FEEDING STRUCTURES AND FUNCTION

Thalia democratica feed by use of a specialised food filtration system. The endostyle organ located anterior to the pharyngeal cavity (fig 1) produces a thich mucous net which lines the pharyngeal cavity and acts as a generalist filter. Because the mucous net is non-specific, T. democratica is able to consume food particles of a range of sizes (Heron, 1972). On contraction of the large circular muscles around the body seawater is pumped through the pharyngeal cavtity. It undergoes filtration as it moves through the mucosal net linging the pharyngeal cavity. Upon capture of food particles, mucous particles detach from the net and are digested in the stomach, thus stimulating the endostyle organ to maintain a constant production of mucous to replace that lost in food capture (Heron, 1972). Filtered water leaves the body cavity via the excurrent siphons, producing propulsive forces enabling both forward motion for swimming and further ingestion of water for feeding.