The scaling of tongue projection in the veiled chameleon, Chamaeleo calyptratus.
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 chameleons grow while needing to maintain function. A previous morphological study showed that the musculoskeletal components of the feeding apparatus grow with negative allometry relative to snout-vent length (SVL) in chameleons. Here, we investigate the scaling of prey capture kinematics and muscle physiological cross-sectional area in the veiled chameleon, Chamaeleo calyptratus. The chameleons used in this study varied in size from approximately 3 to 18 cm SVL (1-200 g). Feeding sequences of 12 chameleons of different sizes were filmed and the timing of movements and the displacements and velocities of the jaws, tongue, and the hyolingual apparatus were quantified. Our results show that most muscle cross-sectional areas as well as tongue and hyoid mass scaled with isometry relative to mandible length, yet with negative allometry relative to SVL. Durations of movement also scaled with negative allometry relative to SVL and mandible length. Distances and angles generally scaled as predicted under geometric similarity (slopes of 1 and 0, respectively), while velocities generally scaled with slopes greater than 0 relative to SVL and mandible length. These data indicate that the velocity of jaw and tongue movements is generally greater in adults compared to juveniles. The discrepancy between the scaling of cross-sectional areas versus movements suggests changes in the energy storage and release mechanisms implicated in tongue projection.
Département d'Ecologie et de Gestion de la Biodiversité, UMR 7179 C.N.R.S/M.N.H.N., 57 rue Cuvier, Case postale 55, 75231 Paris Cedex 5, France; Evolutionary Morphology of Vertebrates, Ghent University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium. Electronic address: anthony.herrel@mnhn.fr.
Anthony
A
Herrel
Department of Biological Sciences, Northern Arizona University, PO Box 5640, Flagstaff, AZ 86011, USA.
Chrystal L
CL
Redding
Department of Biological Sciences, Northern Arizona University, PO Box 5640, Flagstaff, AZ 86011, USA.
J Jay
JJ
Meyers
Department of Biological Sciences, Northern Arizona University, PO Box 5640, Flagstaff, AZ 86011, USA.
Kiisa C
KC
Nishikawa
D000818:Animals; D001696:Biomechanical Phenomena; D005247:Feeding Behavior / Q000502:physiology; D008116:Lizards / Q000033:anatomy & histology* / Q000254:growth & development / Q000502:physiology*; D008297:Male; D008334:Mandible / Q000033:anatomy & histology; D009132:Muscles / Q000502:physiology*; D014059:Tongue / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology*
Feeding apparatus; Feeding kinematics; Lizard; Prey capture