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Information about Polychaetes

Polychaetes
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"A variety of marine worms": plate from Das Meer by M. J. Schleiden (1804–1881).

"A variety of marine worms": plate from Das Meer by M. J. Schleiden (1804–1881).
Scientific classification
Kingdom:Animalia
Phylum:Annelida
Class:Polychaeta
Grube, 1850
Subclasses
Palpata
Scolecida


The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Polychaeta means "many-bristled" (as opposed to the Oligochaeta which are "few-bristled"), and indeed the polychaetes are sometimes referred to as bristle worms. More than 10,000 species are described in this class. Common representatives include the lugworm (Arenicola marina) and the sandworm or clam worm Nereis.

Anatomy and physiology

The polychaetes' paddle-like and highly vascularized parapodia are used for movement and act as the annelid's primary respiratory surfaces (parapodia can be thought of as kinds of external gills that are also used for locomotion). Polychaeta also have well-developed heads compared to other annelids.

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General anatomy of a polychaete


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Tomopteris from plankton

Ecology

Polychaetes are extremely variable in both form and lifestyle and include a few taxa that swim among the plankton. Most burrow or build tubes on the bottom, and some live as commensals. A few are parasitic. The mobile forms or Errantia tend to have well-developed sense organs and jaws, while the Sedentaria (or stationary forms) lack them but may have specialized gills or tentacles used for respiration and deposit or filter feeding, e.g., fanworms.

A few groups have evolved to live in terrestrial environments, like Namanereidinae with many terrestrial species, but are restricted to humid areas. Some have even evolved cutaneous invaginations for aerial gas exchange.

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Sabellastarte indica


One notable polychaete, the Pompeii worm (Alvinella pompejana) is endemic to the hydrothermal vents of the Pacific Ocean. Pompeii worms are thought to be the most heat-tolerant complex animals known.

A recently discovered genus Osedax includes the Bone-eating snot flower.

Another remarkable polychaete is Hesiocaeca methanicola, which lives on methane clathrate deposits.

Lamellibrachia luymesi is a cold seep tube worm that reaches lengths of over 3 meters and may be the most long lived animal at over 250 years old.

Evolutionary history

Cloudina is an Ediacaran fossil that may be an early Serpulid worm. The oldest definite polychaetes are from the Cambrian Period, such as Canadia from the Burgess Shale.

Polychaetes are more commonly known from their fossilized jaws, known as scolecodonts, and from the mineralized tubes that some of them secrete.

Taxonomy

Taxonomically, the polychaetes are thought to be paraphyletic, meaning that as a group it contains its most recent common ancestor, but does not contain all the descendants of that ancestor. Groups that may be descended from the polychaetes include the earthworms, the leeches, sipunculans, and echiurans. The Pogonophora and Vestimentifera were once considered separate phyla, but are now classified in the polychaete family Siboglinidae.

Much of the classification below matches Rouse & Fauchald, 1998, although that paper does not apply ranks above family.
  • Subclass Palpata
  • Order Aciculata
  • Suborder uncertain
  • Family Aberrantidae
  • Family Nerillidae
  • Family Spintheridae
  • Suborder Eunicida
  • Family Amphinomidae
  • Family Diurodrilidae
  • Family Dorvilleidae
  • Family Eunicidae
  • Family Euphrosinidae
  • Family Hartmaniellidae
  • Family Histriobdellidae
  • Family Lumbrineridae
  • Family Oenonidae
  • Family Onuphidae
  • Suborder Phyllodocida
  • Family Acoetidae
  • Family Alciopidae
  • Family Aphroditidae
  • Family Chrysopetalidae
  • Family Eulepethidae
  • Family Glyceridae
  • Family Goniadidae
  • Family Hesionidae
  • Family Ichthyotomidae
  • Family Iospilidae
  • Family Lacydoniidae
  • Family Lopadorhynchidae
  • Family Myzostomatidae
  • Family Nautillienellidae
  • Family Nephtyidae
  • Family Nereididae
  • Family Paralacydoniidae
  • Family Pholoidae
  • Family Phyllodocidae
  • Family Pilargidae
  • Family Pisionidae
  • Family Polynoidae
  • Family Pontodoridae
  • Family Sigalionidae
  • Family Sphaeodoridae
  • Family Syllidae
  • Family Typhloscolecidae
  • Family Tomopteridae
  • Order Canalipalpata
  • Suborder uncertain
  • Family Polygordiidae
  • Family Protodrilidae
  • Family Protodriloididae
  • Family Saccocirridae
  • Suborder Sabellida
  • Family Oweniidae
  • Family Siboglinidae (formerly the phyla Pogonophora & Vestimentifera)
  • Family Serpulidae
  • Family Sabellidae
  • Family Sabellariidae
  • 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
  • Family Poeobiidae
  • Family Sternaspidae
  • Family Terebellidae
  • Family Trichobranchidae
  • Subclass Scolecida
  • Family Aeolosomatidae
  • Family Arenicolidae
  • Family Capitellidae
  • Family Cossunidae
  • Family Maldanidae
  • Family Ophelidae
  • Family Orbiniidae
  • Family Paraonidae
  • Family Parergodrilidae
  • Family Potamodrilidae
  • Family Psammodrilidae
  • Family Questidae
  • Family Scalibregmatidae

See also

  • Epitoky, a form of reproduction of Polychaetae.

