# Canalipalpata

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Order of annelid worms

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Canalipalpata Christmas tree worm (Spirobranchus giganteus) in East Timor. Magnificent feather duster worm (Sabellastarte magnifica) Scientific classification Kingdom: Animalia Phylum: Annelida Clade: Pleistoannelida Clade: Sedentaria Infraclass: Canalipalpata Suborders See text

**Canalipalpata**, also known as bristle-footed [annelids](/source/Annelid) or fan-head worms,[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] is an order of [polychaete](/source/Polychaete) [worms](/source/Worm) consisting of 31 families such as the [Serpulidae](/source/Serpulidae) (tubeworms), [Sabellidae](/source/Sabellidae) (fanworms and feather duster worms), and [Siboglinidae](/source/Siboglinidae) (beardworms) of the suborder [Sabellida](/source/Sabellida), and the [Alvinellidae](/source/Alvinellidae), a family of worms often associated with [hydrothermal vents](/source/Hydrothermal_vent) (though a number of Siboglinids also inhabit hydrothermal vents, like the [giant tube worm](/source/Giant_tube_worm) *Riftia pachyptila*). Most **canalipalpatans** are considered to be [tube worms](/source/Tube_worm), with some exceptions.[*[example needed](https://en.wikipedia.org/wiki/Wikipedia:AUDIENCE)*]

## Description

The Canalipalpata have no teeth or jaws.[1] Most are [filter feeders](/source/Filter_feeder). They have grooved [palpi](https://en.wiktionary.org/wiki/palp), which are covered in [cilia](/source/Cilium). These cilia are used to transport food particles to the mouth. However, the cilia and grooves have been lost in the [Siboglinidae](/source/Siboglinidae) family.[2][*[clarification needed](https://en.wikipedia.org/wiki/Wikipedia:Please_clarify)*]

The head of Canalipalpata is located at the [anterior](/source/Anterior_(anatomy)) end of the body, and is formed by the fusion of a [funnel](/source/Funnel)-shaped, symmetrical [peristomium](/source/Peristomium) with the [prostomium](/source/Prostomium).[3][4][5] The prostomium bears a specialized [mouth](/source/Mouth) [appendage](/source/Appendage) which is referred to as a branchial crown. The crown functions as both a [sieve](/source/Sieve) and a gill. The animal can extend the crown from its [calcareous](/source/Calcareous) tube for feeding and gas exchange, and rapidly retract it when disturbed or threatened.[6]

### Radiole

Radioles extending from the branchial stalk of a *[Spirographis](https://en.wikipedia.org/w/index.php?title=Spirographis&action=edit&redlink=1)* [feather duster worm](/source/Feather_duster_worm)

**Radioles** are heavily ciliated feather-like [tentacle](/source/Tentacle) found in highly organized clusters on the crowns of Canalipalpata. The radioles are primarily for [alimentation](/source/Alimentation), being used for filter feeding, though these also serve as [respiratory](/source/Aquatic_respiration) organs. Because of their role in gas exchange, radioles are often referred to as "[gills](/source/Gill)".[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

The radioles (or sometimes [branchiae](https://en.wiktionary.org/wiki/branchia); [Ancient Greek](/source/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.[6]

The radioles of Canalipalpata vary widely in color across species; those of the [serpulid](/source/Serpulidae) tubeworms are typically red, pink, or orange in color, with white transverse bands. [Astaxanthin](/source/Astaxanthin), a [carotenoid](/source/Carotenoid) pigment, is responsible for the bright red color of the crown of *[Serpula vermicularis](/source/Serpula_vermicularis)*.[7]

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](/source/Operculum_(animal))*, which is a cone-shaped [cartilagenous](/source/Cartilage) 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.[8] The operculum, which is usually similar in color to the other radioles, secretes a mucus which seems to possess [antibiotic](/source/Antibiotic) properties. It is not unusual for the worms to have two crowns, and hence two opercula.[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] Serpulids and sabellids are two [families](/source/Family_(taxonomy)) of the [Sabellida](/source/Sabellida) [suborder](/source/Order_(biology)) of Canalipalpata tubeworms that are very [similar morphologically](/source/Morphology_(biology)), but they can be readily distinguished by the fact that while both have radioles, the sabellids (such as *[Sabella pavonina](/source/Sabella_pavonina)*) lack an operculum.[9]

