Sipunculans, also known as peanut worms, are marine invertebrates belonging to the phylum Sipuncula. They have a soft, elongated body that can retract into a protective, cylindrical structure. Sipunculans are typically found in shallow coastal waters, burrowing into sand or mud, and they play a role in the ecosystem by recycling nutrients. These creatures are characterized by their simple body plan, which includes a mouth surrounded by tentacles at one end and a tail-like structure at the other. Sipunculans feed primarily on detritus and small organic particles, making them important for the health of their habitats, similar to other benthic organisms like polychaetes and bivalves.