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Rieser JM, Chong B, Gong C, Astley HC, Schiebel PE, Diaz K, Pierce CJ, Lu H, Hatton RL, Choset H, Goldman DI. Geometric phase predicts locomotion performance in undulating living systems across scales. Proc Natl Acad Sci U S A 2024; 121:e2320517121. [PMID: 38848301 PMCID: PMC11181092 DOI: 10.1073/pnas.2320517121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Accepted: 04/02/2024] [Indexed: 06/09/2024] Open
Abstract
Self-propelling organisms locomote via generation of patterns of self-deformation. Despite the diversity of body plans, internal actuation schemes and environments in limbless vertebrates and invertebrates, such organisms often use similar traveling waves of axial body bending for movement. Delineating how self-deformation parameters lead to locomotor performance (e.g. speed, energy, turning capabilities) remains challenging. We show that a geometric framework, replacing laborious calculation with a diagrammatic scheme, is well-suited to discovery and comparison of effective patterns of wave dynamics in diverse living systems. We focus on a regime of undulatory locomotion, that of highly damped environments, which is applicable not only to small organisms in viscous fluids, but also larger animals in frictional fluids (sand) and on frictional ground. We find that the traveling wave dynamics used by mm-scale nematode worms and cm-scale desert dwelling snakes and lizards can be described by time series of weights associated with two principal modes. The approximately circular closed path trajectories of mode weights in a self-deformation space enclose near-maximal surface integral (geometric phase) for organisms spanning two decades in body length. We hypothesize that such trajectories are targets of control (which we refer to as "serpenoid templates"). Further, the geometric approach reveals how seemingly complex behaviors such as turning in worms and sidewinding snakes can be described as modulations of templates. Thus, the use of differential geometry in the locomotion of living systems generates a common description of locomotion across taxa and provides hypotheses for neuromechanical control schemes at lower levels of organization.
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Affiliation(s)
- Jennifer M. Rieser
- School of Physics, Georgia Institute of Technology, Atlanta, GA30332
- Department of Physics, Emory University, Atlanta, GA30322
| | - Baxi Chong
- School of Physics, Georgia Institute of Technology, Atlanta, GA30332
| | | | | | - Perrin E. Schiebel
- Mechanical and Industrial Engineering Department, Montana State University, Bozeman, MT59717
| | - Kelimar Diaz
- Physics Department, Oglethorpe University, Brookhaven, GA, 202919
| | | | - Hang Lu
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA30332
| | - Ross L. Hatton
- Collaborative Robotics and Intelligent Systems Institute (CoRIS), Oregon State University, Corvallis, OR97331
| | - Howie Choset
- Robotics Institute, Carnegie Mellon University, Pittsburgh, PA15213
| | - Daniel I. Goldman
- School of Physics, Georgia Institute of Technology, Atlanta, GA30332
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2
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Tingle JL, Garner KL, Astley HC. Functional diversity of snake locomotor behaviors: A review of the biological literature for bioinspiration. Ann N Y Acad Sci 2024; 1533:16-37. [PMID: 38367220 DOI: 10.1111/nyas.15109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2024]
Abstract
Organismal solutions to natural challenges can spark creative engineering applications. However, most engineers are not experts in organismal biology, creating a potential barrier to maximally effective bioinspired design. In this review, we aim to reduce that barrier with respect to a group of organisms that hold particular promise for a variety of applications: snakes. Representing >10% of tetrapod vertebrates, snakes inhabit nearly every imaginable terrestrial environment, moving with ease under many conditions that would thwart other animals. To do so, they employ over a dozen different types of locomotion (perhaps well over). Lacking limbs, they have evolved axial musculoskeletal features that enable their vast functional diversity, which can vary across species. Different species also have various skin features that provide numerous functional benefits, including frictional anisotropy or isotropy (as their locomotor habits demand), waterproofing, dirt shedding, antimicrobial properties, structural colors, and wear resistance. Snakes clearly have much to offer to the fields of robotics and materials science. We aim for this review to increase knowledge of snake functional diversity by facilitating access to the relevant literature.