#### Function

*[Eudistylia vancouveri](https://en.wikipedia.org/w/index.php?title=Eudistylia_vancouveri&action=edit&redlink=1)* outside of its tube

An adult worm typically has about 40 radioles in its crown, with their [ventral](/source/Ventral) surfaces covered by tiny, hair-like branches called [cilia](/source/Cilium). This arrangement gives the crown the appearance of a small fan or feather duster (for which the animals are often referred to as [fanworms](/source/Fanworm), or [feather duster worms](/source/Feather_duster_worm)). When extended, these heavily ciliated radioles trap particles of [organic matter](/source/Organic_matter) and transport them towards the mouth; the radioles rhythmically move in such a way as to create a [current](/source/Current_(fluid)) in the surrounding [water column](/source/Water_column) which carries [planktonic](/source/Plankton) particles from the underside of the crown upwards through the net of radioles to the [dorsal](/source/Dorsal_(anatomy)) surface.[6]

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.[6] Planktonic food particles are swept into these grooves, where they become trapped in a coating of [mucus](/source/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](/source/Digestive_tract).[6]

While they are primarily feeding structures, the radioles also serve as respiratory organs.[6][10][11][12][13][14][15][*[excessive citations](https://en.wikipedia.org/wiki/Wikipedia:Citing_sources#Bundling_citations)*]

#### Growth and regeneration

Smaller bodied worms, such as [juvenile](/source/Juvenile_(organism)), have small crowns and radioles, and so capture and eat very small particles, such as [bacterioplankton](/source/Bacterioplankton) and single-celled [phytoplankton](/source/Phytoplankton) and [zooplankton](/source/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](/source/Predation) by other animals or other [physical trauma](/source/Physical_trauma). Some species even appear to have the ability to control the loss of their tentacular crowns through [autotomy](/source/Autotomy), in much the same manner as when a lizard loses its tail. In certain circumstances, sacrifice of the crown may permit escape[*[dubious](https://en.wikipedia.org/wiki/Wikipedia:Accuracy_dispute#Disputed_statement) – [discuss](https://en.wikipedia.org/wiki/Talk:Canalipalpata#Dubious)*] or confer some other benefit to the animal. Separation of the crown occurs at a pre-established zone of [abscission](/source/Abscission), located at the base of the crown.[14] 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](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] After amputation, Canalipalpata have the ability to [regenerate](/source/Regeneration_(biology)) new radioles or even the entire crown if necessary.[16][17] 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](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

## Fossil record

The earliest known member of the Canalipalpata is *[Terebellites franklini](https://en.wikipedia.org/w/index.php?title=Terebellites_franklini&action=edit&redlink=1)*, which was found in the [Clouds Rapids Formation](https://en.wikipedia.org/w/index.php?title=Clouds_Rapids_Formation&action=edit&redlink=1) of [Newfoundland](/source/Newfoundland_(island)), and dates from the mid [Cambrian](/source/Cambrian) (St David's series).[18]

## Taxonomy

This section needs to be updated. The reason given is: Taxonomy; use the citation to update. Please help update this article to reflect recent events or newly available information. (August 2025)

Order **Canalipalpata** Rouse & Fauchald, 1997 non Linnaean[19]

- Suborder [Sabellida](/source/Sabellida) - Family [Oweniidae](/source/Oweniidae) - Family [Sabellariidae](/source/Sabellariidae) - Family [Sabellidae](/source/Sabellidae) (Feather duster worms) - Family [Serpulidae](/source/Serpulidae) - Family [Siboglinidae](/source/Siboglinidae) (Beard worms) - Family [Spirorbidae](https://en.wikipedia.org/w/index.php?title=Spirorbidae&action=edit&redlink=1)

- Suborder [Spionida](/source/Spionida) - Family [Apistobranchidae](/source/Apistobranchidae) - Family [Chaetopteridae](/source/Chaetopteridae) - Family [Longosomatidae](/source/Longosomatidae) - Family [Magelonidae](/source/Magelonidae) - Family [Poecilochaetidae](/source/Poecilochaetidae) - Family [Spionidae](/source/Spionidae) - Family [Trochochaetidae](/source/Trochochaetidae) - Family [Uncispionidae](/source/Uncispionidae)

