Earthworm , also called angleworm , any one of more than 1, species of terrestrial worms of the class Oligochaeta phylum Annelida —in particular, members of the genus Lumbricus. Seventeen native species and 13 introduced species from Europe occur in the eastern United States, L. Earthworms occur in virtually all soils of the world in which the moisture and organic content are sufficient to sustain them. One of the most detailed studies of earthworm activities was conducted by English naturalist Charles Darwin. Members of one Australian species can grow as long as 3. This species is reddish brown, but some earthworms e. The reddish tinge of L. The earthworm body is divided into ringlike segments as many as in L. Some internal organs, including the excretory organs, are duplicated in each segment. The body is tapered at both ends, with the tail end the blunter of the two.
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All rights reserved. Earthworms do not live in deserts or regions where there is permafrost or permanent snow and ice. Typically only a few inches 7 or 8 centimeters long, some members of this species have been known to grow to a snakelike 14 inches 35 centimeters. Earthworms' bodies are made up of ringlike segments called annuli. These segments are covered in setae, or small bristles, which the worm uses to move and burrow. These terrestrial worms typically dwell in soil and moist leaf litter. Their bodies are characterized by a "tube within a tube" construction, with an outer muscular body wall surrounding a digestive tract that begins with the mouth in the first segment.
Science Insights, Addison-Wesley, 3. They are the main contributors to enriching and improving soil for plants, animals and even humans. Earthworms create tunnels in the soil by burrowing, which aerates the soil to allow air, water and nutrients to reach deep within the soil. Earthworms eat the soil which has organic matter such as decaying vegetation or leaves. Plants cannot use this organic matter directly. After organic matter is digested, the earthworm releases waste from their bodies called castings. Castings contain many nutrients that the plant can use.
An earthworm is a terrestrial invertebrate that belongs to the class Clitellata , order Oligochaeta , phylum Annelida. They exhibit a tube-within-a-tube body plan , are externally segmented with corresponding internal segmentation, usually have setae on all segments. 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.