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Affiliation(s)
| | - Kelsey L Garner
- Department of Biology, University of Akron, Akron, Ohio, USA
| | - Henry C Astley
- Department of Biology, University of Akron, Akron, Ohio, USA
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3
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Tingle JL, Jurestovsky DJ, Astley HC. The relative contributions of multiarticular snake muscles to movement in different planes. J Morphol 2023; 284:e21591. [PMID: 37183497 DOI: 10.1002/jmor.21591] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 04/04/2023] [Accepted: 04/10/2023] [Indexed: 05/16/2023]
Abstract
Muscles spanning multiple joints play important functional roles in a wide range of systems across tetrapods; however, their fundamental mechanics are poorly understood, particularly the consequences of anatomical position on mechanical advantage. Snakes provide an excellent study system for advancing this topic. They rely on the axial muscles for many activities, including striking, constriction, defensive displays, and locomotion. Moreover, those muscles span from one or a few vertebrae to over 30, and anatomy varies among muscles and among species. We characterized the anatomy of major epaxial muscles in a size series of corn snakes (Pantherophis guttatus) using diceCT scans, and then took several approaches to calculating contributions of each muscle to force and motion generated during body bending, starting from a highly simplistic model and moving to increasingly complex and realistic models. Only the most realistic model yielded equations that included the consequence of muscle span on torque-displacement trade-offs, as well as resolving ambiguities that arose from simpler models. We also tested whether muscle cross-sectional areas or lever arms (total magnitude or pitch/yaw/roll components) were related to snake mass, longitudinal body region (anterior, middle, posterior), and/or muscle group (semispinalis-spinalis, multifidus, longissimus dorsi, iliocostalis, and levator costae). Muscle cross-sectional areas generally scaled with positive allometry, and most lever arms did not depart significantly from geometric similarity (isometry). The levator costae had lower cross-sectional area than the four epaxial muscles, which did not differ significantly from each other in cross-sectional area. Lever arm total magnitudes and components differed among muscles. We found some evidence for regional variation, indicating that functional regionalization merits further investigation. Our results contribute to knowledge of snake muscles specifically and multiarticular muscle systems generally, providing a foundation for future comparisons across species and bioinspired multiarticular systems.
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Affiliation(s)
| | - Derek J Jurestovsky
- Department of Biology, University of Akron, Akron, Ohio, USA
- Department of Kinesiology, Biomechanics Laboratory, Pennsylvania State University, Pennsylvania, USA
| | - Henry C Astley
- Department of Biology, University of Akron, Akron, Ohio, USA
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4
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Fu Q, Astley HC, Li C. Snakes combine vertical and lateral bending to traverse uneven terrain. BIOINSPIRATION & BIOMIMETICS 2022; 17:036009. [PMID: 35235918 DOI: 10.1088/1748-3190/ac59c5] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 03/01/2022] [Indexed: 06/14/2023]
Abstract
Terrestrial locomotion requires generating appropriate ground reaction forces which depend on substrate geometry and physical properties. The richness of positions and orientations of terrain features in the 3D world gives limbless animals like snakes that can bend their body versatility to generate forces from different contact areas for propulsion. Despite many previous studies of how snakes use lateral body bending for propulsion on relatively flat surfaces with lateral contact points, little is known about whether and how much snakes use vertical body bending in combination with lateral bending in 3D terrain. This lack had contributed to snake robots being inferior to animals in stability, efficiency, and versatility when traversing complex 3D environments. Here, to begin to elucidate this, we studied how the generalist corn snake traversed an uneven arena of blocks of random height variation five times its body height. The animal traversed the uneven terrain with perfect stability by propagating 3D bending down its body with little transverse motion (11° slip angle). Although the animal preferred moving through valleys with higher neighboring blocks, it did not prefer lateral bending. Among body-terrain contact regions that potentially provide propulsion, 52% were formed by vertical body bending and 48% by lateral bending. The combination of vertical and lateral bending may dramatically expand the sources of propulsive forces available to limbless locomotors by utilizing various asperities available in 3D terrain. Direct measurements of contact forces are necessary to further understand how snakes coordinate 3D bending along the entire body via sensory feedback to propel through 3D terrain. These studies will open a path to new propulsive mechanisms for snake robots, potentially increasing the performance and versatility in 3D terrain.
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Affiliation(s)
- Qiyuan Fu
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218, United States of America
| | - Henry C Astley
- Department of Biology, University of Akron, Akron, OH 44325, United States of America
| | - Chen Li
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218, United States of America
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5
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Jumping with adhesion: landing surface incline alters impact force and body kinematics in crested geckos. Sci Rep 2021; 11:23043. [PMID: 34845262 PMCID: PMC8630229 DOI: 10.1038/s41598-021-02033-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 10/29/2021] [Indexed: 11/20/2022] Open
Abstract
Arboreal habitats are characterized by a complex three-dimensional array of branches that vary in numerous characteristics, including incline, compliance, roughness, and diameter. Gaps must often be crossed, and this is frequently accomplished by leaping. Geckos bearing an adhesive system often jump in arboreal habitats, although few studies have examined their jumping biomechanics. We investigated the biomechanics of landing on smooth surfaces in crested geckos, Correlophus ciliatus, asking whether the incline of the landing platform alters impact forces and mid-air body movements. Using high-speed videography, we examined jumps from a horizontal take-off platform to horizontal, 45° and 90° landing platforms. Take-off velocity was greatest when geckos were jumping to a horizontal platform. Geckos did not modulate their body orientation in the air. Body curvature during landing, and landing duration, were greatest on the vertical platform. Together, these significantly reduced the impact force on the vertical platform. When landing on a smooth vertical surface, the geckos must engage the adhesive system to prevent slipping and falling. In contrast, landing on a horizontal surface requires no adhesion, but incurs high impact forces. Despite a lack of mid-air modulation, geckos appear robust to changing landing conditions.
