Annelida (Segmented Worms)


Annelida contains a large assemblage of mainly marine animals that are commonly referred to as segmented worms. It also contains terrestrial groups such as earthworms and leeches.

Keywords: polychaetes; oligochaetes; leeches; segmented worms

Figure 1.

Micrograph of a dorsal view of the polychaete Apistobranchus sp. (Spionida, Polychaeta) showing the head components and anterior segments of the body. This group of polychaetes has a pair of grooved palps originating from the head that are used for deposit feeding. The segments have well‐developed parapodia with bundles of chaetae.

Figure 2.

Micrograph of the polychaete Nereis sp. (Nereididae, Phyllodocida) showing its jaws retracted into the body. They can be everted for grabbing onto prey.

Figure 3.

Micrograph of the polychaete Myrianida sp. (Syllidae, Phyllodocida) showing a series of schizogamous epitokes budding off from the back end. These fill with gametes and as they mature swim away to spawn with other epitokes. The bottom‐dwelling form never develops gametes.

Figure 4.

Photograph of a clump of feather‐duster worms Demonax sp. (Sabellidae, Sabellida). These worms live in mucus and sediment tubes and project their feather palps into the water where they filter out passing plankton.

Figure 5.

Photograph of a land leech (Hirudinea, Clitellata). This form is predatory on mammals.

Figure 6.

Micrograph of a trochophore larva of a serpulid polychaete. This larva must feed on plankton for some weeks until it can settle as a young worm.


Further Reading

Clark RB (1964) Dynamics in Metazoan Evolution. The Origin of the Coelom and Segments. Oxford: Clarendon Press.

Dales RP (1962) The polychaete stomodeum and the interrelationships of the families of the Polychaeta. Proceedings of the Zoological Society of London 139: 289–328.

Dorresteijn AWC and Westheide W (eds) (1999) Reproductive Strategies and Developmental Patterns in Annelids. Dordecht: Kluwer Academic Publishers.

Fauchald K and Jumars P (1979) The diet of worms: a study of polychaete feeding guilds. Oceanography and Marine Biology, Annual Review 17: 193–284.

Fauchald K and Rouse GW (1997) Polychaete systematics: past and present. Zoologica Scripta 26: 71–138.

Rouse GW and Fauchald K (1997) Cladistics and polychaetes. Zoologica Scripta 26: 139–204.

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How to Cite close
Rouse, Greg W(May 2001) Annelida (Segmented Worms). In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001599]