Terebellida

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Terebellida
Chaetozone setosa (Cirratulidae), a burrowing terebellid
Scientific classification
Kingdom: Animalia Phylum: Annelida Class: Polychaeta Subclass: Palpata Order: Canalipalpata Suborder: Terebellida
Families
Several, see text

Terebellida (sometimes called Terebellomorpha) make up a suborder of the "bristle worm" class (Polychaeta). Together with the Sabellida, the Spionida and a some enigmatic families of unclear relations (e.g. the Saccocirridae), they make up the order Canalipalpata, one of the three main clades of polychaetes^[1].

Almost all are (like polychaetes in general) marine organisms. Most are smallish deposit feeders which frequently live in small tubes they build from mud or similar substrate, or burrow in the sand. Their central nervous system displays characteristic apomorphies.

A well-known member is the Pompeii worm (Alvinella pompejana), an alvinellid. It is the most heat-tolerant complex lifeform known on Earth. Found on hydrothermal vents deep in the Pacific Ocean, it thrives when its body temperature is 50°C (122°F). This is near the technical limit for eukaryotes, whose mitochondria desintegrate at about 55°C (131°F).

[edit] Systematics

There is little consensus on the number of families. Some treatments accept as little as five^[2], while other authors list over a dozen. Here, the more inclusive view of the Terebellida is followed, based on a major review of polychaete systematics^[1].

Cladistic studies have hitherto only analyzed a rather small proportion of polychaetes; hence it may be that some of the families today included in Terebellida by most authors will eventually be again recognized to belong elsewhere.

• Acrocirridae (sometimes placed in Spionida)
• Alvinellidae – alvinellids
• Ampharetidae
• Cirratulidae (sometimes placed in Spionida)
• Ctenodrilidae (sometimes own suborder Ctenodrilida)
• Fauveliopsidae (sometimes own suborder Fauveliopsida)
• Flabelligeridae (sometimes suborder Flabelligerida)
• Flotidae (sometimes included in Flabelligeridae)
• Pectinariidae – trumpet worms, ice cream cone worms, pectinariids
• Poeobiidae (sometimes own suborder Poeobiida or included in Flabelligerida)
• Sternaspidae (sometimes own suborder Sternaspida)
• Terebellidae – spaghetti worms, terebellids
• Trichobranchidae

[edit] Fossil record

Although polychaetes, like all small animals lacking a firm skeleton, do not fossilize well, s number of prehistoric bristle worms have been described. Several of these are placed in the Terebellida, though often only tentatively so owing to the continuing uncertainties about polychaete phylogeny.

However, as the terebellid habit of constructing characteristic tubes to live in seems quite ancient, and such structures are occasionally found in conservation lagerstätten. Polychaete remains associated with such ichnofossils can therefore be quite certainly be allocated to the Terebellida.

Prehistoric polychaete genera presumed to be Terebellida include:

• Arthrophycus Hall, 1852
• Cryptosiphon Prantl, 1948
• Granularia Pomel, 1849
• Harlania Goppert, 1852
• Lepidenteron Fritsch, 1878
• Paraterebella Howell, 1955 (= Terebellopsis Howell, 1953)
• Proterebella Howell, 1953
• Psammosiphon Vine, 1882
• Scalarituba Weller, 1899
• Scolecoderma Salter, 1855
• Terebellites Howell, 1943
• Terebelloides Desio, 1940
• Terebellolites Desio, 1940
• Terebellopsis Leymerie, 1844 (see also Paraterebella)

[edit] Footnotes

[edit] References

• Fauchald, Kristian (1977): The polychaete worms, definitions and keys to the orders, families and genera. Natural History Museum of Los Angeles County Science Series 28: 1-188.
• Holthe, Torleif (2001): The Polychaeta Terebellida homepage. Version of 21001-FEB-09. Retrieved 2008-Mar-21.
• Rouse, Greg W. & Fauchald, Kristian (1998): Recent views on the status, delineation, and classification of the Annelida. Am. Zool. 38(6): 953-964. doi:10.1093/icb/38.6.953 PDF fulltext