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Fiber type composition of epaxial muscles is geared toward facilitating rapid spinal extension in the leaper Galago senegalensis
American Journal of Physical Anthropology (2018)
  • Emranul Huq, Philadelphia College of Osteopathic Medicine
  • Andrea B Taylor
  • Zuowei Su
  • Christine E Wall
Abstract
Objectives: We hypothesized that the vertical leaper Galago senegalensis will have epaxial extensor muscles with a fast fiber phenotype to facilitate rapid spinal extension during leaping in comparison to the slow-moving quadruped Nycticebus coucang. To test this, we determined the percentage of fiber cross-sectional area (%CSA) devoted to Type 2 fibers in epaxial muscles of G. senegalensis compared to those of N. coucang.
Materials and methods: Immunohistochemistry was used to identify Type 1, Type 2, and hybrid fibers in iliocostalis, longissimus, and multifidus muscles of G. senegalensis (n = 3) and N. coucang (n = 3). Serial muscle sections were used to estimate and compare proportions, cross-sectional areas (CSAs), and %CSAs of Type 1, Type 2, and hybrid fibers between species.
Results: Epaxial muscles of G. senegalensis were comprised predominantly of Type 2 fibers with large CSAs (%CSA range ≈ 83-94%; range of mean CSA = 1,218-1,586 μm2 ). N. coucang epaxial muscles were comprised predominantly Type 1 fibers with large CSAs (%CSA range ≈ 69-77%; range of mean CSA = 983-1,220 μm2 ).
Discussion: The predominance of Type 2 fibers in G. senegalensis epaxial muscles facilitates rapid muscle excursion and spinal extension during leaping, and is consistent with their relatively long muscle fibers. The predominance of Type 1 fibers in N. coucang epaxial muscles may aid in maintaining stable postures during bridging and cantilevering behaviors characteristic of slow-climbing. These histochemical characteristics highlight the major divergent locomotor repertoires of G. senegalensis and N. coucang.
Keywords
  • Galago senegalensis,
  • Nycticebus coucang,
  • histochemistry,
  • spinal extensor muscle
Publication Date
May, 2018
DOI
https://doi.org/10.1002/ajpa.23405
Citation Information
Emranul Huq, Andrea B Taylor, Zuowei Su and Christine E Wall. "Fiber type composition of epaxial muscles is geared toward facilitating rapid spinal extension in the leaper Galago senegalensis" American Journal of Physical Anthropology Vol. 166 Iss. 1 (2018) p. 95 - 106
Available at: http://works.bepress.com/emranul-huq/1/