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Polychaeta

(Class)

Overview

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The bristle worms, a class of mainly marine annelid worms, the ragworms, the lugworms etc. characterised by possession of parapodia bearing numerous chaetae which are used for crawling, and a pronounced head bearing tentacles, palps and often eyes.

The largest and most primitive group of annelids, and the majority are marine. They are often strikingly beautiful and very colorful and, unlike the other two groups of annelids, they show enormous variation in form and lifestyle. Apart from the head and terminal segments, all the segments are identical, each with a pair of flattened, fleshy lobelike paddles called parapodia, which are used for swimming, burrowing and creating a feeding current. The bristles, or chaetae, on the parapodia are immensely variable betwen species. In the sea mice, for example, they form a protective mat over the back of the worm and give the animal a furry appearance. The bristles of fireworms, on the other hand, are long and poisonous for defense, and are shed readily if a worm is attacked.

Most of the tube-dwelling, or tubicolous polychaetes, are members of the Subclass Sedentaria, while most of the free-living species are in the Subclass Errantia. The tubicolous species can build tubes of unadorned mud, sand, or parchment (often decorated with sand, shell, algae, hydroids), or of hardened calcium carbonate. Most tubicolous polychaetes are either deposit feeders or filter feeders. Tubicolous polychaetes are often found in dense mats.

Photos

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Taxonomy

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The Class Polychaeta is further organized into finer groupings including:

Orders

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Aciculata

Aciculata is an order of polychaete worms. These worms are found worldwide in marine environments and brackish water. [more]

Aeolosomatida

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Amphinomida

[more]

Canalipalpata

Canalipalpata, also known as bristle-footed annelids or fan-head worms, is an order of polychaete worms, with 31 families in it including the Sabellida (tubeworms, fanworms, and feather duster worms) and the Alvinellidae, a family of deep-sea worms associated with hydrothermal vents. [more]

Eunicida

Eunicida is an order of polychaete worms. [more]

Nerillida

[more]

Not Assigned

Opheliida

[more]

Phyllodocida

Phyllodocida is an order of polychaete worms in the subclass Aciculata. These worms are mostly marine though some are found in brackish water. Most are active benthic creatures, moving over the surface or burrowing in sediments, or living in cracks and crevices in bedrock. A few construct tubes in which they live and some are pelagic, swimming through the water column. There are estimated to be about 3,500 species in the order. [more]

Protodrilida

[more]

Psammodrilida

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Sabellida

Sabellida is a suborder of annelid worms in the class Polychaeta. They are filter feeders with no buccal organ. The prostomium is fused with the peristomium and bears a ring of feathery feeding tentacles. They live in parchment-like tubes made of particles from their environment such as sand and shell fragments cemented together with mucus. [more]

Scolecida

Scolecida is a subclass of polychaete worm. Scolecids are mostly unselective deposit feeders on marine detritus. [more]

Spintherida

[more]

Spionida

Spionida is a suborder of marine polychaete worms in the order Canalipalpata. Spionids are cosmopolitan and live in soft substrates in the littoral or neritic zones. [more]

Terebellida

Terebellida (sometimes called Terebellomorpha) make up a suborder of the Polychaeta class, commonly referred to as "bristle worms". Together with the Sabellida, the Spionida and some enigmatic families of unclear taxonomic relationship (e.g. the Saccocirridae), they make up the order Canalipalpata, one of the three main clades of polychaetes. Like most polychaetes, almost all members of the Terebellida suborder are marine organisms. Most are small, sessile detritivores (deposit feeders) which live in small tubes they build from mud or similar substrate, or burrow in the sand. Their central nervous system displays characteristic apomorphies. [more]

At least 770 species and subspecies belong to the Order Terebellida.

More info about the Order Terebellida may be found here.

Sources

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Last Revised: August 22, 2014
2014/08/22 05:53:15