Latin: sipunculus = little pipe
Sipuncula (peanut worm introduction
About 350 sipunculans have been
described so far. They are found worldwide in soft sediments, crevices and holes. They are generally from 15 - 30 cm in length and burrow in
sediment. They have been found at depths of up to 500 m, but are more commonly found in coastal and shallow waters, and between tidemarks.
The body wall is formed of layers of circular and longitudinal muscles.
They have a retractable organ called the introvert, with the
mouth at its tip (see right Dendrostomum pyroides). The mouth is
surrounded by ciliated tentacles covered in mucous, and food particles are
moved to the mouth along these tentacles. When the introvert is retracted into the trunk the animal takes on the shape of a shelled peanut - hence its common name. The introvert is extended only when the animal is feeding.