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Brief Summary

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Phyllodocida is an order of polychaete worms which contains an estimated 3500+ species. Adults range in size from several millimeters to more than a meter. Morphological studies cite strong support for a monophyletic grouping of the Phyllodocida, based on several characters (anterior enlarged cirri; an axial muscular proboscis (eversible pharynx); ventral position of sensory palps; compound chaetae with a single ligament; lack of dorsolateral folds; see Rouse and Fauchald, 1997).

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Habitat

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The phyllodocida span a range of habitats. While most are marine, some live in brackish waters, and members of the family Nereididae can be found in freshwater and even terrestrial environments. The Phyllodocida make up a large portion of what have been considered the “errant” polychaetes – active burrowing and swimming worms. Most of the marine members of the Phyllodocida are free-living burrowers; some groups spend their adult lives in the water column (these pelagic species are usually transparent). A very few are sessile and live in tubes (Pleijel and Rouse 2004).

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Systematics and Taxonomy

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Several molecular studies carried out since then have questioned the monophyly of the Phyllodocida, although it is recognized that none of these studies have very complete taxon sampling (Rousset et al. 2006, and references within). It has been difficult to root the polychaete tree, and it has been suggested that the root of the polychaetes lies within the Phyllodocida, rendering this group paraphyletic (Rouse and Pleijel, 2001)


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Trophic Strategy

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Worms in the order Phyllodocida generally are predators or scavengers. They have a eversible proboscis, which in many is bestowed with large jaws (many species can deliver a powerful bite to humans), a large head with well developed eyes and sensory structures. The front segments have sensory appendages called cirri, while the segments further back have broad appendages called parapodia for crawling or swimming, and which support bunches of chaetae in species-specific patterns.

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Uses

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Some of the rag worms (Neries and close relatives) and blood worms (Glycera) are harvested commercially for fish bait, and are among the most widely known of the phyllodocida.

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Phyllodocida

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Phyllodocida is an order of polychaete worms in the subclass Aciculata.[1] 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.[2]

Characteristics

Phyllodocida are segmented worms and range in size from a few millimetres long to over a metre. Each segment bears a pair of paddle-like parapodia. The prostomium generally has one or two pairs of eyes, a dorsal pair of antennae, a ventral pair of sensory palps and a pair of organs on the neck. The peristomium is a ring, often hidden dorsally by the prostomium and the first segment. There is a muscular proboscis with one or more pairs of jaws. The next few segments tend to differ from those further back in having enlarged dorsal and ventral cirri (fine appendages) and reduced parapodial lobes and chaetae (bristles). Some species have appendages with specialised functions but most have many segments that are similar to each other but which vary in size and shape along the length of the body without abrupt changes in the chaetae and parapodia from one to the next.[2]

Biology

Worms in this order are generally predators or scavengers.[3]

Phylogenetic relationships

The three main subgroups are Aphroditiformia, Glyceriformia and Nereidiformia. The Aphroditiformia are characterised by the presence of elytrae or scales on alternating segments. The Glyceriformia are characterised by the presence of unique cone-shaped and ringed prostomiums. The Nereidiformia are more problematic, having no universally distinguishing common features. There is agreement on the monophyly of a group including the Hesionidae, Nereididae and Chrysopetalidae families but opinions differ about Pilargidae, and molecular and morphological studies continue.[4][5][6]

Families

Recognised families:[1]

Suborder Aphroditiformia

Superfamily Aphroditoidea
Acoetidae
Aphroditidae
Eulepethidae
Pholoidae
Polynoidae
Sigalionidae
Superfamily Chrysopetalacea
Chrysopetalidae
Superfamily Pisionacea
Pisionidae

Suborder Glyceriformia

Glyceridae
Goniadidae
Lacydoniidae
Paralacydoniidae

Suborder Nereidiformia

Antonbruuniidae
Hesionidae
Nereidae
Pilargidae
Syllidae

Suborder Phyllodocida incertae sedis

Iospilidae
Nephtyidae
Sphaerodoridae
Tomopteridae
Typhloscolecidae
Yndolaciidae

Suborder Phyllodociformia

Alciopidae
Lopadorhynchidae
Phyllodocidae
Pontodoridae

Incertae sedis

Nautiliniellidae

References

  1. ^ a b World Register of Marine Species
  2. ^ a b Tree of Life Web Project
  3. ^ Encyclopedia of Life
  4. ^ Glasby, C.J. 1993. Family revision and cladistic analysis of the Nereidoidea (Polychaeta: Phyllodocida). Invertebr. Taxon. 7:1551-1573.
  5. ^ Pleijel, F., and Dahlgren, T.G. 1998. Position and delineation of Chrysopetalidae and Hesionidae (Annelida, Polychaeta, Phyllodocida). Cladistics 14:129-150.
  6. ^ Dahlgren, T.G., Lundberg, J., Pleijel, F., and Sundberg, P. 2000. Morphological and molecular evidence of the phylogeny of Nereidiform polychaetes (Annelida). J. zool. Syst. evol. Res. 38:249-253.

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Phyllodocida: Brief Summary

provided by wikipedia EN

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.

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