- Suborder [Terebellida](/source/Terebellida) - Family [Acrocirridae](/source/Acrocirridae) - Family [Alvinellidae](/source/Alvinellidae) - Family [Ampharetidae](/source/Ampharetidae) - Family [Cirratulidae](/source/Cirratulidae) - Family [Ctenodrilidae](/source/Ctenodrilidae) - Family [Fauveliopsidae](/source/Fauveliopsidae) - Family [Flabelligeridae](/source/Flabelligeridae) - Family [Flotidae](/source/Flotidae) - Family [Pectinariidae](/source/Pectinariidae) (Trumpet worms) - Family [Poeobiidae](/source/Poeobiidae) - Family [Sternaspidae](/source/Sternaspidae) - Family [Terebellidae](/source/Terebellidae) (Spaghetti worms) - Family [Trichobranchidae](/source/Trichobranchidae)

- *[Incertae sedis](/source/Incertae_sedis)* - Family [Polygordiidae](/source/Polygordiidae) - Family [Protodrilidae](/source/Protodrilidae) - Family [Protodriloididae](/source/Protodriloididae) - Family [Saccocirridae](/source/Saccocirridae)

## Gallery

		- *[Sabellastarte indica](https://en.wikipedia.org/w/index.php?title=Sabellastarte_indica&action=edit&redlink=1)* (Indian feather duster worm)

		- *S. indica*

		- *S. magnifica* (magnificent feather duster worm)

		- *[Sabellastarte sanctijosephi](/source/Sabellastarte_sanctijosephi)* (St. Joseph's feather duster worm)

		- *S. sanctijosephi*

		- *S. sanctijosephi*

		- *[Sabellastarte](/source/Sabellastarte)* sp. (feather duster worm)

		- *[Sabella spallanzanii](/source/Sabella_spallanzanii)*

		- *S. spallanzanii*

		- *[Spirographis](https://en.wikipedia.org/w/index.php?title=Spirographis&action=edit&redlink=1)* sp.

		- *[Bispira](/source/Bispira)* sp.

		- *Bispira* sp.

		- [Sabellidae](/source/Sabellidae) sp.

		- Sabellidae sp.

		- Sabellidae sp.

		- Sabellidae sp.

		- *[Spirobranchus giganteus](/source/Spirobranchus_giganteus)* (Christmas tree worms)

## References

1. **[^](#cite_ref-1)** Robert D. Barnes (1980). *Invertebrate Zoology* (4th ed.). Holt-Saunders. [ISBN](/source/ISBN_(identifier)) [4-8337-0001-8](https://en.wikipedia.org/wiki/Special:BookSources/4-8337-0001-8).

1. **[^](#cite_ref-2)** Peter Ax (1996). *Multicellular Animals: The Phylogenetic System of the Metazoa*. Vol. 2. Springer-Verlag. [ISBN](/source/ISBN_(identifier)) [3-540-67406-3](https://en.wikipedia.org/wiki/Special:BookSources/3-540-67406-3).

1. **[^](#cite_ref-Walla_3-0)** Department of Biology, Walla Walla University: [Serpula vermicularis](http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Annelida/Serpulidae/Serpula_vermicularis.html) [Archived](https://web.archive.org/web/20111002000012/http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Annelida/Serpulidae/Serpula_vermicularis.html) 2 October 2011 at the [Wayback Machine](/source/Wayback_Machine), Rosario Beach Marine Laboratory. Accessed 3 May 2010.

1. **[^](#cite_ref-Moore_4-0)** Colin G. Moore; Graham R. Saunders; Dan B. Harries (1998). ["The status and ecology of reefs of Serpula vermicularis (Polychaeta: Serpulidae) in Scotland"](http://www3.interscience.wiley.com/journal/10006579/abstract?CRETRY=1&SRETRY=0). *Aquatic Conservation: Marine and Freshwater Ecosystems*. **8** (5): 645–656. [Bibcode](/source/Bibcode_(identifier)):[1998ACMFE...8..645M](https://ui.adsabs.harvard.edu/abs/1998ACMFE...8..645M). [doi](/source/Doi_(identifier)):[10.1002/(SICI)1099-0755(199809/10)8:5<645::AID-AQC295>3.0.CO;2-G](https://doi.org/10.1002%2F%28SICI%291099-0755%28199809%2F10%298%3A5%3C645%3A%3AAID-AQC295%3E3.0.CO%3B2-G). Retrieved 3 May 2010.{{[cite journal](https://en.wikipedia.org/wiki/Template:Cite_journal)}}: CS1 maint: deprecated archival service ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_deprecated_archival_service))

1. **[^](#cite_ref-5)** [Fan Worms & Feather Dusters (Annelids)](http://www.peteducation.com/category.cfm?c=16+1900). Accessed 3 May 2010.

