Limnognathia

The digestive system (drawn with bold on the figure) comprises the mouth, pharynx, esophagus and gut. The mouth opening in Limnognathia maerski is located anterior to the jaws. The lips are rather flexible, making the animal capable of protruding the ventral jaws through the mouth opening while eating. The mouth opening leads to the pharynx, with the complex jaws, and the short esophagus. The midgut fills most of the thorax and the anterior part of the abdomen and it probably function as a stomach. It has no cilia but the epithelium is covered with microvilli. There is no real hindgut. From the midgut the gut narrows gradually and is closed posteriorly by an anal plate that can be removed by attached muscles. Hence, the anus in L. maerski is only temporarily functioning.

Defecation has not been recorded in L. maerski but a special "vomit-behavior" has been observed from several specimens. If the animal swallows unwanted or indigestible items, it retracts the muscles in the head region so the dorsal part of the forehead is lifted upward and backward. In this position most of the jaw apparatus is protruded through the mouth and the unwanted items are thrown up.