Worm
Overview
The term worm (ˈwɜrm) refers to an obsolete taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

 (vermes
Vermes
Vermes is an obsolete taxon used by Carolus Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals. In Linnaeus system the group had the rank of class, occupying the 6th slot of his animal systematics...

) used by Carolus Linnaeus and Jean-Baptiste Lamarck
Jean-Baptiste Lamarck
Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck , often known simply as Lamarck, was a French naturalist...

 for all non-arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

 invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

 animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, and stems from the Old English word wyrm
Wyrm
Wyrm , or wurm, is the Old English term for a dragon or a dragon-like creature, especially one that is serpentine. It is used as an archaism in English folklore and modern fantasy to distinguish it from its Modern English counterpart worm...

. Currently it is used to describe many different distantly-related animals that typically have a long cylindrical tube-like body and no leg
Leg
Łęg may refer to the following places in Poland:*A former name for the town of Ełk *Part of the Czyżyny district of Kraków*Łęg, Pleszew County in Greater Poland Voivodeship...

s. Most animals called "worms" are invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s, but the term is also used for the amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

 caecilian
Caecilian
The caecilians are an order of amphibians that superficially resemble earthworms or snakes. They mostly live hidden in the ground, making them the least familiar order of amphibians. All extant caecilians and their closest fossil relatives are grouped as the clade Apoda. They are mostly...

s and the slow worm
Anguis fragilis
Anguis fragilis, or slow worm, slow-worm or slowworm, is a limbless reptile native to Eurasia. It is also sometimes referred to as the blindworm or blind worm, though the Royal Society for the Protection of Birds considers this to be incorrect.Slow worms are semi-fossorial lizards spending much...

 Anguis
Anguis
Anguis, or the slow worm, is a small genus of lizard in the family Anguidae. It has two described species.Although they are lizards, slow worms have lost their limbs completely and are often mistaken as snakes. Slow-worms typically grow to between , with the females slightly larger than the males...

, a legless burrowing lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

.
Encyclopedia
The term worm (ˈwɜrm) refers to an obsolete taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

 (vermes
Vermes
Vermes is an obsolete taxon used by Carolus Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals. In Linnaeus system the group had the rank of class, occupying the 6th slot of his animal systematics...

) used by Carolus Linnaeus and Jean-Baptiste Lamarck
Jean-Baptiste Lamarck
Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck , often known simply as Lamarck, was a French naturalist...

 for all non-arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

 invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

 animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s, and stems from the Old English word wyrm
Wyrm
Wyrm , or wurm, is the Old English term for a dragon or a dragon-like creature, especially one that is serpentine. It is used as an archaism in English folklore and modern fantasy to distinguish it from its Modern English counterpart worm...

. Currently it is used to describe many different distantly-related animals that typically have a long cylindrical tube-like body and no leg
Leg
Łęg may refer to the following places in Poland:*A former name for the town of Ełk *Part of the Czyżyny district of Kraków*Łęg, Pleszew County in Greater Poland Voivodeship...

s. Most animals called "worms" are invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s, but the term is also used for the amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

 caecilian
Caecilian
The caecilians are an order of amphibians that superficially resemble earthworms or snakes. They mostly live hidden in the ground, making them the least familiar order of amphibians. All extant caecilians and their closest fossil relatives are grouped as the clade Apoda. They are mostly...

s and the slow worm
Anguis fragilis
Anguis fragilis, or slow worm, slow-worm or slowworm, is a limbless reptile native to Eurasia. It is also sometimes referred to as the blindworm or blind worm, though the Royal Society for the Protection of Birds considers this to be incorrect.Slow worms are semi-fossorial lizards spending much...

 Anguis
Anguis
Anguis, or the slow worm, is a small genus of lizard in the family Anguidae. It has two described species.Although they are lizards, slow worms have lost their limbs completely and are often mistaken as snakes. Slow-worms typically grow to between , with the females slightly larger than the males...

