Unicyclic sea cucumber (Urechis unicinctus ), common name: sea intestines, sea intestines, belongs to the family of螠虫动物phylum (Echiurioidea), the order螠(Echiurida), the order 螠无管螠(Xenopneusta), and the family 螠(Urchidae). It is an elongated cylindrical mollusk, softly wriggling, hairless and light yellow. Sea intestines not only look like naked sea cucumbers, but their nutritional value is no less than that of sea cucumbers. Individuals are thick, about 100-300mm long, about 25-27mm wide, 200mm-250mm long, body surface is full of granular protuberances of varying sizes, with a conical muzzle; 1 pair of abdominal bristles, thick; there is a circle of 9-13 brown caudal bristles around the anus. Distributed in Russia, Japan, North Korea and China's Bohai Bay, etc., is a common species of benthic organisms in the lower intertidal zone of the mud and sandy coasts of northern China and the shallow subtidal zone, and does not suck blood.