The acorn worms or Enteropneusta are a hemichordate class of invertebrates consisting of one order of the same name.[2] The closest non-hemichordate relatives of the Enteropneusta are the echinoderms.[3] There are 111 known species of acorn worm in the world,[4] the main species for research being Saccoglossus kowalevskii. Two families—Harrimaniidae and Ptychoderidae—separated at least 370 million years ago.[5]
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.[6][7][8][9][10] 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.[11] The body length normally range from 2 centimetres (0.79 in) to 2.5 metres (8 ft 2 in) (Balanoglossus gigas),[12] but one species, Meioglossus psammophilus, only reach 0.6 millimetres (0.024 in).[13] Due to secretions containing elements like iodine, the animals have an iodoform-like smell.[14]
^Yang, X.; Kimmig, J.; Cameron, C. B.; Nanglu, K.; Kimmig, S. R.; de Carle, D.; Zhang, C.; Yu, M.; Peng, S. (2024). "An early Cambrian pelago-benthic acorn worm and the origin of the hemichordate larva". Palaeontologia Electronica. 27 (1). 27.1.a17. doi:10.26879/1356.
^Konikoff, C; van der Land, J (2011). "Enteropneusta". WoRMS. World Register of Marine Species. Retrieved 2017-11-20.
^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.
^Biogeography and adaptations of torquaratorid acorn worms (Hemichordata: Enteropneusta) including two new species from the Canadian Arctic - Research Proposal - Papyrus - Université de Montréal
^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.
^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.
^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.
^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.
^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.
^The secret to an Oesia life: Prehistoric worm built tube-like 'houses' on sea floor
^Encyclopedia of Paleontology
^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.
^Florkin, Marcel (2014). Deuterostomians, Cyclostomes, and Fishes. Elsevier. p. 83. ISBN 9780323163347.
The acornworms or Enteropneusta are a hemichordate class of invertebrates consisting of one order of the same name. The closest non-hemichordate relatives...
Lower or Middle Cambrian and include two main classes: Enteropneusta (acornworms), and Pterobranchia. A third class, Planctosphaeroidea, is known only...
Some acornworms also have a postanal tail which may be homologous to the post-anal tail of vertebrates. The three-section body plan of the acornworm is...
Balanoglossus is a genus of ocean-dwelling acornworms (Enteropneusta). It has zoological importance because, being hemichordates, they are an "evolutionary...
species of large free-living enteropneust (acornworm) found in the Atlantic Ocean. It is the largest acornworm currently known, and has a strong iodoform-like...
Yoda purpurata is a species of acornworm discovered 2.5 km (about 1.5 miles) below the surface of the Atlantic ocean, and was the first of the genus Yoda...
Saccoglossus is a genus of acornworm (Class Enteropneusta). It is the largest genus in this class, with 18 species. This genus is characterized especially...
Ambulacraria Phylum Hemichordata Class Planctosphaeroidea Class Enteropneusta (acornworms) Class Pterobranchia Phylum Echinodermata Subphylum Asterozoa Class Asteroidea...
ventral and dorsal nerve cords like modern acornworms. An archaic survivor from this stage is the acornworm, sporting an open circulatory system (with...
al. (2024). Review of the fossil record and evolutionary history of acornworms and pterobranchs is published by Maletz (2024). Redescription of Stiptognathus...
Balanoglossus australiensis is a species of 20 centimetres (7.9 in) long acornworm in Ptychoderidae family which can be found in Gulf of Carpentaria, New...
internal placement is less certain. Hemichordata (which includes the acornworms) was previously considered a fourth chordate subphylum, but now is treated...
Ptychodera is a genus of acornworm. Ptychodera bahamensis Spengel, 1893 Ptychodera ceylonica author unknown Ptychodera erythrea Spengel Ptychodera flava...
Torquaratoridae (Latin for "neck plow"[citation needed]) is a family of acornworms (Hemichordata) that lives in deep waters between 350 and 4000 meters...
accompanied with reducing numbers of pearl oyster, gorgonian coral, and acornworm. Local fishermen rely on the reef to feed their families, but destructive...
Enteropneusta, with the common name of acornworm. This organism is classified as a Hemichordate, and they are marine worms that use their hydrostatic skeleton...
is the planktonic larva of some species of Hemichordata such as the acornworms. It is very similar in appearance to the bipinnaria larvae of starfishes...
Spartobranchus tenuis is an extinct species of acornworms (Enteropneusta). It existed in the Middle Cambrian (505 million years ago). Petrified mark...
Harrimaniidae is a basal family of acornworms. A taxonomic revision was undertaken in 2010, and a number of new genera and species found in the Eastern...
S2CID 45702564. Brown FD, Prendergast A, Swalla BJ (2008). "Man is but a worm: chordate origins". Genesis. 46 (11): 605–613. doi:10.1002/dvg.20471. PMID 19003926...
lesser phyla of invertebrates are the Hemichordata, or acornworms, and the Chaetognatha, or arrow worms. Other phyla include Acoelomorpha, Brachiopoda, Bryozoa...
Meioglossus psammophilus is a species of acornworm in the family Harrimaniidae, the only known species of the genus Meigolossus. It inhabits the Western...
Glossobalanus marginatus is a species of acornworm within the family Ptychoderidae. The species was first described from a specimen caught off the Northumberland...
Ptychoderidae is a family of acornworms. The World Register of Marine Species lists the following: Contains the following species: Balanoglossus apertus...
Nemertodermatida Order incertae sedis (2 families) Class Enteropneusta (Acornworms) Order Enteropneusta Class Graptolithina † Order Camaroidea † Order Crustoidea...
larva, the larva of the Phoronid species Phoronopsis harmeri and the acornworm larva Schizocardium californicum, do not depend on hox genes in their...
Mesoglossus pygmaeus is a species of acornworm in the family Harrimaniidae, which is found in Europe, precisely in British Isles. Konikoff, C.; Shenkar...
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