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Definition: annelid from Philip's Encyclopedia

Any member of the Annelida phylum of segmented worms. All have encircling grooves usually corresponding to internal partitions of the body. A digestive tube, nerves, and blood vessels run through the entire body, but each segment has its own set of internal organs. The three main classes are: Polychaeta (marine worms), Oligochaeta (freshwater or terrestrial worms), and Hirudinea (leeches).


Annelida

From The Columbia Encyclopedia
(Әnĕl'ĭdӘ) [Lat., anellus =a ring], phylum of soft-bodied, bilaterally symmetrical (see symmetry, biological ), segmented animals, known as the segmented, or annelid, worms. Over 12,000 known species are grouped in three classes: the earthworms and freshwater worms (oligochaetes), the leeches (hirudineans), and the marine worms (polychaetes). Annelids are found throughout the world, from deep ocean bottoms to high mountain glaciers. They live in protected habitats such as mud, sand, and rock crevices, and in and among other invertebrate animals, such as sponges. Many live in tubes they secrete around themselves. Segmented Bodies The fundamental characteristic of the phylum is the division of the body into a linear series of cylindrical segments, or metameres. Each metamere consists of a section of the body wall and a compartment of the body cavity with its internal organs. The external divisions, which may be seen in the common earthworm, correspond to the internal divisions. The…
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PHYLUM ANNELIDA
This phylum of some 9000 species of worms is recognizable by the ring-like divisions of the body, which represent the individual segments. These animals resemble an elongate tube with terminal mouth and anus, and a straight digestive tract between. The body cavity in each segment is separated from…
| 190 words , 2 images

Full text Article Annelida

From The Columbia Encyclopedia
(Әnĕl'ĭdӘ) [Lat., anellus =a ring], phylum of soft-bodied, bilaterally symmetrical (see symmetry, biological ), segmented animals, known as the segmented, or annelid, worms. Over 12,000 known species are grouped in three classes: the earthworms and freshwater worms (oligochaetes), the leeches…
| 3,167 words
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Full text Article Annelida (Annulata)

From Penguin Dictionary of Biology
Soft-bodied, metamerically segmented coelomate worms with, typically, a closed blood system; excretion by NEPHRIDIA ; a central nervous system of paired (joined) nerve cords ventral to the gut, and a brain comprising paired ganglia above the oesophagus, linked by commissures to a pair below it. …
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Full text Article Annelida

From Merriam-Webster's Medical Dictionary
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Full text Article Annelida

From A Concise Dictionary of Paleontology
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(A) grasshoppers (Insecta)
WITH FEW EXCEPTIONS , the animals covered in this book are all classified as members of the phylum Arthropoda —the arthropods. As such, all share certain physical features, including: division of the body into segments; an external skeleton (exoskeleton) and growth that requires periodic shedding of…
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Full text Article coelom

From The Columbia Encyclopedia
(sē'lӘm), fluid-filled body cavity, found in animals, which is lined by cells derived from mesoderm tissue in the embryo , and which provides for free, lubricated motion of the viscera. In animals of the phyla Annelida , Mollusca , and Arthropoda , the mesoderm forms as a mass of tissue from special…
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Full text Article Leuckart, Karl Georg Friedrich Rudolf

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
German zoologist who identified the phylum Coelenterata (now divided into separate phyla, the Cnidaria – jellyfish, sea anemones, and corals – and the Ctenophora – the comb jellies), and was responsible for establishing the first meat inspection laws in the world. His research led to the division of…
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Full text Article leech

From The Columbia Encyclopedia
predacious or parasitic annelid worm of the class Hirudinea, characterized by a cylindrical or slightly flattened body with suckers at either end for attaching to prey. The leech, like other annelids, is segmented, but its numerous surface folds obscure the internal segments. In many forms the mouth…
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Full text Article Leeches

From Black's Veterinary Dictionary
Blood-sucking aquatic annelids of the class Hirudinea, within phylum Annelida (segmented worms). Leeches live in ponds, streams, and on damp vegetation. They have strong muscular suckers; the anterior one surrounds the mouth which, in several species, contains saw-like teeth used to pierce the skin…
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