page_title: Earthworm
section_title: Ecology
hierarchical_section_title: Earthworm / Ecology
caption_attribution_description: English: Earthworm - L. terrestris - permanent vertical burrow photo
context_page_description: An earthworm is a terrestrial invertebrate that belongs to the order Opisthopora. They exhibit a tube-within-a-tube body plan, are externally segmented with corresponding internal segmentation, and usually have setae on all segments. They occur worldwide where soil, water, and temperature allow. Earthworms are commonly found in soil, eating a wide variety of organic matter. This organic matter includes plant matter, living protozoa, rotifers, nematodes, bacteria, fungi, and other microorganisms. An earthworm's digestive system runs the length of its body. It respires through its skin. It has a double transport system made of coelomic fluid that moves within the fluid-filled coelom and a simple, closed circulatory system. It has a central and peripheral nervous system. Its central nervous system consists of two ganglia above the mouth, one on either side, connected to a nerve running along its length to motor neurons and sensory cells in each segment. Large numbers of chemoreceptors concentrate near its mouth. Circumferential and longitudinal muscles edging each segment let the worm move.
context_section_description: Earthworms are classified into three main ecophysiological categories: (1) leaf litter- or compost-dwelling worms that are nonburrowing, live at the soil-litter interface and eat decomposing organic matter (epigeic) e.g. Eisenia fetida; (2) topsoil- or subsoil-dwelling worms that feed (on soil), burrow and cast within the soil, creating horizontal burrows in upper 10–30  cm of soil (endogeic); and (3) worms that construct permanent deep vertical burrows which they use to visit the surface to obtain plant material for food, such as leaves (anecic, meaning "reaching up"), e.g. Lumbricus terrestris.
  Earthworm populations depend on both physical and chemical properties of the soil, such as temperature, moisture, pH, salts, aeration, and texture, as well as available food, and the ability of the species to reproduce and disperse. One of the most important environmental factors is pH, but earthworms vary in their preferences. Most favour neutral to slightly acidic soils. Lumbricus Terrestris is still present in a pH of 5.4, Dendrobaena octaedra at a pH of 4.3 and some Megascolecidae are present in extremely acidic humic soils. Soil pH may also influence the numbers of worms that go into diapause. The more acidic the soil, the sooner worms go into diapause and the longer they remain in diapause at a pH of 6.4.
  Earthworms are preyed upon by many species of birds (e.g. robins, starlings, thrushes, gulls, crows), snakes, wood turtles, mammals (e.g. bears, boars, foxes, hedgehogs, pigs, moles ) and invertebrates (e.g. ants , flatworms, ground beetles and other beetles, snails, spiders, and slugs). Earthworms have many internal parasites, including protozoa, platyhelminthes, and nematodes; they can be found in the worms' blood, seminal vesicles, coelom, or intestine, or in their cocoons.
  Nitrogenous fertilizers tend to create acidic conditions, which are fatal to the worms, and dead specimens are often found on the surface following the application of substances such as DDT, lime sulphur, and lead arsenate. In Australia, changes in farming practices such as the application of superphosphates on pastures and a switch from pastoral farming to arable farming had a devastating effect on populations of the giant Gippsland earthworm, leading to their classification as a protected species. Globally, certain earthworms populations have been devastated by deviation from organic production and the spraying of synthetic fertilizers and biocides, with at least three species now listed as extinct but many more endangered.
  Vermicomposting of all organic "wastes" and addition of this organic matter, preferably as a surface mulch, on a regular basis, will provide earthworms with their food and nutrient requirements, and will create the optimum conditions of temperature and moisture that will naturally stimulate their activity.
  This earthworm activity aerates and mixes the soil, and is conducive to mineralization of nutrients and their uptake by vegetation. Certain species of earthworm come to the surface and graze on the higher concentrations of organic matter present there, mixing it with the mineral soil. Because a high level of organic matter mixing is associated with soil fertility, an abundance of earthworms is generally considered beneficial by farmers and gardeners. As long ago as 1881 Charles Darwin wrote: "It may be doubted whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures."
  Also, while, as the name suggests, the main habitat of earthworms is in soil, they are not restricted to this habitat. The brandling worm Eisenia fetida lives in decaying plant matter and manure. Arctiostrotus vancouverensis from Vancouver Island and the Olympic Peninsula is generally found in decaying conifer logs. Aporrectodea limicola, Sparganophilus spp.,  and several others are found in mud in streams.  Some species are arboreal, some aquatic and some euryhaline (salt-water tolerant) and littoral (living on the sea-shore, e.g. Pontodrilus litoralis). Even in the soil spec
caption: Permanent vertical burrow
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