Priapulida

Priapulids are cylindrical worm-like animals, ranging from 0.2 to 0.3{{cite book|url=https://books.google.com/books?id=MKUab3WegL0C&q=Tubiluchus+mm&pg=PA29 |title=Multicellular Animals: Order in Nature – System Made by Man|isbn=978-3-540-00146-1|last1=Ax|first1=Peter|date=2003-04-08|publisher=Springer }} to 39 centimetres{{cite journal|jstor=3227009|title= Halicryptus higginsi n.sp. (Priapulida): A Giant New Species from Barrow, Alaska |journal= Invertebrate Biology | volume=118 |issue= 4 | pages=404–413|last1= Shirley |first1= Thomas C. |last2= Storch |first2= Volker |year= 1999 |doi= 10.2307/3227009 |bibcode= 1999InvBi.118..404S }} (0.08–0.12 to 15.35 in) long, with a median anterior mouth quite devoid of any armature or tentacles. They show both radial and bilateral symmetry. The gonads, protonephridia and ventral nerve cord are bilateral, while the introvert, pharynx and brain show radial symmetry, and appears to be a secondary trait.[https://www.diva-portal.org/smash/get/diva2:172290/FULLTEXT01.pdf Aspects of priapulid development][https://onlinelibrary.wiley.com/doi/abs/10.1002/1097-4687%28200102%29247%3A2%3C99%3A%3AAID-JMOR1005%3E3.0.CO%3B2-0 Symmetry of priapulids (Priapulida). 1. Symmetry of adults] Also the larvae show inernal and external characteristics of radial symmetry.[https://pubmed.ncbi.nlm.nih.gov/11223922/ Symmetry of priapulids (Priapulida). 2. Symmetry of larvae] The adult body is divided into a main trunk or abdomen and a somewhat swollen proboscis region ornamented with longitudinal ridges. In addition it is ringed and often has circles of spines, which are continued into the slightly protrusible pharynx. Family Priapulidae have species with a tail or a pair of caudal appendages. A slender tail or tail filament is also found in family Tubiluchidae. Appendages are absent in the remaining families.{{Cite journal |last1=Schmidt-Rhaesa |first1=Andreas |last2=Rothe |first2=Birgen H. |last3=Martínez |first3=Alejandro García |date=November 2013 |title=Tubiluchus lemburgi, a new species of meiobenthic Priapulida |url=https://linkinghub.elsevier.com/retrieve/pii/S004452311300051X |journal=Zoologischer Anzeiger - A Journal of Comparative Zoology |language=en |volume=253 |issue=2 |pages=158–163 |doi=10.1016/j.jcz.2013.08.004|bibcode=2013ZooAn.253..158S |url-access=subscription }}{{Cite book |last1=Margulis |first1=Lynn |url=https://books.google.com/books?id=9IWaqAOGyt4C&dq=Priapulus+Meiopriapulus+Halicryptus+Maccabeus+tails&pg=PA286 |title=Kingdoms and Domains: An Illustrated Guide to the Phyla of Life on Earth |last2=Chapman |first2=Michael J. |date=2009-03-19 |publisher=Academic Press |isbn=978-0-08-092014-6 |language=en}} The body has a chitinous cuticle that is moulted as the animal grows.{{cite book | author = Barnes, R. D. | year = 1982 | title = Invertebrate Zoology | publisher = Holt-Saunders International | location = Philadelphia, PA | pages = 873–877 | isbn = 978-0-03-056747-6 }} Members of the family Chaetostephanidae also secretes a gelatinous tube, open in both ends, which they live in.{{Cite book |last=Schmidt-Rhaesa |first=Andreas |url=https://books.google.com/books?id=NBP4bvxp1loC&q=Maccabeus%2520gelatinous%2520tube&pg=PA173 |title=Handbook of Zoology |date=2012-12-21 |publisher=Walter de Gruyter |isbn=978-3-11-027253-6 |volume=11 |language=en}}

There is a wide body-cavity, which has no connection with the renal or reproductive organs, so it is not a coelom; it is probably a blood-space or hemocoel. There are no vascular or respiratory systems, but the body cavity does contain phagocytic amoebocytes and cells containing the respiratory pigment haemerythrin.

