Sipunculids are a group of marine worms with a unique body structure, characterized by a long, muscular proboscis that they can retract into their body. These animals are also commonly referred to as peanut worms, due to their oblong shape and resemblance to a peanut. Other synonyms for sipunculid include gullet worms, acorn worms, and spoon worms. Many species of sipunculids are important members of marine ecosystems, serving as prey for larger animals or playing a role in recycling nutrients in the sediment. They are also sometimes collected as bait for fishing, particularly in Asian countries where they are considered a delicacy.