Polychaeta () is a paraphyletic class of generally marine annelid

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete wo ...

s, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species are described in this class. Common representatives include the

lugworm The lugworm or sandworm (''Arenicola marina'') is a large marine worm of the phylum Annelida. Its coiled castings are a familiar sight on a beach at low tide but the animal itself is rarely seen except by those who, from curiosity or to use as f ...

(''Arenicola marina'') and the sandworm or clam worm ''Alitta''. Polychaetes as a class are robust and widespread, with species that live in the coldest ocean temperatures of the

abyssal plain An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between and . Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. ...

, to forms which tolerate the extremely high temperatures near hydrothermal vents. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...

near the surface, to a 2- to 3-cm specimen (still unclassified) observed by the robot ocean probe ''Nereus'' at the bottom of the

Challenger Deep The Challenger Deep is the deepest-known point of the seabed of Earth, with a depth of by direct measurement from deep-diving submersibles, remotely operated underwater vehicles and benthic landers, and (sometimes) slightly more by sonar bathym ...

, the deepest known spot in the Earth's oceans. Only 168 species (less than 2% of all polychaetes) are known from fresh waters.

Description

Polychaetes are segmented worms, generally less than in length, although ranging at the extremes from to , in ''

Eunice aphroditois ''Eunice aphroditois'' is a Benthic zone, benthic polychaete, bristle worm of warm marine waters. It lives mainly in the Atlantic Ocean, but can also be found in the Indo-Pacific. It ranges in length from less than to . Its iridescent cuticle p ...

''. They can sometimes be brightly coloured, and may be iridescent or even

luminescent Luminescence is spontaneous emission of light by a substance not resulting from heat; or "cold light". It is thus a form of cold-body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions or stress on a crystal ...

. Each segment bears a pair of paddle-like and highly vascularized parapodia, which are used for movement and, in many species, act as the worm's primary

respiratory The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies gre ...

surfaces. Bundles of bristles, called chaetae, project from the parapodia. However, polychaetes vary widely from this generalised pattern, and can display a range of different body forms. The most generalised polychaetes are those that crawl along the bottom, but others have adapted to many different

ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for ...

s, including burrowing, swimming,

pelagic The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or w ...

life, tube-dwelling or boring,

commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fro ...

ism, and parasitism, requiring various modifications to their body structures. The head, or prostomium, is relatively well developed, compared with other annelids. It projects forward over the mouth, which therefore lies on the animal's underside. The head normally includes two to four pair of eyes, although some species are blind. These are typically fairly simple structures, capable of distinguishing only light and dark, although some species have large eyes with lenses that may be capable of more sophisticated vision, including the Alciopids' complex eyes which rival cephalopod and vertebrate eyes. The head also includes a pair of antennae, tentacle-like

palp Pedipalps (commonly shortened to palps or palpi) are the second pair of appendages of chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to the chelicerae ("jaws") ...

s, and a pair of pits lined with cilia, known as "nuchal organs". These latter appear to be

chemoreceptor A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance (endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemorecept ...

s, and help the worm to seek out food.

Internal anatomy and physiology

The outer surface of the body wall consists of a simple columnar epithelium covered by a thin cuticle. Underneath this, in order, are a thin layer of connective tissue, a layer of circular muscle, a layer of longitudinal muscle, and a

peritoneum The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of meso ...

surrounding the

body cavity A body cavity is any space or compartment, or potential space, in an animal body. Cavities accommodate organs and other structures; cavities as potential spaces contain fluid. The two largest human body cavities are the ventral body cavity, and ...

. Additional oblique muscles move the parapodia. In most species the body cavity is divided into separate compartments by sheets of peritoneum between each segment, but in some species it's more continuous. The mouth of polychaetes is located on the peristomium, the segment behind the prostomium, and varies in form depending on their diets, since the group includes predators, herbivores, filter feeders, scavengers, and parasites. In general, however, they possess a pair of jaws and a

pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...

that can be rapidly everted, allowing the worms to grab food and pull it into their mouths. In some species, the pharynx is modified into a lengthy

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...

