Lungfish digestive system

The gastrointestinal tract of lungfishes contains a spiral valve, as do the intestines of lampreys, elasmobranchs, sturgeons and coelacanths. A spiral valve intestine is generally considered an original way of achieving increased surface area for absorption of nutrients. The spiral valves are most commonly confined to the intestine distal to the duodenum or at least distal to the pyloris of the stomach. However, in Neoceratodus, the coiling commences immediately beyond the oesophagus at the point (glottis) where the pneumatic duct exits. This chapter discusses the spiral valve intestine of Neoceratodus and compares it to that of the lepidosirenid lungfishes. The intimate relationship between the spiral valve intestine and the two lobes of spleen and the pancreas is described. The chapter finishes with descriptions of the liver and bile salts, the haemopoietic nature of the spleen and the presence of lymphoid tissues in the lungfish gut. It also includes a note on the only digestive system-related trematode parasite to have been described in lungfish.