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 Earthworms have a profound effect on their environment. The tunnels they make allow for the movement of water and air, bringing water to highly aerobic conditions deep below the surface. They mix and translocate nutrients, organic matter, and soil. They feed on decaying organic matter, grind, mix, and digest with the aid of bacteria in their crop. They leave behind in their casts, more plant available nutrients than prior to ingestion. Research shows 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 (150 mm) of soil. The bacteria in the worm’s digestive tract create glue that binds particles of organic matter together to form their fecal pellets. In this form, the organic matter bonds to the nutrients and the glues bond the organic matter preventing the nutrients from being washed out of the soil. Earthworms have few invertebrate enemies. Their main predators are birds, reptiles, and mammals that eat them on the surface.
Over 7,000 species are divided into three groups:
Epigeic species These species live in, or near surface plant litter. They are typically small, and adapted to highly variable moisture and temperature conditions near the surface.
Endogeic species Some species live in the upper soil strata, and feed primarily on soil and associated organic matter. They do not make permanent burrows, and their tunnels become filled with cast material as they move through the soil, progressively passing it through their intestines.
Aneceic species These inhabit a more permanent burrow system that may extend several yards beneath the surface. They feed mainly on surface litter that they pull down into their burrow, which they may even cover to protect themselves. The ‘night crawler’ (Lumbricus terrestris) is this type of worm.
Earthworm Links: http://en.wikipedia.org/wiki/Earthworm
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