. The digestive tract is a simple tube, usually with a stomach part way along. The smallest species, and those adapted to burrowing, lack

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s, breathing only through their body surfaces. Most other species have external gills, often associated with the parapodia. A simple but well-developed circulatory system is usually present. The two main blood vessels furnish smaller vessels to supply the parapodia and the gut. Blood flows forward in the dorsal vessel, above the gut, and returns down the body in the ventral vessel, beneath the gut. The blood vessels themselves are contractile, helping to push the blood along, so most species have no need of a heart. In a few cases, however, muscular pumps analogous to a heart are found in various parts of the system. Conversely, some species have little or no circulatory system at all, transporting oxygen in the coelomic fluid that fills their body cavities. The blood may be colourless, or have any of three different respiratory pigments. The most common of these is

haemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...

, but some groups have haemerythrin or the green-coloured chlorocruorin, instead. The nervous system consists of a single or double ventral nerve cord running the length of the body, with ganglia and a series of small nerves in each segment. The brain is relatively large, compared with that of other annelids, and lies in the upper part of the head. An

endocrine gland Endocrine glands are ductless glands of the endocrine system that secrete their products, hormones, directly into the blood. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, ...

is attached to the ventral posterior surface of the brain, and appears to be involved in reproductive activity. In addition to the sensory organs on the head, photosensitive eye spots,

statocyst The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, and crustaceans. A similar structure is also found in '' Xenoturbella''. The statocyst c ...

s, and numerous additional sensory nerve endings, most likely in involved with the sense of touch, also occur on the body. Polychaetes have a varying number of

protonephridia The nephridium (plural ''nephridia'') is an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys (which originated from the chordate nephridia). Nephridia remove metabolic wastes from an animal's body. Neph ...

metanephridia The nephridium (plural ''nephridia'') is an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys (which originated from the chordate nephridia). Nephridia remove metabolic wastes from an animal's body. Ne ...

for excreting waste, which in some cases can be relatively complex in structure. The body also contains greenish "chloragogen" tissue, similar to that found in

oligochaete Oligochaeta () is a subclass of animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms. Specifically, oligochaetes comprise the terrestrial megadrile earthworm ...

s, which appears to function in metabolism, in a similar fashion to that of the vertebrate

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...

. The cuticle is constructed from cross-linked fibres of collagen and may be 200 nm to 13 mm thick. Their jaws are formed from sclerotised collagen, and their

setae In biology, setae (singular seta ; from the Latin word for " bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...

from sclerotised chitin.

Ecology

Polychaetes are extremely variable in both form and lifestyle, and include a few taxa that swim among the

or above the

. Most burrow or build tubes in the sediment, and some live as

s. A few are parasitic. The mobile forms (Errantia) tend to have well-developed sense organs and jaws, while the stationary forms (Sedentaria) lack them, but may have specialized gills or tentacles used for respiration and deposit or filter feeding, e.g.,

fanworm Sabellida is an order 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 p ...

s. Underwater polychaetes have eversible mouthparts used to capture prey. 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.

Notable polychaetes

*One notable polychaete, the Pompeii worm (''Alvinella pompejana''), is endemic to the hydrothermal vents of the Pacific Ocean. Pompeii worms are among the most heat-tolerant complex animals known. *A recently discovered genus, ''

Osedax ''Osedax'' is a genus of deep-sea siboglinid polychaetes, commonly called boneworms, zombie worms, or bone-eating worms. ''Osedax'' is Latin for "bone-eater". The name alludes to how the worms bore into the bones of whale carcasses to reach enc ...

