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Animals must perform a huge range of behaviors to survive, but have only a single set of muscles to control those behaviors. How does muscle recruitment change among behaviors to allow the same set of structures to perform a variety of tasks? We have compared limb muscle activity (EMG) across sprawling versus upright limb posture in alligators (Reilly and Blob 2003), and between swimming and walking in turtles (Gillis and Blob 2001; Blob et al. 2008; Rivera and Blob 2010). We found that changes in activity are restricted to specific subsets of muscles, but often not those predicted from differences in mechanical demands between behaviors. In collaboration with Jeanette Wyneken (Florida Atlantic University), PhD student Angie Rivera led comparisons of forelimb motor patterns between swimming freshwater turtles and sea turtles, testing the ‘neuromotor conservation hypothesis’ that the evolution of novel structures (such as the flipper-shaped sea turtle forelimb) need not be accompanied by divergence in the motor patterns of muscles that control those structures (Rivera et al. 2011; Rivera and Blob 2013).
Current directions
• PhD student Christopher Mayerl is extending comparisons within turtles to species to test if the novel attachments of pelvic muscles in pleurodiran turtles are correlated with novel motor patterns compared to cryptodires.
• Recent studies of terrestrial locomotion in turtles with Heiko Schoenfuss from St. Cloud State (Schoenfuss et al. 2010) and Mike Butcher (Youngstown State) and Brett Aiello (University of Chicago) (Aiello et al. 2013) are examining the implications of muscle function for loading of the limb skeleton.
• With PhD graduate Takashi Maie and Heiko Schoenfuss' lab, we are conducting a range of muscle fiber typing and simulation analyses of the feeding and locomotor muscles of Hawaiian gobiid fishes with different feeding preferences and degrees of climbing ability. (Cediel et al. 2008, Maie et al. 2009, Maie et al 2011, Maie et al. 2013).
Related publications
Aiello, B. R., R. W. Blob, M. T. Butcher. 2013. Correlation of muscle function and bone strain in the hindlimb of the river cooter turtle (Pseudemys concinna). Journal of Morphology 274:1060-1069. Available HERE
Blob, R. W., A. R. V. Rivera, M. W. Westneat. 2008. Hindlimb function in turtle locomotion: limb movements and muscular activation across taxa, environment, and ontogeny. Chapter 6 in J. Wyneken, M. H. Godfrey, and V. Bels, (eds.), Biology of Turtles, CRC Press, pp. 139-162. Available HERE
Cediel, R. A., R. W. Blob, G. D. Schrank, R. Plourde, and H. L. Schoenfuss. 2008. Muscle fiber type distribution in climbing Hawaiian gobioid fishes: ontogeny and correlations with locomotor performance. Zoology (Jena) 111: 114-122. Available HERE
Gillis, G. B. and R. W. Blob. 2001. How muscles accommodate movement in different physical environments: aquatic versus terrestrial locomotion. Comparative Biochemistry and Physiology A 131: 61-75. Available HERE
Maie, T., H. L. Schoenfuss, R. W. Blob. 2013. Musculoskeletal determinants of pelvic sucker function in Hawaiian stream gobiid fishes: interspecific comparisons and allometric scaling. Journal of Morphology 733-742. Available HERE
Maie, T., A. B. Meister, G. L. Leonard, G. D. Schrank, R. W. Blob, H. L. Schoenfuss. 2011. Jaw muscle fiber type distribution in Hawaiian gobioid stream fishes: histochemical correlations with feeding ecology and behavior. Zoology (Jena) 114:340-347. Available HERE
Maie, T., H. L. Schoenfuss, R. W. Blob. 2009. Jaw lever analysis of Hawaiian gobioid stream fishes: a simulation study of morphological diversity and functional performance. Journal of Morphology 270: 976-983. Available HERE
Reilly, S. M. and R. W. Blob. 2003. Motor control of locomotor hindlimb posture in the American alligator (Alligator mississippiensis). Journal of Experimental Biology 206: 4327-4340. Available HERE
Rivera, A. R. V., R. W. Blob. 2010. Forelimb kinematics and motor patterns of the slider turtle (Trachemys scripta) during swimming and walking: shared and novel strategies for meeting locomotor demands of water and land. Journal of Experimental Biology 213: 3515-3528. Available HERE
Rivera, A. R. V., J. Wyneken, R. W. Blob. 2011. Forelimb kinematics and motor patterns of swimming loggerhead sea turtles (Caretta caretta): are motor patterns conserved in the evolution of new locomotor strategies? Journal of Experimental Biology 214: 3314-3323. Available HERE
Schoenfuss, H. L., J. D. Roos, A. R. V. Rivera, R. W. Blob. 2010. Motor patterns of distal hind limb muscles in walking turtles: implications for models of limb bone loading. Journal of Morphology 271: 1527-1536. Available HERE
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