Meeting Abstract
P2.68 Jan. 5 Structure and Function of Syringeal Muscles in European Starlings UCHIDA, A.M.*; LEMMON, K.; MCFARLAND, J.C.; COOPER, B.G.; GOLLER, F.; MEYERS, R.A.; Weber State University, Ogden, UT; Weber State University, Ogden, UT; Weber State University, Ogden, UT; University of Utah, Salt Lake City, UT; University of Utah, Salt Lake City, UT; Weber State University, Ogden, UT rmeyers@weber.edu
The avian vocal organ, the syrinx, is a complex organ with 4 pairs of intrinsic muscles (ventral and dorsal tracheobronchialis, vTB/dTB; ventral and dorsal syringealis, vS/dS). EMG recordings from these muscles in singing European Starlings (Sturnus vulgaris) showed activity bursts that correlate with amplitude modulation rates of up to 170 Hz, suggesting that these muscles directly control airflow gating and acoustic parameters at such high rates. Myosin ATPase and immunohistochemistry were used to characterize and quantify muscle fiber type composition and individual fiber diameters. A small fiber type (mean diam 14-20 �m for the 4 muscles) comprised roughly 30% of the muscles and reacted like fast oxidative (type IIa) fibers with ATPase and antifast antibody reactions. A larger fiber type (mean diam 31-38 �m for the 4 muscles) comprised about 70% of the muscles and had intermediate reactions to both acidic and alkaline preincubations and lower oxidative capacity. It reacted negatively to both antislow and antifast antibodies. The unusual staining profile and EMG data support the view that these fibers are possess superfast myosin, as described for rattlesnake tailshaker muscles. Nitric acid digestion, used to measure fiber lengths, revealed fibers 3-4 mm long, spanning the length of vS and dS, but only half the length of vTB and dTB. The latter muscles consisted of two-fiber units arranged serially. Similar patterns of fiber types and sizes were also found in species from 3 other songbird families, indicating that the presence of superfast fibers is likely a common trait of the oscine syrinx. Supported by NIH grant # DC004390 and WSU.
