Revisiting the feeding anatomy of the semi-aquatic lizard Dracaena guianensis Daudin, 1801 (Reptilia, Sauria) from the Western Brazilian Amazon

Abstract

Introduction: There are about 842 reptile species known in Brazil, including 799 Squamata, being the most diverse assemblage, comprising 72 amphisbaenians, 276 lizards, and 405 snakes. Lizards have adapted to different habitats with terrestrial, fossorial, arboreal, and semi-aquatic habits. These ecological differences are reflected in skull morphology, with structures that evolved following their dietary specificity. Teiid lizard Dracaena guianensis Daudin, 1801 inhabits swamps and spends most of its time on low trees, though feeding only occurs in water. Its feeding habits are different from other family members, and its diet is mostly composed of mollusks and crustaceans. Herein, the anatomy of feeding apparatus of D. guianensis population from the Western Brazilian Amazon was dissected and documented in four exemplars for the first time. As result, it presents a dorsoventrally compressed neurocranium, dorsally oriented orbits, and heterodont dentition. Those characteristics were different from the most family members, as observed in comparisons with Ameiva ameiva (Linnaeus, 1758), which presents lateral orbits, a cranium not compressed dorsoventrally, and homodont dentition. Furthermore, in D. guianensis, it was possible to verify that muscles related to food apprehension were extremely developed, such as adductors and hyolingual muscles, which increase bite force according to the force versus cutting area in cross section; while in A. ameiva the muscles presented smaller cross sectional area and consequently, less bite force. The correlation between the anatomy of feeding apparatus and stomach contents allowed a preliminary comparison of osteological and myological characteristics to its food habits, suggesting that heterodont condition was a selective pressure directly related to durophagy.