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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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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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Mathou A, Bonnet X, Daoues K, Ksas R, Herrel A. Evolutionary convergence of muscle architecture in relation to locomotor ecology in snakes. J Anat 2023; 242:862-871. [PMID: 36732067 PMCID: PMC10093152 DOI: 10.1111/joa.13823] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 12/27/2022] [Accepted: 12/30/2022] [Indexed: 02/04/2023] Open
Abstract
The epaxial muscles in snakes are responsible for locomotion and as such can be expected to show adaptations in species living in different environments. Here, we tested whether the structural units that comprise the superficial epaxial muscles (semispinalis-spinalis, SSP; longissimus dorsi, LD; iliocostalis, IC) were different in animals occupying similar habitats. To do so, we analyzed and compared the muscle architecture (mass, fiber length, and physiological cross-sectional area) of the superficial epaxial muscle segments in snakes that differ in their habitat use (e.g., arboreal, terrestrial, and aquatic). Our results showed that arboreal species have on average longer muscles and tendons spanning more segments likely important during gap bridging. Moreover, aquatic snakes show relatively heavier semispinalis-spinalis muscles with a greater cross-sectional area. The longissimus dorsi muscles also showed a greater cross-sectional area compared with terrestrial and especially arboreal snakes. Whereas the more strongly developed muscles in aquatic snakes are likely associated with the dense and viscous environment through which they move, the lighter muscles in arboreal snakes may provide an advantage when climbing. Future studies comparing other ecologies (e.g., burrowing snakes) and additional muscle units (e.g., multifidus; hypaxial muscles) are needed to better understand the structural features driving variation in locomotor performance and efficiency in snakes.
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Affiliation(s)
- Adrien Mathou
- Département Adaptations du Vivant, Bâtiment d'Anatomie Comparée, UMR 7179 C.N.R.S/M.N.H.N., Paris, France
| | - Xavier Bonnet
- CEBC, UMR-7372, CNRS-Université de La Rochelle, Villiers en Bois, France
| | | | - Rémi Ksas
- Venomworld, Saint-Thibault-des-vignes, France
| | - Anthony Herrel
- Département Adaptations du Vivant, Bâtiment d'Anatomie Comparée, UMR 7179 C.N.R.S/M.N.H.N., Paris, France
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Gautreau E, Bonnet X, Sandoval J, Fosseries G, Herrel A, Arsicault M, Zeghloul S, Laribi MA. A Biomimetic Method to Replicate the Natural Fluid Movements of Swimming Snakes to Design Aquatic Robots. Biomimetics (Basel) 2022; 7:biomimetics7040223. [PMID: 36546923 PMCID: PMC9775164 DOI: 10.3390/biomimetics7040223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 11/26/2022] [Accepted: 11/30/2022] [Indexed: 12/12/2022] Open
Abstract
Replicating animal movements with robots provides powerful research tools because key parameters can be manipulated at will. Facing the lack of standard methods and the high complexity of biological systems, an incremental bioinspired approach is required. We followed this method to design a snake robot capable of reproducing the natural swimming gait of snakes, i.e., the lateral undulations of the whole body. Our goal was to shift away from the classical broken line design of poly-articulated snake robots to mimic the far more complex fluid movements of snakes. First, we examined the musculoskeletal systems of different snake species to extract key information, such as the flexibility or stiffness of the body. Second, we gathered the swimming kinematics of living snakes. Third, we developed a toolbox to implement the data that are relevant to technical solutions. We eventually built a prototype of an artificial body (not yet fitted with motors) that successfully reproduced the natural fluid lateral undulations of snakes when they swim. This basis is an essential step for designing realistic autonomous snake robots.
