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Węgrzyn K, Pauwels OSG, Brecko J, Georgalis GL. Vertebral morphology and intracolumnar variation of the iconic African viperid snake Atheris (Serpentes, Viperidae). Anat Rec (Hoboken) 2024. [PMID: 39360337 DOI: 10.1002/ar.25579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2024] [Revised: 09/09/2024] [Accepted: 09/12/2024] [Indexed: 10/04/2024]
Abstract
We here provide a detailed description of the vertebral morphology of the African arboreal viperid snakes of the genus Atheris. Vertebrae of three different species of the genus, i.e., Atheris desaixi, Atheris hispida, and Atheris katangensis, were investigated via the aid of μCT (micro-computed tomography) scanning. We describe several vertebrae from different regions of the vertebral column for all three species, starting from the atlas-axis complex to the caudal tip, in order to demonstrate important differences regarding the intracolumnar variation. Comparison of these three species shows an overall similar general morphology of the trunk vertebrae among the Atheris species. We extensively compare Atheris with other known viperids. As the sole arboreal genus of Viperinae the prehensile nature of the tail of Atheris is reflected in its caudal vertebral morphology, which is characterized by a high number of caudal vertebrae but also robust and anteroventrally oriented pleurapophyses as a skeletal adaptation, linked with the myology of the tail, to an arboreal lifestyle. We anticipate that the extensive figuring of these viperid specimens will also aid identifications in paleontology.
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Affiliation(s)
- Kacper Węgrzyn
- Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland
- Faculty of Biology, Jagiellonian University, Kraków, Poland
- Faculty of Biology and Biotechnology, Warsaw University of Life Sciences, Warsaw, Poland
| | - Olivier S G Pauwels
- Department of Recent Vertebrates, Royal Belgian Institute of Natural Sciences, Brussels, Belgium
| | - Jonathan Brecko
- Department of Recent Vertebrates, Royal Belgian Institute of Natural Sciences, Brussels, Belgium
- Biological Collections, Royal Museum for Central Africa, Tervuren, Belgium
| | - Georgios L Georgalis
- Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Kraków, Poland
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2
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Yuan ML, Westeen EP. Decoupled evolution of ventral and dorsal scales in agamid lizards: ventral keels are associated with arboreality. Biol Lett 2024; 20:20240171. [PMID: 38955224 DOI: 10.1098/rsbl.2024.0171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Accepted: 06/03/2024] [Indexed: 07/04/2024] Open
Abstract
Arboreality has evolved in all major vertebrate lineages and is often associated with morphological adaptations and increased diversification concomitant with accessing novel niche space. In squamate reptiles, foot, claw, and tail morphology are well-studied adaptations shown to be associated with transitions to arboreality. Here, we examined a less well understood trait-the keeled scale-in relation to microhabitat, climate, and diversification dynamics across a diverse lizard radiation, Agamidae. We found that the ancestral agamid had keeled dorsal but not ventral scales; further, dorsal and ventral keels are evolutionarily decoupled. Ventral keeled scales evolved repeatedly in association with arboreality and may be advantageous in reducing wear or by promoting interlocking when climbing. We did not find an association between keeled scales and diversification, suggesting keels do not allow finer-scale microhabitat partitioning observed in other arboreal-associated traits. We additionally found a relationship between keeled ventral scales and precipitation in terrestrial species where we posit that the keels may function to reduce scale degradation. Our results suggest that keeled ventral scales facilitated transitions to arboreality across agamid lizards, and highlight a need for future studies that explore their biomechanical function in relation to microhabitat and climate.
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Affiliation(s)
- Michael L Yuan
- Institute for Biodiversity Science and Sustainability, California Academy of Sciences, San Francisco, CA, USA
| | - Erin P Westeen
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, USA
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3
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Lu J, Tang C, Hu E, Li Z. S-shaped rolling gait designed using curve transformations of a snake robot for climbing on a bifurcated pipe. BIOINSPIRATION & BIOMIMETICS 2024; 19:036010. [PMID: 38507791 DOI: 10.1088/1748-3190/ad3601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Accepted: 03/20/2024] [Indexed: 03/22/2024]
Abstract
In this work, we focus on overcoming the challenge of a snake robot climbing on the outside of a bifurcated pipe. Inspired by the climbing postures of biological snakes, we propose an S-shaped rolling gait designed using curve transformations. For this gait, the snake robot's body presenting an S-shaped curve is wrapped mainly around one side of the pipe, which leaves space for the fork of the pipe. To overcome the difficulty in constructing and clarifying the S-shaped curve, we present a method for establishing the transformation between a plane curve and a 3D curve on a cylindrical surface. Therefore, we can intuitively design the curve in 3D space, while analytically calculating the geometric properties of the curve in simple planar coordinate systems. The effectiveness of the proposed gait is verified by actual experiments. In successful configuration scenarios, the snake robot could stably climb on the pipe and efficiently cross or climb to the bifurcation while maintaining its target shape.
