Fig. 10. Movements of the radular stalk relative to the odontophore during biting versus swallowing. (A-D) Averaged rotation (A) and translation (C) of the radular stalk (black lines are for biting, gray lines for swallowing). Measurements were made of the rotation of the radular stalk relative to the anterior border of muscle I6 (in B, the line of the radular stalk is highlighted with a black line, and the anterior border of muscle I6 is highlighted with a gray line), and the translation of the base of the radular stalk relative to the dorso-ventral height of the odontophore (in D, the distance from the base of the radular stalk to the base of the odontophore is highlighted with a black line). In C, the horizontal gray line indicates when the base of the radular stalk is exactly coincident with the base of the odontophore. When the data lie above this line, the radular stalk has moved towards the dorsal surface of the odontophore; when the data lie below this line, the radula stalk is protruding ventrally out of the odontophore. Values in A and C are means (solid lines) ± 1 s.d. (broken lines). (E,F) Model outputs of the peak of swallowing (E, 7732, S3, frame 26) and the peak of biting (F, 3213, S1, frame 34), to directly compare the positions of the radular stalk near the peak of protraction. The outlines of the radula/odontophore have been rotated so that the prow is straight, and lateral views are shown. Note that the radular stalk is closer to the top of the radula/odontophore at the peak protraction of biting (F) than at the peak protraction of swallowing (E).