1. ^ [***a***](#cite_ref-eudistylia_6-0) [***b***](#cite_ref-eudistylia_6-1) [***c***](#cite_ref-eudistylia_6-2) [***d***](#cite_ref-eudistylia_6-3) [***e***](#cite_ref-eudistylia_6-4) [***f***](#cite_ref-eudistylia_6-5) Richard S. Fox, Invertebrate Anatomy OnLine: [*Eudistylia vancouveri*](http://webs.lander.edu/rsfox/invertebrates/eudistylia.html) [Archived](https://web.archive.org/web/20110801233403/http://webs.lander.edu/rsfox/invertebrates/eudistylia.html) 1 August 2011 at the [Wayback Machine](/source/Wayback_Machine). Lander University, 4 July 2006. Accessed 3 May 2010.

1. **[^](#cite_ref-Beesley_7-0)** Pamela L. Beesley, Graham J. B. Ross, Christopher J. Glasby (eds) (2000). ["Gregory W. Rouse (2000). Family Serpulidae."](https://books.google.com/books?id=Rin4l7QZ1YEC&q=serpula+vermicularis+%22ten+Hove%22&pg=PA187). *Polychaetes & allies: the southern synthesis, Volume 4, Part 1*. Melbourne, Australia: CSIRO Publishing Australia. p. 187. [ISBN](/source/ISBN_(identifier)) [9780643065710](https://en.wikipedia.org/wiki/Special:BookSources/9780643065710). {{[cite book](https://en.wikipedia.org/wiki/Template:Cite_book)}}: |author= has generic name ([help](https://en.wikipedia.org/wiki/Help:CS1_errors#generic_name))CS1 maint: multiple names: authors list ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_multiple_names:_authors_list))

1. **[^](#cite_ref-Hanson221_8-0)** Jean Hanson (1949). ["Observations on the Branchial Crown of the Serpulidae (Annelida, Polychaeta)"](http://jcs.biologists.org/cgi/reprint/s3-90/11/221). *Quarterly Journal of Microscopical Science*. **90** (s3): 221–233.

1. **[^](#cite_ref-Ruppert1_9-0)** Edward E. Ruppert; Richard S. Fox (1988). "Annelida: Segmented Worms". [*Seashore animals of the Southeast: a guide to common shallow-water invertebrates of the southeastern Atlantic Coast*](https://archive.org/details/seashoreanimalso00edwa). Columbia, South Carolina: University of South Carolina Press. p. [219](https://archive.org/details/seashoreanimalso00edwa/page/219). [ISBN](/source/ISBN_(identifier)) [0-87249-535-3](https://en.wikipedia.org/wiki/Special:BookSources/0-87249-535-3). melanostigma operculum.

1. **[^](#cite_ref-serpula_10-0)** Richard S. Fox, Invertebrate Anatomy OnLine: [*Serpula vermicularis*](http://webs.lander.edu/rsfox/invertebrates/serpula.html) [Archived](https://web.archive.org/web/20100719203948/http://webs.lander.edu/rsfox/invertebrates/serpula.html) 19 July 2010 at the [Wayback Machine](/source/Wayback_Machine). Lander University, 4 July 2006. Accessed 3 May 2010.

1. **[^](#cite_ref-11)** An Underwater Field Guide to Point Lobos: [Invertebrates: Worms](http://pt-lobos.com/inverts.html). Accessed 3 May 2010.

1. **[^](#cite_ref-Wells_12-0)** G. P. Wells (27 August 1952). "The Respiratory Significance of the Crown in the Polychaete Worms Sabella and Myxicola". *[Proceedings of the Royal Society B](/source/Proceedings_of_the_Royal_Society_B)*. **140** (898): 70–82. [Bibcode](/source/Bibcode_(identifier)):[1952RSPSB.140...70W](https://ui.adsabs.harvard.edu/abs/1952RSPSB.140...70W). [doi](/source/Doi_(identifier)):[10.1098/rspb.1952.0045](https://doi.org/10.1098%2Frspb.1952.0045). [JSTOR](/source/JSTOR_(identifier)) [82713](https://www.jstor.org/stable/82713). [PMID](/source/PMID_(identifier)) [13003913](https://pubmed.ncbi.nlm.nih.gov/13003913). [S2CID](/source/S2CID_(identifier)) [36440648](https://api.semanticscholar.org/CorpusID:36440648).