The alimentary canal is straight, consisting of an eversible pharynx, an intestine, and a short rectum. The pharynx is muscular and lined by teeth. Three of the five extant families have gone through a significant miniaturization and become detritivores (Tubiluchidae and Meiopriapulidae) and filter feeders (Chaetostephanidae). The two remaining families Priapulidae and Halicryptidae are larger carnivores that feed on other animals, although some species also consume detritus as larvae. The shape of the teeth reflect these different lifestyles, and seem to be adapted mainly towards grasping prey or raking detritus from the sediment into the mouth.{{Cite journal |last1=Wernström |first1=Joel Vikberg |last2=Slater |first2=Ben J. |last3=Sørensen |first3=Martin V. |last4=Crampton |first4=Denise |last5=Altenburger |first5=Andreas |date=2023-08-12 |title=Geometric morphometrics of macro- and meiofaunal priapulid pharyngeal teeth provides a proxy for studying Cambrian "tooth taxa" |journal=Zoomorphology |volume=142 |issue=4 |pages=411–421 |language=en |doi=10.1007/s00435-023-00617-4 |issn=1432-234X|doi-access=free |hdl=10037/30213 |hdl-access=free }}{{Cite journal |last1=Higgins |first1=Robert P. |last2=Storch |first2=Volker |date=1991 |title=Evidence for Direct Development in Meiopriapulus fijiensis (Priapulida) |url=https://www.jstor.org/stable/3226738 |journal=Transactions of the American Microscopical Society |volume=110 |issue=1 |pages=37–46 |doi=10.2307/3226738 |jstor=3226738 |url-access=subscription }} The anus is terminal, although in Priapulus one or two hollow ventral diverticula of the body-wall stretch out behind it.

The nervous system consists of a nerve ring around the pharynx and a prominent cord running the length of the body with ganglia and longitudinal and transversal neurites consistent with an orthogonal organisation.{{Cite journal | last1 = Rothe | first1 = B. H. | last2 = Schmidt-Rhaesa | first2 = A. | doi = 10.1111/j.1744-7410.2010.00185.x | title = Structure of the nervous system in Tubiluchus troglodytes (Priapulida) | journal = Invertebrate Biology | volume = 129 | pages = 39–58 | date = Winter 2010 | issue = 1 | bibcode = 2010InvBi.129...39R }} The nervous system retains a basiepidermal configuration with a connection with the ectoderm, forming part of the body wall. There are no specialized sense organs, but there are sensory nerve endings in the body, especially on the proboscis.

The priapulids are gonochoristic, having two separate sexes (i.e. male and female).{{cite book | last = Pechenik | first = J. A. | title = Biology of the Invertebrates | edition = 6th | year = 2009 | publisher = McGraw-Hill | location = New York | isbn = 978-0-07-302826-2 | page = 454 }} Their male and female organs are closely associated with the excretory protonephridia. They comprise a pair of branching tufts, each of which opens to the exterior on one side of the anus. The tips of these tufts enclose a flame-cell like those found in flatworms and other animals, and these probably function as excretory organs. As the animals mature, diverticula arise on the tubes of these organs, which develop either spermatozoa or ova. These sex cells pass out through the ducts.{{EB1911|last=Shipley|first=Arthur Everett|author-link=Arthur Shipley|wstitle=Priapuloidea|volume=22|page=313|inline=1}} The perigenital area of the genus Tubiluchus exhibit sexual dimorphism.{{cite journal| title = A new meiobenthic priapulid (Priapulida, Tubiluchidae) from a Mediterranean submarine cave| year = 2003| doi = 10.1080/11250000309356499| last1 = Todaro| first1 = M. Antonio| last2 = Shirley| first2 = Thomas C.| journal = Italian Journal of Zoology| volume = 70| pages = 79–87| s2cid = 84539380| doi-access = free| hdl = 11380/303453| hdl-access = free}}

