The unicinctus (Urechis unicinctus ), common name: sea gut, sea gut, belongs to the phylum Marcelliformes, order螠, order螠, order 無管螠, family 螠, genus 螠. An elongated cylindrical annelid, softly wriggling, hairless and light yellow. Sea intestines not only look like naked sea cucumbers, its nutritional value is no less than sea cucumbers. Individuals are thick, about 100-300mm long, about 25-27mm wide, 200mm-250mm long, the body surface is full of granular protuberances of varying sizes, and the muzzle is conical; the abdominal bristles are 1 pair, thick; there is a circle of 9-13 brown caudal-anal hairs 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 and shallow subtidal zone of the mud and sandy coast of northern China, and does not suck blood.