Meeting Abstract

17.3  Tuesday, Jan. 4  Connective tissue design, sonic tissue vibration and sound production in songbirds RIEDE, T.*; GOLLER, F.; Uni. of Utah, Salt Lake City; Uni. of Utah, Salt Lake City t.riede@utah.edu

In songbirds, two independent sound sources in the syrinx are used to produce sound. Laterally positioned labia are set into vibration by a passing airflow. The biomechanical properties of the labia determine the oscillation rate (fundamental frequency) and sound amplitude. Labia are in large part composed of connective tissue, which contains a rich extracellular matrix (ECM) that underpins tissue viscoelasticity. The abundance and distribution of proteins and glycans within this ECM support the biomechanical performance of the labia during phonation. In order to relate the microstructure of the labia to their acoustic function, we investigated labial design in three songbird species with different acoustic characteristics of their vocal repertoires. Histological serial sections of the syrinx and different staining techniques were used to identify collagen, elastin and hyaluronan. The distribution and orientation of elastic and collagen fibers indicates that labia in starlings and white-crowned sparrows are multi-layered structures, whereas they are more uniformly structured in the zebra finch. The ECM of labia demonstrates clearly a species-specific structure. The layer structure in starlings and white-crowned sparrows differs in collagen/elastin ratios and fiber orientation and likely reflects the different ranges of fundamental frequencies in song syllables. It is unknown whether labial composition is altered dynamically with differential use of the labia. To investigate this, we denervated syringeal muscles which results in striking changes to the acoustic properties of the generated sound. Time-dependent alterations in labial morphology were observed and included changes in labia size and alterations in abundance and distribution of proteins and glycans.