- Sipunculans exhibit bilateral symmetry and are coelomic.
- They are gray/brown in color and some species are reddish purple or green.
- They are vermiform and resemble annelids in structure.
- They have a rubbery cuticle covering their body.
- Most species are less than 10 cm long, but a few species can be up to 70 cm long.
- Their mouth is surrounded by a ring of mucus-covered tentacles which are used for feeding.
- Longitudinal and circular muscles allow them to burrow using peristaltic movements.
- The surface of the posterior portion of the body is covered with bumps, warts, tubercles, or spines.
- Tactile receptors are concentrated mainly on the tentacles, but are also found all along the body length.
- Chemosensory organs (nuchal organs) are located dorsally.
- For defense, they can pull their anterior portion, also called the introvert, inside the posterior portion.
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