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| What do gardeners often find when they attempt to dig up soil in order to plant vegetables? It is most likely that they would find earthworms in the soil. As a matter of fact, according to scientists, there are approximately eight million earthworms, or night crawlers, per acre of moist soil. The earthworm, whose scientific name is Lumbricus sp., is a member of the phylum Annelida and the class Oligochaeta, a class that approximately consists of about seven thousand species. The phylum Annelida belongs to the domain of protosome coelomates, which also include such phyla as the phylum Mollusca and the phylum Arthropoda. Being protosome coelomates, they all possess a fluid-filled body cavity, which may too serve as a hydrostatic skeleton against which muscles in the body wall can contract to produce movement. The phylum Mollusca includes such familiar creatures as clams, oysters, snails, and octopi. Even though there is a tremendous diversity amongst all seven classes of the phylum Mollusca, they all feed with help from a rasping tongue called a radula, a tiny little chainsaw-like structure made of chitin. The phylum Arthropoda consists of five classes—most of the members in these five classes possess a protective exoskeleton that is made out of chitin. (Fried and Hademenos, 1999) The common representatives of the phylum Arthropoda include spiders, insects, and crustaceans. Nonetheless, the phylum Annelida is distinctly diverse from the other phyla in the protostome coelomates domain due to their segmentation. | |||
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| In addition to the class Oligochaeta, the phylum Annelida also includes the class Polychaeta, which mostly comprises marine worms, and the class Hirudinea, which mainly consists of leeches. All members of the three classes in the phylum Annelida characteristically have a body that becomes organized into a linear series of identical compartments called segments. Segments allow annelids to move efficiently over solid surfaces; moreover, since all of the segments are identical, if one segment is damaged, the others may be able to survive and repair the damage. All forms of the phylum Annelida demonstrate an excretory system that functions by means of a pair of excretory tubules called metanephridia located in each segment that are connected to nephrostomes, which are tunnels that picks up fluid from the coelom. The metanephridia lead to the nephridiopores, pores that excrete wastes to the outside. Despite sharing numerous physiological similarities with other classes in the phylum Annelida, the class Oligochaeta, or the earthworms, is undoubtedly the most known representative due to its prevalent role as being common subjects in biology teaching and researches. | |||
| <tr><th align="center" bgcolor=pink>''' Worms'''</th></tr> | |||
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| '''Earthworm''' is a common name referering to the segmented worms, phylum ], class ], subclass ], order ]. | |||
| (Photograph by Jack Kelly Clark, 2003) | |||
| This is an image of a live earthworm. | |||
| Earthworms are present all over the world. However, they are often found in deep, dark, narrow, and moist underground burrows. They are called as night crawlers due to the fact that they could not tolerate heat and sun so they come up to the surface only at night whenever the weather is too hot during the day. It is usually common to see a great number of earthworms on the surface after a rain because the wet ground allows the earthworms to move without drying out. Furthermore, they generally remain close to places that could provide an adequate food supply. Without a doubt, the external structure of the earthworm definitely draws a tremendous amount of attention. | |||
| ==Overview== | |||
| External structure of the earthworm, Lumbricus terrestris (Photograph by R.E. Gaddie, 2003) | |||
| A typical earthworm is about twelve to thirty centimeter long. The earthworm has a bilateral body, which means that it has a distinct head, or anterior end, and a tail, or posterior end. Looking at the image of the external structure of the earthworm, one could see that the earthworm has a mouth at the anterior end. There is an area in front of the mouth called the prostomium that plays a major role in the digesting process of the earthworm. The anus is positioned at the earthworm’s posterior end through which metabolic wastes are excreted to the outside. The earthworm’s body is divided into numerous body segments that are typically covered by setae, pairs of hard, chitinous structures that project from the body wall. The setae’s function is to anchor the worm in its burrow as well as help it craw long the moist burrows. All forms of the earthworm have hydrostatic skeleton that consists of fluid held under pressure in a closed body compartment. The hydrostatic skeleton’s principal role is to enable earthworms to move by peristalsis, a type of locomotion produced by rhythmic waves of muscle contractions passing from head to tail. Earthworms characteristically expand by contracting circular muscles, whereas they could shorten the body by invoking contractions of the longitudinal muscles. Although the earthworms lack eyes, they have many light sensitive organs in some segments. The physiological systems such as circulatory, respiratory, and reproductive systems are also worth of interest and consideration. | |||