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Luo M, Wan Z, Sun Y, Skorina EH, Tao W, Chen F, Gopalka L, Yang H, Onal CD. Motion Planning and Iterative Learning Control of a Modular Soft Robotic Snake. Front Robot AI 2021; 7:599242. [PMID: 33501359 PMCID: PMC7805722 DOI: 10.3389/frobt.2020.599242] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 11/09/2020] [Indexed: 11/15/2022] Open
Abstract
Snake robotics is an important research topic with a wide range of applications, including inspection in confined spaces, search-and-rescue, and disaster response. Snake robots are well-suited to these applications because of their versatility and adaptability to unstructured and constrained environments. In this paper, we introduce a soft pneumatic robotic snake that can imitate the capabilities of biological snakes, its soft body can provide flexibility and adaptability to the environment. This paper combines soft mobile robot modeling, proprioceptive feedback control, and motion planning to pave the way for functional soft robotic snake autonomy. We propose a pressure-operated soft robotic snake with a high degree of modularity that makes use of customized embedded flexible curvature sensing. On this platform, we introduce the use of iterative learning control using feedback from the on-board curvature sensors to enable the snake to automatically correct its gait for superior locomotion. We also present a motion planning and trajectory tracking algorithm using an adaptive bounding box, which allows for efficient motion planning that still takes into account the kinematic state of the soft robotic snake. We test this algorithm experimentally, and demonstrate its performance in obstacle avoidance scenarios.
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Affiliation(s)
- Ming Luo
- School of Mechanical and Materials Engineering, Washington State University, Pullman, WA, United States
| | - Zhenyu Wan
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Yinan Sun
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Erik H Skorina
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Weijia Tao
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Fuchen Chen
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Lakshay Gopalka
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Hao Yang
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Cagdas D Onal
- Robotics Engineering and Mechanical Engineering Departments, Worcester Polytechnic Institute, Worcester, MA, United States
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7
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Astley HC, Rieser JM, Kaba A, Paez VM, Tomkinson I, Mendelson JR, Goldman DI. Side-impact collision: mechanics of obstacle negotiation in sidewinding snakes. BIOINSPIRATION & BIOMIMETICS 2020; 15:065005. [PMID: 33111708 DOI: 10.1088/1748-3190/abb415] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Snakes excel at moving through cluttered environments, and heterogeneities can be used as propulsive contacts for snakes performing lateral undulation. However, sidewinding, which is often associated with sandy deserts, cuts a broad path through its environment that may increase its vulnerability to obstacles. Our prior work demonstrated that sidewinding can be represented as a pair of orthogonal body waves (vertical and horizontal) that can be independently modulated to achieve high maneuverability and incline ascent, suggesting that sidewinders may also use template modulations to negotiate obstacles. To test this hypothesis, we recorded overhead video of four sidewinder rattlesnakes (Crotalus cerastes) crossing a line of vertical pegs placed in the substrate. Snakes used three methods to traverse the obstacles: a Propagate Through behavior in which the lifted moving portion of the snake was deformed around the peg and dragged through as the snake continued sidewinding (115/160 runs), Reversal turns that reorient the snake entirely (35/160), or switching to Concertina locomotion (10/160). The Propagate Through response was only used if the anterior-most region of static contact would propagate along a path anterior to the peg, or if a new region of static contact could be formed near the head to satisfy this condition; otherwise, snakes could only use Reversal turns or switch to Concertina locomotion. Reversal turns allowed the snake to re-orient and either escape without further peg contact or re-orient into a posture amenable to using the Propagate Through response. We developed an algorithm to reproduce the Propagate Through behavior in a robophysical model using a modulation of the two-wave template. This range of behavioral strategies provides sidewinders with a versatile range of options for effectively negotiating obstacles in their natural habitat, as well as provide insights into the design and control of robotic systems dealing with heterogeneous habitats.
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Affiliation(s)
- Henry C Astley
- Biomimicry Research & Innovation Center, Department of Biology, University of Akron, 235 Carroll St.Akron, OH 44325, United States of America
| | - Jennifer M Rieser
- Department of Physics, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
| | - Abdul Kaba
- Department of Physics, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
| | - Veronica M Paez
- Department of Physics, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
| | - Ian Tomkinson
- Department of Physics, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
| | - Joseph R Mendelson
- Department of Biology, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
- Zoo Atlanta, Atlanta, GA 30315, United States of America
| | - Daniel I Goldman
- Department of Physics, Georgia Institute of Technology, Atlanta, GA 30332, United States of America
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8
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Abstract
Animals move in diverse ways, as indicated in part by the wide variety of gaits and modes that have been described for vertebrate locomotion. Much variation in the gaits of limbed animals is associated with changing speed, whereas different modes of snake locomotion are often associated with moving on different surfaces. For several decades different types of snake locomotion have been categorized as one of four major modes: rectilinear, lateral undulation, sidewinding, and concertina. Recent empirical work shows that the scheme of four modes of snake locomotion is overly conservative. For example, during aquatic lateral undulation, the timing between muscle activity and lateral bending changes along the length of the snake, which is unlike terrestrial lateral undulation. The motor pattern used to prevent sagging while bridging gaps also suggests that arboreal lateral undulation on narrow surfaces or with a few discrete points of support has a different motor pattern than terrestrial lateral undulation when the entire length of the snake is supported. In all types of concertina locomotion, the distance from the head to the tail changes substantially as snakes alternately flex and then extend different portions of their body. However, snakes climbing cylinders with concertina exert forces medially to attain a purchase on the branch, whereas tunnels require pushing laterally to form an anchoring region. Furthermore, different motor patterns are used for these two types of concertina movement. Some snakes climb vertical cylinders with helical wrapping completely around the cylinder, whereas all other forms of concertina bend regions of the body alternately to the left and right. Current data support rectilinear locomotion and sidewinding as being distinct modes, whereas lateral undulation and concertina are best used for defining categories of gaits with some unifying similarities. Partly as a result of different motor patterns, I propose recognizing five and four distinct types of lateral undulation and concertina, respectively, resulting in a total of 11 distinct gaits previously recognized as only four.
