Acorn worm

Acorn worms
Temporal range:
By Johann Wilhelm Spengel, 1893
Scientific classification e
Kingdom: Animalia
Phylum: Hemichordata
Class: Enteropneusta
Gegenbaur 1870
Order: Enteropneusta

The acorn worms or Enteropneusta are a hemichordate class of invertebrates consisting of one order of the same name.[1] The closest non-hemichordate relatives of the Enteropneusta are the echinoderms.[2] There are 111 known species of acorn worm in the world,[3] the main species for research being Saccoglossus kowalevskii. Two families—Harrimaniidae and Ptychoderidae—separated at least 370 million years ago.[4]

Until recently, it was thought that all species lived in the sediment on the seabed, subsisting as deposit feeders or suspension feeders. However, the early 21st century has seen the description of a new family, the Torquaratoridae, evidently limited to the deep sea, in which most of the species crawl on the surface of the ocean bottom and alternatively rise into the water column, evidently to drift to new foraging sites.[5][6][7][8][9] It is assumed that the ancestors of acorn worms used to live in tubes like their relatives Pterobranchia, but that they eventually started to live a safer and more sheltered existence in sediment burrows instead.[10] The body length normally range from 2 centimetres (0.79 in) to 2.5 metres (8 ft 2 in) (Balanoglossus gigas),[11] but one species, Meioglossus psammophilus, only reach 0.6 millimetres (0.024 in).[12] Due to secretions containing elements like iodine, the animals have an iodoform-like smell.[13]

  1. ^ Konikoff, C; van der Land, J (2011). "Enteropneusta". WoRMS. World Register of Marine Species. Retrieved 2017-11-20.
  2. ^ Cameron, CB; Garey, JR; Swalla, BJ (2000). "Evolution of the chordate body plan: New insights from phylogenetic analyses of deuterostome phyla". Proceedings of the National Academy of Sciences of the United States of America. 97 (9): 4469–74. Bibcode:2000PNAS...97.4469C. doi:10.1073/pnas.97.9.4469. PMC 18258. PMID 10781046.
  3. ^ Biogeography and adaptations of torquaratorid acorn worms (Hemichordata: Enteropneusta) including two new species from the Canadian Arctic - Research Proposal - Papyrus - Université de Montréal
  4. ^ Simakov, Oleg; Kawashima, Takeshi; Marlétaz, Ferdinand; Jenkins, Jerry; Koyanagi, Ryo; Mitros, Therese; Hisata, Kanako; Bredeson, Jessen; Shoguchi, Eiichi; Gyoja, Fuki; Yue, Jia-Xing; Chen, Yi-Chih; Freeman, Robert M.; Sasaki, Akane; Hikosaka-Katayama, Tomoe; Sato, Atsuko; Fujie, Manabu; Baughman, Kenneth W.; Levine, Judith; Gonzalez, Paul; Cameron, Christopher; Fritzenwanker, Jens H.; Pani, Ariel M.; Goto, Hiroki; Kanda, Miyuki; Arakaki, Nana; Yamasaki, Shinichi; Qu, Jiaxin; Cree, Andrew; Ding, Yan; Dinh, Huyen H.; Dugan, Shannon; Holder, Michael; Jhangiani, Shalini N.; Kovar, Christie L.; Lee, Sandra L.; Lewis, Lora R.; Morton, Donna; Nazareth, Lynne V.; Okwuonu, Geoffrey; Santibanez, Jireh; Chen, Rui; Richards, Stephen; Muzny, Donna M.; Gillis, Andrew; Peshkin, Leonid; Wu, Michael; Humphreys, Tom; Su, Yi-Hsien; Putnam, Nicholas H.; Schmutz, Jeremy; Fujiyama, Asao; Yu, Jr-Kai; Tagawa, Kunifumi; Worley, Kim C.; Gibbs, Richard A.; Kirschner, Marc W.; Lowe, Christopher J.; Satoh, Noriyuki; Rokhsar, Daniel S.; Gerhart, John (November 2015). "Hemichordate genomes and deuterostome origins". Nature. 527 (7579): 459–465. doi:10.1038/nature16150. PMC 4729200. PMID 26580012.
  5. ^ Smith, KL; Holland, ND; Ruhl, HA (July 2005). "Enteropneust production of spiral fecal trails on the deep-sea floor observed with time-lapse photography". Deep Sea Research Part I: Oceanographic Research Papers. 52 (7): 1228–1240. Bibcode:2005DSRII..52.1228S. doi:10.1016/j.dsr.2005.02.004.
  6. ^ Holland, ND; Clague, DA; Gordon, DP; Gebruk, A; Pawson, DL; Vecchione, M (2005). "'Lophenteropneust' hypothesis refuted by collection and photos of new deep-sea hemichordates". Nature. 434 (7031): 374–376. Bibcode:2005Natur.434..374H. doi:10.1038/nature03382. PMID 15772659. S2CID 4417341.
  7. ^ Holland ND, Jones WJ, Elena J, Ruhl HA, Smith KL (2009) A new deep-sea species of epibenthic acorn worm (Hemichordata, Enteropneusta). Zoosystema 31: 333—346.
  8. ^ Osborn KL, Kuhnz LA, Priede IG, Urata M, Gebruk AV, and Holland ND (2012) Diversication of acorn worms (Hemichordata, Enteropneusta) revealed in the deep sea. Proc. R. Soc. Lond. B 279: 1646—1654.
  9. ^ Priede IG, Osborn KJ, Gebruk AV, Jones D, Shale D, Rogacheva A, Holland ND (2012) Observations on torquaratorid acorn worms (Hemichordata, Enteropneusta) from the North Atlantic with descriptions of a new genus and three new species. Invert. Biol. 131: 244-257.
  10. ^ The secret to an Oesia life: Prehistoric worm built tube-like 'houses' on sea floor
  11. ^ Encyclopedia of Paleontology
  12. ^ Worsaae, Katrine; Sterrer, Wolfgang; Kaul-Strehlow, Sabrina; Hay-Schmidt, Anders; Giribet, Gonzalo (7 November 2012). "An Anatomical Description of a Miniaturized Acorn Worm (Hemichordata, Enteropneusta) with Asexual Reproduction by Paratomy". PLOS ONE. 7 (11): e48529. doi:10.1371/journal.pone.0048529. PMC 3492459. PMID 23144898.
  13. ^ Florkin, Marcel (2014). Deuterostomians, Cyclostomes, and Fishes. Elsevier. p. 83. ISBN 9780323163347.

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