Biology
Document Type
Article
Abstract
Although typically possessing four limbs and short bodies, lizards have evolved diverse morphologies, including elongate trunks with tiny limbs. Such forms are hypothesized to aid locomotion in cluttered/fossorial environments but propulsion mechanisms (e.g., the use of body and/or limbs to interact with substrates) and potential body/limb coordination remain unstudied. Here, we use biological experiments, a geometric theory of locomotion, and robophysical models to investigate body–limb coordination in diverse lizards. Locomotor field studies in short-limbed, elongate lizards (Brachymeles and Lerista) and laboratory studies of fully limbed lizards (Uma scoparia and Sceloporus olivaceus) and a snake (Chionactis occipitalis) reveal that body-wave dynamics can be described by a combination of standing and traveling waves; the ratio of the amplitudes of these components is inversely related to the degree of limb reduction and body elongation. The geometric theory (which replaces laborious calculation with diagrams) helps explain our observations, predicting that the advantage of traveling-wave body undulations (compared with a standing wave) emerges when the dominant thrust-generation mechanism arises from the body rather than the limbs and reveals that such soil-dwelling lizards propel via “terrestrial swimming” like sand-swimming lizards and snakes. We test our hypothesis by inducing the use of traveling waves in stereotyped lizards via modulating the ground-penetration resistance. Study of a limbed/undulatory robophysical model demonstrates that a traveling wave is beneficial when propulsion is generated by body–environment interaction. Our models could be valuable in understanding functional constraints on the evolutionary processes of elongation and limb reduction as well as advancing robot designs.
Publication Title
Proceedings of the National Academy of Sciences of the United States of America
Publication Date
7-5-2022
Volume
119
Issue
27
ISSN
0027-8424
DOI
10.1073/pnas.2118456119
Keywords
biomechanics, evolution, lizard, locomotion, robotics
Repository Citation
Chong, Baxi; Wang, Tianyu; Erickson, Eva; Bergmann, Philip J.; and Goldman, Daniel I., "Coordinating tiny limbs and long bodies: Geometric mechanics of lizard terrestrial swimming" (2022). Biology. 79.
https://commons.clarku.edu/faculty_biology/79
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Copyright Conditions
Chong, B., Wang, T., Erickson, E., Bergmann, P. J., & Goldman, D. I. (2022). Coordinating tiny limbs and long bodies: Geometric mechanics of lizard terrestrial swimming. Proceedings of the National Academy of Sciences, 119(27), e2118456119.