'', includes a species nicknamed 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 A tubeworm is any worm-like sessile invertebrate that anchors its tail to an underwater surface and secretes around its body a mineral tube, into which it can withdraw its entire body. Tubeworms are found among the following taxa: * Annelida, the ...

that reaches lengths of over 3 m and may be the most long-lived animal, being over 250 years old. *A still unclassified multilegged predatory polychaete worm was identified only by observation from the underwater vehicle ''Nereus'' at the bottom of the

, the greatest depth in the oceans, near in depth. It was about an inch long visually, but the probe failed to capture it, so it could not be studied in detail. *The Bobbit worm (''

'') is a predatory species that can achieve a length at ), with an average diameter of . *''Dimorphilus gyrociliatus'', which has the smallest known genome of any annelid. The species shows an extreme

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...

, with females measuring just ~1 mm long and has a simplified segmented body with only six segments, reduced coelom, and no appendages, parapodia or chaetae. The males are only 50 µm long, consist of just a few hundred cells, lack a digestive system, only live for about a week and has just 68 neurons.

Reproduction

Most polychaetes have separate sexes, rather than being hermaphroditic. The most primitive species have a pair of gonads in every segment, but most species exhibit some degree of specialisation. The gonads shed immature

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce ...

s directly into the body cavity, where they complete their development. Once mature, the gametes are shed into the surrounding water through ducts or openings that vary between species, or in some cases by the complete rupture of the body wall (and subsequent death of the adult). A few species copulate, but most fertilize their eggs externally. The fertilized eggs typically hatch into

trochophore A trochophore (; also spelled trocophore) is a type of free-swimming planktonic marine larva with several bands of cilia. By moving their cilia rapidly, they make a water eddy, to control their movement, and to bring their food closer, to captur ...

larvae, which float among the

, and eventually

metamorphose Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some insec ...

into the adult form by adding segments. A few species have no larval form, with the egg hatching into a form resembling the adult, and in many that do have larvae, the trochophore never feeds, surviving off the yolk that remains from the egg. However, some polychaetes exhibit remarkable reproductive strategies. Some species reproduce by epitoky. For much of the year, these worms look like any other burrow-dwelling polychaete, but as the breeding season approaches, the worm undergoes a remarkable transformation as new, specialized segments begin to grow from its rear end until the worm can be clearly divided into two halves. The front half, the atoke, is asexual. The new rear half, responsible for breeding, is known as the epitoke. Each of the epitoke segments is packed with eggs and sperm and features a single eyespot on its surface. The beginning of the last lunar quarter is the cue for these animals to breed, and the epitokes break free from the atokes and float to the surface. The eye spots sense when the epitoke reaches the surface and the segments from millions of worms burst, releasing their eggs and sperm into the water. A similar strategy is employed by the deep sea worm '' Syllis ramosa'', which lives inside a

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throug ...

. The rear end of the worm develops into a "stolon" containing the eggs or sperm; this stolon then becomes detached from the parent worm and rises to the sea surface, where fertilisation takes place.

Fossil record

Stem-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

polychaete fossils are known from the

Sirius Passet Sirius Passet is a Cambrian Lagerstätte in Peary Land, Greenland. The Sirius Passet Lagerstätte was named after the Sirius sledge patrol that operates in North Greenland. It comprises six places in Nansen Land, on the east shore of J.P. Koch F ...

Lagerstätte A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These f ...

, a rich, sedimentary deposit in Greenland tentatively dated to the late Atdabanian (early Cambrian). The oldest found is Phragmochaeta canicularis. Many of the more famous

Burgess Shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest fo ...

organisms, such as '' Canadia'', may also have polychaete affinities. ''

Wiwaxia ''Wiwaxia'' is a genus of soft-bodied animals that were covered in carbonaceous scales and spines that protected it from predators. ''Wiwaxia'' fossils – mainly isolated scales, but sometimes complete, articulated fossils – are known from ear ...