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Affiliation(s)
- Bruce C Jayne
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA
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Astley HC. Long Limbless Locomotors Over Land: The Mechanics and Biology of Elongate, Limbless Vertebrate Locomotion. Integr Comp Biol 2020; 60:134-139. [PMID: 32699901 DOI: 10.1093/icb/icaa034] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Elongate, limbless body plans are widespread in nature and frequently converged upon (with over two dozen independent convergences in Squamates alone, and many outside of Squamata). Despite their lack of legs, these animals move effectively through a wide range of microhabitats, and have a particular advantage in cluttered or confined environments. This has elicited interest from multiple disciplines in many aspects of their movements, from how and when limbless morphologies evolve to the biomechanics and control of limbless locomotion within and across taxa to its replication in elongate robots. Increasingly powerful tools and technology enable more detailed examinations of limbless locomotor biomechanics, and improved phylogenies have shed increasing light on the origins and evolution of limblessness, as well as the high frequency of convergence. Advances in actuators and control are increasing the capability of "snakebots" to solve real-world problems (e.g., search and rescue), while biological data have proven to be a potent inspiration for improvements in snakebot control. This collection of research brings together prominent researchers on the topic from around the world, including biologists, physicists, and roboticists to offer new perspective on locomotor modes, musculoskeletal mechanisms, locomotor control, and the evolution and diversity of limbless locomotion.
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Affiliation(s)
- Henry C Astley
- Biomimicry Research & Innovation Center, Department of Biology & Polymer Science, University of Akron, 235 Carroll St, Akron, OH 44325, USA
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10
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Kano T, Ishiguro A. Decoding Decentralized Control Mechanism Underlying Adaptive and Versatile Locomotion of Snakes. Integr Comp Biol 2020; 60:232-247. [PMID: 32215573 DOI: 10.1093/icb/icaa014] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Snakes have no limbs and can move in various environments using a simple elongated limbless body structure obtained through a long-term evolutionary process. Specifically, snakes have various locomotion patterns, which they change in response to conditions encountered. For example, on an unstructured terrain, snakes actively utilize the terrain's irregularities and move effectively by actively pushing their bodies against the "scaffolds" that they encounter. In a narrow aisle, snakes exhibit concertina locomotion, in which the tail part of the body is pulled forward with the head part anchored, and this is followed by the extension of the head part with the tail part anchored. Furthermore, snakes often exhibit three-dimensional (3-D) locomotion patterns wherein the points of ground contact change in a spatiotemporal manner, such as sidewinding and sinus-lifting locomotion. This ability is achieved possibly by a decentralized control mechanism, which is still mostly unknown. In this study, we address this aspect by employing a synthetic approach to understand locomotion mechanisms by developing mathematical models and robots. We propose a Tegotae-based decentralized control mechanism and use a 2-D snake-like robot to demonstrate that it can exhibit scaffold-based and concertina locomotion. Moreover, we extend the proposed mechanism to 3D and use a 3-D snake-like robot to demonstrate that it can exhibit sidewinding and sinus-lifting locomotion. We believe that our findings will form a basis for developing snake-like robots applicable to search-and-rescue operations as well as understanding the essential decentralized control mechanism underlying animal locomotion.
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Affiliation(s)
- Takeshi Kano
- Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba Ward, Sendai, Miyagi 980-8577, Japan
| | - Akio Ishiguro
- Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba Ward, Sendai, Miyagi 980-8577, Japan
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11
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Capano JG. Reaction Forces and Rib Function During Locomotion in Snakes. Integr Comp Biol 2020; 60:215-231. [PMID: 32396605 DOI: 10.1093/icb/icaa033] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Locomotion in most tetrapods involves coordinated efforts between appendicular and axial musculoskeletal systems, where interactions between the limbs and the ground generate vertical (GV), horizontal (GH), and mediolateral (GML) ground-reaction forces that are transmitted to the axial system. Snakes have a complete absence of external limbs and represent a fundamental shift from this perspective. The axial musculoskeletal system of snakes is their primary structure to exert, transmit, and resist all motive and reaction forces for propulsion. Their lack of limbs makes them particularly dependent on the mechanical interactions between their bodies and the environment to generate the net GH they need for forward locomotion. As organisms that locomote on their bellies, the forces that enable the various modes of snake locomotion involve two important structures: the integument and the ribs. Snakes use the integument to contact the substrate and produce a friction-reservoir that exceeds their muscle-induced propulsive forces through modulation of scale stiffness and orientation, enabling propulsion through variable environments. XROMM work and previous studies suggest that the serially repeated ribs of snakes change their cross-sectional body shape, deform to environmental irregularities, provide synergistic stabilization for other muscles, and differentially exert and transmit forces to control propulsion. The costovertebral joints of snakes have a biarticular morphology, relative to the unicapitate costovertebral joints of other squamates, that appears derived and not homologous with the ancestral bicapitate ribs of Amniota. Evidence suggests that the biarticular joints of snakes may function to buttress locomotor forces, similar to other amniotes, and provide a passive mechanism for resisting reaction forces during snake locomotion. Future comparisons with other limbless lizard taxa are necessary to tease apart the mechanics and mechanisms that produced the locomotor versatility observed within Serpentes.
