Fiber type composition of epaxial muscles is geared toward facilitating rapid spinal extension in the leaper Galago senegalensis.

Conference Paper

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.

Full Text

Duke Authors

Cited Authors

  • Huq, E; Taylor, AB; Su, Z; Wall, CE

Published Date

  • May 2018

Published In

Volume / Issue

  • 166 / 1

Start / End Page

  • 95 - 106

PubMed ID

  • 29318571

Pubmed Central ID

  • PMC5910278

Electronic International Standard Serial Number (EISSN)

  • 1096-8644

Digital Object Identifier (DOI)

  • 10.1002/ajpa.23405

Conference Location

  • United States