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Ecdysozoa
Ecdysozoa
/ˌɛkdɪsoʊˈzoʊə/ is a group of protostome animals,[1] including Arthropoda
Arthropoda
(insects, chelicerata, crustaceans, and myriapods), Nematoda, and several smaller phyla. They were first defined by Aguinaldo et al. in 1997, based mainly on phylogenetic trees constructed using 18S ribosomal RNA genes.[2] A large study in 2008 by Dunn et al. strongly supported the Ecdysozoa
Ecdysozoa
as a clade, that is, a group consisting of a common ancestor and all its descendants.[3] The group is also supported by morphological characters, and includes all animals that grow by ecdysis, moulting their exoskeleton. The group was initially contested by a significant minority of biologists. Some argued for groupings based on more traditional taxonomic techniques,[4] while others contested the interpretation of the molecular data.[5][6]

Contents

1 Characteristics 2 Phylogeny 3 Older alternative groupings

3.1 Articulata hypothesis 3.2 Coelomata hypothesis

4 References 5 External links

Characteristics[edit] See also: List of bilaterial animal orders The most notable characteristic shared by ecdysozoans is a three-layered cuticle (four in Tardigrada[7]) composed of organic material, which is periodically molted as the animal grows. This process of molting is called ecdysis, and gives the group its name. The ecdysozoans lack locomotory cilia and produce mostly amoeboid sperm, and their embryos do not undergo spiral cleavage as in most other protostomes. Ancestrally, the group exhibited sclerotized teeth within the foregut, and a ring of spines around the mouth opening, though these features have been secondarily lost in certain groups.[8] Phylogeny[edit] The Ecdysozoa
Ecdysozoa
include the following phyla: Arthropoda, Onychophora, Tardigrada, Kinorhyncha, Priapulida, Loricifera, Nematoda, and Nematomorpha. A few other groups, such as the gastrotrichs, have been considered possible members but lack the main characters of the group, and are now placed elsewhere. The Arthropoda, Onychophora, and Tardigrada
Tardigrada
have been grouped together as the Panarthropoda
Panarthropoda
because they are distinguished by segmented body plans.[9] Dunn et al. in 2008 suggested that the tardigrada could be grouped along with the nematodes, leaving Onychophora
Onychophora
as the sister group to the arthropods.[3] The non-panarthropod members of Ecdysozoa
Ecdysozoa
have been grouped as Cycloneuralia but they are more usually considered paraphyletic in as representing the primitive condition from which the Panarthropoda
Panarthropoda
evolved.[10] A modern (2011) consensus phylogenetic tree for the protostomes is shown below.[11][12][13][14][15][16][17][14] It is indicated when approximately clades radiated into newer clades in millions of years ago (Mya).[18]