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Affiliation(s)
- John G Capano
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
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12
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Fu Q, Li C. Robotic modelling of snake traversing large, smooth obstacles reveals stability benefits of body compliance. ROYAL SOCIETY OPEN SCIENCE 2020; 7:191192. [PMID: 32257305 PMCID: PMC7062058 DOI: 10.1098/rsos.191192] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 01/27/2020] [Indexed: 06/11/2023]
Abstract
Snakes can move through almost any terrain. Although their locomotion on flat surfaces using planar gaits is inherently stable, when snakes deform their body out of plane to traverse complex terrain, maintaining stability becomes a challenge. On trees and desert dunes, snakes grip branches or brace against depressed sand for stability. However, how they stably surmount obstacles like boulders too large and smooth to gain such 'anchor points' is less understood. Similarly, snake robots are challenged to stably traverse large, smooth obstacles for search and rescue and building inspection. Our recent study discovered that snakes combine body lateral undulation and cantilevering to stably traverse large steps. Here, we developed a snake robot with this gait and snake-like anisotropic friction and used it as a physical model to understand stability principles. The robot traversed steps as high as a third of its body length rapidly and stably. However, on higher steps, it was more likely to fail due to more frequent rolling and flipping over, which was absent in the snake with a compliant body. Adding body compliance reduced the robot's roll instability by statistically improving surface contact, without reducing speed. Besides advancing understanding of snake locomotion, our robot achieved high traversal speed surpassing most previous snake robots and approaching snakes, while maintaining high traversal probability.
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Affiliation(s)
| | - Chen Li
- Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD, USA
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13
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Baken EK, Adams DC. Macroevolution of arboreality in salamanders. Ecol Evol 2019; 9:7005-7016. [PMID: 31380029 PMCID: PMC6662381 DOI: 10.1002/ece3.5267] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 04/25/2019] [Accepted: 04/28/2019] [Indexed: 11/21/2022] Open
Abstract
Evolutionary theory predicts that selection in distinct microhabitats generates correlations between morphological and ecological traits, and may increase both phenotypic and taxonomic diversity. However, some microhabitats exert unique selective pressures that act as a restraining force on macroevolutionary patterns of diversification. In this study, we use phylogenetic comparative methods to investigate the evolutionary outcomes of inhabiting the arboreal microhabitat in salamanders. We find that arboreality has independently evolved at least five times in Caudata and has arisen primarily from terrestrial ancestors. However, the rate of transition from arboreality back to terrestriality is 24 times higher than the converse. This suggests that macroevolutionary trends in microhabitat use tend toward terrestriality over arboreality, which influences the extent to which use of the arboreal microhabitat proliferates. Morphologically, we find no evidence for an arboreal phenotype in overall body proportions or in foot shape, as variation in both traits overlaps broadly with species that utilize different microhabitats. However, both body shape and foot shape display reduced rates of phenotypic evolution in arboreal taxa, and evidence of morphological convergence among arboreal lineages is observed. Taken together, these patterns suggest that arboreality has played a unique role in the evolution of this family, providing neither an evolutionary opportunity, nor an evolutionary dead end.
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Affiliation(s)
- Erica K. Baken
- Department of Ecology, Evolution, and Organismal BiologyIowa State UniversityAmesIowa
| | - Dean C. Adams
- Department of Ecology, Evolution, and Organismal BiologyIowa State UniversityAmesIowa
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14
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Gart SW, Mitchel TW, Li C. Snakes partition their body to traverse large steps stably. ACTA ACUST UNITED AC 2019; 222:jeb.185991. [PMID: 30936272 DOI: 10.1242/jeb.185991] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 03/21/2019] [Indexed: 11/20/2022]
Abstract
Many snakes live in deserts, forests and river valleys and traverse challenging 3-D terrain such as rocks, felled trees and rubble, with obstacles as large as themselves and variable surface properties. By contrast, apart from branch cantilevering, burrowing, swimming and gliding, laboratory studies of snake locomotion have focused on locomotion on simple flat surfaces. Here, to begin to understand snake locomotion in complex 3-D terrain, we studied how the variable kingsnake, a terrestrial generalist, traversed a large step of variable surface friction and step height (up to 30% snout-vent length). The snake traversed by partitioning its body into three sections with distinct functions. Body sections below and above the step oscillated laterally on horizontal surfaces for propulsion, whereas the body section in between cantilevered in a vertical plane to bridge the large height increase. As the animal progressed, these three sections traveled down its body, conforming overall body shape to the step. In addition, the snake adjusted the partitioned gait in response to increase in step height and decrease in surface friction, at the cost of reduced speed. As surface friction decreased, body movement below and above the step changed from a continuous lateral undulation with little slip to an intermittent oscillatory movement with much slip, and initial head lift-off became closer to the step. Given these adjustments, body partitioning allowed the snake to be always stable, even when initially cantilevering but before reaching the surface above. Such a partitioned gait may be generally useful for diverse, complex 3-D terrain.
