow the species to survive harsh conditions and disperse to distant habitats.

Description

They are mostly 0.2–6.0 millimetres (0.008–0.236 in) long, with the exception of Leptodora, which can be up to 18 mm (0.71 in) long.[1] The body is not obviosuly segmented and bears a folded carapace which covers the thorax and abdomen.[2]

The head is angled downwards, and may separated from the rest of the body by a "cervical sinus" or notch.[2] It bears a single black compound eye, located on the animal's midline, in all but two genera, and there is often a single ocellus.[3] 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.[2] The first antennae bear olfactory setae, while the second are used for swimming by most species.[3] The pattern of setae on the second antennae is useful for identification; Daphnia.[2] The part of the head which projects in front of the first antennae is known as the rostrum or "beak".[2]

The mouthparts are small, and consist of an unpaired labrum, a pair of mandibles, a pair of maxillae, and an unpaired labium.[2] They are used to eat "organic detritus of all kinds" and bacteria.[2]

The thorax bears five or six pairs of lobed, leaf-like appendages, each with numerous hairs or setae.[2] Carbon dioxide is lost, and oxygen taken up, through the body surface.[2]

Life cycle

With the exception of a few purely asexual species, the life cycle of cladocerans is dominated by asexual reproduction, with occasional periods of sexual reproduction; this is known as cyclical parthenogenesis. The system evolved in the Permian, at the same time that the Cladocera arose.[4] 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.[2]

Ecology

Most cladoceran species live in fresh water and other inland water bodies, with only eight species being truly neritic (oceanic).[3] The marine species are all in the family Podonidae, except for the genus Penilia.[3]

Taxonomy

The order Cladocera is included in the class Branchiopoda, and forms a monophyletic group, which is currently divided into four suborders. Around 620 species have been described, but many more species remain undescribed.[1] The genus Daphnia alone contains around 150 species.[4]

The following families are recognised:[5]

Order Cladocera Latreille, 1829

* Suborder Ctenopoda Sars, 1865
o Holopediidae Sars, 1865
o Sididae Baird, 1850
* Suborder Anomopoda Stebbing, 1902
o Bosminidae Baird, 1845
o Chydoridae Stebbing, 1902
o Daphniidae Straus, 1820
o Gondwanotrichidae Van Damme et al., 2007[6][7]
o Macrotrichidae Norman & Brady, 1867
* Suborder Onychopoda Sars, 1865
o Cercopagididae Mordukhai-Boltovskoi, 1968
o Podonidae Mordukhai-Boltovskoi, 1968
o Polyphemidae Baird, 1845
* Suborder Haplopoda Sars, 1865
o Leptodoridae Lilljeborg, 1900

Etymology

The word "Cladocera" derives via New Latin from the Ancient Greek κλάδος (kládos, "branch") and κέρας (kéras, "horn").[8]
References

1. ^ a b L. Forró, N. M. Korovchinsky, A. A. Kotov & A. Petrusek (2008). Global diversity of cladocerans (Cladocera; Crustacea) in freshwater. In Estelle V. Balian, Christian Lévêque, Hendrik Segers & Koen Martens. "Freshwater Animal Diversity Assessment" (PDF). Hydrobiologia. Developments in Hydrobiology 198 595 (1): 177–184. doi:10.1007/s10750-007-9013-5. ISBN 978-1-4020-8259-7. http://decapoda.nhm.org/pdfs/27704/27704.pdf. doi:10.1007/978-1-4020-8259-7_19
2. ^ a b c d e f g h i j Douglas Grant Smith & Kirstern Work (2001). "Cladoceran Branchiopoda (water fleas)". In Douglas Grant Smith. Pennak's Freshwater Invertebrates of the United States: Porifera to Crustacea (4th ed.). John Wiley and Sons. pp. 453–488. ISBN 9780471358374. http://books.google.co.uk/books?id=GqIctb8IqPoC&pg=PA468.
3. ^ a b c d Denton Belk (2007). "Branchiopoda". In Sol Felty Light & James T. Carlton. The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon (4th ed.). University of California Press. pp. 414–417. ISBN 9780520239395. http://books.google.co.uk/books?id=64jgZ1CfmB8C&pg=PA416.
4. ^ a b Ellen Decaestecker, Luc De Meester & Joachim Mergaey (2009). "Cyclical parthenogeness in Daphnia: sexual versus asexual reproduction". In Isa Schön, Koen Martens & Peter van Dijk. Lost Sex: The Evolutionary Biology of Parthenogenesis. Springer. pp. 295–316. doi:10.1007/978-90-481-2770-2_15. ISBN 9789048127696. http://books.google.co.uk/books?id=GaWD_OtE0AMC&pg=PA296.
5. ^ Joel W. Martin & George E. Davis (2001). An Updated Classification of the Recent Crustacea. Natural History Museum of Los Angeles County. pp. 1–132. http://atiniui.nhm.org/pdfs/3839/3839.pdf.
6. ^ K. Van Damme, R. J. Shiel & H. J. Dumont (2007). "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". Zoologica Scripta 36 (5): 465–487. doi:10.1111/j.1463-6409.2007.00292.x.
7. ^ K. Van Damme, R. J. Shiel & H. J. Dumont (2007). "Gondwanotrichidae nom. nov. pro Nototrichidae Van Damme, Shiel & Dumont, 2007". Zoologica Scripta 36 (5): 623. doi:10.1111/j.1463-6409.2007.00304.x.
8. ^ "Webster's II New College Dictionary". Webster's II New College Dictionary (3rd ed.). Houghton Mifflin Harcourt. 2005. p. 211. ISBN 9780618396016. http://books.google.co.uk/books?id=OL60E3r2yiYC&pg=PA211.