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Affiliation(s)
- Elie Gautreau
- Department of GMSC, Pprime Institute, University of Poitiers, CNRS, ISAE-ENSMA, UPR 3346 Poitiers, France
- Correspondence:
| | - Xavier Bonnet
- CEBC Center of Biological Studies of Chizé, CNRS & University of La Rochelle, Villiers-en-Bois, UMR 7372 Deux-Sèvres, France
| | - Juan Sandoval
- Department of GMSC, Pprime Institute, University of Poitiers, CNRS, ISAE-ENSMA, UPR 3346 Poitiers, France
| | - Guillaume Fosseries
- CEBC Center of Biological Studies of Chizé, CNRS & University of La Rochelle, Villiers-en-Bois, UMR 7372 Deux-Sèvres, France
| | - Anthony Herrel
- MNHN National Museum of Natural History, CNRS, UMR 7179 Paris, France
| | - Marc Arsicault
- Department of GMSC, Pprime Institute, University of Poitiers, CNRS, ISAE-ENSMA, UPR 3346 Poitiers, France
| | - Saïd Zeghloul
- Department of GMSC, Pprime Institute, University of Poitiers, CNRS, ISAE-ENSMA, UPR 3346 Poitiers, France
| | - Med Amine Laribi
- Department of GMSC, Pprime Institute, University of Poitiers, CNRS, ISAE-ENSMA, UPR 3346 Poitiers, France
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Jurestovsky DJ, Tingle JL, Astley HC. Corn Snakes Show Consistent Sarcomere Length Ranges Across Muscle Groups and Ontogeny. Integr Org Biol 2022; 4:obac040. [PMID: 36158732 PMCID: PMC9492312 DOI: 10.1093/iob/obac040] [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: 04/15/2022] [Revised: 07/08/2022] [Indexed: 11/22/2022] Open
Abstract
The force-generating capacity of muscle depends upon many factors including the actin-myosin filament overlap due to the relative length of the sarcomere. Consequently, the force output of a muscle may vary throughout its range of motion, and the body posture allowing maximum force generation may differ even in otherwise similar species. We hypothesized that corn snakes would show an ontogenetic shift in sarcomere length range from being centered on the plateau of the length-tension curve in small individuals to being on the descending limb in adults. Sarcomere lengths across the plateau would be advantageous for locomotion, while the descending limb would be advantageous for constriction due to the increase in force as the coil tightens around the prey. To test this hypothesis, we collected sarcomere lengths from freshly euthanized corn snakes, preserving segments in straight and maximally curved postures, and quantifying sarcomere length via light microscopy. We dissected 7 muscles (spinalis, semispinalis, multifidus, longissimus dorsi, iliocostalis (dorsal and ventral), and levator costae) in an ontogenetic series of corn snakes (mass = 80–335 g) at multiple regions along the body (anterior, middle, and posterior). Our data shows all of the muscles analyzed are on the descending limb of the length-tension curve at rest across all masses, regions, and muscles analyzed, with muscles shortening onto or past the plateau when flexed. While these results are consistent with being advantageous for constriction at all sizes, there could also be unknown benefits of this sarcomere arrangement for locomotion or striking.
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Affiliation(s)
- Derek J Jurestovsky
- Biomechanics Laboratory, Department of Kinesiology, Pennsylvania State University, University Park , PA 16802 , USA
- Department of Biology, University of Akron , 302 E. Buchtel Avenue, Akron, OH 44325 , USA
| | - Jessica L Tingle
- Department of Biology, University of Akron , 302 E. Buchtel Avenue, Akron, OH 44325 , USA
| | - Henry C Astley
- Department of Biology, University of Akron , 302 E. Buchtel Avenue, Akron, OH 44325 , USA
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Capano JG, Boback SM, Weller HI, Cieri RL, Zwemer CF, Brainerd EL. Modular lung ventilation in Boa constrictor. J Exp Biol 2022; 225:274764. [PMID: 35325925 DOI: 10.1242/jeb.243119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 02/11/2022] [Indexed: 12/13/2022]
Abstract
The evolution of constriction and of large prey ingestion within snakes are key innovations that may explain the remarkable diversity, distribution and ecological scope of this clade, relative to other elongate vertebrates. However, these behaviors may have simultaneously hindered lung ventilation such that early snakes may have had to circumvent these mechanical constraints before those behaviors could evolve. Here, we demonstrate that Boa constrictor can modulate which specific segments of ribs are used to ventilate the lung in response to physically hindered body wall motions. We show that the modular actuation of specific segments of ribs likely results from active recruitment or quiescence of derived accessory musculature. We hypothesize that constriction and large prey ingestion were unlikely to have evolved without modular lung ventilation because of their interference with lung ventilation, high metabolic demands and reliance on sustained lung convection. This study provides a new perspective on snake evolution and suggests that modular lung ventilation evolved during or prior to constriction and large prey ingestion, facilitating snakes' remarkable radiation relative to other elongate vertebrates.
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Affiliation(s)
- John G Capano
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
| | - Scott M Boback
- Department of Biology, Dickinson College, Carlisle, PA 17013, USA
| | - Hannah I Weller
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
| | - Robert L Cieri
- School of Science and Engineering, University of the Sunshine Coast, Maroochydore, QLD 4558, Australia
| | - Charles F Zwemer
- Department of Biology, Dickinson College, Carlisle, PA 17013, USA
| | - Elizabeth L Brainerd
- Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA
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Is There Always a Need for Speed? Testing for Differences in the Striking Behavior of Western Ratsnakes (Pantherophis obsoletus) When Encountering Predators and Prey. J HERPETOL 2021. [DOI: 10.1670/20-105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Astley HC. The Biomechanics of Multi-articular Muscle-Tendon Systems in Snakes. Integr Comp Biol 2020; 60:140-155. [PMID: 32211841 DOI: 10.1093/icb/icaa012] [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
The geometry of the musculoskeletal system, such as moment arms and linkages, determines the link between muscular functions and external mechanical results, but as the geometry becomes more complex, this link becomes less clear. The musculoskeletal system of snakes is extremely complex, with several muscles that span dozens of vertebrae, ranging from 10 to 45 vertebrae in the snake semispinalis-spinalis muscle (a dorsiflexor). Furthermore, this span correlates with habitat in Caenophidians, with burrowing and aquatic species showing shorter spans while arboreal species show longer spans. Similar multi-articular spans are present in the prehensile tails of primates, the necks of birds, and our own digits. However, no previous analysis has adequately explained the mechanical consequences of these multi-articular spans. This paper uses techniques from the analysis of static systems in engineering to analyze the consequences of multiarticular muscle configurations in cantilevered gap bridging and compares these outcomes to a hypothetical mono-articular system. Multi-articular muscle spans dramatically reduce the forces needed in each muscle, but the consequent partitioning of muscle cross-sectional area between numerous muscles results in a small net performance loss. However, when a substantial fraction of this span is tendinous, performance increases dramatically. Similarly, metabolic cost is increased for purely muscular multi-articular spans, but decreases rapidly with increasing tendon ratio. However, highly tendinous spans require increased muscle strain to achieve the same motion, while purely muscular systems are unaffected. These results correspond well with comparative data from snakes and offer the potential to dramatically improve the mechanics of biomimetic snake robots.