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Affiliation(s)
- Sean W Gart
- Department of Mechanical Engineering, Johns Hopkins University, 3400 N. Charles Street, 126 Hackerman Hall, Baltimore, MD 21218-2683, USA
| | - Thomas W Mitchel
- Department of Mechanical Engineering, Johns Hopkins University, 3400 N. Charles Street, 126 Hackerman Hall, Baltimore, MD 21218-2683, USA
| | - Chen Li
- Department of Mechanical Engineering, Johns Hopkins University, 3400 N. Charles Street, 126 Hackerman Hall, Baltimore, MD 21218-2683, USA
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15
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Mauro AA, Jayne CB. Perch compliance and experience affect destination choice of brown tree snakes (Boiga irregularis). ZOOLOGY 2016; 119:113-118. [DOI: 10.1016/j.zool.2015.12.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2015] [Revised: 11/18/2015] [Accepted: 12/02/2015] [Indexed: 10/22/2022]
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16
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The Axial Level of the Heart in Snakes. Evol Biol 2016. [DOI: 10.1007/978-3-319-41324-2_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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17
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Jayne BC, Newman SJ, Zentkovich MM, Berns HM. Why arboreal snakes should not be cylindrical: body shape, incline and surface roughness have interactive effects on locomotion. J Exp Biol 2015; 218:3978-86. [DOI: 10.1242/jeb.129379] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
ABSTRACT
Depending on animal size, shape, body plan and behaviour, variation in surface structure can affect the speed and ease of locomotion. The slope of branches and the roughness of bark both vary considerably, but their combined effects on the locomotion of arboreal animals are poorly understood. We used artificial branches with five inclines and five peg heights (≤40 mm) to test for interactive effects on the locomotion of three snake species with different body shapes. Unlike boa constrictors (Boa constrictor), corn snakes (Pantherophis guttatus) and brown tree snakes (Boiga irregularis) can both form ventrolateral keels, which are most pronounced in B. irregularis. Increasing peg height up to 10 mm elicited more of the lateral undulatory behaviour (sliding contact without gripping) rather than the concertina behaviour (periodic static gripping) and increased the speed of lateral undulation. Increased incline: (1) elicited more concertina locomotion, (2) decreased speed and (3) increased the threshold peg height that elicited lateral undulation. Boiga irregularis was the fastest species, and it used lateral undulation on the most surfaces, including a vertical cylinder with pegs only 1 mm high. Overall, B. constrictor was the slowest and used the most concertina locomotion, but this species climbed steep, smooth surfaces faster than P. guttatus. Our results illustrate how morphology and two different aspects of habitat structure can have interactive effects on organismal performance and behaviour. Notably, a sharper keel facilitated exploiting shorter protrusions to prevent slipping and provide propulsion, which became increasingly important as surface steepness increased.
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Affiliation(s)
- Bruce C. Jayne
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA
| | - Steven J. Newman
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA
| | - Michele M. Zentkovich
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA
| | - H. Matthew Berns
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA
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18
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Sheehy CM, Albert JS, Lillywhite HB. The evolution of tail length in snakes associated with different gravitational environments. Funct Ecol 2015. [DOI: 10.1111/1365-2435.12472] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Coleman M. Sheehy
- Department of Biology University of Florida Gainesville Florida32611 USA
| | - James S. Albert
- Department of Biology University of Louisiana Lafayette Louisiana70504 USA
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19
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Jayne BC, Byrnes G. The effects of slope and branch structure on the locomotion of a specialized arboreal colubrid snake (Boiga irregularis). ACTA ACUST UNITED AC 2015; 323:309-21. [DOI: 10.1002/jez.1920] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 12/19/2014] [Accepted: 01/20/2015] [Indexed: 02/03/2023]
Affiliation(s)
- Bruce C. Jayne
- Department of Biological Sciences; University of Cincinnati; Cincinnati Ohio
| | - Greg Byrnes
- Department of Biology; Siena College; Loudonville New York
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20
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Hit or miss: branch structure affects perch choice, behaviour, distance and accuracy of brown tree snakes bridging gaps. Anim Behav 2014. [DOI: 10.1016/j.anbehav.2013.12.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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21
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Rupp MF, Hulsey CD. Influence of substrate orientation on feeding kinematics and performance of algae grazing Lake Malawi cichlid fishes. J Exp Biol 2014; 217:3057-66. [DOI: 10.1242/jeb.105080] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Abstract
Lake Malawi cichlids have been studied extensively in an effort to elucidate the mechanisms underlying their adaptive radiation. Both habitat partitioning and trophic specialization have been suggested to be critical ecological axes underlying the exceptional diversification of these fishes, but the mechanisms facilitating this divergence are often unclear. For instance, in the rock-dwelling mbuna of Lake Malawi, coexistence is likely tightly linked to how and where species feed on the algae coating all the surfaces of the rocky reefs they exclusively inhabit. Yet, although mbuna species often preferentially graze from particular substrate orientations, we understand very little about how substrate orientation influences feeding kinematics or feeding rates in any group of organisms. Therefore, for three species of mbuna, we quantified feeding kinematics and inferred the rates that algae could be ingested on substrates that mimicked the top, sides, and bottoms of the algae covered boulders these species utilize in Lake Malawi. A number of differences in feeding kinematics were found among species, and several of the kinematic variables were found to differ even within species when the fish grazed from different surface orientations. However, despite their preferences for particular microhabitats, we found no evidence for clear tradeoffs in the rates that the three species were inferred to be able to obtain algae from different substrate orientations. Nevertheless, our results indicate microhabitat divergence linked to differences in feeding kinematics could have played a role in the origin and maintenance of the vast diversity of co-occurring Lake Malawi mbuna species.
