Time ms

Figure 9. Schematic diagram of gape and hyoid kinematic profiles during prey transport in (A) Chamaeleo jacksonii, and (B) Ctenosaura similis. Note that the hyoid is protracted during the SO phase and retracted during FO. Modified from So etal. (1992); panel B after Smith (1984).

in many gape cycles, as there is only a slight change in slope of gape distance versus time (Fig. 9). Given that any increase in gape is likely to begin slowly, accelerate to a maximum rate of change, and finally decrease toward a maximum excursion, there must mathematically be an inflection point in the gape curve that could be identified as the end of slow opening and the start of fast opening. The existence of this inflection point need not be a reflection of any active neurological control or biomechanical feature of the feeding mechanism. The presence and extent of the SO phase is clearly highly variable both among transport cycles, among manipulatory behaviors, and among taxa.

Transport of prey following capture involves repeated cycles of hyoid protraction and retraction that move prey toward the esophagus. During the slow opening phase of the gape cycle the hyoid is protracted (Fig. 9). Retraction begins either just prior to or during fast opening and continues through the closing phase. This general pattern of gape and hyoid movements is superficially similar to that seen during the four-phase prey capture cycle seen in most terrestrial salamanders but contrasts substantially with that seen during prey transport in the only terrestrial salamander in which transport has been examined, Ambystoma tigrinum. In A. tigrinum, recall that the hyoid is retracted over the first portion of the gape cycle (during mouth opening) and protracted during a recovery phase after the gape cycle is finished (after mouth closing). Without further examination of terrestrial prey transport in other anamniotes, it will be hard to determine to what extent transport behavior in amniotes has diverged relative to that in terrestrial anamniotic ancestors.

Delheusy and Bels (1992) have conducted quantitative statistical analyses of transport behavior and compared kinematic transport patterns to jaw movements during chewing, initial capture, and cleaning. An analysis of variance showed chewing and transport cycles to differ significantly in duration and time to maximal lower jaw depression, and So et ah (1992) also found numerous significant differences between transport and chewing cycles in chameleons. A principal component analysis of these behaviors in Oplurus shows that cleaning behavior is the most distinctive and that there is considerable overlap between initial capture, transport, and reduction behaviors. These behaviors, although statistically distinct, nonetheless share a number of common kinematic patterns.

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