Bilateria

Xenacoelomorpha
Xenacoelomorpha

Nephrozoa

Protostomia

Ecdysozoa

Scalidophora

Priapulida
Priapulida

Kinorhyncha
Kinorhyncha

Nematoida

Nematoda
Nematoda

Nematomorpha
Nematomorpha

Loricifera
Loricifera

Panarthropoda

Onychophora
Onychophora

Tactopoda

Tardigrada
Tardigrada

Arthropoda
Arthropoda

>529 mya

Spiralia
Spiralia

Deuterostomia
Deuterostomia

610 mya

Older alternative groupings[edit] Articulata hypothesis[edit] The grouping proposed by Aguinaldo et al. is almost universally accepted, replacing an older hypothesis that Panarthropoda
Panarthropoda
should be classified with Annelida
Annelida
in a group called the Articulata, and that Ecdysozoa
Ecdysozoa
are polyphyletic. Nielsen has suggested that a possible solution is to regard Ecdysozoa
Ecdysozoa
as a sister-group of Annelida,[19] though later considered them unrelated.[20] Inclusion of the roundworms within the Ecdysozoa
Ecdysozoa
was initially contested[5][21] but since 2003, a broad consensus has formed supporting the Ecdysozoa
Ecdysozoa
[22] and in 2011 the Darwin–Wallace Medal
Darwin–Wallace Medal
was awarded to James Lake for the discovery of the New Animal
Animal
Phylogeny consisting of the Ecdysozoa, the Lophotrochozoa, and the Deuterostomia.[23] Coelomata hypothesis[edit] Before Ecdysozoa, one of the prevailing theories for the evolution of the bilateral animals was based on the morphology of their body cavities. There were three types, or grades of organization: the Acoelomata
Acoelomata
(no coelom), the Pseudocoelomata (partial coelom), and the Eucoelomata
Eucoelomata
(true coelom). Adoutte and coworkers were among the first to strongly support the Ecdysozoa.[24] With the introduction of molecular phylogenetics, the coelomate hypothesis was abandoned, although some molecular, phylogenetic support for the Coelomata continued until as late as 2005.[25] References[edit]

