Comparative study of the innervation patterns of the hyobranchial musculature in three iguanian lizards: Sceloporus undulatus, Pseudotrapelus sinaitus, and Chamaeleo jacksonii

Abstract

The neuroanatomy and musculature of the hyobranchial system was studied in three species of iguanian lizards: Sceloporus undulatus, Pseudotrapelus sinaitus, and Chamaeleo jacksonii. The goal of this study was to describe and compare the innervation and arrangement of the hyobranchial musculature in the context of its function during tongue protrusion. A comparison of the hyobranchial innervation patterns revealed a relatively conserved innervation pattern in S. undulatus and P. sinaitus, and a modified version of this basic layout in C. jacksonii. All three species show anastomoses between sensory neurons of the trigeminal nerve and motor neurons of the hypoglossal nerve, suggesting that feedback may be important in coordinating tongue, jaw, and hyoid movements. The hyobranchial musculature of S. undulatus is very similar to that of P. sinaitus; however, there are minor differences, including the presence of an M. genioglossus internus (GGI) muscle in S. undulatus. Further differences are found mainly in functional aspects of the hyobranchial musculature, such as changes in the muscle lengths and the origins and insertions of the muscles. In C. jacksonii the hyobranchial system is comprised of largely the same components, but it has become highly modified compared to the other two species. Based on the innervation and morphological data gathered here, we propose a revision of the terminology for the hyobranchial musculature in iguanian lizards.

Comparative functional analysis of the hyolingual anatomy in lacertid lizards

“…In chameleons, on the other hand, both the extrinsic (m. hyoglossus) and intrin- sic (m. verticalis) tongue muscles that function to project and retract the tongue are hypertrophied (see Herrel et al, 2001 and references therein). Additionally, changes in the position and the orientation of the hyolingual retractors associated with the changes in the morphology and use of the hyobranchium are observed in chameleons (Meyers et al, 2002).…”

“…The most striking difference lies in the origin of the musculus mandibulohyoideus 2. Whereas this muscle originates tendinously at the jaw symphysis in iguanians (Avery and Tanner, 1971;Smith, 1988;Delheusy et al, 1994;Herrel et al, 1998;Meyers and Nishikawa 2000;Meyers et al, 2002) and derived lizards such as helodermatids and varanids (McDowell, 1972;Smith, 1986), it does not originate at the mandibular symphysis in lacertid lizards. Rather, it originates at the mesial side of the mandible, about one-third down its length away from the symphysis (Fig.…”

Quantitative analysis of the effect of prey properties on feeding kinematics in two species of lizards

“…Pogona and Tiliqua are both generalized omnivores that include a variety of plant and animal materials in their natural diet (Kennerson and Cochrane, 1981;Greer, 1989;MacMillen et al, 1989;Dubas and Bull, 1991;Houston, 1998;Hauschild et al, 2000). Similarity in body size (snout-vent length) between all individuals also contributed to choice of species in order to eliminate the potential confounding effects of size on feeding kinematics (Richard and Wainwright, 1995;Wainwright and Shaw, 1999;Hernández, 2000;Meyers et al, 2002;Robinson and Motta, 2002;Van Wassenbergh et al, 2005). Animals were purchased through commercial dealers and housed in terrariums located at the Laboratory for Functional Morphology in the Department of Biology, University of Antwerp, Belgium.…”

Prey snapping and visual distance estimation in Texas horned lizards, Phrynosoma cornutum

“…By contrast, horned lizards do not jump, have shorter tongues than chameleons and do not shoot their tongue out of the mouth in the ballistic manner of a chameleon (Sherbrooke, 2003). The body of the tongue in all members of the Iguanidae remains on the entoglossal process during the tongue strike (Meyers and Nishikawa, 2000). The direction of the tongue snap can thus be changed during the strike by turns of the head.…”

“…The kinematics of the tongue strike was investigated together with the muscular activity of the hyolingual apparatus in several iguanian species using slow-motion video recording (Herrel et al, 1996;Meyers and Nishikawa, 2000). The present paper investigates aspects of the sensorimotor activity of a preysnapping lizard, the Texas horned lizard (Phrynosoma cornutum).…”