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Marine Worms - Annelids

Polychaetes (Bristle Worms)

Bristle worms are another group of the polychaetes. They are cylindrical, soft-bodied annelids with segmented bodies. They have bristles (setae) along both sides of their bodies along their entire lengthThey range in size from around 2.5 to 40 cm in length. Some burrow or build tubes, while others crawl or swim. Each species falls into one of two general categories:

  • "Errant worms" that wander among the shoreline and shallows in search of food. Some may build tubes or burrows that they return to, while others move around freely.
  • Sessile or sedentary worms that build permanent tube or burrow “homes” on shoreline flats. Since they wait for their prey to come to them, tube-building bristle worms have specialized appendages to help them gather food.

Bristle worm
Image © James van den Broek Flickr


Sedentary Bristle worms feed on plankton and other bits of organic matter, including algae or pieces of dead organisms. Others like fireworms, are carnivores feeding on colonial animals eg: sponges and ascidians.

Most bristle worms are either male or female. They reproduce by releasing sperm and eggs into the water. Larvae metamorphose from a free-swimming stage to a segmented stage before maturing. A few bristle worm species take care of their young.

In Fireworms, the bristles have become 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.

Fire worm
Image © Ken Traub Flickr




Marine animal behavior-Identification
The Bearded Fireworm, a member of the segmented worm family, can grow up to
12 inches in length. For defense they have developed sensory hairs on each side
of their bodies segments. These bristles are tiny, white and sharp. If touched,
they can cause severe irritation, pain and wounds. Also protruding from
each body segment are irregular gill filaments, which are part of their
circulatory system. You will often see them crawling on and around reefs,
rocky shorelines and sea grass beds. they feed on soft corals (gorgonians)
such as sea fans and sea rods, and mollusks.

Next:  ...  Nematodes (Roundworms) 


Polyclad Flatworms
Segmented worms
Arrow worms
Acorn worms
Horseshoe worms
Ribbon worms
Peanut worms



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