Neuromuscular control of the calling apparatus in the túngara frog (Engystomops pustulosus)
Poster Number
15
Introduction/Abstract
Most frogs produce simple, repetitive mating calls but male túngara frogs have a complex “whine-chuck” mating call. The whine is a frequency sweep that is used for species recognition, while the chuck is a repeated pulse that enhances the call’s attractiveness to females. The mechanism behind the facultative second component of the call, the “chuck” involves vibrating a pair of laryngeal fibrous masses that are attached to the vocal cords. The muscular control of this mechanism has not yet been explained, however. Previous studies in our lab have produced anatomical and electrophysiological evidence that the deep dilator muscle could be responsible for positioning the fibrous masses for chuck production.
Purpose
It was previously known that the larynx contained three constrictor muscles, and one dilator muscle. However, recent studies in our lab have revealed that the dilator muscle, the muscle involved in opening the larynx, is actually formed by two muscles: the deep dilator muscle and the superficial dilator muscle. The deep dilator is a novel muscle with unique attachments, innervation and likely function. The goal of this study is to evaluate the mechanical effects of contraction of each of the laryngeal muscles in isolation or combined with others, to elucidate the control of laryngeal function, including the production of the chucks.
Method
The five muscles of the larynx allowed us to stimulate them in 32 combinations with at least 3-5 repeats of each. We used suction glass electrodes to stimulate the branches of the laryngeal nerves of excised larynges. In each trial, we employed pulse or train stimuli at two currents and identified any differences in the movement of the larynx.
Results
Our results confirm that contraction of the deep dilator muscle is required and sufficient to move the fibrous masses. On the contrary, there is no movement of the fibrous mass in any combination without the deep dilator muscle. Shortening of the superficial dilator opens the arytenoid cartilages due to the origin and insertion points at the posteromedial process of the hyoid and the medial attachments to the apical cartilage. Shortening of the external constrictor causes the muscles to pull away from the hyoid plate. Quantitatively, the movement of the anterior and posterior constrictor are very small in comparison to the other three muscles.
Significance
The current model of vocalization in frogs does not explain the production of the chuck and does not consider the existence of the deep dilator muscle. Our lab is currently describing the new muscle and the current study shows that it can control the production of the chuck. These data will shed new light on our understanding of the mechanisms behind the evolution of signal complexity in animal communication systems.
Location
DUC Ballroom A&B
Format
Poster Presentation
Poster Session
Morning
Neuromuscular control of the calling apparatus in the túngara frog (Engystomops pustulosus)
DUC Ballroom A&B
Most frogs produce simple, repetitive mating calls but male túngara frogs have a complex “whine-chuck” mating call. The whine is a frequency sweep that is used for species recognition, while the chuck is a repeated pulse that enhances the call’s attractiveness to females. The mechanism behind the facultative second component of the call, the “chuck” involves vibrating a pair of laryngeal fibrous masses that are attached to the vocal cords. The muscular control of this mechanism has not yet been explained, however. Previous studies in our lab have produced anatomical and electrophysiological evidence that the deep dilator muscle could be responsible for positioning the fibrous masses for chuck production.