^ Telford MJ, Bourlat SJ, Economou A, Papillon D, Rota-Stabelli O (April 2008). "The evolution of the Ecdysozoa". Philosophical Transactions of the Royal Society B: Biological Sciences. 363 (1496): 1529–37. doi:10.1098/rstb.2007.2243. PMC 2614232 . PMID 18192181.  ^ Aguinaldo, A. M. A.; J. M. Turbeville; L. S. Linford; M. C. Rivera; J. R. Garey; R. A. Raff; J. A. Lake (29 May 1997). "Evidence for a clade of nematodes, arthropods, and other moulting animals". Nature. 387 (6632): 489–493. Bibcode:1997Natur.387R.489A. doi:10.1038/387489a0. PMID 9168109.  ^ a b Dunn, CW; Hejnol, A; Matus, DQ; Pang, K; Browne, WE; Smith, SA; Seaver, E; Rouse, GW; et al. (10 April 2008). "Broad phylogenomic sampling improves resolution of the animal tree of life". Nature. 452 (7188): 745–749. Bibcode:2008Natur.452..745D. doi:10.1038/nature06614. PMID 18322464. CS1 maint: Explicit use of et al. (link) ^ Nielsen, Claus (1995). Animal
Animal
Evolution: Interrelationships of the Living Phyla. Oxford University Press. ISBN 978-0-19-850682-9.  ^ a b Blair, J. E.; Kazuho Ikeo; Takashi Gojobori; S. Blair Hedges (8 April 2002). "The evolutionary position of nematodes". BMC Evolutionary Biology. 2: 7. doi:10.1186/1471-2148-2-7. PMC 102755 . PMID 11985779.  ^ Wägele, J. W.; T. Erikson; P. Lockhart; B. Misof (December 1999). "The Ecdysozoa: Artifact or monophylum?". Journal of Zoological Systematics and Evolutionary Research. 37 (4): 211–223. doi:10.1111/j.1439-0469.1999.tb00985.x.  ^ Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 877–880. ISBN 0-03-056747-5.  ^ Smith, Martin R.; Caron, Jean-Bernard (2 July 2015). "Hallucigenia's head and the pharyngeal armature of early ecdysozoans". Nature. 523 (7558): 75–8. Bibcode:2015Natur.523...75S. doi:10.1038/nature14573. PMID 26106857.  ^ Paleos Invertebrates: Panarthropoda, retrieved February 17, 2007 ^ Webster, Bonnie L.; Copley, Richard R.; Jenner, Ronald A.; Mackenzie-Dodds, Jacqueline A.; Bourlat, Sarah J.; Rota-Stabelli, Omar; Littlewood, D. T. J.; Telford, Maximilian J. (November 2006). "Mitogenomics and phylogenomics reveal priapulid worms as extant models of the ancestral Ecdysozoan". Evolution & Development. 8 (6): 502–510. doi:10.1111/j.1525-142X.2006.00123.x.  ^ Edgecombe, Gregory D.; Giribet, Gonzalo; Dunn, Casey W.; Hejnol, Andreas; Kristensen, Reinhardt M.; Neves, Ricardo C.; Rouse, Greg W.; Worsaae, Katrine; Sørensen, Martin V. (June 2011). "Higher-level metazoan relationships: recent progress and remaining questions". Organisms, Diversity & Evolution. 11 (2): 151–172. doi:10.1007/s13127-011-0044-4.  ^ Fröbius, Andreas C.; Funch, Peter (2017-04-04). "Rotiferan Hox genes give new insights into the evolution of metazoan bodyplans". Nature Communications. 8 (1). doi:10.1038/s41467-017-00020-w.  ^ Smith, Martin R.; Ortega-Hernández, Javier (2014). "Hallucigenia's onychophoran-like claws and the case for Tactopoda". Nature. 514 (7522): 363–366. doi:10.1038/nature13576.  ^ a b "Palaeos Metazoa: Ecdysozoa". palaeos.com. Retrieved 2017-09-02.  ^ Yamasaki, Hiroshi; Fujimoto, Shinta; Miyazaki, Katsumi (June 2015). "Phylogenetic position of Loricifera
Loricifera
inferred from nearly complete 18S and 28S rRNA gene sequences". Zoological Letters. 1: 18. doi:10.1186/s40851-015-0017-0.  ^ Nielsen, C. (2002). Animal
Animal
Evolution: Interrelationships of the Living Phyla (2nd ed.). Oxford University Press. ISBN 0-19-850682-1.  ^ "Bilateria". Tree of Life Web Project. 2001. Retrieved August 11, 2014.  ^ Peterson, Kevin J.; Cotton, James A.; Gehling, James G.; Pisani, Davide (2008-04-27). "The Ediacaran emergence of bilaterians: congruence between the genetic and the geological fossil records". Philosophical Transactions of the Royal Society of London B: Biological Sciences. 363 (1496): 1435–1443. doi:10.1098/rstb.2007.2233. PMC 2614224 . PMID 18192191.  ^ Nielsen, C (September 2003). "Proposing a solution to the Articulata– Ecdysozoa
Ecdysozoa
controversy". Zoologica Scripta. 32 (5): 475–482. doi:10.1046/j.1463-6409.2003.00122.x.  ^ Nielsen, Claus (2012). Animal
Animal
Evolution: Interrelationships of the Living Phyla 3rd ed. Oxford University Press. ISBN 978-0-19-960603-0.  ^ Wägele, J. W.; B. Misof (September 2001). "On quality of evidence in phylogeny reconstruction: a reply to Zrzavý's defence of the 'Ecdysozoa' hypothesis". Journal of Zoological Systematics and Evolutionary Research. 39 (3): 165–176. doi:10.1046/j.1439-0469.2001.00177.x.  ^ Maximilian J Telford; D. Timothy J Littlewood (27 April 2008). "The evolution of the animals: introduction to a Linnean tercentenary celebration". Philosophical Transactions of the Royal Society B: Biological Sciences. 363: 1421–1424. doi:10.1098/rstb.2007.2231. PMC 2394567 . PMID 18192193.  ^ "The Darwin-Wallace Medal". The Linnean Society of London. Retrieved 28 February 2018.  ^ Adoutte, A.; Balavoine, G.; Lartillot, N.; Lespinet, O.; Prud'homme, B.; de Rosa, R. (25 April 2000). " Special
Special
Feature: The new animal phylogeny: Reliability and implications". Proceedings of the National Academy of Sciences. 97 (9): 4453–4456. doi:10.1073/pnas.97.9.4453. PMC 34321 . PMID 10781043. Retrieved 5 April 2013.  ^ Philip, G.K.; C.J. Creevey; J.O. McInerney (9 February 2005). "The Opisthokonta and the Ecdysozoa
Ecdysozoa
May Not Be Clades: Stronger Support for the Grouping of Plant and Animal
Animal
than for Animal
Animal
and Fungi and Stronger Support for the Coelomata than Ecdysozoa". Molecular Biology and Evolution. 22 (5): 1175–1184. doi:10.1093/molbev/msi102. PMID 15703245. Retrieved 5 April 2013. 