References

  • Campbell, Reece, and Mitchell. Biology. 1999.
  • Rouse, Greg W.; Fauchald, Kristian (1998). "Recent views on the status, delineation, and classification of the Annelida". American Zoologist 38: 953-964. 

External links

Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. Scientific classification also can be called scientific taxonomy, but should be distinguished from folk taxonomy, which lacks scientific basis.
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Annelida
Lamarck, 1809

Classes and subclasses

Class Polychaeta (paraphyletic?)
Class Clitellata*
   Oligochaeta - earthworms, etc.
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class is the rank in the scientific classification of organisms in biology below Phylum and above Order.

For example, Mammalia is the class used in the classification of dogs, whose phylum is Chordata (animals with notochords) and order is Carnivora (mammals that eat meat).
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Annelida
Lamarck, 1809

Classes and subclasses

Class Polychaeta (paraphyletic?)
Class Clitellata*
   Oligochaeta - earthworms, etc.
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Parapodia (Gr. para, beyond or beside + podia, feet), singular parapodium, are paired un-jointed lateral outgrowths. They are characteristic of Polychaeta, but they also occur in opisthobranch mollusks.

Parapodia are either uniramous or biramous.
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A chaeta or cheta (see spelling differences) is a bristle or seta found on annelid worms such as the earthworm. The plural form is chaetae or chetae.

In the Polychaeta, they are located on the parapodia.
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Chitin (C8H13O5N)n (IPA: [ˈkaɪtn̩]) is a long-chain polymer of beta-glucose that forms a hard, semitransparent material found throughout the natural world.
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Oligochaeta

Orders

Haplotaxida
Lumbriculida
Oligochaeta (singular Oligochaete, IPA /ˈɒlɪgoʊˌkiːt/
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A. marina

Binomial name
Arenicola marina

The lugworm or sandworm is a large marine worm of the phylum Annelida.
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Sandworm may refer to:
  • Sandworm (Dune), a fictional desert-dwelling creature from the science fiction series Dune
  • Sandworm (UK), a large marine worm
  • Sandworm (US), a polychaete worm of the family Nereidae

See also


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Nereis

Species: N. succinea

Binomial name
Nereis succinea
(Frey & Leuchart, 1847)

The Common clam worm (Nereis succinea
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Annelida
Lamarck, 1809

Classes and subclasses

Class Polychaeta (paraphyletic?)
Class Clitellata*
   Oligochaeta - earthworms, etc.
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Gas exchange or respiration takes place at a respiratory surface - a boundary between the external environment and the interior of the body. For unicellular organisms the respiratory surface is simply the cell membrane, but for large organisms it usually is carried out in
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A gill is a respiration organ that functions for the extraction of oxygen from water and the excretion of carbon dioxide. Unlike many small aquatic animals, which can absorb oxygen through the entire surface of their bodies, more complex aquatic organisms have gills specially
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Plankton are any drifting organism that inhabits the pelagic zone of oceans, seas, or bodies of fresh water. It is a description of life-style rather than a genetic classification.
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Commensalism is a term employed in ecology to describe a relationship between two living organisms where one benefits and the other is not significantly harmed or helped. It is derived from the English word commensal
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A. pompejana

Binomial name
Alvinella pompejana
Desbruyéres and Laubier, 1980

The Pompeii worm (Alvinella pompejana
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A hydrothermal vent, also called a "black smoker", is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, tectonic plates that are moving apart, ocean basins, and hotspots.
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Earth's oceans
(World Ocean)
  • Arctic Ocean
  • Atlantic Ocean
  • Indian Ocean
  • Pacific Ocean
  • Southern Ocean


The Pacific Ocean (from the Latin name Mare Pacificum
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Osedax
Rouse et al., 2004

Species

Osedax frankpressi
Osedax rubiplumus
Osedax mucofloris
Osedax
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Osedax
Rouse et al., 2004

Species

Osedax frankpressi
Osedax rubiplumus
Osedax mucofloris
Osedax
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H. methanicola

Binomial name
Hesiocaeca methanicola
Desbruyères & Toulmond, 1998

Methane clathrate deposits in the ocean floor have been found to be inhabited by polychaete worms of the species
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Methane clathrate, also called methane hydrate or methane ice, is a solid form of water that contains a large amount of methane within its crystal structure (a clathrate hydrate).
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Lamellibrachia is a genus of the tube worm related to the giant tube worm, Riftia pachyptila. It lives at deep-sea cold seeps where hydrocarbons (oil and methane) are leaking out of the seafloor.
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cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs. Cold seeps are distinct from hydrothermal vents: the former's emissions are of the same temperature as the surrounding
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tube worm may refer to any of a number of unrelated tube-dwelling worm-like invertebrates.

These include chiefly various polychaetes, specifically the family Siboglinidae (beard worms), Serpulidae, and related families of the order Canalipalpata.
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Cloudinidae
Hahn and Pflug, 1985

Genus: Cloudina
Germs, 1972

Species
  • C. hartmannae Germs 1972
  • C.

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Cryogenian

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The Cambrian is a major division of the geologic timescale that begins about 542 ± 1.0 Ma (million years ago) at the end of the Proterozoic eon and ended about 488.3 ± 1.7 Ma with the beginning of the Ordovician period (ICS, 2004).
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