Overview
Eucarida is a superorder of the Malacostraca, a class of the crustacean subphylum, comprising the decapods, krill and Amphionides.2] They are characterised by having the carapace fused to all thoracic segments, and by the possession of stalked eyes.[3]
Orders
Eucarida is a diverse and abundant group, comprising the following three orders:
Euphausiacea
The members of the Euphausiacea are commonly called krill and are all marine shrimp-like species whose pleopods (abdominal appendages) function as swimmerets, they swarm and mostly feed on plankton, this group is composed of only 90 species, but some of these are one of the most abundant species on the planet, in fact, it is estimated th at the biomass of the Antarctic krill Euphausia superba' is 500 million tons.[4]
Decapoda
The Decapoda is a group with 15,000 species[5] which have 5 pairs of thoracopods and a well-developed carapace that covers the gills (which are exposed in krill). They include lobsters, crabs, shrimp and prawns. The decapods are further subdivided on the basis of the gill structure into two suborders Dendrobranchiata (prawns) and Pleocyemata, which is further subdivided into several infraorders, such as the Caridea (true shrimps), the Stenopodidea (boxer shrimp) and the Anomura and the Brachyura (crabs) and so forth.[6][7]
Amphionidacea
In addition, there is an enigmatic eucarid species, Amphionides reynaudii, which is the sole representative of its order, but due to the loss of several features resulting from its small size, its classification has been unclear.[8]
Phylogeny
The phylogeny of the Malacostraca is debated.[6] In particular, the monophyly of Eucarida is also under question:
- Monophyletic: many argu e that the Eucarida group is a clade, sister to the Peracarida clade[9][6] or to the basal Malacostraca.[7][10] or to Mysida (paraphyletic Schizopoda)[11]
- Paraphyletic: some have proposed a paraphyletic Eucarida forming a clade with a nested Peracarida.[12]
- Polyphyletic: some have grouped Euphausiacea with Mysida to form the Schizopoda,[13][14] or the Euphausiacea with the Hoplocarida,[15] with Decapoda basal to the Peracarida.[15][14]
Orders
Eucarida is a diverse and abundant group, comprising the following three orders:
Euphausiacea
The m embers of the Euphausiacea are commonly called krill and are all marine shrimp-like species whose pleopods (abdominal appendages) function as swimmerets, they swarm and mostly feed on plankton, this group is composed of only 90 species, but some of these are one of the most abundant species on the planet, in fact, it is estimated that the biomass of the Antarctic krill Euphausia superba' is 500 million tons.[4]
Decapoda
The Decapoda is a group with 15,000 species[5] which have 5 pairs of thoracopods and a well-developed carapace that covers the gills (which are exposed in krill). They include lobsters, crabs, shrimp and prawns. The decapods are further subdivided on the basis of the gill structure into two suborders Dendrobranchiata (prawns) and Pleocyemata, which is further subdivided into several infraorders, such as the Caridea (true shrimps), the Stenopodidea (boxer shrimp) and the Anomura and the Brachyura (crabs) and so forth.[6][7]
Amphionidacea
In addition, there is an enigmatic eucarid species, Amphionides reynaudii, which is the sole representative of its order, but due to the loss of several features resulting from its small size, its classification has been unclear.[8]
Phylogeny
The phylogeny of the Malacostraca is debated.[6] In particular, the monophyly of Eucarida is also under question:
- Monophyletic: many argue that the Eucarida group is a clade, sister to the Peracarida clade[9][6] or to the basal Malacostraca.[7][10] or to Mysida (paraphyletic Schizopoda)[11]
- Paraphyletic: some have proposed a paraphyletic Eucarida forming a clade with a nested Peracarida.[12]
- Polyphyletic: some have grouped Euphausiacea with Mysida to form the Schizopoda,[13][14] or the Euphausiacea with the Hoplocarida,[15] with Decapoda basal to the Peracarida.[15][14]
References
- ^ "Eucarida Calman, 1904". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=95495. Retrieved February 7, 2011.
- ^ WoRMS (2010). "Eucarida". World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=1089. Retrieved February 7, 2011.
- ^ L. A. Borradaile, F. A. Potts, L. E. S. Eastman & J. T. Saunders (1961). "The Class Crustacea". In Gerald A. Kerkut. The Invertebrata (4th ed.). Cambridge University Press. pp. 340?419.
- ^ 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.