, a legless burrowing lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

. Invertebrate animals commonly called "worms" include annelid
Annelid
The annelids , formally called Annelida , are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches...

s (earthworm
Earthworm
Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...

s), nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s (roundworm
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s), flatworm
Flatworm
The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...

s, marine polychaete
Polychaete
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. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...

 worms (bristle worm
Polychaete
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. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...

s), marine nemertea
Nemertea
Nemertea is a phylum of invertebrate animals also known as "ribbon worms" or "proboscis worms". Alternative names for the phylum have included Nemertini, Nemertinea and Rhynchocoela. Although most are less than long, one specimen has been estimated at , which would make it the longest animal ever...

n worms ("bootlace worm
Lineus longissimus
The bootlace worm is one of the longest known animals, with specimens up to long and up to wide being reported. Its mucus is toxic.-Taxonomy:The bootlace worm is in the phylum Nemertea or ribbon worms...

s"), marine Chaetognatha
Chaetognatha
Chaetognatha, meaning hair-jaws, and commonly known as arrow worms, are a phylum of predatory marine worms that are a major component of plankton worldwide. About 20% of the known species are benthic, that is belonging to the lowest zone of the ocean, or benthic zone, and can attach to algae and...

 (arrow worms) and insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

 larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e such as caterpillar
Caterpillar
Caterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...

s, grubs, and maggot
Maggot
In everyday speech the word maggot means the larva of a fly ; it is applied in particular to the larvae of Brachyceran flies, such as houseflies, cheese flies, and blowflies, rather than larvae of the Nematocera, such as mosquitoes and Crane flies...

s. Historical English-speaking cultures have used the (now deprecated) terms worm, Wurm, or wyrm to describe carnivorous reptiles
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

 ("serpents"), and the related mythical beasts dragons
European dragon
European dragons are legendary creatures in folklore and mythology among the overlapping cultures of Europe.In European folklore, a dragon is a serpentine legendary creature. The Latin word draco, as in constellation Draco, comes directly from Greek δράκων,...

.

Worms vary in size from microscopic to over 1 metres (3.3 ft) in length for marine polychaete worms (bristle worms), 6.7 metres (22 ft) for the African giant earthworm, Microchaetus, and 55 metres (180.4 ft) for the marine nemertean worm (bootlace worm), Lineus longissimus
Lineus longissimus
The bootlace worm is one of the longest known animals, with specimens up to long and up to wide being reported. Its mucus is toxic.-Taxonomy:The bootlace worm is in the phylum Nemertea or ribbon worms...

.

Various types of worm occupy a small variety of parasitic
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...

 niches, living inside the bodies of other animals. Free-living worm species may live on land, in marine or freshwater environments, or burrow.

Distribution and habitat

Worms live in almost all parts of the world including marine, freshwater, and terrestrial habitats. Some worms living in the ground help to condition the soil (e.g., annelid
Annelid
The annelids , formally called Annelida , are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches...

s, aschelminth
Aschelminth
The Aschelminthes , closely associated with the Platyhelminthes, are an obsolete phylum of pseudocoelomate and other similar animals that are no longer considered closely related and have been promoted to phyla in their own right...

s). Many thrive as parasites
Parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...

 of plants (e.g., aschelminths) and animals, including humans (e.g., platyhelminths
Flatworm
The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...

, aschelminths). Several other worms may be free-living, or nonparasitic. There are worms that live in freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

, seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

, and even on the seashore
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...

. Ecologically, worms form an important link in the food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...

s in virtually all the ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

s of the world.

Classification

In everyday language, the term worm is also applied to various other living forms such as larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e, insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, centipede
Centipede
Centipedes are arthropods belonging to the class Chilopoda of the subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of...

s, shipworm
Shipworm
Shipworms are not worms at all, but rather a group of unusual saltwater clams with very small shells, notorious for boring into wooden structures that are immersed in sea water, such as piers, docks and wooden ships...

s (teredo worms), or even some vertebrates (creatures with a backbone) such as blindworms
Anguis fragilis
Anguis fragilis, or slow worm, slow-worm or slowworm, is a limbless reptile native to Eurasia. It is also sometimes referred to as the blindworm or blind worm, though the Royal Society for the Protection of Birds considers this to be incorrect.Slow worms are semi-fossorial lizards spending much...

 and caecilians. Worms can be divided into several groups, but are still technically decomposers.
  • The first of these, Platyhelminthes, includes the flatworm
    Flatworm
    The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...

    s, tapeworms
    Cestoda
    This article describes the flatworm. For the medical condition, see Tapeworm infection.Cestoda is the name given to a class of parasitic flatworms, commonly called tapeworms, of the phylum Platyhelminthes. Its members live in the digestive tract of vertebrates as adults, and often in the bodies...

    , and flukes
    Trematoda
    Trematoda is a class within the phylum Platyhelminthes that contains two groups of parasitic flatworms, commonly referred to as "flukes".-Taxonomy and biodiversity:...

