Myosin Isoform Fiber Type and Fiber Size in the Tail of the Virginia Opossum (Didelphis virginiana)
Article first published online: 14 NOV 2012
Copyright © 2012 Wiley Periodicals, Inc.
The Anatomical Record
Volume 296, Issue 1, pages 96–107, January 2013
How to Cite
Hazimihalis, P.J., Gorvet, M.A. and Butcher, M.T. (2013), Myosin Isoform Fiber Type and Fiber Size in the Tail of the Virginia Opossum (Didelphis virginiana). Anat Rec, 296: 96–107. doi: 10.1002/ar.22614
- Issue published online: 15 DEC 2012
- Article first published online: 14 NOV 2012
- Manuscript Accepted: 17 AUG 2012
- Manuscript Revised: 29 MAY 2012
- Manuscript Received: 12 DEC 2011
- University Research Council (URC). Grant Number: #01-10
- Youngstown State University
Muscle fiber type is a well studied property in limb muscles, however, much less is understood about myosin heavy chain (MHC) isoform expression in caudal muscles of mammalian tails. Didelphid marsupials are an interesting lineage in this context as all species have prehensile tails, but show a range of tail-function depending on either their arboreal or terrestrial locomotor habits. Differences in prehensility suggest that MHC isoform fiber types may also be different, in that terrestrial opossums may have a large distribution of oxidative fibers for object carrying tasks instead of faster, glycolytic fiber types expected in mammals with long tails. To test this hypothesis, MHC isoform fiber type and their regional distribution (proximal/transitional/distal) were determined in the tail of the Virginia opossum (Didelphis virginiana). Fiber types were determined by a combination of myosin-ATPase histochemistry, immunohistochemistry, and SDS-PAGE. Results indicate a predominance of the fast MHC-2A and -2X isoforms in each region of the tail. The presence of two fast isoforms, in addition to the slow MHC-1 isoform, was confirmed by SDS-PAGE analysis. The overall MHC isoform fiber type distribution for the tail was: 25% MHC-1, 71% MHC-2A/X hybrid, and 4% MHC-1/2A hybrid. Oxidative MHC-2A/X isoform fibers were found to be relatively large in cross-section compared to slow, oxidative MHC-1 and MHC-1/2A hybrid fibers. A large percentage of fast MHC-2A/X hybrids fibers may be suggestive of an evolutionary transition in MHC isoform distribution (fast-to-slow fiber type) in the tail musculature of an opossum with primarily a terrestrial locomotor habit and adaptive tail-function. Anat Rec, 2013. © 2012 Wiley Periodicals, Inc.