- ^ Sammy De Grave, N. Dean Pentcheff, Shane T. Ahyong et al. (2009). "A classification of living and fossil genera of decapod crustaceans". Raffles Bulletin of Zoology Suppl. 21: 1?109. http://rmbr.nus.edu.sg/rbz/biblio/s21/s21rbz1-109.pdf.
- ^ a b c Frederick Schram (1986). Crustacea. Oxford University Press. ISBN 0-19-503742-1.
- ^ a b M. A. Wills (1998). "A phylogeny of recent and fossil Crustacea derived from morphological characters". In Richard A. Fortey & Richard H. Thomas. Arthropod Relationships. Volume 55 of Systematics Association Series. Springer. pp. 189?210. ISBN 9780412754203. http://books.google.co.uk/books?id=Pj-q9eHyIx0C&pg=PA189.
- ^ Richard C. Brusca and Gary J. Brusca (2003). Invertebrates (2nd ed.). Sunderland, Massachusetts: Sinauer Associates. ISBN 9780878930975.
- ^ R. Siewing (1963). "Studies in malacostracan morphology: results and problems". In H. B. Whittington & W. D. Rolfe. Phylogeny and Evolution of Crustacea. Cambridge, Massachusetts: Museum of Comparative Zoology. pp. 85?103.
- ^ Trisha Spears, Ronald W. DeBry, Lawrence G. Abele & Katarzyna Chodyla (2005). "Peracarid monophyly and interordinal phylogeny inferred from nuclear small-subunit ribosomal DNA sequences (Crustacea: Malacostraca: Peracarida)" (PDF). Proceedings of the Biological Society of Washington 118 (1): 117?157. doi:10.2988/0006-324X(2005)118[117:PMAIPI]2.0.CO;2. http://decapoda.nhm.org/pdfs/10231/10231.pdf.
- ^ L. Watling (1999). "Towards understanding the relationship of the peracaridan orders: the necessity of determining exact homologies". In Frederick R. Schram & J. Carel von Vaupel Klein. Crustaceans and the Biodiversity Crisis. Proceedings of the Fourth International Crustacean Congress, Amsterdam: The Netherlands, July 20?24, 1998, Vol. I. Brill Publishers. pp. 73?89. ISBN 9789004113879.
- ^ Stefan Richter & Gerhard Scholtz (2001). "Phylogenetic analysis of the Malacostraca (Crustacea)". Journal of Zoological Systematics and Evolutionary Research 39 (3): 113?136. doi:10.1046/j.1439-0469.2001.00164.x.
- ^ Georg Ossian Sars (1870). Carcinologiske Bidrag til Norges Fauna over de ved Norges Kysters forekommende Mysider. Vol. 1. Christiana: Br?gger & Christies Bogtrykkeri.
- ^ a b Simon N. Jarman, Stephen Nicol, Nicholas G. Elliott & Andrew McMinn (2000). "28S rDNA evolution in the Eumalacostraca and the phylogenetic position of krill". Molecular Phylogenetics and Evolution 17 (1): 26?36. doi:10.1006/mpev.2000.0823. PMID 11020302.
- ^ a b K. Meland & E. Willassen (2007). "The disunity of "Mysidacea" (Crustacea)" (PDF). Molecular Phylogenetics and Evolution 44 (3): 1083?1104. doi:10.1016/j.ympev.2007.02.009. PMID 17398121. http://decapoda.nhm.org/pdfs/31293/31293.pdf.
Taxonomy
The Superorder Eucarida is further organized into finer groupings including:
- Order (3): Amphionidacea · Decapoda · Euphausiacea
Orders
Amphionidacea
Amphionides reynaudii is the sole representative of the order Amphionidacea, and is a small (less than one inch long) planktonic crustacean found throughout the world's tropical oceans, mostly in shallow waters. [more]
Decapoda
The decapods or Decapoda (literally "ten-footed") are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with approximately 3,300 fossil species. Nearly half of these species are crabs, with the shrimp (?3000 species) and Anomura (including hermit crabs, porcelain crabs, squat lobsters: c.?2500 species), making up the bulk of the remainder. The earliest fossil decapod is the Devonian Palaeopalaemon. [more]
Euphausiacea
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world. The common name krill comes from the Norwegian word , meaning "young fry of fish", which is also often attributed to other species of fish. [more]
At least 120 species and subspecies belong to the Order Euphausiacea.
More info about the Order Euphausiacea may be found here.
References
Sources
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