Meeting Abstract
P1.203 Saturday, Jan. 4 15:30 Lack of Song in Females Does Not Drive Sexual Dimorphism in Syringeal Muscle Composition CHRISTENSEN, L.A.*; MEYERS, R.A.; GOLLER, F.; Weber State University, Ogden, UT; Weber State University, Ogden, UT; University of Utah rmeyers@weber.edu
The avian syrinx uses four pairs of intrinsic muscles to control song production. Previous work in our lab using immunohistochemistry revealed two fiber types, fast and superfast. Superfast fibers are rare fibers found in sound-producing animals and contract up to 250 Hz in songbirds. We studied songbird species from different families to understand the role of superfast fibers in singing. Male songbirds typically sing more complex songs than females, who may sing occasionally or not at all. In species where males sing and females sing at least occasionally (European Starlings, Sturnus vulgaris; White-crowned Sparrows, Zonotrichia leucophrys; House Sparrows, Passer domesticus; Red-winged Blackbirds, Agelaius phoeniceus; Yellow-headed Blackbirds, X. xanthocephalus), both sexes had similar composition with superfast fibers outnumbering fast. In two Estrildids where males sing and females do not (Zebra Finches, Taeniopygia guttata; Bengalese Finches, Lonchura domestica), males possess a greater percentage of superfast fibers than females (80% in males, 25% in females). This difference in fiber percentage supports the hypothesis that superfast fibers are important in singing. However, two other species with sexually dimorphic singing behavior (Brewer’s Sparrows, Spizella breweri; Brown-headed Cowbirds, Molothrus ater), had superfast fibers outnumbering fast in both males and females. These findings suggest that singing does not account for the occurrence of superfast fibers in the syrinx and the presence of these fibers is likely a taxonomic factor. Our lab is currently investigating other Estrildids to test that hypothesis. Further investigation is needed to determine if superfast fibers are necessary for other non-singing functions.