For the species Priapulus caudatus, the 80 μm egg undergoes a total and radial cleavage following a symmetrical and subequal pattern.{{Cite journal | last1 = Wennberg | first1 = S. A. | last2 = Janssen | first2 = R. | last3 = Budd | first3 = G. E. | doi = 10.1111/j.1525-142X.2008.00241.x | title = Early embryonic development of the priapulid worm Priapulus caudatus | journal = Evolution & Development | volume = 10 | issue = 3 | pages = 326–338 | date = May–June 2008 | pmid = 18460094| s2cid = 11175247 | url = http://uu.diva-portal.org/smash/get/diva2:172287/FULLTEXT01 }} Development is remarkably slow, with the first cleavage taking place 15 hours after fertilization, gastrulation after several days and hatching of the first 'lorica' larvae after 15 to 20 days.{{Cite journal | last1 = Janssen | first1 = R. | last2 = Wennberg | first2 = S. A. | last3 = Budd | first3 = G. E. | title = The hatching larva of the priapulid worm Halicryptus spinulosus | doi = 10.1186/1742-9994-6-8 | journal = Frontiers in Zoology | volume = 6 | page = 8 | date = 26 May 2009 | pmid = 19470151| pmc = 2693540 | doi-access = free }} The species Meiopriapulus fijiensis have direct development.{{cite journal |title=Evidence for Direct Development in Meiopriapulus fijiensis (Priapulida) |journal=Transactions of the American Microscopical Society |volume=110 |issue=1 |pages=37–46 |date=January 1991 | jstor = 3226738 |last1=Higgins |first1=Robert P. |last2=Storch |first2=Volker |doi=10.2307/3226738 }} In current systematics, they are described as protostomes, despite having a deuterostomic development.{{Cite journal | doi = 10.1016/j.cub.2012.09.037|title = Deuterostomic development in the protostome Priapulus caudatus | journal = Current Biology| volume = 22| issue = 22| pages = 2161–2166 | year = 2012| last1 = Martín-Durán | first1 = J. M. | last2 = Janssen | first2 = R. | last3 = Wennberg | first3 = S. | last4 = Budd | first4 = G. E. | last5 = Hejnol | first5 = A. | pmid=23103190| doi-access = free |bibcode = 2012CBio...22.2161M }} Because the group is so ancient, it is assumed the deuterostome condition which appears to be ancestral for bilaterians have been maintained.{{cite web| url = https://www.sciencedaily.com/releases/2012/10/121026084350.htm| title = Penis worms show the evolution of the digestive system}}

File:Ottoia tricuspida ROM 63057.jpg in the Burgess Shale (Middle Cambrian)]]

File:Ottoia prolifica Type B tooth.png of a priapulid tooth (Ottoia, Cambrian); from Smith et al. 2015]]

Stem-group priapulids are known from the Middle Cambrian Burgess Shale, where their soft-part anatomy is preserved, often in conjunction with their gut contents – allowing a reconstruction of their diets.{{cite journal| last1 = Vannier | first1 = J.| last2 = Calandra | first2 = I.| last3 = Gaillard | first3 = C.| last4 = Zylinska | first4 = A. | title = Priapulid worms: Pioneer horizontal burrowers at the Precambrian-Cambrian boundary | journal = Geology | year = 2010 | volume = 38 | issue = 8 | pages = 711–714| doi = 10.1130/G30829.1 | bibcode = 2010Geo....38..711V }} In addition, isolated microfossils (corresponding to the various teeth and spines that line the pharynx and introvert) are widespread in Cambrian deposits,{{Cite journal |last1=Slater |first1=Ben J. |last2=Harvey |first2=Thomas H. P. |last3=Guilbaud |first3=Romain |last4=Butterfield |first4=Nicholas J. |date=January 2017 |editor-last=Rahman |editor-first=Imran |title=A cryptic record of Burgess Shale-type diversity from the early Cambrian of Baltica |journal=Palaeontology |language=en |volume=60 |issue=1 |pages=117–140 |doi=10.1111/pala.12273|doi-access=free |bibcode=2017Palgy..60..117S |hdl=2381/38663 |hdl-access=free }} allowing the distribution of priapulids – and even individual species – to be tracked widely through Cambrian oceans.{{Cite journal | doi = 10.1111/pala.12168| title = The macro- and microfossil record of the Cambrian priapulid Ottoia| journal = Palaeontology| date = July 2015| volume = 58 | issue = 4 | pages = 705–721|last1 = Smith | first1 = M. R. | last2 = Harvey | first2 = T. H. P. | last3 = Butterfield | first3 = N. J. | url = http://dro.dur.ac.uk/18218/1/18218.pdf| doi-access = free | bibcode = 2015Palgy..58..705S}} Trace fossils that are morphologically almost identical to modern priapulid burrows (Treptichnus pedum) officially mark the start of the Cambrian period, suggesting that priapulids, or at least close anatomical relatives, evolved around this time. Crown-group priapulid body fossils are first known from the Carboniferous.