| The circulatory system in earthworms is closed and complex. There is a row of muscular blood vessels in earthworms that function as hearts in gas exchange and food transport. The earthworm does not have an internal respiratory. In fact, it does not have lungs; it is a skin breather in the sense that it respires through the skin—therefore the earthworm could definitely suffer from dehydration if its skin dries out. Earthworms are hermaphrodites. In other words, they possess both male and female organs in the same body. However, earthworms cross-fertilize simultaneously with the help of a special external structure called a clitellum. The clitellum secretes mucus that helps hold the earthworms together during mating; it also secretes a mucous cocoon that collects as well as protects the fertilized eggs. After picking up the fertilized eggs by sliding along the worm’s body, the mucous cocoon would stoop off the worm’s head and deposit into the soil until the eggs hatch. The digestive system of the earthworm is too extremely interesting. | |||
| (Phylum Annelida link, 2003) | |||
| This is a diagram of the earthworm’s digestive system. | |||
| Earthworms are deposit feeders in the essence that they would ingest the soil and then extract the nutrients from the soil. Since earthworms have no jaws or teeth, they create a high suction by using its muscular pharynx along with prostomium in order to pull food into its mouth. The food particles and soil are passed along the esophagus into the crop, which is an organ that stores the food temporarily. The food is then ground up into small digestible pieces in the gizzard. After being ground up into small pieces, the nutrients are being absorbed into the body in the small intestine. The indigestible material is then excreted along with feces through the anus to the outside. | |||
| Earthworms are often preys of birds such as robins and mammals such as badgers and moles. Earthworms are very important to the soil, which certainly has direct effects towards our agriculture. The burrows that are formed by earthworms allow water and air easy entry into the soil; it would let water enter the rooting zone where it can be used by plants. The burrows also allow roots to move easily through the soil into new spaces. However, despite their beneficial contributions to the soil, insecticides that are targeted at other insects sometimes wipe out earthworms. | |||
| There are over 2,200 species known worldwide, existing everywhere but ] and ] ]s. They range in size from two centimeters (about one inch) to over three meters (eleven feet). Amongst the main earthworm species commonly found in the soil are the red coloured '']'', which dwells close to and leaves its deposits on the surface, whilst the greyish blue '']'' is deeper burrowing. | |||
| External references: | |||
| In temperate zone areas, most commonly seen earthworms are lumbricids (]), mostly due to the recent rapid spread of a relatively few European species, but there are several other families, e.g. ], ], ], ], and others. These other families are often very different from the lumbricids in ], ] and ]. | |||
| Martin, J.P. et al. “Earthworm Biology and Production.” | |||
| http://edis.ifas.ufl.edu/IN047 (November 2, 2003) | |||
| ==Anatomy== | |||
| “Phylum Annelida” | |||
| http://www.esu.edu/~milewski/intro_biol_two/lab__12_annel_arthro/lumbr_internal_anat.html (November 2, 2003) | |||
| Earthworms have a closed circulatory system. They have two main blood vessels that extend through the length of their body- a ventral bood vessel which leads the blood to the posterior end, and a dorsal blood vessel which leads to the anterior end. These two blood vessels are connected by paired "hearts" found in the anterior end of the worm. Their blood is transported by blood vessels and capillaries that permit exchange of nutrients and gases with body tissues. | |||
| “Phylum Annelida: Polychaetes, Earthworms, Leeches” | |||
| http://216.239.53.104/search?q=cache:mgbskuIB4E0J:www.tulane.edu/~bfleury/diversity/diversitylectures/annelids.rtf+Lumbricus+respiration&hl=en&ie=UTF-8 (November 2, 2003) | |||
