The larynx and trachea of the barking gecko, Ptenopus garrulus maculatus (Reptilia: Gekkonidae) and their relation to vocalization

Abstract

Since its discovery by science almost 150 years ago, Ptenopus garrulus has been recognized as a highly vocal gekkonid. While this ability has been the subject of ecological and ethological investigations, and while its call has been sonographically analysed, the means of sound production has remained uninvestigated. This has been partly due to a lack of context in which to place morphological investigations of the gekkonid vocal apparatus. In recent years greater attention has been paid to the functional morphology of this system, and its form in Ptenopus can now be evaluated in a comparative light. Herein we document the morphology of the larynx and trachea by way of dissection, histological investigation, computer-assisted three-dimensional reconstruction, and scanning electron microscopy. These investigations reveal a highly unusual structure of the laryngeal skeleton: the cricoid cartilage is a flattened plate of cartilage; the trachea is highly folded and inserted deeply into the larynx; the laryngeal constrictor muscle is asymmetrical in males; the vocal cords are horizontally disposed; the laryngeal aditus is also horizontal and is placed much more anteriorly than in any other geckos for which this relationship is known. Ptenopus garrulus maculatus exhibits the most anuran-like vocal apparatus yet discovered in gekkonids.