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. The coelom is reduced in leeches, and setae are lacking a few specialized forms, including leeches.
Worms & Annelids Encyclopedia Articles
See articlesFeatured Articles
peanut worm
Peanut worm, any member of the invertebrate phylum Sipuncula, a group of unsegmented marine worms. The head bears a retractable “introvert” with the mouth at its end. The mouth is usually surrounded by...
sea mouse
Sea mouse, (Aphrodita), any of a genus of marine worms of the class Polychaeta (phylum Annelida), named for their mouselike appearance and behaviour. Sea mice are usually 7.5–15 centimetres (3–6 inches)...
palolo worm
Palolo worm, any of various segmented marine worms of the families Eunicidae and Nereidae (class Polychaeta, phylum Annelida). The palolo worm exhibits unique breeding behaviour: during the breeding season,...
arrowworm
Arrowworm, any member of a group of free-living wormlike marine carnivores that belong to the invertebrate phylum Chaetognatha. The bodies of arrowworms appear transparent to translucent or opaque and...
feather-duster worm
Feather-duster worm, any large, segmented marine worm of the family Sabellidae (class Polychaeta, phylum Annelida). The name is also occasionally applied to members of the closely related polychaete family...
earthworm
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...
fireworm
Fireworm, any of certain segmented marine worms of the class Polychaeta (phylum Annelida), including species of the genera Hermodice and Eurythoe. Fireworms produce a stinging sensation if touched. The...
flatworm
Flatworm, any of the phylum Platyhelminthes, a group of soft-bodied, usually much flattened invertebrates. A number of flatworm species are free-living, but about 80 percent of all flatworms are parasitic—i.e.,...
medicinal leech
Medicinal leech, any of certain leech species (phylum Annelida), particularly Hirudo medicinalis, H. verbana, and H. orientalis, once used in the treatment of human diseases and used at present as a source...
spoonworm
Spoonworm, any member of the invertebrate phylum Echiura, also known as Echiuroidea, or Echiurida. Nearly all spoonworms are exclusively marine. They are sausage-shaped organisms with a flattened extension...
beard worm
Beard worm, (family Siboglinidae), any of a group of polychaetes (marine worms) constituting the family Siboglinidae. Beard worms live sedentary lives in long protective tubes on the seafloor throughout...
ribbon worm
Ribbon worm, any member of the invertebrate phylum Nemertea (sometimes called Nemertinea, or Rhynchocoela), which includes mainly free-living forms but also a few parasites of crustaceans, mollusks, and...