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Affiliation(s)
- Jingwen Lu
- School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou, People's Republic of China
| | - Chaoquan Tang
- School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou, People's Republic of China
| | - Eryi Hu
- Information Institute, Ministry of Emergency Management of the People's Republic of China, Beijing, People's Republic of China
| | - Zhipeng Li
- School of Mechatronic Engineering, China University of Mining and Technology, Xuzhou, People's Republic of China
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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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5
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Banci KRDS, Guimarães M, Siqueira LHC, Muscat E, Sazima I, Marques OAV. Body shape and diet reflect arboreality degree of five congeneric snakes sympatric in the Atlantic forest. Biotropica 2022. [DOI: 10.1111/btp.13107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Murilo Guimarães
- Departamento de Zoologia Universidade Federal do Rio Grande do Sul Porto Alegre Brazil
| | | | - Edelcio Muscat
- Projeto Dacnis, São Francisco Xavier and Ubatuba Ubatuba Brazil
| | - Ivan Sazima
- Projeto Dacnis, São Francisco Xavier and Ubatuba Ubatuba Brazil
- Museu de Biodiversidade Biológica, Instituto de Biologia Universidade Estadual de Campinas Campinas Brazil
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Martinez A, Nguyen D, Basson MS, Medina J, Irschick DJ, Baeckens S. Quantifying surface topography of biological systems from 3D scans. Methods Ecol Evol 2021. [DOI: 10.1111/2041-210x.13603] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alejandro Martinez
- Department of Civil and Environmental Engineering University of California Davis Davis CA USA
| | - Damon Nguyen
- Department of Civil and Environmental Engineering University of California Davis Davis CA USA
| | - Mandeep S. Basson
- Department of Civil and Environmental Engineering University of California Davis Davis CA USA
| | - Josh Medina
- Department of Biology University of Massachusetts Amherst MA USA
| | | | - Simon Baeckens
- Functional Morphology Lab Department of Biology University of Antwerp Wilrijk Belgium
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7
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Abstract
The diverse ways and environments in which animals move are correlated with morphology1, but morphology is not sufficient to predict how animals move because behavioral innovations can create new capacities. We document a new mode of snake locomotion - 'lasso locomotion' - that allows the brown treesnake (Boiga irregularis) to ascend much larger smooth cylinders than any previously known behavior. This lasso locomotion may facilitate exploiting resources that might otherwise be unobtainable and contribute to the success and impact of this highly invasive species. VIDEO ABSTRACT.
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Tingle JL, Garland T. Morphological evolution in relationship to sidewinding, arboreality and precipitation in snakes of the family Viperidae. Biol J Linn Soc Lond 2021. [DOI: 10.1093/biolinnean/blaa208] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
AbstractCompared with other squamates, snakes have received relatively little ecomorphological investigation. We examined morphometric and meristic characters of vipers, in which both sidewinding locomotion and arboreality have evolved multiple times. We used phylogenetic comparative methods that account for intraspecific variation (measurement error models) to determine how morphology varied in relationship to body size, sidewinding, arboreality and mean annual precipitation (which we chose over other climate variables through model comparison). Some traits scaled isometrically; however, head dimensions were negatively allometric. Although we expected sidewinding specialists to have different body proportions and more vertebrae than non-sidewinding species, they did not differ significantly for any trait after correction for multiple comparisons. This result suggests that the mechanisms enabling sidewinding involve musculoskeletal morphology and/or motor control, that viper morphology is inherently conducive to sidewinding (‘pre-adapted’) or that behaviour has evolved faster than morphology. With body size as a covariate, arboreal vipers had long tails, narrow bodies and lateral compression, consistent with previous findings for other arboreal snakes, plus reduced posterior body tapering. Species from wetter environments tended to have longer tails, wider heads and reduced anterior tapering. This study adds to the growing evidence that, despite superficial simplicity, snakes have evolved various morphological specializations in relationship to behaviour and ecology.