| Earthworms are ]s (both female and male organs within the same individual) but cannot fertilize their own eggs. They have testes, ] and male pores which produce, store and release the sperm, and ovaries and ovipores. However, they also have one or more pairs of ]e (depending on the species) that are internal sacs which receive and store sperm from the other worm in copulation. ] and ] are separate processes in earthworms. The mating pair overlap front ends ]ly and each exchanges sperm with the other. The cocoon, or egg case, is secreted by the clitellum, the glandular band which is near the front of the worm, but behind the spermathecae. Some indefinite time after copulation, long after the worms have separated, the clitellum secretes the cocoon which forms a ring around the worm. The worm then backs out of the ring, and as it does so, injects its own eggs and the other worm's sperm into it. As the worm slips out, the ends of the cocoon seal to form a vaguely lemon-shaped incubator (]) in which the embryonic worms develop. They emerge as small, but fully formed earthworms, except for lacking the sexual structures, which develop later. Some earthworm species are mostly ], in which case the male structures and spermathecae may become abnormal, or missing. | |||
| “The Earthworm” | |||
| http://web.ukonline.co.uk/webwise/spinneret/pot/odds/worm.htm (November 2, 2003) | |||
| One often sees earthworms come to the surface in large numbers after a rainstorm. There are three theories for this behavior. The first is that the waterlogged soil has insufficient oxygen for the worms, therefore, earthworms come to the surface to get the oxygen they need and breathe more easily. Secondly, some species (notably ]) come to the surface to mate. This behavior is, however, limited to a few species. Thirdly, the worms may be using the moist conditions on the surface to travel more quickly than they can underground, thus colonizing new areas more quickly. This is in any event a dangerous activity in the daytime, since earthworms die quickly when exposed to direct sunlight with its strong ] content. | |||
| University of California. Sustainable Agriculture Research and Education Program. | |||
| http://www.sarep.ucdavis.edu/worms/image6.htm (November 2, 2003) | |||
| Biology 226 Home Page. “Outline for Annelids.” http://faculty.vassar.edu/mehaffey/academic/animalstructure/outlines/annelida.html | |||
| (November 2, 2003) | |||
| ] | |||
| Delahut, Haut and Koval. “Earthworms: Beneficials or Pests?” | |||
| http://www.uwex.edu/ces/wihort/turf/Earthworms.htm (November 2, 2003) | |||
| ''Above; anatomy of the earthworm'' | |||
| ==Functions== | |||
| The Earthworm travels underground by employing a combination of a series of tiny bristles (]) set along its segmented length and the secretion of a slimy lubricating mucous. The worm is thus able to propel itself forward by means of rippling muscular contractions, ingesting organic materials from even the heaviest soil as it burrows, which it helps to decompose. | |||
| The ingested soil is ground up, digested, and the waste deposited behind the worm. This process aerates and mixes the soil, and is often considered greatly helpful by gardeners and farmers. Because a high level of organic matter is associated with soil fertility, an abundance of earthworms is a happy sight for the ]. In fact as long ago as 1881 ] wrote; | |||
| :''"It may be doubted whether there are any other animals which have played so important a part in the history of the world, as have these lowly creatures"''<br> | |||
| :(''The Formation Of Vegetable Mould Through The Action Of Worms'', Charles Darwin) | |||
| Indeed, it is probably not much of an exaggeration to state that the humble earthworm is one of the most vital living creatures on the planet, for its actions are essential for the creation and vitality of soil, upon which every living thing is dependent. | |||
| ==Benefits== | |||
| The major benefits of earthworm activities to soil fertility can be summarised as; | |||
| * Biological; The earthworm is essential to composting; the process of converting dead organic matter into rich ], a medium vital to the growth of healthy plants, and thus ensuring the continuance of the cycle of fertility. This is achieved by the worm's actions of pulling down below any organic matter deposited on the soil surface (eg, leaf fall, manure, etc) either for food or when it needs to plug its burrow. Once in the burrow, the worm will shred the leaf and partially digest it, then mingle it with the earth by saturating it with intestinal secretions. Worm casts (see below) can contain 40% more humus than the top 6" of soil in which the worm is living. | |||
| * Chemical; As well as dead organic matter, the earthworm also ingests any other soil particles that are small enough (including stones up to one-twentieth of an inch across) into it's 'crop' wherein minute fragments of grit grind everything into a fine paste which is then digested in the stomach. When the worm excretes this in the form of casts which are deposited on the surface or deeper in the soil, a perfectly balanced selection of minerals and plant nutrients is made available in an accessible form. Investigations in the ] show that fresh earthworm casts are 5 times richer in available ], 7 times richer in available ]s and 11 times richer in available potash than the surrounding upper 6 inches of soil. In conditions where there is plenty of available humus, the weight of casts produced may be greater than 4.5 kg (lOlb) per worm per year, in itself an indicator of why it pays the gardener or farmer to keep worm populations high. | |||