'', long interpreted as an annelid, is now considered to represent a mollusc. An even older fossil, '' Cloudina'', dates to the terminal Ediacaran period; this has been interpreted as an early polychaete, although consensus is absent. Being soft-bodied organisms, the fossil record of polychaetes is dominated by their fossilized jaws, known as scolecodonts, and the

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

ized tubes that some of them secrete. Most important biomineralising polychaetes are serpulids, sabellids, and cirratulids. Polychaete cuticle does have some preservation potential; it tends to survive for at least 30 days after a polychaete's death. Although biomineralisation is usually necessary to preserve soft tissue after this time, the presence of polychaete muscle in the nonmineralised Burgess shale shows this need not always be the case. Their preservation potential is similar to that of

jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrell ...

Taxonomy and systematics

Taxonomically, polychaetes are thought to be paraphyletic, meaning the group excludes some descendants of its most recent common ancestor. Groups that may be descended from the polychaetes include the oligochaetes (

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...

s and leeches),

sipuncula The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a class containing about 162 species of unsegmented marine annelid worms. The name ''Sipuncula'' is from the genus name ''Sipunculus'', and comes from the Latin ' ...

ns, and

echiura The Echiura, or spoon worms, are a small group of marine animals. Once treated as a separate phylum, they are now considered to belong to Annelida. Annelids typically have their bodies divided into segments, but echiurans have secondarily los ...

ns. The Pogonophora and

Vestimentifera Siboglinidae is a family of polychaete annelid worms whose members made up the former phyla Pogonophora and Vestimentifera (the giant tube worms). The family is composed of about 100 species of vermiform creatures which live in thin tubes buried ...

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. Older classifications recognize many more (sub)orders than the layout presented here. As comparatively few polychaete

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

have been subject to

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

analysis, some groups which are usually considered invalid today may eventually be reinstated. These divisions were shown to be mostly paraphyletic in recent years. * Basal or ''

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

'' **Family Diurodrilidae **Family

Histriobdellidae Histriobdellidae is a family of annelids belonging to the order Eunicida. Genera: * ''Histriobdella'' Van Beneden, 1858 * ''Histriodrilus'' Foettinger, 1884 * ''Steineridrilus'' Zhang, 2014 * ''Stratiodrilus'' Haswell, 1900 References

{ ...

**Family Nerillidae **Family Parergodrilidae **Family Potamodrilidae **Family Psammodrilidae **Family Spintheridae **Family Protodriloididae **Family Saccocirridae **Order Haplodrili **Order

Myzostomida The Myzostomida or Myzostomatida are an order of small marine worms, which are parasitic on echinoderms, mostly crinoids. These highly unusual and diverse annelids were first discovered by Friedrich Sigismund Leuckart in 1827. Morphology A ...

***Family Endomyzostomatidae ***Family Asteromyzostomatidae ***Family Myzostomidae *Subclass

Palpata Palpata is a subclass of polychaete worm. Members of this subclass are mostly deposit feeders on marine detritus or filter feeders. Palpata has become superfluous with the elevation of Canalipalpata to subclass. Characteristics Palpata includes ...

**Family Protodrilidae **Family Polygordiidae *Subclass

Aciculata Errantia is a diverse group of marine polychaete worms in the phylum Annelida. Traditionally a subclass of the paraphyletic class "Polychaeta", it is currently regarded as a monophyletic group within the larger Pleistoannelida, composed of Err ...

**Family Levidoridae **Order Amphinomida ***Family Amphinomidae ***Family Euphrosinidae **Order Eunicida ***Family Dorvilleidae ***Family Eunicidae ***Family Hartmaniellidae ***Family Ichthyotomidae ***Family Lumbrineridae ***Family Oenonidae ***Family Onuphidae **Order

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 c ...

***Suborder Aphroditiformia ****Family Acoetidae ****Family Aphroditidae ****Family Eulepethidae ****Family Iphionidae ****Family Pholoidae ****Family Polynoidae ****Family Sigalionidae ***Suborder Glyceriformia ****Family

Glyceridae Glyceridae is a family of polychaete worms. They are commonly referred to as beak-thrower worms or bloodworms. They are bright red, segmented, aquatic worms. The proboscis worm '' Glycera'' is sometimes called bloodworm. The Glyceridae are epi- a ...