    . They have a flat, ribbon- or leaf-shaped body with a pair of eyes at the front. Some are parasites.
  • The second group contains the threadworms
    Pinworm
    The pinworm , also known as threadworm or seatworm, is a nematode and a common human intestinal parasite, especially in children...

    , roundworms
    Nematode
    The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

    , and hookworm
    Hookworm
    The hookworm is a parasitic nematode that lives in the small intestine of its host, which may be a mammal such as a dog, cat, or human. Two species of hookworms commonly infect humans, Ancylostoma duodenale and Necator americanus. A. duodenale predominates in the Middle East, North Africa, India...

    s. This phylum is called Nematoda. Threadworms may be microscopic, such as the vinegar eelworm, or more than 1 metre (3 feet) long. They are found in damp earth, moss, decaying substances, fresh water, or salt water. Some roundworms are also parasites. The Guinea worm, for example, gets under the skin of the feet and legs of people living in tropical countries.
  • The third group consists of the segmented worms, with bodies divided into segments, or rings. This phylum is called Annelida. Among these are the earthworm
    Earthworm
    Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...

    s and the bristle worms
    Polychaete
    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. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...

     of the sea.

In earlier taxonomic classification, all the above were included in the now obsolete group Vermes
Vermes
Vermes is an obsolete taxon used by Carolus Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals. In Linnaeus system the group had the rank of class, occupying the 6th slot of his animal systematics...

.

There are hundreds of thousands of species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 that live in a wide variety of habitats other than soil
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

. Over time this broad definition narrowed to the modern definition, although this still includes several different animal groups. Phyla
Phylum
In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....

 that include worms include:
  • Annelida (segmented worms)
  • Arthropoda (inchworms)
  • Chaetognatha
    Chaetognatha
    Chaetognatha, meaning hair-jaws, and commonly known as arrow worms, are a phylum of predatory marine worms that are a major component of plankton worldwide. About 20% of the known species are benthic, that is belonging to the lowest zone of the ocean, or benthic zone, and can attach to algae and...

     (arrow worms)
  • Gnathostomulid
    Gnathostomulid
    Gnathostomulids, or jaw worms, are a small phylum of nearly microscopic marine animals. They inhabit sand and mud beneath shallow coastal waters and can survive in relatively anoxic environments. They were first recognised and described in 1956....

     (jaw worms)
  • Hemichordata
    Hemichordata
    Hemichordata is a phylum of marine deuterostome animals, generally considered the sister group of the echinoderms. They date back to the Lower or Middle Cambrian and include two main classes: Enteropneusta , and Pterobranchia. A third class, Planctosphaeroidea, is known only from the larva of a...

     (acorn/tongue worms)
  • Nematoda (roundworms)
  • Nematomorpha
    Nematomorpha
    Nematomorpha is a phylum of parasitic animals that are superficially morphologically similar to nematode worms, hence the name. They range in size in most species from long and can reach in extreme cases up to 2 metres, and in diameter...

     (horsehair worms)
  • Nemertea
    Nemertea
    Nemertea is a phylum of invertebrate animals also known as "ribbon worms" or "proboscis worms". Alternative names for the phylum have included Nemertini, Nemertinea and Rhynchocoela. Although most are less than long, one specimen has been estimated at , which would make it the longest animal ever...

     (ribbonworms)
  • Onychophora (velvet worms)
  • Phoronida (horseshoe worms)
  • Platyhelminthes (flatworms)
  • Priapulida
    Priapulida
    Priapulida is a phylum of marine worms. They are named for their extensible spiny proboscis, which, in some species, may have a shape like that of a human penis...

     (phallus worms)
  • Sipuncula
    Sipuncula
    The Sipuncula or Sipunculida is a group containing 144-320 species of bilaterally symmetrical, unsegmented marine worms...

     (peanut worms)


To most people the most familiar worms are the earthworm
Earthworm
Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...

s, members of phylum Annelida. Earthworms in general have been around for 120 million years, and are theorized to have evolved during the time of the dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s. They enrich and aerate the soil; Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...

 found that worms turn over the top six inches (15 cm) of topsoil every 20 years in a field near where he lived. In less favourable conditions, such as waterlogged soils or hard soil deficient in suitable organic matter, or in seasonally dry soils, they cannot achieve anything like that. They lack a brain in the sense of the vertebrate brain, but have nerve centers (called ganglia); they also lack eyes but can sense light with photoreceptors
Ocellus
A simple eye refers to a type of eye design or optical arrangement that contains a single lens which detect light. A "simple eye" is so-called in distinction from a multi-lensed "compound eye", and is not necessarily at all simple in the usual sense of the word...