| * Physical; By its burrowing actions the earthworm is of great value in keeping the soil structure open, creating a multitude of channels which allow the processes of both aeration and drainage to occur. ] co-founder] points out that by sliding in their tunnels, earthworms "act as an innumerable army of pistons pumping air in and out of the soils on a 24 hour cycle (more rapidly at night)" (''Permaculture- A Designer's Manual'', Tagari Press, 1988)- thus the earthworm not only creates passages for air and water to traverse, but is itself a vital component in the living biosystem that is healthy soil. | |||
| It is important that we do not take the humble earthworm for granted. Dr W E ] observed "tremendous numerical differences between adjacent gardens" (''Soil, Humus And Health''), and worm populations are affected by a host of environmental factors, many of which can be influenced by good management practices on the part of the gardener or farmer. | |||
| Darwin estimated that arable land carries up to 53,000 worms to the acre (131,000 per hectare), but more recent research from ] has produced figures suggesting that even poor soil may support 250,000 worms to the acre, whilst rich fertile farmland may have up to 1,750,000. | |||
| Professor I L Heiberg of New York College of Forestry has stated that in optimum conditions the worm population may even reach 250,000,000 per acre (6,200,000 per hectare), meaning that the weight of earthworms beneath the farmer's soil could be greater than that of his livestock upon its surface. One thing is certain however. Rich, fertile soil that is cared for organically and well fed and husbanded by its steward will reap its reward in a healthy worm population, whilst denuded, overworked and eroded land will almost certainly contain little more than a few scrawny, undernourished specimens. | |||
| ==Threats== | |||
| The application of chemical fertilisers, sprays and dusts can have a disastrous effect on earthworm populations. Nitrogenous fertilisers tend to create ], which are fatal to the worms, and often dead specimens are to be found on the surface following the application of substances like ], ] and ]. In ], the use of ] on ]s almost totally wiped out the giant 9' ]. | |||
| In addition, as earthworms are processors of large amounts of plant and mineral materials, even if not killed themselves they can accumulate pollutants such as ], ], ], and ]s at levels up to 20 times higher than in the soil, which in turn are passed on at lethal dosages to the wildlife which feed upon them such as ]es, ]s or ]s. | |||
| Therefore, the most reliable way to maintain or increase the levels of worm population in the soil is to avoid the application of artificial chemicals, as well as adding organic matter, preferably as a surface mulch, on a regular basis. This will not only provide them with their food and nutrient requirements, but also creates the optimum conditions of heat (cooler in summer and warmer in winter) and moisture to stimulate their activity. | |||
| A recent threat to earthworm populations in the ] is the ] (''Artiposthia triangulata''), which feeds upon the earthworm, but in this country has no natural predator itself. At present sightings of the NZFW have been mainly localised, but this is no reason for complacency as it has spread extensively since its introduction in 1960 through contaminated soil and plant pots. Any sightings of the flatworm should be reported to the ], who are monitoring its spread. | |||
| ==Economic Impact== | |||
| Various species of worms are used in ], the practice of feeding organic waste to earthworms to decompose (digest) it, a form of ]ing by the use of worms. These are usually '']'' or the Brandling worm, also known as the Tiger worm or Red Wriggler, and are distinct from soil dwelling earthworms. | |||
| Earthworms make big contributions to our ''economy.''They are sold all over the world for the profit of some lucky ones. The earthworm market is enormous. As Collicut mentioned, ''In 1980, 370 million worms were exported from Canada, with a Canadian export value of $13 million and an American retail value of $54 million.'' | |||
| ''See also:'' ] | |||
| == External References == | |||
| *http://www.sarep.ucdavis.edu/worms/ | |||
| *http://www.encyclopedia.com/articles/03910.html | |||
| *http://www.naturenorth.com/fall/ncrawler/ncrawlF.html | |||
Revision as of 20:04, 24 November 2003
| Worms | ||||||||||
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| Scientific classification | ||||||||||
|
Earthworm is a common name referering to the segmented worms, phylum Annelida, class Clitellata, subclass Oligochaeta, order Opisthopora.
Overview
There are over 2,200 species known worldwide, existing everywhere but Arctic and arid climates. They range in size from two centimeters (about one inch) to over three meters (eleven feet). Amongst the main earthworm species commonly found in the soil are the red coloured Lumbricus terrestris, which dwells close to and leaves its deposits on the surface, whilst the greyish blue Allolobophora caliginosa is deeper burrowing.