****Family Goniadidae ****Family

Lacydoniidae Lacydoniidae is a family of polychaetes belonging to the order Phyllodocida. Genera: * '' Lacydonia'' Marion, 1874 References Polychaetes {{Annelid-stub ...

****Family Paralacydoniidae ***Suborder Nereidiformia ****Family Antonbruunidae ****Family Chrysopetalidae ****Family Hesionidae ****Family

Nereididae Nereididae (formerly spelled Nereidae) are a family of polychaete worms. It contains about 500 – mostly marine – species grouped into 42 genera. They may be commonly called ragworms or clam worms. Characteristics The prostomium of ...

****Family

Pilargidae Pilargidae is a family of polychaetes. These marine worms are cylindrical, somewhat flattened, and can be ribbon-like. They can be found free-living on sediment, or shallowly in sediment. Some species within the genera Hermundura and Litocorsa ...

****Family Syllidae ***Suborder Phyllodocida incertae sedis ****Family

Iospilidae Iospilidae is a family of polychaetes belonging to the order Phyllodocida. Genera: * ''Iospilopsis'' Augener, 1922 * ''Iospilus'' Viguier, 1886 * ''Paraiospilus'' Viguier, 1911 * ''Phalacrophorus'' Greeff, 1879 References

{{Taxonbar, from= ...

****Family

Nautiliniellidae Nautiliniellidae is a family of polychaetes belonging to the order Phyllodocida. Genera: * ''lascarpia'' * ''Iheyomytilidicola'' * ''Laubierus'' References

{{Taxonbar, from=Q5180094 Phyllodocida ...

****Family Nephtyidae ****Family Typhloscolecidae ****Family

Tomopteridae Tomopteridae is a family of holopelagic polychaetes belonging to the order Phyllodocida. The genus Tomopteris consist of about 70 species, and the three other genera of one known species each. Length varies from just 1-2 cm to 30 cm. These are ver ...

***Suborder Phyllodociformia ****Family Alciopidae ****Family Lopadorhynchidae ****Family

Phyllodocidae Phyllodocidae is a family of polychaete worms. Worms in this family live on the seabed and may burrow under the sediment. Characteristics Members of the Phyllodocidae are characterised by an eversible pharynx and leaf-like dorsal cirri. The hea ...

****Family Pontodoridae *Subclass Sedentaria **Family

Chaetopteridae The Chaetopteridae are a family of marine filter-feeding polychaete worms that live in vertical or U-shaped tubes in tunnels buried in the sedimentary or hard substrate of marine environments. The worms are highly adapted to the hard tube they ...

**Infraclass

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 suborder Sabellida (families Serpulidae (tubeworms) and Sabellidae (fanworms and feather duster worms) ...

***Order

Sabellida Sabellida is an order 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 p ...

****Family Caobangidae ****Family Fabriciidae ****Family

Oweniidae Oweniidae is a family of marine polychaete worms in the suborder Sabellida. The worms live in tubes made of sand and are selective filter feeders, detritivores and grazers. Characteristics Members of this family live in tubes made of sand and sh ...

****Family

Sabellariidae Sabellariidae is a family of marine polychaete worms in the suborder Sabellida. The worms live in tubes made of sand and are filter feeders and detritivores. Characteristics Members of this family live in tubes made of sand and shell fragments c ...

****Family Sabellidae ****Family

Serpulidae The Serpulidae are a family of sessile, tube-building annelid worms in the class Polychaeta. The members of this family differ from other sabellid tube worms in that they have a specialized operculum that blocks the entrance of their tubes wh ...

****Family Siboglinidae (formerly the phyla Pogonophora & Vestimentifera) ***Order Spionida ****Suborder Spioniformia *****Family Apistobranchidae *****Family Longosomatidae *****Family Magelonidae *****Family Poecilochaetidae *****Family Spionidae *****Family

Trochochaetidae Trochochaetidae is a family of polychaetes Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear ...

