Fig. 14.

Schematic diagram that illustrates current conceptualizations of how radula movements are thought to change as food is ingested (Weiss et al., 1986). A, When food is not ingested, it has been suggested that opening/protraction occurs as the radula moves from a neutral position to a point where it is extended through the animal’s open jaws (arrow 1). It has been suggested that the radula then returns to a neutral state (arrow 2). B, When animals make swallowing responses, the radula moves from a rest position to a hyper-retracted position so that food can be deposited in the esophagus (arrow 1). The radula then returns to the rest position (arrow 2).