{{Short description|Order of annelid worms}} {{More citations needed|date=August 2025}} {{Automatic Taxobox | name = Canalipalpata | image = Christmas tree worm.jpg | image_caption = Christmas tree worm (''[[Spirobranchus giganteus]]'') in East Timor. | image2 = Sabellastarte magnifica (Magnificent feather duster worm).jpg | image2_caption = Magnificent feather duster worm (''[[Sabellastarte magnifica]]'') | taxon = Canalipalpata | authority = | synonyms = | subdivision_ranks = Suborders | subdivision = {{Center|See text}} }}
'''Canalipalpata''', also known as bristle-footed [[annelid]]s or fan-head worms,{{Citation needed|date=August 2025|reason=Who uses these common names?}} is an order of [[polychaete]] [[worm]]s consisting of 31 families such as the [[Serpulidae]] (tubeworms), [[Sabellidae]] (fanworms and feather duster worms), and [[Siboglinidae]] (beardworms) of the suborder [[Sabellida]], and the [[Alvinellidae]], a family of worms often associated with [[hydrothermal vent]]s (though a number of Siboglinids also inhabit hydrothermal vents, like the [[giant tube worm]] ''Riftia pachyptila''). Most '''canalipalpatans''' are considered to be [[tube worm]]s, with some exceptions.{{Example needed|date=August 2025}}
==Description== The Canalipalpata have no teeth or jaws.<ref>{{cite book|title=Invertebrate Zoology|author=Robert D. Barnes|year=1980|edition=4th|isbn=4-8337-0001-8|publisher=Holt-Saunders}}</ref> Most are [[filter feeder]]s. They have grooved [[wikt:palp|palp]]i, which are covered in [[Cilium|cilia]]. These cilia are used to transport food particles to the mouth. However, the cilia and grooves have been lost in the [[Siboglinidae]] family.<ref>{{cite book|title=Multicellular Animals: The Phylogenetic System of the Metazoa|author=Peter Ax|year=1996|volume=2|isbn=3-540-67406-3|publisher=Springer-Verlag}}</ref>{{Clarify|reason=Are these palps the [[radiole]]s?|date=August 2025}}
The head of Canalipalpata is located at the [[Anterior (anatomy)|anterior]] end of the body, and is formed by the fusion of a [[funnel]]-shaped, symmetrical [[peristomium]] with the [[prostomium]].<ref name=Walla>Department of Biology, Walla Walla University: [http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Annelida/Serpulidae/Serpula_vermicularis.html Serpula vermicularis] {{webarchive|url=https://web.archive.org/web/20111002000012/http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Annelida/Serpulidae/Serpula_vermicularis.html |date=2 October 2011 }}, Rosario Beach Marine Laboratory. Accessed 3 May 2010.</ref><ref name=Moore>{{cite journal |author1=Colin G. Moore |author2=Graham R. Saunders |author3=Dan B. Harries |title=The status and ecology of reefs of Serpula vermicularis (Polychaeta: Serpulidae) in Scotland |journal=Aquatic Conservation: Marine and Freshwater Ecosystems |volume=8 |issue=5 |pages=645–656 |year=1998 |url=http://www3.interscience.wiley.com/journal/10006579/abstract?CRETRY=1&SRETRY=0 |archive-url=https://archive.today/20130105063729/http://www3.interscience.wiley.com/journal/10006579/abstract?CRETRY=1&SRETRY=0 |url-status=dead |archive-date=5 January 2013 |accessdate=3 May 2010 |doi=10.1002/(SICI)1099-0755(199809/10)8:5<645::AID-AQC295>3.0.CO;2-G|bibcode=1998ACMFE...8..645M |url-access=subscription }}</ref><ref>[http://www.peteducation.com/category.cfm?c=16+1900 Fan Worms & Feather Dusters (Annelids)]. Accessed 3 May 2010.</ref> The prostomium bears a specialized [[mouth]] [[appendage]] which is referred to as a branchial crown. The crown functions as both a [[sieve]] and a gill. The animal can extend the crown from its [[calcareous]] tube for feeding and gas exchange, and rapidly retract it when disturbed or threatened.<ref name=eudistylia>Richard S. Fox, Invertebrate Anatomy OnLine: [http://webs.lander.edu/rsfox/invertebrates/eudistylia.html ''Eudistylia vancouveri''] {{webarchive|url=https://web.archive.org/web/20110801233403/http://webs.lander.edu/rsfox/invertebrates/eudistylia.html |date=1 August 2011 }}. Lander University, 4 July 2006. Accessed 3 May 2010.</ref>
