The Sipuncula or Sipunculida, sipunculid worms or peanut worms, are a phylum containing 144-320 species (estimates vary) of bilaterally symmetrical, unsegmented marine worms. Sipunculid worm jelly is a delicacy in the town of Xiamen in Fujian province of China.
Sipunculids are relatively common, and live in shallow waters, either in burrows or in discarded shells like hermit crabs do. Some bore into solid rocks to make a shelter for themselves. Although typically less than 10 cm long, some sipunculans may reach several times that length.
Sipunculans are worm-like animals ranging from 2 to 720 millimetres in length, with most species being under 10 centimetres The body consists of a narrow anterior section, called the introvert and a larger trunk section. The introvert is retractable into the trunk, and resembles a proboscis, although it actually includes the whole of the head.
Sipunculans have a coelom, and a body wall somewhat similar to that of annelids. he body wall is strong and muscular; when threatened, Sipunculids can retract their body into a shape resembling a peanut kernel - a practice that has given rise to the name "peanut worm
| Wikipedia, the free encyclopedia