External links[edit]

Wikispecies
Wikispecies
has information related to Ecdysozoa

UCMP- Ecdysozoa
Ecdysozoa
introduction https://web.archive.org/web/20030313115747/http://www.palaeos.com/Kingdoms/Animalia/Ecdysozoa.html http://www.nematodes.org/tardigrades/Tardigrades_and_Ecdysozoa.html https://web.archive.org/web/20100510081324/http://chuma.cas.usf.edu/~garey/articulata.html https://web.archive.org/web/20030313065540/http://chuma.cas.usf.edu/~garey/essential.html http://www.nematomorpha.net

v t e

Extant Animal
Animal
phyla

Domain Archaea Bacteria Eukaryota (Supergroup Plant Hacrobia Heterokont Alveolata Rhizaria Excavata Amoebozoa Opisthokonta

Animal Fungi)

A n i m a l i a

Porifera (sponges)

Diploblasts (Eumetazoa)

Ctenophora
Ctenophora
(comb jellies)

ParaHoxozoa

Placozoa
Placozoa
(Trichoplax)

Planulozoa

Cnidaria
Cnidaria
(jellyfish and relatives)

Bilateria (Triploblasts)

(see below↓)

Bilateria

Xenacoelomorpha

Xenoturbellida (Xenoturbella) Acoelomorpha

acoels nemertodermatids

N e p h r o z o a

Deuterostomia

Chordata

lancelets tunicates craniates / vertebrates

Ambulacraria

Echinodermata (starfish and relatives) Hemichordata

acorn worms pterobranchs

P r o t o s t o m i a

Ecdysozoa

Scalidophora

Kinorhyncha
Kinorhyncha
(mud dragons) Priapulida
Priapulida
(penis worms)

N+L+P

Nematoida

Nematoda
Nematoda
(roundworms) Nematomorpha
Nematomorpha
(horsehair worms)

L+P

Loricifera

Panarthropoda

Arthropoda
Arthropoda
(arthropods) Tardigrada
Tardigrada
(waterbears) Onychophora
Onychophora
(velvet worms)

S p i r a l i a

Gnathifera¹

Chaetognatha
Chaetognatha
(arrow worms) Gnathostomulida (jaw worms) Micrognathozoa (Limnognathia) Syndermata

Rotifera Acanthocephala

Platytrochozoa

R+M

Mesozoa

Orthonectida Dicyemida
Dicyemida
or Rhombozoa

Rouphozoa¹

Platyhelminthes (flatworms) Gastrotricha (hairybacks)

Lophotrochozoa

Cycliophora (Symbion) Mollusca
Mollusca
(molluscs)

A+N

Annelida
Annelida
(ringed worms) Nemertea
Nemertea
(ribbon worms)

Lophophorata

Bryozoa

Entoprocta
Entoprocta
or Kamptozoa Ectoprocta (moss animals)

Brachiozoa

Brachiopoda (lamp shells) Phoronida (horseshoe worms)

Major groups within phyla

Sponges

Calcareous Hexactinellid Demosponge Homoscleromorpha

Cnidarians

Anthozoa
Anthozoa
inc. corals Medusozoa
Medusozoa
inc. jellyfish Myxozoa

Vertebrates

Jawless fish Cartilaginous fish Bony fish Amphibians Reptiles/Birds Mammals

Echinoderms

Sea lilies Asterozoa
Asterozoa
inc. starfish Echinozoa

Nematodes

Chromadorea Enoplea Secernentea

Arthropods

Chelicerates/Arachnids Myriapods Crustaceans Hexapods/Insects

Platyhelminths

Turbellaria Trematoda Monogenea Cestoda

Bryozoans

Phylactolaemata Stenolaemata Gymnolaemata

Annelids

Polychaetes Clitellata Echiura

Molluscs

Gastropods Cephalopods Bivalves Chitons Tusk shells

Phyla with ≥5000 extant species bolded See also Diploblasts Monoblastozoa (nomen dubium)

¹Platyzoa

Taxon identifiers

Wd: Q5176 ADW: Ecdysozoa EoL: 8880788 Fossilworks: 67124 ITIS: 914158 N