{{citation needed|date=January 2024}}

{{clade

|label1=Ecdysozoa|sublabel1=>529 mya

|1={{clade

|label1=Scalidophora

|1={{clade

|1=Priapulida 50px

|2=Kinorhyncha 80 px

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|2={{clade

|label1=Nematoida

|1={{clade

|1=Nematoda 70px

|2=Nematomorpha 60px

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|label2=Panarthropoda

|2={{clade

|1=Onychophora 80 px

|label2=Tactopoda

|2={{clade

|1=Tardigrada 60 px

|2=Arthropoda 60 px

}}

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{{citation needed|date=January 2024}}

{{clade| style=font-size:100%;line-height:80%

|1={{clade

|1=†Archaeopriapulida [paraphyletic]

|2=†Ancalagonida Adrianov & Malakhov 1995

|3={{clade

|1=†Markuelia Valkov 1983

|2={{clade

|1=†Palaeoscolecida Conway Morris & Robinson 1986

|2={{clade

|1=Kinorhyncha Reinhard 1887 (Spiny crown worms; Mud dragons)

|label2=Priapulida

|2={{clade

|label1=Meiopriapulomorpha

|1={{clade

|label1=Tubiluchidae

|1={{clade

|1=†Paratubiluchus Han et al. 2004

|2=Meiopriapulus Morse 1981

|3=Tubiluchus van der Land 1968

}}

}}

|label2=Priapulimorpha

|2={{clade

|label1=Maccabeidae

|1=Maccabeus Por 1973

|2={{clade

|label1=Halicryptidae

|1=Halicryptus von Siebold 1849

|label2=Priapulidae

|2={{clade

|1={{clade

|1=†Priapulites Schram 1973

|2=†Xiaoheiqingella Hu 2002

}}

|2={{clade

|1=Priapulopsis Koren & Danielssen 1875

|2={{clade

|1=Acanthopriapulus van der Land 1970

|2=Priapulus Lamarck 1816

}}

}}

}}

}}

}}

}}

}}

}}

}}

}}

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{{See also|List of bilateral animal orders}}

There are 22 known extant species:{{cite book| url = https://books.google.com/books?id=YHetDwAAQBAJ&dq=We+follow+here+the+familial+classification+of+Schmidt-Rhaesa+%282013b%29.&pg=PA167| title = The Invertebrate Tree of Life| isbn = 978-0-691-17025-1| last1 = Giribet| first1 = Gonzalo| last2 = Edgecombe| first2 = Gregory D.| date = 3 March 2020| publisher = Princeton University Press}}[http://www.catalogueoflife.org/annual-checklist/2019/browse/classification/kingdom/Animalia/phylum/Cephalorhyncha/class/Priapulida/fossil/0/match/1 2019 Annual Checklist : Browse taxonomic classification phylum: Cephalorhyncha, class: Priapulida]

File:Ottoia reconstruction.jpg, a prehistoric priapulid.]]

