Annelids Fossil range: Cambrian - Recent
Glycera sp.
Scientific classification
Kingdom: Animalia Superphylum: Lophotrochozoa Phylum: Annelida Lamarck, 1809
Classes and subclasses
Class Polychaeta (paraphyletic?) Class Clitellata*    Oligochaeta - earthworms, etc.    Acanthobdellida    Branchiobdellida    Hirudinea - leeches Class Myzostomida Class Archiannelida (polyphyletic) *Some authors consider the subclasses under Clitellata to be classes System Shock 2 (commonly abbreviated SS2 or Shock2) is a science fiction horror-themed hybrid game which incorporates a number of elements commonly seen in computer role-playing games and first-person shooters. ... The Many is one of the two main antagonists of the Irrational Games computer game System Shock 2. ... For other uses, see Cambrian (disambiguation). ... Operation Autumn Clouds: Israel Defense Forces troops kill two Palestinian terrorists in anorthern Gaza Strip operation. ... Image File history File links Download high-resolution version (1600x1064, 298 KB) North Inlet - Winyah Bay National Estuarine Research Reserve. ... For other uses, see Scientific classification (disambiguation). ... For other uses, see Animal (disambiguation). ... Phyla Trochozoa Mollusca Annelida Sipuncula Nemertea Lophophorata Brachiopoda Phoronida Bryozoa Entoprocta The Lophotrochozoa are one of two or three major groups of protostome animals. ... Portrait of Jean-Baptiste Lamarck Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck (August 1, 1744 – December 18, 1829) was a French soldier, naturalist, academic and an early proponent of the idea that evolution occurred and proceeded in accordance with natural laws. ... Orders Amphinomida Capitellida Chaetopterida Cirratulida Cossurida Ctenodrillidae Eunicida Flabelligerida Magelonida Myzostomida Nerillida Opheliida Orbiniida Orweniida Phyllodocida Pisionidae Polygordiida Protodrilida Psammodrilidae Sabellida Spionida Spintheridae Sternaspida Terebellida The Polychaeta or Polychaetes are a class of annelid worms, generally marine, with a pair of fleshy protrusions on each body segment called parapodia that... In phylogenetics, a grouping of organisms is said to be paraphyletic (Greek para = near and phyle = race) if all the members of the group have a common ancestor, but the group does not include all the descendants of the most recent common ancestor of all group members. ... Clitellata is a Class of Annelid worms. ... This Tree of Life article needs to be cleaned up to conform to a higher standard of quality. ... For the LPG album, see The Earthworm (album). ... Orders Arhynchobdellida Rhynchobdellida *There is some dispute as to whether Hirudinea should be a class itself, or a subclass of the Clitellata. ... For other uses, see Leech (disambiguation). ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata    Oligochaeta - Earthworms and others    Acanthobdellida    Branchiobdellida    Hirudinea - Leeches Class Myzostomida Class Archiannelida (polyphyletic) Class Echiura *Some authors consider the subclasses under Clitellata to be classes The annelids, collectively called Annelida (from Latin annellus little ring), are a large phylum of animals, comprising... In phylogenetics, a taxon is polyphyletic (Greek for of many races) if the trait its members have in common evolved separately in different places in the phylogenetic tree. ...

The annelids, collectively called Annelida (from Latin anellus "little ring"), are a large phylum of animals comprising the segmented worms, with about 15,000 modern species including the well-known earthworms and leeches. They are found in most wet environments, and include many terrestrial, freshwater, and especially marine species (such as the polychaetes), as well as some which are parasitic or mutualistic. They range in length from under a millimeter to over 3 meters (the seep tube worm Lamellibrachia luymesi). For other uses, see Latin (disambiguation). ... For other uses, see Scientific classification (disambiguation). ... For other uses, see Animal (disambiguation). ... For other uses, see Worm (disambiguation). ... For the LPG album, see The Earthworm (album). ... For other uses, see Leech (disambiguation). ... Terrestrial animals are animals that live predominantly or entirely on land, as compared with aquatic animals, which live predominantly or entirely in the water (e. ... For the village on the Isle of Wight, see Freshwater, Isle of Wight. ... Marine is an umbrella term for things relating to the ocean, as with marine biology, marine geology, and as a term for a navy, etc. ... Subclasses Palpata Scoleoida Tomopteris from plankton The Polychaeta or polychaetes are a class of annelid worms, generally marine. ... Low Temperature Scanning Electron Microscope (LTSEM) image of Varroa destructor on a honey bee host Mites parasitising a harvestman Parasitism is one version of symbiosis (living together), a phenomenon in which two organisms which are phylogenetically unrelated co-exist over a prolonged period of time, usually the lifetime of one... In biology, mutualism is an interaction between two or more species, where both species derive benefit. ... Species See text Lamellibrachia is a genus of the tube worm related to the giant tube worm, Riftia pachyptila. ...

