Anatomy and histochemistry of hindlimb flight posture in birds. I. The extended hindlimb posture of shorebirds

Abstract

Birds utilize one of two hindlimb postures during flight: an extended posture (with the hip and knee joints flexed, while the ankle joint is extended caudally) or a flexed posture (with the hip, knee, and ankle joints flexed beneath the body). American Avocets (Recurvirostra americana) and Black-necked Stilts (Himantopus mexicanus) extend their legs caudally during flight and support them for extended periods. Slow tonic and slow twitch muscle fibers are typically found in muscles functioning in postural support due to the fatigue resistance of these fibers. We hypothesized that a set of small muscles composed of high percentages of slow fibers and thus dedicated to postural support would function in securing the legs in the extended posture during flight. This study examined the anatomy and histochemical profile of eleven hindlimb muscles to gain insight into their functional roles during flight. Contrary to our hypothesis, all muscles possessed both fast twitch and slow twitch or slow tonic fibers. We believe this finding is due to the versatility of dynamic and postural functions the leg muscles must facilitate, including standing, walking, running, swimming, and hindlimb support during flight. Whether birds use an extended or flexed hindlimb flight posture may be related to the aerodynamic effect of leg position or may reflect evolutionary history.

Is sexual dimorphism in singing behavior related to syringeal muscle composition?

“…diameter ¼ 21 lm). Thus, superfast fibers seem to be within the normal range of avian fast fibers (see Kaplan and Goslow 1989), whereas the fast fibers of syringeal muscles are smaller than those found in avian leg muscles (see Suzuki andTamate 1979, McFarland andMeyers 2008), though comparative data are minimal. Interestingly, the superfast fibers, which contract at rates reaching 250 Hz, are, in some cases, double the size of fast fibers.…”

“…Muscle fiber types were identified using a series of histochemical techniques described in McFarland and Meyers (2008) and Uchida et al (2010). Serial sections were reacted for myosin ATPase using acidic (pH 4.2-4.3) pre-incubations.…”

Age-related changes in the Bengalese finch song motor program

“…Fiber types were characterized following protocols described elsewhere (McFarland and Meyers, 2008). We then compared the fiber type composition of m. scalenus , an inspiratory muscle, and syringeal muscles.…”

Fibre architecture and song activation rates of syringeal muscles are not lateralized in the European starling

“…Following a previously used protocol (McFarland and Meyers, 2008), muscle sections were reacted for myosin ATPase using pH4.2-4.3 (acidic) or pH10.2-10.4 (alkaline) pre-incubations. Staining procedures with antifast antibody MY32 (Sigma Chemical Co., St Louis, MO, USA) and antislow antibody ALD58 (University of Iowa, Hybridoma Bank) were as previously described (Meyers and Stakebake, 2005).…”