Onychopoda

Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Ecdysozoa
Cladus: Panarthropoda
Phylum: Arthropoda
Subphylum: Crustacea
Superclassis: Allotriocarida
Classis: Branchiopoda
Superordo: Cladocera
Ordo: Onychopoda
Familiae (3): Cercopagidae - Podonidae - Polyphemidae

References

Dumont H.J., & Negrea S.V.. 2002: Introduction to the Class Branchiopoda. Guides to the identification of the macroinvertebrates of the continental waters of the world. (Ed. H.J. F. Dumont). Backhuys Publishers, Leiden. 19:1-398. ISBN 90-5782-112-5
Sars G.O.. 1865: Norges ferskvandskrebsdyr. Første afsnit. Branchiopoda. I. Cladocera Ctenopoda (fam. Sididae & Holopedidae). Med Hs. Majt. Kongens guldemedaille prisbelønnet afhandling. Udgivet som Univeritets-program for 1ste halvaar 1863 ved dr M. Sars, Brøgger & Christie's bogtrykkeri, Christiana (Oslo). VIII+71pp., pls. 1-4
Webber, W.R. et al. 2010: [Chapter] EIGHT Phylum ARTHROPODA SUBPHYLUM CRUSTACEA shrimps, crabs, lobsters, barnacles, slaters, and kin. Pp. 98-232 in Gordon, D.P. (ed.): New Zealand inventory of biodiversity. Volume 2. Kingdom Animalia. Chaetognatha, Ecdysozoa, ichnofossils. Canterbury University Press, Christchurch, New Zealand. ISBN 978-1-87725793-3 [p. 211, as subordo of Diplostraca]

Links

WoRMS (2010). Onychopoda. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=106261 on 2010-12-27

Vernacular names
中文: 钩足目

Onychopoda are a specialised order of branchiopod crustaceans, belonging to the superorder Cladocera.

The order Onychopoda is "one of the most morphologically distinctive groups of cladocerans".[2] They have only four pairs of legs, compared to five or six pairs in Ctenopoda and Anomopoda.[3] Unusually among branchiopod crustaceans, Onychopoda share with Haplopoda the presence of segmented appendages, which are used for grasping prey.[4]

Most species of Onychopoda live in the waters of the Ponto-Caspian basin (Caspian Sea, Aral Sea, Black Sea including Sea of Azov), in remnants of the ancient Paratethys ocean.[5] Some other species live in fresh water or in the oceans, where they can be widespread.[5]

There are three families, containing 10 genera and around 33 described species, most of which are endemic to the Ponto-Caspian basin:[2]

Cercopagididae Mordukhai-Boltovskoi, 1968 – 2 genera (Cercopagis and Bythotrephes), 14 species; Black Sea & Caspian Sea
Podonidae Mordukhai-Boltovskoi, 1968 – 7 genera, 17 species; Pont-Caspian (Caspievadne, Cornigerius and Podonevadne) and marine (Evadne, Pleopis, Podon and Pseudevadne)
Polyphemidae Baird, 1845 – 1 genus (Polyphemus), 2 species; fresh water

The embryos are protected by a brood pouch, which also secretes nutrients to aid their development. This may be related to the colonisation of the oceans, since the only other marine cladoceran, Penilia avirostris, has a similar pouch as a result of convergent evolution.[2]
See also

Bythotrephes longimanus
Cercopagis pengoi

References

J. W. Martin & G. E. Davis (2001). An Updated Classification of the Recent Crustacea (PDF). Natural History Museum of Los Angeles County. pp. 1–132.
M. E. A. Cristescu & P. D. N. Hebert (2002). "Phylogeny and adaptive radiation in the Onychopoda (Crustacea, Cladocera): evidence from multiple gene sequences" (PDF). Journal of Evolutionary Biology. 15 (5): 838–849. doi:10.1046/j.1420-9101.2002.00466.x.
D. R. Khanna (2004). "Segmentation in arthropods". Biology of Arthropoda. Discovery Publishing House. pp. 316–394. ISBN 978-81-7141-897-8.
G. Fryer (1998). "A defence of arthropod polyphyly". In Richard A. Fortey; Richard H. Thomas (eds.). Arthropod Relationships. Volume 55 of Systematics Association Series. Springer. pp. 23–34. ISBN 978-0-412-75420-3.
Stefan Richter; Anke Braband; Nikolai Aladin; Gerhard Scholtz (2001). "The phylogenetic relationships of "predatory water-fleas" (Cladocera: Onychopoda, Haplopoda) inferred from 12S rDNA". Molecular Phylogenetics and Evolution. 19 (1): 105–113. doi:10.1006/mpev.2000.0901. PMID 11286495.