Polychaete Worms (Bristle worms)

Polychaete worms are closely related to leeches and earthworms and together make up the Phylum ANNELIDA. Polychaetes are often called bristleworms because each of the body segments has an upper and lower bundle of bristles (called setae or chaetae) on each side. In free-living polychaetes, the bristles, combined with snake-like body waves, help the worm to move along. In Fireworms, Eurythoe spp (A), the bristles have evolved into defensive organs. They are fragile, hollow tubes filled with poison. They are easily broken when the worm is touched and the pain they cause when they pierce the skin makes their common name very appropriate.

The bristles found in worms that live in tubes or burrows (sessile or sedentary worms) have often evolved into hooks to help anchor the worm in place. Sedentary worms make a whole variety of homes. Many make a hard calcareous tube (C - Spirorbis), which is attached to a hard surface or even large algae. Other sedentary worms have a leathery tube, sometimes decorated with pieces of broken shell, or sand and mud particles.

Free-living worms include carnivores, herbivores and scavengers. Some, such as the fireworms, are active carnivores feeding on colonial animals eg: sponges and ascidians). On the other hand, sedentary worms, (which cannot move about), usually feed on microscopic plants and animals or fine particles. Many sedentary worms filter plankton out of the water by a crown of feathery tentacles that surround their mouth and give them their common name of 'fanworm' or 'feather duster' worm (B).

Worm is a common name which applies to a 'shape' rather than a particular phylum or class of animals, much as 'slug' applies to much more than opisthorbanch molluscs. There are a few slug-like worms, such as Aphrodite which are sometimes mistaken for sea slugs.

Authorship details
Rudman, W.B., 2004 (July 27) Polychaete Worms (Bristle worms). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/polychaete

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