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Affiliation(s)
- Jessica L Tingle
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, USA
| | - Theodore Garland
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, USA
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Zamore SA, Araujo N, Socha JJ. Visual acuity in the flying snake, Chrysopelea paradisi. Integr Comp Biol 2020; 63:icaa143. [PMID: 33084888 DOI: 10.1093/icb/icaa143] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Revised: 09/02/2020] [Accepted: 09/04/2020] [Indexed: 12/15/2022] Open
Abstract
Visual control during high-speed aerial locomotion requires a visual system adapted for such behaviors. Flying snakes (genus: Chrysopelea) are capable of gliding at speeds up to 11 m s-1 and perform visual assessments before take-off. Determining nuances of control requires a closed-loop experimental system, such as immersive virtual arenas. To characterize vision in the flying snake Chrysopelea paradisi, we used digitally reconstructed models of the head to determine a 3D field of vision. We also used optokinetic drum experiments and compared slowphase optokinetic nystagmus (OKN) speeds to calculate visual acuity and conducted preliminary experiments to determine whether snakes would respond to closed-loop virtual stimuli. Visual characterization showed that C. paradisi likely has a large field of view (308.5 ± 6.5° azimuthal range), with a considerable binocular region (33.0 ± 11.0° azimuthal width) that extends overhead. Their visual systems are broadly tuned and motion-sensitive, with peak OKN response gains of 0.50 ± 0.11 seen at 46.06 ± 11.08 Hz, and a low spatial acuity, with peak gain of 0.92 ± 0.41 seen at 2.89 ± 0.16 cpd (cycles per degree). These characteristics were used to inform settings in an immersive virtual arena, including framerate, brightness, and stimulus size. In turn, the immersive virtual arena was used to reproduce the optokinetic drum experiments. We elicited OKN in open-loop experiments, with a mean gain of 0.21 ± 0.9 seen at 0.019 ± 6x10-5 cpd and 1.79 ± 0.01 Hz. In closed-loop experiments, snakes did not exhibit OKN, but held the image fixed, indicating visual stabilization. These results demonstrate for that C. paradisi responds to visual stimuli in a digital virtual arena. The accessibility and adaptability of the virtual setup make it suitable for future studies of visual control in snakes and other animals in an unconstrained setting.
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Affiliation(s)
- Sharri A Zamore
- ATLAS Institute, University of Colorado Boulder, Boulder, CO, 80309, United States
| | - Nicole Araujo
- Dept. of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, United States
| | - John J Socha
- Dept. of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA, United States
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10
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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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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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Nafus MG, Yackel Adams AA, Boback SM, Siers SR, Reed RN. Behavior, size, and body condition predict susceptibility to management and reflect post-treatment frequency shifts in an invasive snake. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2019.e00834] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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13
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Gripshover ND, Jayne BC. Visual Contrast and Intensity Affect Perch Choice of Brown Tree Snakes (Boiga irregularis) and Boa Constrictors (Boa constrictor). ZOOLOGY 2020; 139:125744. [PMID: 32070798 DOI: 10.1016/j.zool.2020.125744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 01/15/2020] [Accepted: 01/16/2020] [Indexed: 10/25/2022]
Abstract
Habitat structure can affect animal movement both by affecting the mechanical demands of locomotion and by influencing where animals choose to go. Arboreal habitats facilitate studying path choice by animals because variation in branch structure has known mechanical consequences, and different branches create discrete choices. Recent laboratory studies have found that arboreal snakes can use vision to select shapes and locations of destinations that mechanically facilitate bridging gaps. However, the extent to which the appearance of objects unrelated to biomechanical demands affects the choice of destinations remains poorly understood for most animal taxa including snakes. Hence, we manipulated the intensity (black, gray, or white), contrast, structure, and locations of destinations to test for their combined effects on perch choice during gap bridging of brown tree snakes and boa constrictors. For a white background and a given perch structure and location, both species had significant preferences for darker perches. The preference for darker destinations was strong enough to override or reduce some preferences for biomechanically advantageous destinations such as those having secondary branches or being located closer or along a straighter trajectory. These results provide a striking example of how visual cues unrelated to the physical structure of surfaces, such as contrast and intensity, can bias choice and, in some cases, supersede a preference for mechanically beneficial surfaces. Because these two species are so phylogenetically distant, some of their similar preferences suggest a sensory bias that may be widespread in snakes. The manipulation of surface color may facilitate management of invasive species, such as the brown tree snakes, by enhancing the efficiency of traps or making certain objects less attractive to them.
