title: Morphology and fibre-type distribution in the tongue of the Pogona vitticeps lizard (Iguania, Agamidae).
abstract: Agamid lizards use tongue prehension for capturing all types of prey. The purpose of this study was to investigate the functional relationship between tongue structure, both surface and musculature, and function during prey capture in Pogona vitticeps. The lack of a detailed description of the distribution of fibre-types in the tongue muscles in some iguanian lizards has hindered the understanding of the functional morphology of the lizard tongue. Three methodological approaches were used to fill this gap. First, morphological analyses were performed (i) on the tongue surface through scanning electron microscopy, and (ii) on the lingual muscle by histological coloration and histochemistry to identify fibre-typing. Secondly, kinematics of prey capture was quantified by using high-speed video recordings to determine the movement capabilities of the tongue. Finally, electromyography (EMG) was used to identify the motor pattern tongue muscles during prey capture. Morphological and functional data were combined to discuss the functional morphology of the tongue in agamid lizards, in relation to their diet. During tongue protraction, M. genioglossus contracts 420 ± 96 ms before tongue-prey contact. Subsequently, Mm. verticalis and hyoglossus contract throughout tongue protraction and retraction. Significant differences are found between the timing of activity of the protractor muscles between omnivorous agamids (Pogona sp., this study) and insectivorous species (Agama sp.), despite similar tongue and jaw kinematics. The data confirm that specialisation toward a diet which includes more vegetal materials is associated with significant changes in tongue morphology and function. Histoenzymology demonstrates that protractor and retractor muscles differ in fibre composition. The proportion of fast glycolytic fibres is significantly higher in the M. hyoglossus (retractor muscle) than in the M. genioglossus (protractor muscle), and this difference is proposed to be associated with differences in the velocity of tongue protrusion and retraction (5 ± 5 and 40 ± 13 cm s(-1) , respectively), similar to Chamaeleonidae. This study provides a way to compare fibre-types and composition in all iguanian and scleroglossan lizards that use tongue prehension to catch prey.
authors.affiliation: Laboratory of Histology, Faculty of Medicine and Pharmacy, Institute of BioSciences, University of Mons, Mons, Belgium.
authors.forename: Leïla-Nastasia
authors.initials: LN
authors.lastname: Zghikh
authors.forename: Emilie
authors.initials: E
authors.lastname: Vangysel
authors.forename: Denis
authors.initials: D
authors.lastname: Nonclercq
authors.forename: Alexandre
authors.initials: A
authors.lastname: Legrand
authors.forename: Bernard
authors.initials: B
authors.lastname: Blairon
authors.forename: Cécile
authors.initials: C
authors.lastname: Berri
authors.forename: Thierry
authors.initials: T
authors.lastname: Bordeau
authors.forename: Christophe
authors.initials: C
authors.lastname: Rémy
authors.forename: Carmen
authors.initials: C
authors.lastname: Burtéa
authors.forename: Stéphane J
authors.initials: SJ
authors.lastname: Montuelle
authors.forename: Vincent
authors.initials: V
authors.lastname: Bels
mesh_terms: D000818:Animals; D004576:Electromyography; D005247:Feeding Behavior / Q000502:physiology*; D008116:Lizards / Q000033:anatomy & histology* / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008855:Microscopy, Electron, Scanning; D018485:Muscle Fibers, Skeletal / Q000166:cytology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology; D011235:Predatory Behavior / Q000502:physiology*; D014059:Tongue / Q000033:anatomy & histology* / Q000502:physiology / Q000648:ultrastructure; D014741:Video Recording
keywords: Agamidae; capture; electromyography; fibre typing; muscle; tongue
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