Annelid | Definition, Characteristics, Habitat, Reproduction, Diet ...
2024年10月5日 · A major invertebrate phylum of the animal kingdom, the annelids number more than 9,000 species distributed among three classes: the marine worms (Polychaeta), which are divided into free-moving and sedentary, or tube-dwelling, forms; the earthworms (Oligochaeta); and the leeches (Hirudinea).
Earthworm | Annelid, Burrowing & Soil Fertility | Britannica
Earthworm, any one of more than 1,800 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 …
Structure and classes of annelid | Britannica
annelid , Any member of a phylum (Annelida) of invertebrate animals that possess a body cavity (coelom), movable bristles (setae), and a body divided into segments by crosswise rings. Known as segmented worms, annelids are divided into three classes: marine worms (Polychaeta; see polychaete), earthworms (Oligochaeta), and leeches (Hirudinea).
Worms & Annelids Portal | Britannica
Worms & Annelids. Annelid, phylum name Annelida, also called segmented worm, any member of a phylum of invertebrate animals that are characterized by the possession of a body cavity (or coelom), movable bristles (or setae), and a body divided into segments by transverse rings, or annulations, from which they take their name.
Annelid - Segmentation, Setae, Metamerism | Britannica
2024年10月5日 · The number of segments varies from seven in some aquatic species to 600 in the earthworms. Setae, embedded in the body wall, may be simple, S-shaped, forked, or hairlike. Except for the first, each segment may have either two pairs of …
Worm | Segmented, Annelid, Invertebrate | Britannica
2024年9月4日 · Worm, any of various unrelated invertebrate animals that typically have soft, slender, elongated bodies. Worms usually lack appendages; polychaete annelids are a conspicuous exception. Worms are members of several invertebrate phyla, including Platyhelminthes (flatworms), Annelida (segmented.
Annelid - Segmented Worms, Clitellates, Polychaetes | Britannica
2024年10月5日 · Chiefly aquatic worms; male gonopores in segment immediately behind testes; seminal receptacle at or near segment containing testes; size, minute to 1–3 cm; examples of genera: Nais, Tubifex (sludge worm).
Annelid - Leech, Parasitic, Bloodsucking | Britannica
2024年10月5日 · Annelid - Leech, Parasitic, Bloodsucking: Leeches are segmented worms characterized by a small sucker at the anterior end of the body and a large sucker at the posterior end; the medicinal use of leeches, which dates from antiquity, reached its peak in the first half of the 19th century.
Nervous system - Annelids, Reflexes, Sensory | Britannica
2024年9月25日 · Nervous system - Annelids, Reflexes, Sensory: The brain of most annelids (phylum Annelida; segmented worms, including the leeches and terrestrial earthworms) is relatively simple in structure. The earthworm brain is a bilobed mass lying above the pharynx in the third body segment.
Polychaete | Marine, Segmented, Worms | Britannica
A major invertebrate phylum of the animal kingdom, the annelids number more than 9,000 species distributed among three classes: the marine worms (Polychaeta), which are divided into free-moving and sedentary, or tube-dwelling, forms; the earthworms (Oligochaeta); and …