Meeting Abstract

50.6  Thursday, Jan. 6  Forelimb muscle architecture of the American badger (Taxidea taxus) and groundhog (Marmota monax). MOORE, A.L.*; BUTCHER, M.T.; Youngstown State Univ. almoore@student.ysu.edu

The arrangement and orientation of muscle fibers reflect functional specializations of muscle. Relating muscle architecture with function is fundamental to understanding the roles of limb muscles. Limb muscles are often studied for their properties related to locomotion, but studies of architectural properties in limb muscles of animals specialized for other behaviors, such as digging, are far less common. This study quantified muscle architectural properties in the forelimbs of two digging taxa, badgers (Taxidea taxus) and groundhogs (Marmota monax), and estimated maximum force production and power output of their major forelimb muscles. Badgers and groundhogs belong to different clades (Carnivora vs. Rodentia), yet both species display fossorial specializations including robust forelimbs and foreclaws, and both employ the scratch mode of digging. Architectural properties quantified included: muscle mass, belly length, volume, physiological cross-sectional area (PCSA), fascicle length and fiber pennation angle. Both species showed massive elbow extensors and digital flexors that together accounted for over 60% of total forelimb muscle mass. The elbow extensors displayed a low degree of pennation with longer fascicles, an architecture consistent with shortening capability and high power. The digital flexors showed relatively greater pennation and shorter fascicle lengths in addition to compartmentalization among the muscle heads for both force production and range of contraction. These findings suggest both the elbow extensors and digital flexor muscles in badgers and groundhogs have the capacity for high force production during scratch-digging, while the elbow extensors are better suited for high power generation for rapid digging movements. URC #3-11.