The annelids, collectively called asselida (from your mom)

Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome....

anellus "little ring"), are a large phylumScientific classification Overview

Scientific classification or biological classification is how biologists group and categorize extinct and living speci...

of animalAnimal

Animals are a major group of organisms, classified as the kingdom Animalia or Metazoa....

s comprising the segmented wormWorm

A worm is an elongated soft-bodied invertebrate animal....

s, with about 15,000 modern species including the well-known earthwormEarthworm

planetworm is the common name for the larger members of the bayarcheatica in the phylum Annelida....

s and leechLeech

Leeches are annelids comprising the subclass fliericeee....

es. They are found in most wet environments, and include many terrestrialTerrestrial animal Summary

Animal environments are classified as either aquatic, terrestrial, or amphibious....

, freshwaterFresh water

Fresh water is water with less than 0.5 parts per thousand dissolved salts....

, and especially marineMarine (ocean)

Marine is an umbrella term for things relating to the ocean, as with marine biology, marine geology, and as a term for a nav...

species (such as the polychaeteFacts About Polychaete

The Polychaeta or Polychaetes are a class of annelid worms, generally marine, with a pair of fleshy protrusions on eac...

s), as well as some which are parasiticParasitism

Parasitism is one version of symbiosis , a phenomenon in which two organisms which are phylogenetically unrelated co-exist o...

or mutualisticMutualism

In biology, mutualism is an interaction between two or more species where both species derive benefit....

. They range in length from under a millimeter to over 3 meters (the seep tube worm LamellibrachiaLamellibrachia

Lamellibrachia is a genus of tube wormsrelated to the giant tube worm, Riftia pachyptila....

luymesi).

Annelids are bilaterally symmetricBilateria

The Bilateria, having bilateral symmetry, are a subregnum of animals, including the majority of phyla; the most notable exc...

and triploblastic protostomeProtostome

Protostomes are a taxon of animals....

s with a coelomBody cavity

By the broadest definition, a body cavity is any fluid filled space in a multicellular organism....

(which makes them coelomates), closed circulatory system and true segmentation. Their segmented bodies and coelom have given them evolutionary advantages over other worms. Oligochaetes and polychaetePolychaete

The Polychaeta or Polychaetes are a class of annelid worms, generally marine, with a pair of fleshy protrusions on eac...

s typically have spacious coelomCoelom

The coelom is a fluid filled cavity formed within the mesoderm....

s; in leeches, the coelom is 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 septaSeptum

A septum, in Latin meaning "something that encloses", is a partition separating two cavities or two spaces containing a less...

. 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 hemoglobinHemoglobin

Hemoglobin or haemoglobin is the iron-containing oxygen-transport metalloprotein in the red cells of the blood in mam...

. 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 annuliAnnulus

Annulus, being the Latin for 'ring' is a term used to describe various ring-shaped objects:...

. Each segment also has an outer layer of circular muscleMuscle

Muscle is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells....

underneath a thin cuticleCuticle

In biology, cuticle or cuticula is a tough but flexible, non-mineral covering of an organism, or part of it....

and epidermisFacts About Squamous epithelium

The squamous epithelium is epithelium consisting of one or more cell layers, the most superficial of which is composed of fl...

, 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 setaSeta

A seta is a stiff hair, bristle, or bristle-like process or part of an organism....

e, and among the polychaetes a pair of appendages, called parapodia.

Anterior to the true segments lies the prostomiumProstomium

Prostomium is the first body segment in annelids worms....

and peristomium, which carries the mouthMouth

The mouth, also known as the buccal cavity or the oral cavity, is the opening through which an animal takes in f...

, and posterior to them lies the pygidium, where the anusAnus

In anatomy, the butthole is the external opening of the anal pore....

is located. The digestive tract is quite variable but is usually specialized. For example, in some groups (notably most planetworms) it has a typhlosoleTyphlosole

A typhlosole is an internal fold of the intestine or intestine inner wall....

(to increase surface area) along much of its length. Different species of annelids have a wide variety of diets, including active and passive hunters, scavengerScavenger

The word scavenger, in zoology, refers to animals that consume already dead organic life-forms....

s, filter feederFilter feeder

Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the w...

s, direct deposit feederDeposit feeder

Deposit feeders are organisms that feed on the particles of matter in the soil, usually the top sediment where it is filled ...

s which simply ingest the sediments, and blood-suckers. Annelids can also grow up to six inches.

The vascular system and the nervous systemNervous system

The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops inpu...

are separate from the digestive tract. The vascular system includes a dorsal vesselBlood vessel

The blood vessels are part of the circulatory system and function to transport blood throughout the body....

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.

The nervous system has a nerve cordNerve cord

Nerve cord may refer to the following structures:...

from which lateral nerveNerve

A nerve is an enclosed, cable-like bundle of nerve fibers or axons, which includes the glia that ensheath the axons in...

s 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.

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

Asexual reproductionAsexual reproduction

Asexual reproduction is a form of reproduction which does not involve meiosis, gamete formation, or fertilization....

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. LumbriculusLumbriculus

Lumbriculus is a genus of oligochaetes. ...

and Aulophorus, for example, are known to reproduce by the penis breaking into such fragments. This complete regenerationRegeneration (biology)

Regeneration is a form of tissue repair....

is noteworthy as these Annelid species are the most highly organized animals to have this capability. Many other taxa (such as most earthworms) cannot reproduce this way, though they have varying abilities to regrow amputated segments.

