Meeting Abstract

42.5  Jan. 6  Anatomy and Histochemistry of Golden Eagle Flight Muscles MEYERS, R.A.*; MCFARLAND, J.C.; Weber State University, Ogden, UT; Weber State University, Ogden, UT rmeyers@weber.edu

Previous research in our laboratory and elsewhere has show that soaring birds such as albatrosses, vultures and pelicans possess a slow-contracting deep layer to the pectoralis that is presumed to function during sustained periods of gliding and soaring flight. Albatrosses even possess a collagenous �shoulder lock� to further reduce energy expenditure during soaring. As part of our ongoing study of avian posture, we examined the flight musculature of Golden and Bald Eagles (Aquila chrysaetos and Halieeatus leucocephalus) and used immunohistochemistry to test for the presence morphological specializations and slow muscle fibers suitable for soaring in these species. Contrary to our expectations, both species lacked a deep layer to the pectoralis, and had pectoralis muscles typical for raptors, though much larger. In addition, there were no significant numbers of slow muscle fibers; most muscles that have been found to be soaring-specialized in other birds (e.g., M. coracobrachialis cranialis, cranial border and deep region of M. pectoralis) lacked any slow fibers or had very small, functionally-insignificant fiber populations (~25). It is unknown if fast fibers perform the soaring role in these birds, as has been suggested for gulls, or if the collagenous fascia of the pectoralis may aid in wing support, as in albatrosses. This lack of slow fibers in the flight muscles of eagles may represent a functional or phylogenetic constraint. Supported by NIH grant # DC004390.