Physiology

Annelids are triploblastic protostomes with a coelom, closed circulatory system and true segmentation. Their segmented bodies and coelom have given them evolutionary advantages over other worms. Oligochaetes and polychaetes typically have spacious coeloms; in leeches, the coelom is largely filled in with tissue and reduced to a system of narrow canals; archiannelids may lack the coelom entirely. The coelom is divided into a sequence of compartments by walls called septa. In the most general forms each compartment corresponds to a triple segment of the body, which also includes a portion of the nervous and (closed) circulatory systems, allowing it to function relatively independently. The closed circulatory system consists of networks of vessels containing blood with oxygen-carrying hemoglobin. Dorsal and ventral vessels are connected by segmental pairs of vessels. The dorsal vessel and five pairs of vessels that circle the esophagus of an earthworm are muscular and pump blood through the circulatory system. Tiny blood vessels are abundant in the earthworm's skin, which function as its respiratory organ. Each segment (metamere) is marked externally by one or more rings, called annuli. Each segment also has an outer layer of circular muscle underneath a thin cuticle and epidermis, and a system of longitudinal muscles. In earthworms and in daria the longitudinal muscles are strengthened by collagenous lamellae; the leeches have a double layer of muscles between the outer circulars and inner longitudinals. In most forms they also carry a varying number of bristles, called setae, and among the polychaetes a pair of appendages, called parapodia. Triploblastic is a condition of the ovum in which there are three primary germinal layers: the ectoderm, mesoderm, and endoderm. ... Groups Ecdysozoa Lophotrochozoa Platyzoa Protostomes (from the Greek: first the mouth) are a taxon of animals. ... Picture of Human body cavities - dorsal body cavity to the left and ventral body cavity to the right. ... Orders Arhynchobdellida Haplotaxida Rhynchobdellida The Oligochaeta or few-bristled worms (singular Oligochaete, IPA /ˈɒlɪgoʊˌkit/) are well-segmented Annelids, most with a spacious coelom that is used as a hydroskeleton. ... Subclasses Palpata Scoleoida Tomopteris from plankton The Polychaeta or polychaetes are a class of annelid worms, generally marine. ... A body cavity is an aspect of a number of basic animal body plans (phyla) that incorporate a central body cavity, known as a coelom. ... Look up septum in Wiktionary, the free dictionary. ... Structure of hemoglobin. ... An annulus In mathematics, an annulus (the Latin word for little ring, with plural annuli) is a ring-shaped geometric figure, or more generally, a term used to name a ring-shaped object. ... For other uses of Muscles, see Muscles (disambiguation). ... Eponychium is the anatomical term for the human cuticle In biology, the term cuticle or cuticula is given to to a variety of tough but flexible, non-mineral outer coverings of an organism, or part of an organism, that provide prtoection. ... A comparison of squamous epithelia to other epithelial types In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scalelike cells called squamous cells. ... Look up seta in Wiktionary, the free dictionary. ... Parapodia (almost feet) are paired lateral outgrowths, bearing bristles known as chaetae. ...

