Aquatic locomotion in turtles

Turtles are often viewed as an evolutionarily conservative lineage because all species have a rigid, bony shell. However, turtles show tremendous diversity in shell and limb shape; they also live in diverse habitats, ranging from fully aquatic (like softshell turtles) to fully terrestrial (like tortoises). These features make turtles an ideal group for studies of correlations between morphological and functional evolution in a phylogenetic context. My lab has a strong emphasis on comparative studies of aquatic locomotion in turtles, including comparisons of limb kinematics and muscle function across habitat specialists and generalists (Gillis and Blob 2001; Pace et al. 2001; Blob et al. 2008; Rivera and Blob 2010; Rivera et al. 2011; Rivera et al. 2013; Rivera and Blob 2013), studies of aquatic walking (Willey and Blob 2004), and (led by former PhD student Gabriel Rivera) comparisons of aquatic stability and maneuverability across species with different shell shapes (Rivera et al. 2006; Dougherty et al. 2010; Rivera et al. 2011).

Current directions

• Flow visualization to compare thrust production between turtle forelimbs and hindlimbs during swimming (with George Lauder, Harvard).

• PhD student Vanessa Young is leading comparisons of limb bone loading between swimming and walking in turtles to evaluate implications for the evolution of limb bone flattening in secondarily aquatic vertebrates (Young and Blob 2015).

• PhD student Christopher Mayerl is leading work to test for differences in locomotor performance between pleurodire and cryptodire turtles that relate to differences in the fusion of the pelvis to the shell.

Related publications

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

Blob, R. W., G. Rivera. 2008. Going with the flow: ecomorphological variation across aquatic flow regimes: an introduction to the symposium. Integrative and Comparative Biology 48: 699-701. Available HERE

Dougherty, E. E., G. Rivera, R. W. Blob, J. Wyneken. 2010. A comparison of stability in swimming loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtle posthatchlings. Zoology (Jena) 113: 158-167. 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

Gosnell, J. S., G. Rivera, R. W. Blob. 2009. A phylogenetic analysis of sexual size dimorphism in turtles. Herpetologica 65: 70-81. Available HERE

Pace, C. M., R. W. Blob, and M. W. Westneat. 2001. Comparative kinematics of the forelimb during swimming in red-eared slider (Trachemys scripta) and spiny softshell (Apalone spinifera) turtles. Journal of Experimental Biology 202: 3261-3271. 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

Rivera, A. R. V., G. Rivera, R. W. Blob. 2013. Forelimb kinematics during swimming in the pig-nosed turtle, Carettochelys insculpta, compared with other turtle taxa: rowing versus flapping, convergence versus intermediacy. Journal of Experimental Biology 216:668-680. Available HERE

Rivera, A. R. V., R. W. Blob. 2013. Forelimb muscle function in pig-nosed turtles, Carettochelys insculpta: testing neuromotor conservation between rowing and flapping in swimming turtles. Biology Letters 9:20130471. http://dx.doi.org/10.1098/rsbl.2013.0471. Available HERE

Rivera, G., A. R. V. Rivera, R. W. Blob. 2011. Hydrodynamic stability of the painted turtle (Chrysemys picta): effects of four-limbed rowing versus forelimb flapping in rigid-bodied tetrapods. Journal of Experimental Biology 214: 1153-1162. Available HERE

Rivera, G., Rivera, A. R. V., Dougherty, E. E., Blob, R. W. 2006. Aquatic turning performance of painted turtles (Chrysemys picta) and functional consequences of a rigid body design. Journal of Experimental Biology 209: 4203-4213. Available HERE

Willey, J. S. and R. W. Blob. 2004. Tail kinematics of juvenile common snapping turtles during aquatic walking. Journal of Herpetology 38: 360-369. Available HERE

Young, V. K H., R. W. Blob. 2015. Limb-bone loading in swimming turtles: Changes in loading facilitate transitions from tubular to flipper-shaped limbs during aquatic invasions. Biology Letters 11, DOI: 10.1098/rsbl.2015.0110. (write for PDF)

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