From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Spiral cleavage in Trochus.png
Spiral cleavage in Trochus
Scientific classification edit
Kingdom: Animalia
(unranked): Protostomia
(unranked): Spiralia
sensu Edgecombe et al. 2011

The Spiralia are a morphologically diverse clade of protostome animals, including within their number the molluscs, annelids, platyhelminths and other taxa.[1] The term Spiralia is applied to those phyla that exhibit canonical spiral cleavage, a pattern of early development found in most (but not all) members of the Lophotrochozoa.[2]

Distribution of spiralian development across phylogeny[edit]

Members of the molluscs, annelids, platyhelminths and nemerteans have all been shown to exhibit spiral cleavage in its classical form. Other spiralian phyla (rotifers, brachiopods, phoronids, gastrotrichs, and bryozoans) are also said to display a derived form of spiral cleavage in at least a portion of their constituent species, although evidence for this is sparse.[3]

Lophotrochozoa within Spiralia[edit]

Previously, spiral cleavage was thought to be unique to the Spiralia in the strictest sense—animals such as molluscs and annelids which exhibit classical spiral cleavage. The presence of spiral cleavage in animals such as platyhelminths could be difficult to correlate with some phylogenies.[4]

Evidence of the relationship between molluscs, annelids and lophophorates was found in 1995.[5] More recent research has established the Lophotrochozoa as a superphylum within the Metazoa.[6] With this understanding, the presence of spiral cleavage in polyclad platyhelminths, as well as the more traditional Spiralia, has led to the hypothesis that spiral cleavage was present ancestrally across the Lophotrochozoa as a whole.[3] With the introduction of Platytrochozoa and Rouphozoa, the cladogram is as follows, with an indication approximately how many million years ago (Mya) the clades radiated into newer clades.[7][8][9][10][11][12]


Ecdysozoa Long nosed weevil edit.jpg


Gnathifera Chaetoblack.png





Platyhelminthes Sorocelis reticulosa.jpg



Annelida Polychaeta (no).JPG

Mollusca Grapevinesnail 01.jpg







580 mya
610 mya


  1. ^ Giribet G (April 2008). "Assembling the lophotrochozoan (=spiralian) tree of life". Philos. Trans. R. Soc. Lond. B Biol. Sci. 363 (1496): 1513–22. doi:10.1098/rstb.2007.2241. PMC 2614230. PMID 18192183.
  2. ^ "Explanations.html". Retrieved 2009-06-28.
  3. ^ a b Hejnol, A. (4 August 2010). "A Twist in Time—The Evolution of Spiral Cleavage in the Light of Animal Phylogeny". Integrative and Comparative Biology. 50 (5): 695–706. doi:10.1093/icb/icq103. PMID 21558233.
  4. ^ Boyer, Barbara C.; Henry, Jonathan Q.; Martindale, Mark Q. (1 November 1996). "Dual Origins of Mesoderm in a Basal Spiralian: Cell Lineage Analyses in the Polyclad Turbellarian Hoploplana inquilina". Developmental Biology. 179 (2): 329–338. doi:10.1006/dbio.1996.0264. PMID 8903349.
  5. ^ Halanych, K.; Bacheller, J.; Aguinaldo, A.; Liva, S.; Hillis, D.; Lake, J. (17 March 1995). "Evidence from 18S ribosomal DNA that the lophophorates are protostome animals". Science. 267 (5204): 1641–1643. doi:10.1126/science.7886451. PMID 7886451.
  6. ^ Dunn, C.W.; Hejnol, A.; Matus, D.Q.; Pang, K.; Browne, W.E.; Smith, S.A.; Seaver, E.; Rouse, G.W.; Obst, M.; Sørensen, M. V.; Haddock, S.H.D.; Schmidt-Rhaesa, A.; Okusu, A.; Kristensen, R.M.; Wheeler, W.C.; Martindale, M.Q.; Giribet, G. (10 April 2008). "Broad phylogenomic sampling improves resolution of the animal tree of life". Nature. 452 (7188): 745–749. doi:10.1038/nature06614. PMID 18322464.
  7. ^ Struck, Torsten H.; Wey-Fabrizius, Alexandra R.; Golombek, Anja; Hering, Lars; Weigert, Anne; Bleidorn, Christoph; Klebow, Sabrina; Iakovenko, Nataliia; Hausdorf, Bernhard (July 2014). "Platyzoan Paraphyly Based on Phylogenomic Data Supports a Noncoelomate Ancestry of Spiralia". Molecular Biology and Evolution. 31 (7): 1833–1849. doi:10.1093/molbev/msu143. PMID 24748651.
  8. ^ 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.
  9. ^ Hankeln, Thomas; Wey-Fabrizius, Alexandra; Herlyn, Holger; Witek, Alexander; Weber, Mathias; Nesnidal, Maximilian; Struck, Torsten (2014). "Phylogeny of platyzoan taxa based on molecular data". In Wägele, J. Wolfgang; Bartolomaeus, Thomas. Deep Metazoan Phylogeny: The Backbone of the Tree of Life. Walter de Gruyter GmbH,. pp. 105–125.
  10. ^ Laumer, Christopher E.; Bekkouche, Nicolas; Kerbl, Alexandra; Goetz, Freya; Neves, Ricardo C.; Sørensen, Martin V.; Kristensen, Reinhardt M.; Hejnol, Andreas; Dunn, Casey W. (2015). "Spiralian Phylogeny Informs the Evolution of Microscopic Lineages". Current Biology. 25 (15): 2000–2006. doi:10.1016/j.cub.2015.06.068.
  11. ^ Lu, Tsai-Ming; Kanda, Miyuki; Satoh, Noriyuki; Furuya, Hidetaka (2017-05-29). "The phylogenetic position of dicyemid mesozoans offers insights into spiralian evolution". Zoological Letters. 3: 6. doi:10.1186/s40851-017-0068-5.
  12. ^ Luo, Yi-Jyun; Kanda, Miyuki; Koyanagi, Ryo; Hisata, Kanako; Akiyama, Tadashi; Sakamoto, Hirotaka; Sakamoto, Tatsuya; Satoh, Noriyuki (2017-12-04). "Nemertean and phoronid genomes reveal lophotrochozoan evolution and the origin of bilaterian heads". Nature Ecology & Evolution. 2 (1): 141–151. doi:10.1038/s41559-017-0389-y.