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Affiliation(s)
- Noah D Gripshover
- Department of Biological Sciences, PO Box 210006, University of Cincinnati, Cincinnati, OH, 45221-0006, USA.
| | - Bruce C Jayne
- Department of Biological Sciences, PO Box 210006, University of Cincinnati, Cincinnati, OH, 45221-0006, USA
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14
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Gerald GW, Wass ED. Correcting for individual quality reveals trade-offs in performance among multiple modes of limbless locomotion in snakes. Biol J Linn Soc Lond 2019. [DOI: 10.1093/biolinnean/blz086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
Trade-offs among performance traits are often difficult to detect despite the physiological and morphological incompatibilities that underlie disparate traits being well understood. However, recent studies that have corrected for individual quality have found trade-offs in human athletes performing various performance tasks. Few studies have found trade-offs among multiple performance tasks after correcting for individual quality in non-human animals because of the difficulty in motivating many animals to perform biomechanically different tasks. We examined potential trade-offs in maximal speeds among ten locomotor conditions that involved the utilization of different locomotor modes in cornsnakes (Pantherophis guttatus). Snakes were assessed during terrestrial lateral undulation, swimming, concertina movements (small and large width) and six conditions of arboreal locomotion (combinations of three perch diameters and two inclines). We found no trade-offs among locomotor conditions when analysing uncorrected speeds or speeds corrected for body condition. However, we found several trade-offs among modes and treatments for speeds corrected for individual quality. Terrestrial lateral undulation speeds were negatively related to speeds of concertina and two of the arboreal locomotion conditions. A trade-off between speeds on large and small perch diameters on a 30° incline was also detected and probably reflects potential conflicts in traits that maximize lateral undulation and concertina.
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Affiliation(s)
| | - Emma D Wass
- Department of Biology, Nebraska Wesleyan University, Lincoln, NE, USA
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15
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Rafsanjani A, Zhang Y, Liu B, Rubinstein SM, Bertoldi K. Kirigami skins make a simple soft actuator crawl. Sci Robot 2018; 3:3/15/eaar7555. [PMID: 33141681 DOI: 10.1126/scirobotics.aar7555] [Citation(s) in RCA: 187] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 02/02/2018] [Indexed: 11/02/2022]
Abstract
Bioinspired soft machines made of highly deformable materials are enabling a variety of innovative applications, yet their locomotion typically requires several actuators that are independently activated. We harnessed kirigami principles to significantly enhance the crawling capability of a soft actuator. We designed highly stretchable kirigami surfaces in which mechanical instabilities induce a transformation from flat sheets to 3D-textured surfaces akin to the scaled skin of snakes. First, we showed that this transformation was accompanied by a dramatic change in the frictional properties of the surfaces. Then, we demonstrated that, when wrapped around an extending soft actuator, the buckling-induced directional frictional properties of these surfaces enabled the system to efficiently crawl.
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Affiliation(s)
- Ahmad Rafsanjani
- John A. Paulson School of Engineering Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Yuerou Zhang
- John A. Paulson School of Engineering Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Bangyuan Liu
- John A. Paulson School of Engineering Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Shmuel M Rubinstein
- John A. Paulson School of Engineering Applied Sciences, Harvard University, Cambridge, MA 02138, USA
| | - Katia Bertoldi
- John A. Paulson School of Engineering Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
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16
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Jorgensen RM, Jayne BC. Three-dimensional trajectories affect the epaxial muscle activity of arboreal snakes crossing gaps. J Exp Biol 2017; 220:3545-3555. [DOI: 10.1242/jeb.164640] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 07/28/2017] [Indexed: 11/20/2022]
Abstract
The need for long-axis support is widespread among non-aquatic vertebrates and may be particularly acute for arboreal snakes when many vertebrae span sizable gaps between branches with diverse orientations. Hence, we used brown tree snakes (Boiga irregularis) bridging gaps to test how three-dimensional trajectories affected muscle activity and whether these motor patterns differed from those for the locomotion of terrestrial snakes and movements of other vertebrates. We used five trajectories: pitch angles of 90, 0 and -90 deg (downward) when yaw=0, and 90 deg yaw angles to the left and right when pitch=0 deg. We recorded movement and EMGs from the three largest epaxial muscles, which from dorsal to ventral are the semispinalis-spinalis (SSP), longissimus dorsi (LD), and iliocostalis (IL). Overall, the SSP had extensive bilateral activity, which resembled the motor pattern during the dorsiflexion of sidewinding snakes. Unlike any previously described terrestrial snake locomotion, bilateral activity of the LD and IL was also common during gap bridging. The largest amounts of muscle activity usually occurred for horizontal gaps, and muscle activity decreased markedly as soon as the snake's head touched the far edge of the gap. Snakes had the least amount of muscle activity for pitch=-90 deg. While turning sideways, muscles on the convex side had less activity when turning compared to the concave side. Hence, the orientation relative to gravity profoundly affected muscle activity during gap bridging, and these complex three-dimensional movements involved several previously undescribed variants of axial motor pattern.
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Affiliation(s)
- Ryan M. Jorgensen
- 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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17
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Knight K. Tree snakes’ keel gets a grip. J Exp Biol 2015. [DOI: 10.1242/jeb.135434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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