In temperate zone areas, most commonly seen earthworms are lumbricids (Lumbricidae), mostly due to the recent rapid spread of a relatively few European species, but there are several other families, e.g. Megascolecidae, Sparganophilidae, Glossoscolecidae, Haplotaxidae, and others. These other families are often very different from the lumbricids in behavior, physiology and habitat.
Anatomy
Earthworms have a closed circulatory system. They have two main blood vessels that extend through the length of their body- a ventral bood vessel which leads the blood to the posterior end, and a dorsal blood vessel which leads to the anterior end. These two blood vessels are connected by paired "hearts" found in the anterior end of the worm. Their blood is transported by blood vessels and capillaries that permit exchange of nutrients and gases with body tissues.
Earthworms are hermaphrodites (both female and male organs within the same individual) but cannot fertilize their own eggs. They have testes, seminal vesicles and male pores which produce, store and release the sperm, and ovaries and ovipores. However, they also have one or more pairs of spermathecae (depending on the species) that are internal sacs which receive and store sperm from the other worm in copulation. Copulation and Reproduction are separate processes in earthworms. The mating pair overlap front ends ventrally and each exchanges sperm with the other. The cocoon, or egg case, is secreted by the clitellum, the glandular band which is near the front of the worm, but behind the spermathecae. Some indefinite time after copulation, long after the worms have separated, the clitellum secretes the cocoon which forms a ring around the worm. The worm then backs out of the ring, and as it does so, injects its own eggs and the other worm's sperm into it. As the worm slips out, the ends of the cocoon seal to form a vaguely lemon-shaped incubator (cocoon) in which the embryonic worms develop. They emerge as small, but fully formed earthworms, except for lacking the sexual structures, which develop later. Some earthworm species are mostly parthenogenetic, in which case the male structures and spermathecae may become abnormal, or missing.
One often sees earthworms come to the surface in large numbers after a rainstorm. There are three theories for this behavior. The first is that the waterlogged soil has insufficient oxygen for the worms, therefore, earthworms come to the surface to get the oxygen they need and breathe more easily. Secondly, some species (notably Lumbricus terrestris) come to the surface to mate. This behavior is, however, limited to a few species. Thirdly, the worms may be using the moist conditions on the surface to travel more quickly than they can underground, thus colonizing new areas more quickly. This is in any event a dangerous activity in the daytime, since earthworms die quickly when exposed to direct sunlight with its strong UV content.
Above; anatomy of the earthworm
Functions
The Earthworm travels underground by employing a combination of a series of tiny bristles (setae) set along its segmented length and the secretion of a slimy lubricating mucous. The worm is thus able to propel itself forward by means of rippling muscular contractions, ingesting organic materials from even the heaviest soil as it burrows, which it helps to decompose.
The ingested soil is ground up, digested, and the waste deposited behind the worm. This process aerates and mixes the soil, and is often considered greatly helpful by gardeners and farmers. Because a high level of organic matter is associated with soil fertility, an abundance of earthworms is a happy sight for the organic gardener. In fact as long ago as 1881 Charles Darwin wrote;
- "It may be doubted whether there are any other animals which have played so important a part in the history of the world, as have these lowly creatures"
- (The Formation Of Vegetable Mould Through The Action Of Worms, Charles Darwin)
Indeed, it is probably not much of an exaggeration to state that the humble earthworm is one of the most vital living creatures on the planet, for its actions are essential for the creation and vitality of soil, upon which every living thing is dependent.
Benefits
The major benefits of earthworm activities to soil fertility can be summarised as;
- Biological; The earthworm is essential to composting; the process of converting dead organic matter into rich humus, a medium vital to the growth of healthy plants, and thus ensuring the continuance of the cycle of fertility. This is achieved by the worm's actions of pulling down below any organic matter deposited on the soil surface (eg, leaf fall, manure, etc) either for food or when it needs to plug its burrow. Once in the burrow, the worm will shred the leaf and partially digest it, then mingle it with the earth by saturating it with intestinal secretions. Worm casts (see below) can contain 40% more humus than the top 6" of soil in which the worm is living.
