Introduction

Sipuncula (Greek, siphunculus, "little tube") are commonly known as "peanut worms" because of their resemblance to shelled peanuts. Only 320 species of peanut worms are known and all are marine. Sipuncula burrow into the sand and mud, live in rock crevices or in empty shells, like a hermit crab, in shallow waters. They are quite common and are routinely found when digging clams. Some species burrow into calcareous reefs or other hard substrates, and are found at depths ranging from intertidal to 5000 m. Most peanut worms are less than 10 cm long, but a few reach lengths up to 72 cm.