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

Anterior to the true segments lies the prostomium and peristomium, which carries the mouth, and posterior to them lies the pygidium, where the anus is located. The digestive tract is quite variable but is usually specialized. For example, in some groups (notably most earthworms) it has a typhlosole (to increase surface area) along much of its length. Different species of annelids have a wide variety of diets, including active and passive hunters, scavengers, filter feeders, direct deposit feeders which simply ingest the sediments, and blood-suckers. Image File history File links Download high resolution version (1072x1644, 1209 KB) Borstenwurmer des Meeres. A variety of marine worms. ... Image File history File links Download high resolution version (1072x1644, 1209 KB) Borstenwurmer des Meeres. A variety of marine worms. ... Orders Amphinomida Capitellida Chaetopterida Cirratulida Cossurida Ctenodrillidae Eunicida Flabelligerida Magelonida Myzostomida Nerillida Opheliida Orbiniida Orweniida Phyllodocida Pisionidae Polygordiida Protodrilida Psammodrilidae Sabellida Spionida Spintheridae Sternaspida Terebellida The Polychaeta or Polychaetes are a class of annelid worms, generally marine, with a pair of fleshy protrusions on each body segment called parapodia that... Prostomium (sometimes also called acron) is the first body segment in annelids worms. ... For other uses, see Mouth (disambiguation). ... This article is about the bodily orifice. ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... A dorsal flap of an Annelidss intestine, along its entire length, that increases its surface area for absorption of digested nutrients. ... For a person who scavenges, see Waste picker. ... Filter feeders (also known as suspension feeders) are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized structure, such as the baleen of baleen whales. ... Deposite Feeders Feed on the deposites of other animals (feces). ...

The vascular system and the nervous system are separate from the digestive tract. The vascular system includes a dorsal vessel conveying the blood toward the front of the worm, and a ventral longitudinal vessel which conveys the blood in the opposite direction. The two systems are connected by a vascular sinus and by lateral vessels of various kinds, including in the true earthworms, capillaries on the body wall. It has been suggested that Circulation (physiology) be merged into this article or section. ... The Human Nervous System. ... f you all The blood vessels are part of the circulatory system and function to transport blood throughout the body. ...

The nervous system has a nerve cord from which lateral nerves come in contact with each segment. Every segment has an autonomy; however, they unite to perform as a single body for functions such as locomotion. Growth in many groups occurs by replication of individual segmental units, in others the number of segments is fixed in early development. Nerves (yellow) Nerves redirects here. ...

Reproduction

Depending upon the species, annelids can reproduce both sexually and asexually.

Asexual reproduction

Asexual reproduction by fission is a method used by some annelids and allows them to reproduce quickly. The posterior part of the body breaks off and forms a new identical worm. The position of the break is usually determined by an epidermal growth. Lumbriculus and Aulophorus, for example, are known to reproduce by the penis breaking into such fragments. This complete regeneration is noteworthy as these Annelid species are the most highly organized animals to have this capability.^[1] Many other taxa (such as most earthworms) cannot reproduce this way, though they have varying abilities to regrow amputated segments. It has been suggested that Parthenogenesis be merged into this article or section. ... Species Lumbriculus ambiguus Lumbriculus genitosetosus Lumbriculus illex Lumbriculus japonicus Lumbriculus kareliensis Lumbriculus mukoensis Lumbriculus variegatus Lumbriculus multiatriatus . ... In biology, regeneration is an organisms ability to replace body parts. ... Amputation is the removal of a body extremity by trauma or surgery. ...

Sexual reproduction

Sexual reproduction allows a species to better adapt to its environment. Some annelida species are hermaphroditic, while others have distinct sexes. Sexual reproduction is a union that results in increasing genetic diversity of the offspring. ... For other uses, see Hermaphrodite (disambiguation). ...

Most polychaete worms are gonochoristic, that is, they have separate males and females and external fertilization. The earliest larval stage, which is lost in some groups, is a ciliated trochophore, similar to those found in other phyla. The animal then begins to develop its segments, one after another, until it reaches its adult size. A larval insect A larva (Latin; plural larvae) is a juvenile form of animal with indirect development, undergoing metamorphosis (for example, insects or amphibians). ... trochophore A - episphere B - hyposphere 1 - ganglia 2 - apical tuft 3 - prototroch 4 - metatroch 5 - nephridium 6 - anus 8 - gastrointestinal tract 9 - buccal opening 10 - blastocoele A trochophore (or trocophore) is a type of larva with several bands of cilia. ...