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Affiliation(s)
- Henry C Astley
- Departments of Biology and Polymer Science, Biomimicry Research and Innovation Center, The University of Akron, Akron, OH 44325, USA
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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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Penning DA, Sawvel B, Moon BR. The scaling of terrestrial striking performance in western ratsnakes (
Pantherophis obsoletus
). JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2019; 333:96-103. [DOI: 10.1002/jez.2328] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 09/11/2019] [Accepted: 09/23/2019] [Indexed: 11/09/2022]
Affiliation(s)
- David A. Penning
- Department of Biology and Environmental Health Missouri Southern State University Joplin Missouri
| | - Baxter Sawvel
- Department of Biology University of Louisiana at Lafayette Lafayette Louisiana
| | - Brad R. Moon
- Department of Biology University of Louisiana at Lafayette Lafayette Louisiana
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Moving beyond the surface: Comparative head and neck myology of threadsnakes (Epictinae, Leptotyphlopidae, Serpentes), with comments on the 'scolecophidian' muscular system. PLoS One 2019; 14:e0219661. [PMID: 31318886 PMCID: PMC6638936 DOI: 10.1371/journal.pone.0219661] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Accepted: 06/28/2019] [Indexed: 11/25/2022] Open
Abstract
Studies on the cephalic myology of snakes provide a series of relevant data on their biology and systematics. Despite the great amount of descriptive studies currently available for the group, much of the knowledge remains obscure for most scolecophidian taxa. This study aimed to describe in detail the cephalic (head and neck) myology of members of the tribe Epictinae, Leptotyphlopidae. We provide the first report of the presence of extrinsic ocular muscles, and a double Musculus pterygoideus acessorius in Leptotyphlopidae. A well-developed M. levator anguli oris is exclusive to the subtribes Renina and Epictina, being reduced in Tetracheilostomina species. Both inter- and intraspecific variations are reported for the head and neck muscles, and such results provide additional data and raise an interesting discussion on the neck-trunk boundaries in snakes. We also provide a discussion on the terminology of a few head muscles in Leptoyphlopidae in comparison to the other lineages of ´Scolecophidia´ (Anomalepididae and Typhlopoidea).
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Abstract
Because the musculoskeletal anatomy of the trunk is the framework for the behaviors of locomotion, ventilation, and body support in lepidosaurs, comparative study of trunk anatomy in this group is critical for unraveling the selective pressures leading to extant diversity in axial form and function among vertebrates. This work uses gross dissection and computed tomography to describe the muscular and skeletal anatomy of the trunk of varanid lizards (Varanidae, Anguimorpha). Gross muscle dissections were conducted to investigate the axial muscular anatomy of Varanus exanthematicus, Varanus giganteus, Varanus rosenbergi, and Varanus panoptes. Computed tomography scans of these and additional varanid lizards from the Varanus and Odatria subgenera were conducted to investigate rib and vertebral number and gross morphology. The number of vertebrae differs between species, with 27-35 presacral and 47-137 postsacral vertebrae. Although the number of floating and abdominal ribs in varanids is variable, most species examined have three to four cervical ribs and three true ribs. Attachment and insertion points of the epaxial and hypaxial musculature are detailed. The body wall has four main hypaxial layers, from superficial to deep: oliquus externus, intercostalis externi, intercostalis internii, and transversus. Varanids differ from other investigated lepidosaurs in having supracostalis dorsus brevis (epaxial) and levator costae (hypaxial), which independently connect each rib to the vertebral column. Although more basic muscle descriptions of the body wall in reptiles are needed, comparisons with the condition in the green iguana (Iguana iguana) can be made.
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Affiliation(s)
- Robert L Cieri
- Department of Biology, University of Utah, Salt Lake City, UT, USA
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