1. **[^](#cite_ref-memorial_13-0)** Department of Biology, Memorial University of Newfoundland: [Eudistylia_vancouveri *Eudistylia vancouveri*](https://www.mun.ca/osc/oscedu/sabella.php), Ocean Sciences Centre. Accessed 3 May 2010.

1. ^ [***a***](#cite_ref-Kennedy_14-0) [***b***](#cite_ref-Kennedy_14-1) Bill Kennedy; Harald Kryvi (October 1980). "Autotomy in a polychaete: Abscission zone at the base of the tentacular crown of Sabella penicillus". *Zoomorphology*. **96** (1–2): 33–43. [doi](/source/Doi_(identifier)):[10.1007/BF00310075](https://doi.org/10.1007%2FBF00310075). [S2CID](/source/S2CID_(identifier)) [24021108](https://api.semanticscholar.org/CorpusID:24021108).

1. **[^](#cite_ref-Pernet_15-0)** Bruno Pernet (April 2001). ["Escape Hatches for the Clonal Offspring of Serpulid Polychaetes"](https://archive.org/stream/biologicalbullet200mari/biologicalbullet200mari_djvu.txt). *Biological Bulletin*. **200** (2): 107–117. [doi](/source/Doi_(identifier)):[10.2307/1543304](https://doi.org/10.2307%2F1543304). [JSTOR](/source/JSTOR_(identifier)) [1543304](https://www.jstor.org/stable/1543304). [PMID](/source/PMID_(identifier)) [11341572](https://pubmed.ncbi.nlm.nih.gov/11341572). [S2CID](/source/S2CID_(identifier)) [24189960](https://api.semanticscholar.org/CorpusID:24189960). Retrieved 3 May 2010.

1. **[^](#cite_ref-Fitzharris_16-0)** Timothy P. Fitzharris (1976). ["Regeneration in Sabellid Annelids"](https://doi.org/10.1093%2Ficb%2F16.3.593). *American Zoologist*. **16** (3): 593–616. [doi](/source/Doi_(identifier)):[10.1093/icb/16.3.593](https://doi.org/10.1093%2Ficb%2F16.3.593).

1. **[^](#cite_ref-Walla2_17-0)** Department of Biology, Walla Walla University: [Eudistylia_vancouveri](http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Annelida/Sabellidae/Eudistylia_vancouveri.html), Rosario Beach Marine Laboratory. Accessed 3 May 2010.

1. **[^](#cite_ref-18)** M.J.Benton, ed. (1993). [*The Fossil Record 2*](https://archive.org/details/fossilrecord20000unse). Chapman & Hall. [ISBN](/source/ISBN_(identifier)) [0-412-39380-8](https://en.wikipedia.org/wiki/Special:BookSources/0-412-39380-8).

1. **[^](#cite_ref-19)** Read G, Fauchald K (eds.). ["Canalipalpata Rouse & Fauchald, 1997 non Linnaean"](https://www.marinespecies.org/aphia.php?p=taxdetails&id=154974). *World Polychaeta Database*. [World Register of Marine Species](/source/World_Register_of_Marine_Species). Retrieved 2025-08-24.

## External links

- Encyclopedia of Life: [http://www.eol.org/pages/124?category_id=226](http://www.eol.org/pages/124?category_id=226)

- Images from the canalipalpata order: [http://zipcodezoo.com/index.php/Canalipalpata](http://zipcodezoo.com/index.php/Canalipalpata)

Taxon identifiers Canalipalpata Wikidata: Q3817224 Wikispecies: Canalipalpata ADW: Canalipalpata BOLD: 125421 EoL: 124 iNaturalist: 194008 IRMNG: 10251 ITIS: 555669 NBN: NHMSYS0021049225 NCBI: 105391 NZOR: c45aa9a0-1a0f-4d3c-a413-9c9c9b1a4bbf Open Tree of Life: 717917 WoRMS: 154974

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Adapted from the Wikipedia article [Canalipalpata](https://en.wikipedia.org/wiki/Canalipalpata) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Canalipalpata?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.