Abstract The scavenging cirolanid isopod Natatolana obtusata was caught using primarily meat-baited traps at a station in the Weddell Sea at Kap Norvegica. The hindguts of most specimens were densely stuffed with meat from the traps. The anatomy and the ultrastructure of different sections of the digestive system are described. The large and extremely expandable mouth opens into a short oesophagus which extends posteriorly into a small stomach. Lateralia and primary filter can be observed directly when the mouth opening is widened to its extreme. The anterior hindgut is extremely variable in its lumen and very distensible, depending on the nutritional condition. The cuticle of the hindgut is colonized by fungi. The length of the midgut glands varies with the nutritional conditions. Morphology and anatomy of the digestive system of Natatolana obtusata are discussed with the background of the lifestyle of the species and compared with other taxa.