==={{Visible anchor|Radiole}}=== [[File:Feather duster worm.jpg|250px|thumb|left|Radioles extending from the branchial stalk of a ''[[Spirographis]]'' [[feather duster worm]]]] '''Radioles''' are heavily ciliated feather-like [[tentacle]] found in highly organized clusters on the crowns of Canalipalpata. The radioles are primarily for [[alimentation]], being used for filter feeding, though these also serve as [[Aquatic respiration|respiratory]] organs. Because of their role in gas exchange, radioles are often referred to as "[[gill]]s".{{Citation needed|date=August 2025}}
The radioles (or sometimes [[wikt:branchia|branchia]]e; [[Ancient Greek]] for gills) forms the crown, which consists of two radiole bundles (one right and one left). Each of these bundles consists of a single row of radioles attached to a branchial stalk and curved into a semicircle. These two semicircles form the funnel-shaped branchial crown. The mouth is located at the apex (top) of the funnel, between the two branchial stalks.<ref name=eudistylia />
The radioles of Canalipalpata vary widely in color across species; those of the [[Serpulidae|serpulid]] tubeworms are typically red, pink, or orange in color, with white transverse bands. [[Astaxanthin]], a [[carotenoid]] pigment, is responsible for the bright red color of the crown of ''[[Serpula vermicularis]]''.<ref name=Beesley>{{cite book |title=Polychaetes & allies: the southern synthesis, Volume 4, Part 1 |chapter=Gregory W. Rouse (2000). Family Serpulidae. |author=Pamela L. Beesley, Graham J. B. Ross, Christopher J. Glasby (eds) |year=2000 |publisher=CSIRO Publishing Australia |location=Melbourne, Australia |page=187 |isbn=9780643065710 |chapter-url=https://books.google.com/books?id=Rin4l7QZ1YEC&q=serpula+vermicularis+%22ten+Hove%22&pg=PA187}}</ref>
In addition to "ordinary" radioles, some Canalipalpata possess one or more highly modified radioles located on the dorsal part of the head; These are the ''[[Operculum (animal)|operculum]]'', which is a cone-shaped [[cartilage]]nous structure located at the distal end of a long cartilaginous stalk. When threatened or disturbed, the animal withdraws rapidly into its protective calcareous tube and employs the operculum as a "plug" to occlude (close) the entrance to the tube.<ref name=Hanson221>{{cite journal |author=Jean Hanson |title=Observations on the Branchial Crown of the Serpulidae (Annelida, Polychaeta) |journal=Quarterly Journal of Microscopical Science |volume=90 |issue=s3 |pages=221–233 |year=1949 |url=http://jcs.biologists.org/cgi/reprint/s3-90/11/221 }}</ref> The operculum, which is usually similar in color to the other radioles, secretes a mucus which seems to possess [[antibiotic]] properties. It is not unusual for the worms to have two crowns, and hence two opercula.{{Citation needed|date=August 2025}} Serpulids and sabellids are two [[Family (taxonomy)|families]] of the [[Sabellida]] [[Order (biology)|suborder]] of Canalipalpata tubeworms that are very [[Morphology (biology)|similar morphologically]], but they can be readily distinguished by the fact that while both have radioles, the sabellids (such as ''[[Sabella pavonina]]'') lack an operculum.<ref name=Ruppert1>{{cite book |title=Seashore animals of the Southeast: a guide to common shallow-water invertebrates of the southeastern Atlantic Coast |chapter=Annelida: Segmented Worms |author1=Edward E. Ruppert |author2=Richard S. Fox |year=1988 |publisher=University of South Carolina Press |location=Columbia, South Carolina |page=[https://archive.org/details/seashoreanimalso00edwa/page/219 219] |url=https://archive.org/details/seashoreanimalso00edwa |url-access=registration |quote=melanostigma operculum. |isbn=0-87249-535-3 }}</ref>