- Chemical; As well as dead organic matter, the earthworm also ingests any other soil particles that are small enough (including stones up to one-twentieth of an inch across) into it's 'crop' wherein minute fragments of grit grind everything into a fine paste which is then digested in the stomach. When the worm excretes this in the form of casts which are deposited on the surface or deeper in the soil, a perfectly balanced selection of minerals and plant nutrients is made available in an accessible form. Investigations in the USA show that fresh earthworm casts are 5 times richer in available nitrogen, 7 times richer in available phosphates and 11 times richer in available potash than the surrounding upper 6 inches of soil. In conditions where there is plenty of available humus, the weight of casts produced may be greater than 4.5 kg (lOlb) per worm per year, in itself an indicator of why it pays the gardener or farmer to keep worm populations high.
- Physical; By its burrowing actions the earthworm is of great value in keeping the soil structure open, creating a multitude of channels which allow the processes of both aeration and drainage to occur. Permaculture co-founderBill Mollison points out that by sliding in their tunnels, earthworms "act as an innumerable army of pistons pumping air in and out of the soils on a 24 hour cycle (more rapidly at night)" (Permaculture- A Designer's Manual, Tagari Press, 1988)- thus the earthworm not only creates passages for air and water to traverse, but is itself a vital component in the living biosystem that is healthy soil.
It is important that we do not take the humble earthworm for granted. Dr W E Shewell Cooper observed "tremendous numerical differences between adjacent gardens" (Soil, Humus And Health), and worm populations are affected by a host of environmental factors, many of which can be influenced by good management practices on the part of the gardener or farmer.
Darwin estimated that arable land carries up to 53,000 worms to the acre (131,000 per hectare), but more recent research from Rothamstead Experimental Station has produced figures suggesting that even poor soil may support 250,000 worms to the acre, whilst rich fertile farmland may have up to 1,750,000.
Professor I L Heiberg of New York College of Forestry has stated that in optimum conditions the worm population may even reach 250,000,000 per acre (6,200,000 per hectare), meaning that the weight of earthworms beneath the farmer's soil could be greater than that of his livestock upon its surface. One thing is certain however. Rich, fertile soil that is cared for organically and well fed and husbanded by its steward will reap its reward in a healthy worm population, whilst denuded, overworked and eroded land will almost certainly contain little more than a few scrawny, undernourished specimens.
Threats
The application of chemical fertilisers, sprays and dusts can have a disastrous effect on earthworm populations. Nitrogenous fertilisers tend to create acid conditions, which are fatal to the worms, and often dead specimens are to be found on the surface following the application of substances like DDT, lime sulphur and lead arsenate. In Australia, the use of superphosphate on pastures almost totally wiped out the giant 9' Gippsland earthworm.
In addition, as earthworms are processors of large amounts of plant and mineral materials, even if not killed themselves they can accumulate pollutants such as DDT, lead, cadmium, and dioxins at levels up to 20 times higher than in the soil, which in turn are passed on at lethal dosages to the wildlife which feed upon them such as foxes, moles or birds.
Therefore, the most reliable way to maintain or increase the levels of worm population in the soil is to avoid the application of artificial chemicals, as well as adding organic matter, preferably as a surface mulch, on a regular basis. This will not only provide them with their food and nutrient requirements, but also creates the optimum conditions of heat (cooler in summer and warmer in winter) and moisture to stimulate their activity.
A recent threat to earthworm populations in the UK is the New Zealand Flatworm (Artiposthia triangulata), which feeds upon the earthworm, but in this country has no natural predator itself. At present sightings of the NZFW have been mainly localised, but this is no reason for complacency as it has spread extensively since its introduction in 1960 through contaminated soil and plant pots. Any sightings of the flatworm should be reported to the Scottish Crop Research Institute, who are monitoring its spread.
Economic Impact
Various species of worms are used in vermiculture, the practice of feeding organic waste to earthworms to decompose (digest) it, a form of composting by the use of worms. These are usually Eisenia foetida or the Brandling worm, also known as the Tiger worm or Red Wriggler, and are distinct from soil dwelling earthworms.
Earthworms make big contributions to our economy.They are sold all over the world for the profit of some lucky ones. The earthworm market is enormous. As Collicut mentioned, In 1980, 370 million worms were exported from Canada, with a Canadian export value of $13 million and an American retail value of $54 million.
See also: soil life