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22
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Jayne BC, Baum JT, Byrnes G. Incline and peg spacing have interactive effects on the arboreal locomotor performance and kinematics of brown tree snakes (Boiga irregularis). J Exp Biol 2013; 216:3321-31. [DOI: 10.1242/jeb.086652] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Summary
Many animals move using lateral undulations, but snakes are noteworthy for using this type of locomotion in an unusual diversity of environments, including trees in which both the spacing and orientation of branches vary considerably. Despite branches providing discrete locations for snakes to generate propulsive forces during lateral undulation, the consequences of branch spacing for the locomotion of snakes are poorly understood. Hence, we determined maximal speeds and kinematics of an arboreal snake (Boiga irregularis) crawling on horizontal and vertical cylinders with pegs that simulated different spacing between secondary branches. Peg spacing, perch orientation, and their two-way interaction term had widespread, significant effects on both performance and kinematics. For the horizontal surfaces, maximal locomotor speed occurred with intermediate peg spacing, and it was nearly twice as fast as for both the smallest and largest peg spacings. By contrast, the locomotor speeds of snakes on the vertical surfaces were unaffected by peg spacing, and they were uniformly slower than those for the horizontal surfaces. For both perch orientations, the number of pegs touched by the snake decreased as peg spacing increased, and while touching only one peg the snakes crawled with apparent ease and steady speed. The snakes crawled vertically with only one peg as quickly as they did using 2-10 pegs. Pegs on a horizontal cylinder are probably important both for propulsion of snakes and preventing long-axis rolling, whereas pegs protruding from vertical cylinders and those protruding from horizontal planar surfaces are probably used almost exclusively for propulsion.
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Affiliation(s)
- Bruce C Jayne
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA.
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23
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Kano T, Sato T, Kobayashi R, Ishiguro A. Local reflexive mechanisms essential for snakes' scaffold-based locomotion. BIOINSPIRATION & BIOMIMETICS 2012; 7:046008. [PMID: 22918023 DOI: 10.1088/1748-3182/7/4/046008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Most robots are designed to work in predefined environments, and irregularities that exist in the environment interfere with their operation. For snakes, irregularities play the opposite role: snakes actively utilize terrain irregularities and move by effectively pushing their body against the scaffolds that they encounter. Autonomous decentralized control mechanisms could be the key to understanding this locomotion. We demonstrate through modelling and simulations that only two local reflexive mechanisms, which exploit sensory information about the stretching of muscles and the pressure on the body wall, are crucial for realizing locomotion. This finding will help develop robots that work in undefined environments and shed light on the understanding of the fundamental principles underlying adaptive locomotion in animals.
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Affiliation(s)
- Takeshi Kano
- Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
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24
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Hyams SE, Jayne BC, Cameron GN. Arboreal habitat structure affects locomotor speed and perch choice of white-footed mice (Peromyscus leucopus). ACTA ACUST UNITED AC 2012; 317:540-51. [PMID: 22927206 DOI: 10.1002/jez.1746] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 06/14/2012] [Accepted: 06/19/2012] [Indexed: 02/03/2023]
Abstract
Arboreal habitats pose several challenges for locomotion resulting from narrow cylindrical surfaces, steep slopes, and secondary branches that can form obstructions. We used laboratory trials to test whether different diameters, slopes, or complexity of branches affected maximum speeds and perch choice of the semi-arboreal white-footed mouse (Peromyscus leucopus). We tested locomotor performance of mice running horizontally and up and down 45° slopes for cylindrical artificial branches with five diameters ranging from 10 to 116 mm and on a subset of diameters for cylinders that were horizontal and had pegs (e.g., secondary branches) every 10 or 20 cm. Slope, diameter, and presence of pegs on top of cylinders had significant and interactive effects on locomotor performance. On horizontal cylinders the speed of mice increased with increased diameter among the three smallest diameters, but changed little with further increases in diameter, whereas for sloped surfaces the extreme diameters had lower speeds than an intermediate diameter. For a given diameter, the speeds of mice were usually faster when running horizontally rather than running uphill or downhill. The presence of pegs greatly decreased running speed compared to unobstructed surfaces, but the magnitude of this effect decreased as diameter increased. The difficulties of maintaining balance and avoiding toppling may have caused much of the decrease in speed and associated increased amounts of pausing. Only 1 of 11 choice tests detected a significant bias of mice favoring the perch that maximized locomotor performance.
