Fig. 7. Kinematics of the line of widest extent. (A) The line of widest extent is measured on the moving isolated odontophore as the line of dark shadow produced from a light source directly above the odontophore (shadow line). In addition, the line joining the tip of the prow and the top of the radula is measured (top line). The angles of the lines are measured relative to the line of the pin, which is the line connecting the tip of the prow with the bottom of the prow. (B) Comparison of the angle of the line of widest extent (shadow line) with the line connecting the tip of the prow and the top of the radula (top line) (measured in the side view). The two lines consistently differ by 44±5° (mean ± S.D., N=15). The left and right parts show data measured from an isolated odontophore induced to perform movements by application of dopamine or carbachol crystals (respectively) to the cerebral ganglion. Event 1, rest, closed radula; event 2, widest radular opening; event 3, immediately prior to radular closure; event 4, radular closure; event 5, odontophore elongation; event 6, maximum elongation; event 7, elongation relaxed. (C) Averaged and normalized changes in angle of the line connecting the top of the radula and the tip of the prow during four in vivo swallows. The feeding cycle was normalized on the basis of definitions of the components of the swallowing cycle from our previous work (Drushel et al., 1997, 1998; Neustadter et al., 2002). The time intervals for this and all subsequent figures are defined as follows, using the nomenclature adopted in our original papers for consistency: t4, start of anterior buccal mass movement to peak protraction; t1, peak protraction to peak retraction; t2, peak retraction to the loss of the shape, i.e. the shape in which the base of the elongated radula/odontophore extends ventral to the long axis of the buccal mass (see fig. 3A of Drushel et al., 1997). Cycle times are normalized to the sum of the times t4+t1+t2. Lengths l were normalized to 100(l—l_min)/(l_max—l_min), so that lengths range from 0 at l_min to 100 at l_max. After normalization and averaging, the data were smoothed using an interpolation function that fitted cubic polynomials between successive data points. The average function is displayed as a solid line. A function representing ± 1 S.D. was calculated from the individual functions of the data and is displayed using dashed lines. The overall pattern of angular changes is similar to that observed in vitro.

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