====Function==== [[File:Eudistylia vancouveri 422858383.jpg|thumb|''[[Eudistylia vancouveri]]'' outside of its tube]] An adult worm typically has about 40 radioles in its crown, with their [[ventral]] surfaces covered by tiny, hair-like branches called [[Cilium|cilia]]. This arrangement gives the crown the appearance of a small fan or feather duster (for which the animals are often referred to as [[fanworm]]s, or [[feather duster worm]]s). When extended, these heavily ciliated radioles trap particles of [[organic matter]] and transport them towards the mouth; the radioles rhythmically move in such a way as to create a [[Current (fluid)|current]] in the surrounding [[water column]] which carries [[plankton]]ic particles from the underside of the crown upwards through the net of radioles to the [[Dorsal (anatomy)|dorsal]] surface.<ref name=eudistylia />
The dorsal or upper side of each radiole has a ciliated longitudinal radiolar food groove running down its center, extending along its longitudinal axis from the tip to the center of the crown.<ref name=eudistylia /> Planktonic food particles are swept into these grooves, where they become trapped in a coating of [[mucus]]. At this point, the animal subjects the particles to an examination and selection process, whereby any particles determined to be unsuitable due to size or chemical composition are rejected by the animal and discarded back into the water column. Once the selection process is complete, the cilia transport the particles towards the mouth, from where they enter the [[digestive tract]].<ref name=eudistylia />
While they are primarily feeding structures, the radioles also serve as respiratory organs.<ref name=eudistylia /><ref name=serpula>Richard S. Fox, Invertebrate Anatomy OnLine: [http://webs.lander.edu/rsfox/invertebrates/serpula.html ''Serpula vermicularis''] {{Webarchive|url=https://web.archive.org/web/20100719203948/http://webs.lander.edu/rsfox/invertebrates/serpula.html |date=19 July 2010 }}. Lander University, 4 July 2006. Accessed 3 May 2010.</ref><ref>An Underwater Field Guide to Point Lobos: [http://pt-lobos.com/inverts.html Invertebrates: Worms]. Accessed 3 May 2010.</ref><ref name=Wells>{{Cite journal|author=G. P. Wells |title=The Respiratory Significance of the Crown in the Polychaete Worms Sabella and Myxicola|journal=[[Proceedings of the Royal Society B]] |volume=140 |issue=898 |pages=70–82 |date=27 August 1952 |jstor=82713|doi=10.1098/rspb.1952.0045|pmid=13003913 |bibcode=1952RSPSB.140...70W |s2cid=36440648}}</ref><ref name=memorial>Department of Biology, Memorial University of Newfoundland: [https://www.mun.ca/osc/oscedu/sabella.php Eudistylia_vancouveri ''Eudistylia vancouveri''], Ocean Sciences Centre. Accessed 3 May 2010.</ref><ref name=Kennedy>{{cite journal |author1=Bill Kennedy |author2=Harald Kryvi |title=Autotomy in a polychaete: Abscission zone at the base of the tentacular crown of Sabella penicillus |journal=Zoomorphology |volume=96 |issue=1–2 |pages=33–43 |date= October 1980 |doi=10.1007/BF00310075 |s2cid=24021108 }}</ref><ref name=Pernet>{{cite journal |author=Bruno Pernet |title=Escape Hatches for the Clonal Offspring of Serpulid Polychaetes |journal=Biological Bulletin |volume=200 |issue=2 |pages=107–117 |date= April 2001|pmid=11341572 |doi=10.2307/1543304 |jstor=1543304 |s2cid=24189960 |url=https://archive.org/stream/biologicalbullet200mari/biologicalbullet200mari_djvu.txt |accessdate=3 May 2010}}</ref>{{Excessive citations inline|date=March 2026}}
====Growth and regeneration==== Smaller bodied worms, such as [[Juvenile (organism)|juvenile]], have small crowns and radioles, and so capture and eat very small particles, such as [[bacterioplankton]] and single-celled [[phytoplankton]] and [[zooplankton]]. As a worm matures and grows in size, so does its crown. The larger crown allows the animal to feed on larger multicellular plankton. The preferred food size depends on the maximum size achieved by the adult worm.
