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Thus, the earthworm not only creates passages for air and water to traverse the soil, but also modifies the vital organic component that makes a soil healthy (see Bioturbation). Earthworms promote the formation of nutrient-rich casts (globules of soil, stable in soil mucus) that have high soil aggregation and soil fertility and quality. [60]
However, this cannot be the case since L. terrestris, like other earthworms, can live in oxygenated water for long periods of time, stretching to weeks. Under less severe environmental conditions where air temperature and moisture are sufficient, the worm often moves around on the surface.
Worms vary in size from microscopic to over 1 metre (3.3 ft) in length for marine polychaete worms (bristle worms); [1] 6.7 metres (22 ft) for the African giant earthworm, Microchaetus rappi; [2] and 58 metres (190 ft) for the marine nemertean worm (bootlace worm), Lineus longissimus. [3]
They range in size from one-celled bacteria, algae, fungi, and protozoa, to more complex nematodes and micro-arthropods, to the visible earthworms, insects, small vertebrates, and plants. As these organisms eat, grow, and move through the soil, they make it possible to have clean water, clean air, healthy plants, and moderated water flow.
Microchaetus rappi, the African Giant Earthworm, is a large earthworm in the family Microchaetidae, the largest of the segmented worms (commonly called earthworms). It averages about 1.4 meters (4.5 feet) in length, but can reach a length of as much as 6.7 meters (22 feet) and can weigh over 1.5 kilograms (3.3 pounds).
Up to 60 cm in length, this earthworm is one of the largest European species. [ 1 ] [ 2 ] It weighs between 25 and 35 g and lives in subterranean tubes which are up to 2.5 m deep. It feeds on organic matter it ingests from the surface and aerates the soil as it moves through it, contributing to the formation of humus .
Earthworms store their partners' sperm in spermathecae ("sperm stores") and then the clitellum produces a cocoon that collects ova from the ovaries and then sperm from the spermathecae. Fertilization and development of earthworm eggs takes place in the cocoon. Leeches' eggs are fertilized in the ovaries, and then transferred to the cocoon.
Oligochaetes are well-segmented worms and most have a spacious body cavity (coelom) used as a hydroskeleton.They range in length from less than 0.5 mm (0.02 in) up to 2 to 3 metres (6.6 to 9.8 ft) in the 'giant' species such as the giant Gippsland earthworm (Megascolides australis) and the Mekong worm (Amynthas mekongianus).