Annelid | Definition, Characteristics, Habitat, Reproduction, Diet ...
2024年10月5日 · Annelid, 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 body of an annelid is often described as a tube within a tube. The inner tube, or digestive tract , is separated from the outer tube, or body wall, by the coelom. The head region (prostomium) is followed by a series of segments similar to each other in appearance.
Coelom | biology | Britannica
In annelid …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. The coelom is reduced in leeches, and setae are lacking a few specialized forms, including leeches. A major invertebrate phylum of the animal… Read More
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).
Animal reproductive system - Annelids, Mollusks, Reproduction
Annelids have a well-developed body cavity (coelom), a part of the lining of which gives rise to gonads. In some annelids, gonads occur in several successive body segments. This is true, for example, in polychaetes , most of which are dioecious.
Animal - Coelomates, Invertebrates, Protostomes | Britannica
2024年9月15日 · Within the coelomates, the coelom has been of variable significance to the form and diversity of the various phyla. For example, it is essential for the burrowing abilities of annelids and related phyla.
Annelid - Segmentation, Metamorphosis, Reproduction | Britannica
2024年10月5日 · As these mesodermal bands hollow out to form the coelom, mesenchymal cells from the lining of the coelom begin to form one large coelomic cavity extending the entire length of the worm; as the number of mesenchymal cells increases, however, the …
Circulatory system - Coelomates, Blood Vessels, Heart | Britannica
2024年9月12日 · Annelida. While some small segmented worms of the phylum Annelida have no separate circulatory system, most have a well-developed closed system.
Worms & Annelids Portal | Britannica
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),...
Coelomic fluid | zoology | Britannica
The coelomic fluid of annelids plays a role in many important functions— e.g., locomotion and regulation of fluid transfer through the body wall (osmoregulation). Many metabolic processes occur in the coelom, which also serves as a site for temporary food storage, for excretion of nitrogen-containing wastes, and….