Canalipalpata worms often lose one or more radioles, or even the entire crown as a result of [[predation]] by other animals or other [[physical trauma]]. Some species even appear to have the ability to control the loss of their tentacular crowns through [[autotomy]], in much the same manner as when a lizard loses its tail. In certain circumstances, sacrifice of the crown may permit escape{{Dubious|date=August 2025|reason=the worms are sessile so can't move or escape}} or confer some other benefit to the animal. Separation of the crown occurs at a pre-established zone of [[abscission]], located at the base of the crown.<ref name="Kennedy"/> Any would-be predators that pass by after a worm has lost its crown will get the impression that the worm has died; this protects the animal from further attack.{{Citation needed|date=August 2025}} After amputation, Canalipalpata have the ability to [[Regeneration (biology)|regenerate]] new radioles or even the entire crown if necessary.<ref name=Fitzharris>{{cite journal |author=Timothy P. Fitzharris |title=Regeneration in Sabellid Annelids |journal=American Zoologist |volume=16 |issue=3 |pages=593–616 |year=1976 |doi=10.1093/icb/16.3.593 |doi-access=free}}</ref><ref name=Walla2>Department of Biology, Walla Walla University: [http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Annelida/Sabellidae/Eudistylia_vancouveri.html Eudistylia_vancouveri], Rosario Beach Marine Laboratory. Accessed 3 May 2010.</ref> The crown typically reappears after about two weeks. When it does reappear, it is initially smaller in size, but it eventually grows back to its former size and color.{{Citation needed|date=August 2025}}
==Fossil record== The earliest known member of the Canalipalpata is ''[[Terebellites franklini]]'', which was found in the [[Clouds Rapids Formation]] of [[Newfoundland (island)|Newfoundland]], and dates from the mid [[Cambrian]] (St David's series).<ref>{{cite book|title=The Fossil Record 2|editor=M.J.Benton|year=1993|isbn=0-412-39380-8|publisher=Chapman & Hall|url-access=registration|url=https://archive.org/details/fossilrecord20000unse}}</ref>
==Taxonomy== {{Update section|date=August 2025|reason=Taxonomy; use the citation to update}} Order '''Canalipalpata''' <small>Rouse & Fauchald, 1997 non Linnaean</small><ref>{{Cite WoRMS|title=Canalipalpata Rouse & Fauchald, 1997 non Linnaean|id=154974|access-date=2025-08-24|db=Polychaeta}}</ref> {{Div col|colwidth=24 em}} * Suborder [[Sabellida]] ** Family [[Oweniidae]] ** Family [[Sabellariidae]] ** Family [[Sabellidae]] (Feather duster worms) ** Family [[Serpulidae]] ** Family [[Siboglinidae]] (Beard worms) ** Family [[Spirorbidae]] * Suborder [[Spionida]] ** Family [[Apistobranchidae]] ** Family [[Chaetopteridae]] ** Family [[Longosomatidae]] ** Family [[Magelonidae]] ** Family [[Poecilochaetidae]] ** Family [[Spionidae]] ** Family [[Trochochaetidae]] ** Family [[Uncispionidae]] * Suborder [[Terebellida]] ** Family [[Acrocirridae]] ** Family [[Alvinellidae]] ** Family [[Ampharetidae]] ** Family [[Cirratulidae]] ** Family [[Ctenodrilidae]] ** Family [[Fauveliopsidae]] ** Family [[Flabelligeridae]] ** Family [[Flotidae]] ** Family [[Pectinariidae]] (Trumpet worms) ** Family [[Poeobiidae]] ** Family [[Sternaspidae]] ** Family [[Terebellidae]] (Spaghetti worms) ** Family [[Trichobranchidae]] * ''[[Incertae sedis]]'' ** Family [[Polygordiidae]] ** Family [[Protodrilidae]] ** Family [[Protodriloididae]] ** Family [[Saccocirridae]] {{Div col end}}
==Gallery== <gallery class="center" mode="nolines" noborder="no"> File:Sabellastarte indica (Feather duster worm).jpg|''[[Sabellastarte indica]]'' (Indian feather duster worm) File:Sabellastarte indca (Feather duster worm).jpg|''S. indica'' File:Sabellastarte magnifica (Magnificent feather duster worm).jpg|''S. magnifica'' (magnificent feather duster worm) File:Sabellastarte sanctijosephi (Feather duster worm) in Oceanapia amboinensis (Sponge).jpg|''[[Sabellastarte sanctijosephi]]'' (St. Joseph's feather duster worm) File:Sabellastarte sanctijosephi.jpg|''S. sanctijosephi'' File:Sabellastarte sanctijosephi (Tubeworm).jpg|''S. sanctijosephi'' File:Sabellastarte sp..jpg|''[[Sabellastarte]]'' sp. (feather duster worm) File:Sabella spallanzanii.jpg|''[[Sabella spallanzanii]]'' File:Sabella spallanzanii 2.jpg|''S. spallanzanii'' File:Immagine_045.jpg|''[[Spirographis]]'' sp. File:Bispira sp. (Feather duster worm).jpg|''[[Bispira]]'' sp. File:Bispira sp. (Tubeworm).jpg|''Bispira'' sp. Image:Sabellidae (feather duster worm) yellow.jpg|[[Sabellidae]] sp. Image:Sabellidae (feather duster worm).jpg|Sabellidae sp. File:Polychaeta Sabellidae (Tubeworms) Timor.jpg|Sabellidae sp. File:Reef0200.jpg|Sabellidae sp. File:Spirobrancheus_giganteus.jpg|''[[Spirobranchus giganteus]]'' (Christmas tree worms) </gallery>
==References== {{Reflist}}
==External links== * Encyclopedia of Life: http://www.eol.org/pages/124?category_id=226 * Images from the canalipalpata order: http://zipcodezoo.com/index.php/Canalipalpata
{{Taxonbar|from=Q3817224}}
[[Category:Canalipalpata| ]] [[Category:Protostome orders]]