Earthworms and other oligochaetes, as well as the leeches, are hermaphroditic and mate periodically throughout the year in favored environmental conditions. They mate by copulation. Two worms which are attracted by each other's secretions lay their bodies together with their heads pointing opposite directions. The fluid is transferred from the male pore to the other worm. Different methods of sperm transference have been observed in different genera, and may involve internal spermathecae (sperm storing chambers) or spermatophores that are attached to the outside of the other worm's body. The clitella lack the free-living ciliated trochophore larvae present in the polychaetes, the embryonic worms developing in a fluid-filled "cocoon" secreted by the clitellum. This Tree of Life article needs to be cleaned up to conform to a higher standard of quality. ... For other uses, see Leech (disambiguation). ... A pair of lions copulating in the Maasai Mara, Kenya. ... Secretion is the process of segregating, elaborating, and releasing chemicals from a cell, or a secreted chemical substance or amount of substance. ... A spermatozoon or spermatozoan ( spermatozoa), from the ancient Greek σπέρμα (seed) and (living being) and more commonly known as a sperm cell, is the haploid cell that is the male gamete. ... The spermatheca is a part of the female reproductive tract in insects, some molluscs, and certain other invertebrates. ... A spermatophore is a capsule or mass created by males of various invertebrate species, containing spermatozoa and transferred in entirety to the female during sex. ... In earth worms and other annelids, the Clitellum is a thickened glandular section of the body wall that secretes a viscid sac in which the eggs are deposited. ...

Fossil record

Serpulid tubes on a marine shell; Duck Harbor Beach on Cape Cod Bay, Wellfleet, Massachusetts.

The annelid fossil record is sparse, but a few definite forms are known as early as the Cambrian, and there are some signs they were around in the earlier Precambrian, but the earliest unequivocal annelid fossils are only known from the former. Because the creatures have soft bodies, fossilization of a body is an especially rare event. However, a few annelids, such as the living polychaetes in the Serpulidae, secrete calcareous tubes, and such tubes are fairly common as fossils (although these are not necessarily from annelida, as other animal phyla can also secrete tubes). The hard jaws of certain polychaetes, known as scolecodonts, are known from the Ordovician onward, and are common enough to be used for stratigraphic correlation in some cases. The best-preserved and oldest annelid body fossils come from the Cambrian Lagerstätten such as the Burgess Shale of Canada, and the Middle Cambrian strata of the House Range in Utah. The Annelids are also diversely represented in the Pennsylvanian-age Mazon Creek fauna of Illinois. A few small groups have been treated as separate phyla: the Pogonophora and Vestimentifera, now included in the family Siboglinidae, and the Echiura. For other uses, see Fossil (disambiguation). ... For other uses, see Cambrian (disambiguation). ... The Precambrian (Pre-Cambrian) is an informal name for the supereon comprising the eons of the geologic timescale that came before the current Phanerozoic eon. ... Genus see text. ... Scolecodonts are the jaws of polychaete annelids (worms). ... Artist impression of the Ordovician Sea. ... Stratigraphy, a branch of geology, studies rock layers and layering (stratification). ... Lagerstätten (German, singular: Lagerstätte, literally: place(s) of storage or resting place(s)) are sedimentary deposits that exhibit extraordinary fossil richness or completeness. ... Hallucigenia sparsa, one of the organisms unique to the Burgess Shale. ... The Pennsylvanian is an epoch of the Carboniferous period lasting from roughly 325 Ma to 299 Ma (million years ago). ... The Mazon Creek fossils are conservation lagerstätten found near Chicago, Illinois. ... Genera Birsteinia Choanophorus Cyclobrachia Lamellibrachia Lamellisabella Osedax Paraescarpia Ridgeia Riftia Siboglinoides Siboglinum Volvobrachia . ... The Echiura, or spoon worms, are a small group of marine animals. ...