. Worms are hermaphrodites (both sexes in one animal) but can cross fertilize.

Other invertebrate groups may be called worms, especially colloquially. In particular, many unrelated insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

 larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e are called "worms", such as the railroad worm
Railroad worm
A railroad worm is a larva or larviform female adult of a beetle of the genus Phrixothrix in the family Phengodidae, characterized by their unique possession of two different colors of bioluminescence...

, woodworm
Woodworm
A woodworm is not a specific species. It is the larval stage of certain woodboring beetles including:*Ambrosia beetles *Bark borer beetle / Waney edge borer *Common furniture beetle...

, glowworm
Glowworm
Glowworm, or glow worm, is the common name for various groups of insect larvae and adult larviform females that glow through bioluminescence. They may sometimes resemble worms, but all are insects .-Classification:Major families are:* Lampyridae , found around the world...

, bloodworm
Midge (insect)
Midges comprise many kinds of very small two-winged flies found world-wide. The term does not encapsulate a well-defined taxonomic group, but includes animals in several families of Nematoceran Diptera. While some midges are vectors for disease, many others play useful roles as prey items for...

, inchworm
Geometer moth
The geometer moths or Geometridae are a family of the order Lepidoptera...

, mealworm
Mealworm
Mealworms are the larval form of the mealworm beetle, Tenebrio molitor, a species of darkling beetle. Like all holometabolic insects, they go through four life stages: egg, larva, pupa, and adult...

, silkworm, Wooly bear worm.

Worms may also be called helminths, particularly in medical terminology when referring to parasitic worm
Parasitic worm
Parasitic worms or helminths are a division of eukaryoticparasites that, unlike external parasites such as lice and fleas, live inside their host. They are worm-like organisms that live and feed off living hosts, receiving nourishment and protection while disrupting their hosts' nutrient...

s, especially the Nematoda (roundworms) and Cestoda
Cestoda
This article describes the flatworm. For the medical condition, see Tapeworm infection.Cestoda is the name given to a class of parasitic flatworms, commonly called tapeworms, of the phylum Platyhelminthes. Its members live in the digestive tract of vertebrates as adults, and often in the bodies...

 (tapeworms). Hence "helminthology
Helminthology
Helminthology is the study of worms, especially parasitic worms. This field deals with the study of their taxonomy and the effect on their hosts....

" is the study of parasitic worms. When an animal, such as a dog
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

, is said to "have worms", it means that it is infested with parasitic worm
Parasitic worm
Parasitic worms or helminths are a division of eukaryoticparasites that, unlike external parasites such as lice and fleas, live inside their host. They are worm-like organisms that live and feed off living hosts, receiving nourishment and protection while disrupting their hosts' nutrient...

s, typically roundworm
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s or tapeworms.

"Ringworm" is not a worm at all, but a skin fungus.

Characteristics

Worms usually have a cylindrical, flattened, or leaf-like body shape and are often without any true limbs or appendages. Instead, they may have bristles or fins that help them move. A few have light-sensing organs. Worms vary in size from less than 1 mm (0.04 inch) in certain aschelminth
Aschelminth
The Aschelminthes , closely associated with the Platyhelminthes, are an obsolete phylum of pseudocoelomate and other similar animals that are no longer considered closely related and have been promoted to phyla in their own right...

s to more than 30 m (100 feet) in certain ribbon worms.

Some worms reproduce sexually. Hermaphroditism, the condition in which a single individual possesses both male and female reproductive parts, is common in many groups of worms. Asexual reproduction
Asexual reproduction
Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. A more stringent definition is agamogenesis which is reproduction without...

, whereby new individuals develop from the body cells of another, also occurs in some worms.

Worm species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 differ in their abilities to move about on their own. Many species have bodies with no major muscles, and cannot move on their own—they must be moved by forces or other animals in their environment. Many other species have bodies with major muscles and can move on their own; they are a type of muscular hydrostat
Muscular hydrostat
A muscular hydrostat is a biological structure found in animals. It is used to manipulate items or to move its host about and consists mainly of muscles with no skeletal support...

. Many species of worms are decomposers; they break down dead plants and animals to return nutrients to the soil. They have also been known to infiltrate households feeding on food in the early stages of its decomposition namely breads and cheeses.

