Meeting Abstract
P1.73 Saturday, Jan. 4 15:30 Species Differences in the Restructuring of Syringeal Muscles After Denervation SPAINHOWER, K.B.*; MILLIGAN, C.A.; CHRISTENSEN, L.A.; GOLLER, F.; MEYERS, R.A.; Weber State University, Ogden, UT; Weber State University, Ogden, UT; Weber State University, Ogden, UT; University of Utah; Weber State University, Ogden, UT rmeyers@weber.edu
The muscles of the avian vocal organ, the syrinx, are composed of fast and superfast muscle fibers, which enables them to rapidly control song features. Unilateral denervation of the syrinx results in the reduction of cross-sectional area and a shift to slower fiber types. Our previous denervation experiments on male Zebra Finches (Taeniopygia guttata) showed a 10% reduction of total muscle cross-sectional area and a 30% reduction of superfast fibers seven days after unilateral denervation of the syrinx. Decrease in cross-sectional area and superfast fiber percentage reached a maximum at eleven days at 72% and 70% of their original values. By 40 days, the cross-sectional area and fiber percentage of the denervated side had almost returned to their original values. Because this post-denervation recovery is unusually rapid in Zebra Finches, we repeated the experiment on male Yellow-headed Blackbirds (X. xanthocephalus) for comparison. Four birds were unilaterally denervated between three and 35 days. We quantified the cross-sectional area and the average fiber diameter for each bird, and the results differed greatly from those of the Zebra Finch experiments. By day seven, blackbird cross-sectional area was reduced to 85% of its original value, average diameter of both fiber types decreased, and each continued to decrease post-denervation. In contrast to the finches, cross-sectional area of the blackbird denervated syrinx was reduced to 40% of control by day 17. Results from the Yellow-headed Blackbirds are consistent with the results from work done on mammals and suggest that innervation of the syrinx in Zebra Finches may be unusual. Further studies will repeat the experiment at additional time intervals and increased sample size.
