Fig. 13. Movements internal to the odontophore during swallowing. Measurements were made of the rotation of the radular stalk relative to the anterior border of muscle I6 (left panels) and the translation of the base of the radular stalk as a percentage of the dorso-ventral height of the odontophore (right panels). (A—D) Data from individual swallowing sequences. (E) These data normalized, averaged and smoothed ± 1 S.D. Angle (degrees) is plotted as a function of time (ms) in the left panels. Percentage of the odontophore height is plotted as a function of time (ms) in the right panels. (F) Schematic diagrams indicating the rotation of the radular stalk within the odontophore for frames 1, 9, 18 and 22. The anterior margin of the odontophore is highlighted with a gray line, and the line of the radular stalk is highlighted with a black line; the angle is measured relative to the gray line. The translation of the radular stalk for frames 1, 9, 18 and 22 is shown on the right. A gray line highlights the anterior margin of the odontophore, and a black line parallel to this line indicates the distance from the base of the radula to the base of the odontophore. Compare original frames in Fig. 5. For definitions of periods t1, t2 and t4, see Materials and methods.