earthworm

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earthworm,

terrestrial, cylindrical segmented worm of the class Oligochaeta. There are 2,200 earthworm species, found all over the world except in arid and arctic regions and ranging in size from 1 in. (2.5 cm) to the 11-ft (330-cm) giant worms of the tropics. Some earthworms are pallid in color, many are reddish brown to purple, and one Philippino species is bright blue. Earthworms burrow in the ground, swallowing soil from which the organic material is extracted and ground up in the gizzard and depositing the residue as castings outside the burrow. They come to the surface only on cloudy days and at night (hence the name night crawlers) unless they are flooded out by heavy rainfalls. In cold and dry weather they retreat into their burrows and remain dormant. The segments of the earthworm, visible externally as rings, are separated by internal partitions. On each segment are four pairs of bristles, or setae, with which the worm anchors itself to the walls of the burrow, drawing itself forward by rhythmic muscular contractions. There is a nerve cord, with ganglia in each segment and an enlarged cerebral ganglion (a primitive brain) at the anterior end. Although they have no prominent sense organs, earthworms are sensitive to light, touch, vibration, and chemicals. The circulatory system is enclosed in vessels; the blood (which contains hemoglobin) is pumped by muscular contractions of five linearly arranged hearts. Earthworms are hermaphroditic, but they cross-fertilize. Two worms exchange sperm cells during copulation; fertilization occurs after the worm's own eggs and the received sperm are encased in a tough sheath secreted by the clitellum, a conspicuous band of tissue near the anterior end. The sheath slips over the worm's head and is deposited underground, where it serves as a cocoon for the developing young. There is no larval stage; the young hatch as miniature adults. The common American and European earthworm, Lumbricus terrestris, up to 10 in. (25 cm) long, with about 150 segments, is used for laboratory dissection and study. Earthworms are also used as live bait and are eaten by some peoples—such as the Maoris, who consider certain species delicacies. The earthworm's greatest service, however, of immense importance to agriculture, is aerating and mixing the soil. Earthworm castings bring to the surface from 7 to 18 tons of soil per acre annually. This invaluable function of the earthworm was first pointed out in a detailed study by Charles Darwin. Earthworms are classified in the phylum AnnelidaAnnelida
[Lat., anellus=a ring], phylum of soft-bodied, bilaterally symmetrical (see symmetry, biological), segmented animals, known as the segmented, or annelid, worms.
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, class Oligochaeta, order Opisthopora.

earthworm

[′ərth‚wərm]
(invertebrate zoology)
The common name for certain terrestrial members of the class Oligochaeta, especially forms belonging to the family Lumbricidae.

earthworm

any of numerous oligochaete worms of the genera Lumbricus, Allolobophora, Eisenia, etc., which burrow in the soil and help aerate and break up the ground
References in periodicals archive ?
Biological activity is higher in organic soils: more earth worms, arthropods, mycorrhizal and other fungi, and micro-organisms, all beneficial for nutrient recycling and suppression of disease.
ACID rain is wiping out earth worms, which is affecting bird life.
The straw will keep the weeds down over winter and will provide protection for earth worms, which will find the manure and work it into the soil.
On the lawn is the famous `wormstone' which Darwin scrutinised for movement in the belief that this was the result of soil displacement by earth worms. The greenhouse and laboratory where he cultivated and studied orchids and other plants have already been repaired and there is also the `Sand Walk', a circuitous route through a small wood which Darwin trod each day along what he called his `thinking path'.
He also stressed for adopting natural farming making judicious and proper use of every drop of water for more crops increasing the fertility of land with friendly earth worms for recharging of the ground water.
While her sister cat Scully has decimated the mice population of Canton, the only prey Pumpkin dragged through the cat flap were a couple of earth worms - so elusive - and a half-eaten tuna sandwich.
Earth worms, beetles and caterpillars are staples of the hedgehog's diet.
Tenders are invited for Procurement of Zinc Sulphate, Gypsum, Bio-Pesticides, Pseudomonas fluorescence, Vermi Bag, Earth Worms, Poles and Shade nets for Lower Palar Sub Basin in Kanchipuram District
They eat considerable quantities of earth worms, which is one of the reasons they come into conflict with humans who are proud of their lawns or golf greens.
Aston University's Bio-Energy Research Group is looking into bio-oil, a fuel which looks like espresso coffee but which can be made from any living organism, from trees to dried earth worms - although the former is far more viable.