Meeting Abstract

9.2  Jan. 4  The scaling of tongue projection in chameleons: morphology and kinematics REDDING, Chrystal L.*; MEYERS, Jay J.; HERREL, Anthony; NISHIKAWA, Kiisa C.; Northern Arizona University; Tulane University; University of Antwerp, Belgium; Northern Arizona University chrystal.redding@nau.edu

Within a year of hatching, chameleons can grow by up to two orders of magnitude in body mass. Rapid growth of the feeding mechanism means that bones, muscles and movements change as the chameleon grows. In this study, we investigated the structural and functional scaling of prey capture kinematics in the veiled chameleon, Chamaeleo calyptratus. Snout-vent length (SVL), jaw length, head width, and muscle lengths and masses were measured in order to identify patterns of growth. The chameleons used in this study varied in size from approximately 3 � 18 cm SVL (1-200 g). Feeding sequences of each chameleon (N= 12) were filmed at 250 frames per second with a high-speed digital camera. Timing of movement, velocity, and acceleration of the jaws, tongue and the hyolingual apparatus were quantified. The data were log transformed and graphed against log SVL. Results showed that lengths of external morphological variables grew with negative allometry. Muscle lengths and masses scaled isometrically with a few exceptions. Kinematic durations scaled with negative allometry. Distances and angles scaled with isometry, while velocities and accelerations scaled either with isometry or with positive allometry. These data suggest that head size of chameleons becomes smaller relative to SVL with growth, whereas velocities and accelerations of ballistic tongue projection are the same or faster relative to SVL in adults than in juveniles. This surprising result may be due in part to the isometry of many of the hyolingual muscles despite negative allometry of the hyoid. The involvement of elastic-energy storage and recovery also appears likely.