Sexual reproductionSexual reproduction

Sexual reproduction is a type of reproduction that results in increasing genetic diversity of the offspring....

allows a species to better adapt to its environment. Some annelida species are hermaphroditicFacts About Hermaphrodite

In zoology and botany, a hermaphrodite is an organism that possesses both male and female sex organs during its life....

, while others have distinct sexes.

Most polychaete worms are gonochoristic, that is, they have separate males and females and external fertilization. The earliest larvaLarva

A larva is a juvenile form of animal with indirect development, undergoing metamorphosis ....

l stage, which is lost in some groups, is a ciliated trochophoreTrochophore

A trochophore is a type of larva with several bands of cilia....

, similar to those found in other phyla. The animal then begins to develop its segments, one after another, until it reaches its adult size.

Earthworms and other oligochaetesOligochaeta

The Oligochaeta are well-segmented Annelids, most with a spacious coelom that is used as a hydroskeleton....

, as well as the leechLeech

Leeches are annelids comprising the subclass Hirudinea....

es, 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 secretionSecretion

Secretion is the process of segregating, elaborating, and releasing chemicals from a cell, or a secreted chemical substance ...

s 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 spermSpermatozoon

A spermatozoon or spermatozoan , from the ancient Greek spe?a and ??? and more commonly known as a sperm ...

transference have been observed in different genera, and may involve internal spermathecaSpermatheca

The spermatheca is an organ of the female reproductive tract in insects, some molluscs, and certain other invertebrates....

e (sperm storing chambers) or spermatophoreSpermatophore

A spermatophore is a capsule or mass created by males of various invertebrate species, containing spermatozoa and transferre...

s 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 clitellumClitellum

In earthworms and some other annelids, the Clitellum is a thickened glandular section of the body wall that secretes a visci...

The annelid fossilFossil

Fossils are the mineralized or otherwise preserved remains or traces of animals, plants, and other organisms....

record is sparse, but a few definite forms are known as early as the CambrianCambrian

The Cambrian is a major division of the geologic timescale that begins about 542 mya at the end of the Proterozoic eon and...

. 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 SerpulidaeSerpulidae

Serpulidae is a family of sessile, tube-building annelid worms in the class Polychaeta....

, 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). A fossil group has recently been assigned to the annelids, the machaeridians. These forms were polychaetes with rows of dorsalDorsal

Dorsal may refer to:* Dorsum, a part of an animal...

overlapping shell plates. The hard jaws of certain polychaetes, known as scolecodontsScolecodonts

A scolecodont is the jaw of a polychaete annelid, a common type of fossil-producing segmented worm....

, are known from the OrdovicianOrdovician

The Ordovician period is the second of the six periods of the Paleozoic era....

onward, and are common enough to be used for stratigraphic correlationStratigraphy

Stratigraphy, a branch of geology, is basically the study of rock layers and layering....

in some cases. The best-preserved and oldest annelid body fossils come from the Cambrian Lagerstätten such as the Burgess ShaleBurgess Shale

The Burgess Shale is a black shale fossil bed named after Mount Burgess, close to where it was found, high up in the Canadi...

of Canada, and the Middle Cambrian strata of the House Range in Utah. The Annelids are also diversely represented in the PennsylvanianPennsylvanian

The Pennsylvanian is an epoch of the Carboniferous period lasting from roughly 325 Ma to 299 Ma ....

-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 SiboglinidaeSiboglinidae

Siboglinidae is a family of annelid worms whose members formerly made up the phyla Pogonophora and Vestimentifera...

, and the EchiuraEchiura

The Echiura, or spoon worms, are a small group of marine animals....

The arthropodArthropod

Arthropods are the largest phylum of animals and include the insects, arachnids, crustaceans, and others....

s 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 ArticulataArticulata

Articulata has three meanings in zoology:...

. However, a number of differences between the two groups suggest this may be convergent evolutionConvergent evolution

In evolutionary biology, convergent evolution describes the process whereby organisms not closely related independently acqu...

. The other major phylum which is of definite relation to the annelids are the molluscs, which share with them the presence of trochophoreTrochophore

A trochophore is a type of larva with several bands of cilia....

larvae. Annelids and Molluscs are thus united as the Trochozoa, a taxon more strongly supported by molecular evidence.

SipunculaSipuncula

The Sipuncula, sipunculid worms or peanut worms, are a phylum containing 144-320 species of bilaterally symmetrical, ...

, EchiuraEchiura

The Echiura, or spoon worms, are a small group of marine animals....

and SiboglinidaeSiboglinidae

Siboglinidae is a family of annelid worms whose members formerly made up the phyla Pogonophora and Vestimentifera...

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 PolychaetePolychaete

The Polychaeta or Polychaetes are a class of annelid worms, generally marine, with a pair of fleshy protrusions on eac...

, even if some of these groups have lost their segmentation(*).

== * ClitellataClitellata Summary

Clitellata is a Class of Annelid worms, characterized by having a clitellum during part of their life cycle....

** OligochaetaOligochaeta

The Oligochaeta are well-segmented Annelids, most with a spacious coelom that is used as a hydroskeleton....

- The class Oligochaeta includes the megadriles, which are both aquatic and terrestrial, and the microdrile families such as tubificids, which include many marine members as well. ** LeechLeech

Leeches are annelids comprising the subclass Hirudinea....

es (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.

* i will name my first born child chuck. and the second norris. so when im angry i can yell " chuck norris!"

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