*****Family Uncispionidae ***Order

Terebellida Terebellida make up an order 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 ...

****Suborder Cirratuliformia *****Family Acrocirridae (sometimes placed in Spionida) *****Family Cirratulidae (sometimes placed in Spionida) *****Family Ctenodrilidae (sometimes own suborder Ctenodrilida) *****Family

Fauveliopsidae Fauveliopsidae is a family of polychaetes belonging to the order Terebellida. The genus name honours Pierre Fauvel. It is a small family, containing only three genera and about twenty species. They are benthic animals, noted for their habit of ...

(sometimes own suborder Fauveliopsida) *****Family

Flabelligeridae Flabelligeridae is a family of polychaete worms, known as bristle-cage worms, notable for their cephalic cage: long slender chaetae forming a fan-like arrangement surrounding the eversible (able to be turned inside-out) head. Unlike many polychae ...

(sometimes suborder Flabelligerida) *****Family

Flotidae Flotidae is a family of pelagic polychaete worms, sometimes synonymized with Flabelligeridae, which they closely resemble. Other sources consider them the sister taxon to Flabelligeridae and closely allied to the latter group.Zhadan, A. E., and ...

(sometimes included in Flabelligeridae) *****Family Poeobiidae (sometimes own suborder Poeobiida or included in Flabelligerida) *****Family Sternaspidae (sometimes own suborder Sternaspida) ****Suborder Terebellomorpha *****Family Alvinellidae *****Family Ampharetidae *****Family Pectinariidae *****Family Terebellidae *****Family Trichobranchidae **Infraclass Scolecida ***Family Arenicolidae ***Family

Capitellidae Capitellidae is a polychaete worm family in the subclass Scolecida. Genera * '' Abyssocapitella'' * '' Amastigos'' * '' Anotomastus'' * '' Baldia'' * '' Barantolla'' * '' Branchiocapitella'' * '' Capitella'' * '' Capitellethus'' * '' Capitobr ...

***Family Cossuridae ***Family Maldanidae ***Family Opheliidae ***Family Orbiniidae ***Family Paraonidae ***Family Scalibregmatidae ***Order Capitellida ( nomen dubium) ***Order Cossurida (nomen dubium) ***Order Opheliida (nomen dubium) ***Order Orbiniida (nomen dubium) ***Order Questida (nomen dubium) ***Order Scolecidaformia (nomen dubium) *Subclass

Echiura The Echiura, or spoon worms, are a small group of marine animals. Once treated as a separate phylum, they are now considered to belong to Annelida. Annelids typically have their bodies divided into segments, but echiurans have secondarily los ...

** Order Bonelliida *** Family Bonelliidae *** Family Ikedidae ** Order Echiurida *** Family

Echiuridae Echiuridae is a family of spoon worms in the suborder Echiurida. It is a monotypic family, the only genus being ''Echiurus''. These worms burrow into soft sediment on the seabed. Species The World Register of Marine Species recognises the fo ...

*** Family

Thalassematidae Thalassematidae is a family of spoonworms in the suborder Echiurida. Genera The World Register of Marine Species includes these genera in this family:- *'' Anelassorhynchus'' Annandale, 1922 *'' Arhynchite'' Satô, 1937 *'' Ikedosoma'' Bock, ...

*** Family Urechidae

References

Bibliography

* Campbell, Reece, and Mitchell. Biology. 1999. *

Notes

External links

World Polychaeta Database

Special issue of ''Marine Ecology''
dedicated to polychaetes

a guide to the marine zooplankton of south eastern Australia

Natural History Museum A natural history museum or museum of natural history is a scientific institution with natural history collections that include current and historical records of animals, plants, fungi, ecosystems, geology, paleontology, climatology, and more. ...

{{Authority control * Extant Cambrian first appearances Paraphyletic groups

Description

Internal anatomy and physiology

Ecology

Notable polychaetes

Reproduction

Fossil record

Taxonomy and systematics

See also

References

Bibliography

Notes

External links