Earthworms split into three different categories. The first are the surface dwellers, the Epigeic worms. Then there are the upper soil worms, the Endogeic worms. Finally,there are the deep burrowing species, the Anecic.

Image in mythology, literature, and art

Worms are sometimes used as a metaphor of putrefaction or corruption; a corpse may be said to be "fed to the worms".

The word "worm" and its cognates "wyrm" were used for dragon
European dragon
European dragons are legendary creatures in folklore and mythology among the overlapping cultures of Europe.In European folklore, a dragon is a serpentine legendary creature. The Latin word draco, as in constellation Draco, comes directly from Greek δράκων,...

s in medieval European languages, and by extension for Satan
Satan
Satan , "the opposer", is the title of various entities, both human and divine, who challenge the faith of humans in the Hebrew Bible...

, Hell
Hell
In many religious traditions, a hell is a place of suffering and punishment in the afterlife. Religions with a linear divine history often depict hells as endless. Religions with a cyclic history often depict a hell as an intermediary period between incarnations...

, or death.

Egyptian empress Cleopatra reportedly made it a crime to kill worms in Egypt in 50 BCE due to their contribution to agriculture.

Examples:
  • Hamlet, Shakespeare
  • Twelfth Night, Shakespeare
  • The Battleship Potemkin
    The Battleship Potemkin
    The Battleship Potemkin , sometimes rendered as The Battleship Potyomkin, is a 1925 silent film directed by Sergei Eisenstein and produced by Mosfilm...

  • "The Conqueror Worm
    The Conqueror Worm
    "The Conqueror Worm" is a poem by Edgar Allan Poe about human mortality and the inevitability of death. It was first published separately in Graham's Magazine in 1843, but quickly became associated with Poe's short story "Ligeia" after Poe added the poem to a revised publication of the story in 1845...

    ", a poem in Edgar Allan Poe
    Edgar Allan Poe
    Edgar Allan Poe was an American author, poet, editor and literary critic, considered part of the American Romantic Movement. Best known for his tales of mystery and the macabre, Poe was one of the earliest American practitioners of the short story and is considered the inventor of the detective...

    's short story "Ligeia
    Ligeia
    "Ligeia" is an early short story by American writer Edgar Allan Poe, first published in 1838. The story follows an unnamed narrator and his wife Ligeia, a beautiful and intelligent raven-haired woman. She falls ill, composes "The Conqueror Worm", and quotes lines attributed to Joseph Glanvill ...

    "
  • "The Festival
    The Festival (short story)
    "The Festival" is a short story by H. P. Lovecraft written in October 1923 and published in the January 1925 issue of Weird Tales. It is considered to be one of the first of his Cthulhu Mythos stories.-Inspiration:...

    ", a short story by H. P. Lovecraft
    H. P. Lovecraft
    Howard Phillips Lovecraft --often credited as H.P. Lovecraft — was an American author of horror, fantasy and science fiction, especially the subgenre known as weird fiction....

  • The Wall
    The Wall
    The Wall is the eleventh studio album by English progressive rock group Pink Floyd. Released as a double album on 30 November 1979, it was subsequently performed live with elaborate theatrical effects, and adapted into a feature film, Pink Floyd—The Wall.As with the band's previous three...

    , Pink Floyd
    Pink Floyd
    Pink Floyd were an English rock band that achieved worldwide success with their progressive and psychedelic rock music. Their work is marked by the use of philosophical lyrics, sonic experimentation, innovative album art, and elaborate live shows. Pink Floyd are one of the most commercially...

    . Worms are used to represent the main character's slipping grasp on reality, and are "eating into his brain"


See also

  • Sea worm
    Sea worm
    Sea worm is a general term that may refer to a number of phyla of animals, or may refer specifically to:*Acanthocephala, parasitic worm*Annelida, segmented worms*Chaetognatha, arrow worms*Cycliophora, lobster worms*Entoprocta*Echiura, spoon worms...

    , lists various types of marine worms
  • Vermicompost
    Vermicompost
    Vermicompost is the product or process of composting utilizing various species of worms, usually red wigglers, white worms, and earthworms to create a heterogeneous mixture of decomposing vegetable or food waste, bedding materials, and vermicast...

  • Worm cast
    Worm cast
    A worm cast is a structure created by worms, typically on soils such as those on beaches that gives the appearance of multiple worms.-External links:*...

  • Worm charming
    Worm charming
    Worm charming, worm grunting, and worm fiddling are methods of attracting earthworms from the ground. The activity is usually performed to collect bait for fishing but can also take the form of a competitive sport...

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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