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Affiliation(s)
- Sara E Hyams
- Department of Biological Sciences, Department of Biological Sciences, Cincinnati, OH, USA
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25
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Jones ZM, Jayne BC. Perch diameter and branching patterns have interactive effects on the locomotion and path choice of anole lizards. J Exp Biol 2012; 215:2096-107. [DOI: 10.1242/jeb.067413] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Natural branches vary conspicuously in their diameter, density and orientation, but how these latter two factors affect animal locomotion is poorly understood. Thus, for three species of arboreal anole lizards found on different size branches and with different limb lengths, we tested sprinting performance on cylinders with five diameters (5–100 mm) and five patterns of pegs, which simulated different branch orientations and spacing. We also tested whether the lizards preferred surfaces that enhanced their performance. The overall responses to different surfaces were similar among the three species, although the magnitude of the effects differed. All species were faster on cylinders with larger diameter and no pegs along the top. The short-limbed species was the slowest on all surfaces. Much of the variation in performance resulted from variable amounts of pausing among different surfaces and species. Lizards preferred to run along the top of cylinders, but pegs along the top of the narrow cylinders interfered with this. Pegs on top of the 100-mm diameter cylinder, however, had little effect on speed as the lizards ran quite a straight path alongside pegs without bumping into them. All three species usually chose surfaces with greater diameters and fewer pegs, but very large diameters with pegs were preferred to much smaller diameter cylinders without pegs. Our results suggest that preferring larger diameters in natural vegetation has a direct benefit for speed and an added benefit of allowing detouring around branches with little adverse effect on speed.
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Affiliation(s)
- Zachary M. Jones
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA
| | - Bruce C. Jayne
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006, USA
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26
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Jayne BC, Herrmann MP. Perch size and structure have species-dependent effects on the arboreal locomotion of rat snakes and boa constrictors. J Exp Biol 2011; 214:2189-201. [DOI: 10.1242/jeb.055293] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Arboreal habitats create diverse challenges for animal locomotion, but the numerical and phylogenetic diversity of snakes that climb trees suggest that their overall body plan is well suited for this task. Snakes have considerable diversity of axial anatomy, but the functional consequences of this diversity for arboreal locomotion are poorly understood because of the lack of comparative data. We simulated diverse arboreal surfaces to test whether environmental structure had different effects on the locomotion of snakes belonging to two distantly related species with differences in axial musculature and stoutness. On most cylindrical surfaces lacking pegs, both species used concertina locomotion, which always involved periodic stopping and gripping but was kinematically distinct in the two species. On horizontal cylinders that were a small fraction of body diameter, the boa constrictors used a balancing form of lateral undulation that was not observed for rat snakes. For all snakes the presence of pegs elicited lateral undulation and enhanced speed. For both species maximal speeds decreased with increased incline and were greatest on cylinders with intermediate diameters that approximated the diameter of the snakes. The frictional resistances that we studied had small effects compared with those of cylinder diameter, incline and the presence of pegs. The stouter and more muscular boa constrictors were usually faster than the rat snakes when using the gripping gait, whereas rat snakes were faster when using lateral undulation on the surfaces with pegs. Thus, variation in environmental structure had several highly significant effects on locomotor mode, performance and kinematics that were species dependent.
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Affiliation(s)
- Bruce C. Jayne
- Department of Biological Sciences, University of Cincinnati, PO Box 210006, Cincinnati, OH 45221-0006, USA
| | - Michael P. Herrmann
- Department of Biological Sciences, University of Cincinnati, PO Box 210006, Cincinnati, OH 45221-0006, USA
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27
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Arboreal habitat structure affects route choice by rat snakes. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2010; 197:119-29. [PMID: 20957373 DOI: 10.1007/s00359-010-0593-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 09/20/2010] [Accepted: 10/02/2010] [Indexed: 02/02/2023]
Abstract
In arboreal habitats gaps between branches and branch structure profoundly affect the ability of animals to move; hence, an ability to perceive such attributes could facilitate choosing routes that enhance the speed and ease of locomotion. Although many snakes are arboreal, no previous study has determined whether they can perceive structural variation of branches that is mechanically relevant to their locomotion. We tested whether the gap distance, location, and attributes of two destination perches on the far side of a crossable gap affected the route travelled by North American rat snakes (Pantherophis), which are proficient climbers. Snakes usually chose routes with shorter gaps. Within a horizontal plane, the snakes usually went straight rather than crossing an equal distance gap with a 90° turn, which was consistent with our finding that crossing a straight gap was easier. However, decreasing the distance of the gap with a 90° turn eliminated the preference for going straight. Additional factors, such as the width of the landing surface and the complexity of branching of the destination perches, resulted in non-random route choice. Thus, many of the observed biases in route choice suggested abilities to perceive structural variation and select routes that are mechanically beneficial.
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