Phylum Priapulida Théel 1906

• Order Halicryptomorpha Salvini-Plawen 1974 [Adrianov & Malakhov 1995; Salvini-Plawen 1974; Eupriapulida Lemburg, 1999]
• Family Halicryptidae Salvini-Plawen 1974
• Genus Halicryptus
• Species H. higginsi (Shirley & Storch, 1999)
• Species H. spinulosus (von Siebold, 1849)
• Order Priapulomorpha Adrianov & Malakhov 1995 (assigned its own order by Adrianov A. V, Malakhov V. V. 2001. Symmetry of priapulids (Priapulida). 1. Symmetry of adults. 247:99–110.)
• Family Priapulidae Gosse 1855 [Xiaoheiqingidae (sic) Hu 2002]
• Genus Acanthopriapulus
• Species A. horridus (Théel, 1911)
• Genus Priapulopsis
• Species P. australis (de Guerne, 1886)
• Species P. bicaudatus (Danielssen, 1869)
• Species P. cnidephorus (Salvini-Plawen, 1973)
• Genus Priapulus
• Species P. abyssorum (Menzies, 1959)
• Species P. caudatus (Lamarck, 1816)
• Species P. tuberculatospinosus (Baird, 1868)
• Family Tubiluchidae van der Land 1970 [Meiopriapulidae Adrianov & Malakhov 1995]
• Genus Tubiluchus
• Species T. arcticus (Adrianov, Malakhov, Tchesunov & Tzetlin, 1989)
• Species T. australensis (van der Land, 1985)
• Species T. corallicola (van der Land, 1968)
• Species T. lemburgi (Schmidt-Rhaesa, Rothe & Martínez, 2013)
• Species T. pardosi (Schmidt-Rhaesa, Panpeng & Yamasaki, 2017)
• Species T. philippinensis (van der Land, 1985)
• Species T. remanei (van der Land, 1982)
• Species T. soyoae (Schmidt-Rhaesa, Panpeng & Yamasaki, 2017)
• Species T. troglodytes (Todaro & Shirley, 2003)
• Species T. vanuatensis (Adrianov & Malakhov, 1991)
• Genus Meiopriapulus
• Species M. fijiensis

(Morse, 1981)

• Order Seticoronaria
• Family Chaetostephanidae Por & Bromley 1974 [Chaetostephanidae Salvini-Plawen 1974]
• Genus Maccabeus
• Species M. cirratus (Malakhov, 1979)
• Species M. tentaculatus (Por, 1973)

Stem-group †Scalidophora

• Order †Ancalagonida Adrianov & Malakhov 1995 [Fieldiida Adrianov & Malakhov 1995]
• Family †Ancalagonidae Conway Morris 1977
• Genus †Ancalagon Conway Morris 1977
• Family †Fieldiidae Conway Morris 1977
• Genus †Fieldia Walcott 1912

Stem-group †Palaeoscolecida

• Family †Selkirkiidae Conway Morris 1977
• Genus †Selkirkia Walcott 1911 non Hemsley 1884
• Order †Ottoiomorpha Adrianov & Malakhov 1995
• Genus †Scolecofurca Conway Morris 1977
• Family †Ottoiidae Walcott 1911
• Genus †Ottoia Walcott 1911
• Family †Corynetidae Huang, Vannier & Chen 2004
• Genus †Corynetis Luo & Hu 1999 [Anningvermis Huang, Vannier & Chen 2004]
• Family †Miskoiidae Walcott 1911
• Genus †Miskoia Walcott 1911
• Genus †Louisella Conway Morris 1977

{{Reflist}}

{{Wikispecies|Priapulida}}

• {{cite news | publisher = University of Bristol | url = http://www.bris.ac.uk/news/2006/1052.html | title = Evolution of the penis worm | work = Press Releases | date = 2006-08-09 }}

{{Animalia}}

{{Life on Earth}}

{{Taxonbar|from=Q5184}}

{{Authority control}}

Category:Ecdysozoa phyla

Category:Extant Pennsylvanian first appearances