Relationships

The arthropods and their kin have long been considered the closest relatives of the annelids, on account of their common segmented structure, giving rise to the grouping of Articulata. However, a number of differences between the two groups suggest this may be convergent evolution. The other major phylum which is of definite relation to the annelids are the molluscs, which share with them the presence of trochophore larvae. Annelids and Molluscs are thus united as the Trochozoa, a taxon more strongly supported by molecular evidence. Subphyla and Classes Subphylum Trilobitomorpha Trilobita - trilobites (extinct) Subphylum Chelicerata Arachnida - spiders,scorpions, etc. ... Articulata has two meanings in zoology: One of two main divisions of the brachiopods having two valves with an articulating hinge (as opposed to the Inarticulata, which have no hinge). ... In evolutionary biology, convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. ... Classes Caudofoveata Aplacophora Polyplacophora - Chitons Monoplacophora Bivalvia - Bivalves Scaphopoda - Tusk shells Gastropoda - Snails and Slugs Cephalopoda - Squids, Octopuses, etc. ... trochophore A - episphere B - hyposphere 1 - ganglia 2 - apical tuft 3 - prototroch 4 - metatroch 5 - nephridium 6 - anus 8 - gastrointestinal tract 9 - buccal opening 10 - blastocoele A trochophore (or trocophore) is a type of larva with several bands of cilia. ... The Trochozoa comprise four phyla of animals: the molluscs, the annelids, and the smaller phyla Sipuncula and Nemertea. ...

Sipuncula, Echiura and Siboglinidae have traditionally been placed in their own phyla, while Clitellata has been considered separated from the polychaete annelids. But recent research indicates that all of them actually belongs within the Polychaete, even if some of these groups have lost their segmentation^[1]. The Sipuncula, sipunculid worms or peanut worms, are a phylum of marine worms with a tentacle surrounded mouth on a completely invertible head end. ... The Echiura, or spoon worms, are a small group of marine animals. ... Genera Birsteinia Choanophorus Cyclobrachia Lamellibrachia Lamellisabella Osedax Paraescarpia Ridgeia Riftia Siboglinoides Siboglinum Volvobrachia . ... Subclasses Palpata Scoleoida Tomopteris from plankton The Polychaeta or polychaetes are a class of annelid worms, generally marine. ...

Classes and subclasses of Annelida

• Clitellata
  • Oligochaeta - The class Oligochaeta includes the megadriles (earthworms), which are both aquatic and terrestrial, and the microdrile families such as tubificids, which include many marine members as well.
  • Leeches (Hirudinea) - These include both bloodsucking external parasites and predators of small invertebrates.
• Aphanoneura
• Polychaeta - This is the largest group of annelids and the majority are marine. All segments are identical each with a pair of parapodia. The parapodia are used for swimming, burrowing and the creation of a feeding current.

Clitellata is a Class of Annelid worms. ... This Tree of Life article needs to be cleaned up to conform to a higher standard of quality. ... For the LPG album, see The Earthworm (album). ... Subfamilies Tubificidae Naidinae Phallodrilinae Limnodriloidinae Rhyacodrilinae Telmatodrilinae The Tubificidae are a family of clitellate oligochaete worms like the sludge worm, Tubifex tubifex. ... For other uses, see Leech (disambiguation). ... Orders Amphinomida Capitellida Chaetopterida Cirratulida Cossurida Ctenodrillidae Eunicida Flabelligerida Magelonida Myzostomida Nerillida Opheliida Orbiniida Orweniida Phyllodocida Pisionidae Polygordiida Protodrilida Psammodrilidae Sabellida Spionida Spintheridae Sternaspida Terebellida The Polychaeta or Polychaetes are a class of annelid worms, generally marine, with a pair of fleshy protrusions on each body segment called parapodia that... Parapodia (almost feet) are paired lateral outgrowths, bearing bristles known as chaetae. ...

References

1. ^ Hickman, Cleveland; Roberts L. Keen S. Larson A. Eisenhour D. Animal Diversity, 4 th (in English), New York: Mc Graw Hill, 204. ISBN 978-0-07-252844-2. 

• Annelid Fossils (Web page). The Virtual Fossil Museum (2006). Retrieved on May 20, 2006. – Descriptions and images of annelid fossils from Mazon Creek and the Utah House Range.

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