Hind Foot Drumming: Muscle Architecture of the Hind Limb in Three Bathyergidae Species

Abstract

The relationship between muscle architectural properties and hind foot drumming of African mole-rats has yet to be determined using established methodology. Therefore, the internal structure of 32 hind limb muscles was evaluated in two drumming and one non-drumming species of Bathyergidae. The muscle mass (MM), fascicle length (Lf), and angle of pennation were measured to calculate the physiological cross-sectional area (PCSA) as well as estimate the maximum isometric force of contraction (Fmax). The most significant differences for the various muscle architecture parameters analyzed in synergistic muscle groups and individual muscles were observed between the rapid drumming Georychus capensis and the non-drumming Cryptomys hottentotus natalensis. The PCSA values of the hip extensors, hip adductors, knee extensors, and knee flexors of G. capensis were significantly larger than that of C. h. natalensis. Additionally, the hip extensors and knee flexors of both the drumming species (G. capensis and Bathyergus suillus) were shown to be capable of higher power output compared to the non-drumming species, and the hip adductors of G. capensis capable of faster contraction. M. gracilis anticus may play a key role in facilitating hind foot drumming as it was the only muscle to be significantly different in G. capensis and C. h. natalensis for all three muscle architecture parameters analyzed. Furthermore, it features in the high shortening capacity quadrant of the functional space plot of both G. capensis and B. suillus but not the non-drumming C. h. natalensis.