Muscular mechanisms of snake locomotion: An electromyographic study of lateral undulation of the florida banded water snake (<i>Nerodia fasciata</i>) and the yellow rat snake (<i>Elaphe obsoleta</i>)

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SUMMARYArboreal 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.Supplementary material available online at

Section: Modes Of Locomotionmentioning

confidence: 60%

Section: Modes Of Locomotionmentioning

confidence: 99%

Perch size and structure have species-dependent effects on the arboreal locomotion of rat snakes and boa constrictors

Jayne

Herrmann

2011

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“…The use of epaxial musculature for bending in the sandfish resembles the case in other taxa [e.g. amphibians (Frolich and Biewener, 1992) and snakes (Jayne, 1988)] that use epaxial muscle for lateral bending. There is some evidence that epaxial muscle may be used during high-speed (>3SVL s −1…”

Section: Discussion the Role Of Epaxial Musculature In Lateral Undulamentioning

confidence: 89%

“…Studies have shown that for elongate animals with uniform body shape, such as the eel (Gillis, 1998a) and lamprey (Williams et al, 1989;Wardle et al, 1995), EMG duration changes are small along the length of the body compared with those in fish with differing body diameter and shape (Wardle et al, 1995;Altringham and Ellerby, 1999). Also, the duty cycle in sandfish was comparable to that in other animals such as the terrestrial snake [~0.45 in iliocostalis of Nerodia fasciata) (Jayne, 1988)] and aquatic lamprey [~0.5 (Williams et al, 1989)], despite differences in environment. Currently, we do not understand what factors influence this timing and how the environment might play a role.…”

Section: Activation Timing During Subsurface Swimmingmentioning

confidence: 99%

Environmental interaction influences muscle activation strategy during sand-swimming in the sandfish lizard Scincus scincus

Sharpe

Ding

Goldman

2013

SUMMARYAnimals like the sandfish lizard (Scincus scincus) that live in desert sand locomote on and within a granular medium whose resistance to intrusion is dominated by frictional forces. Recent kinematic studies revealed that the sandfish utilizes a wave of body undulation during swimming. Models predict that a particular combination of wave amplitude and wavelength yields maximum speed for a given frequency, and experiments have suggested that the sandfish targets this kinematic waveform. To investigate the neuromechanical strategy of the sandfish during walking, burial and swimming, here we use high-speed X-ray and visible light imaging with synchronized electromyogram (EMG) recordings of epaxial muscle activity. While moving on the surface, body undulation was not observed and EMG showed no muscle activation. During subsurface sand-swimming, EMG revealed an anterior-to-posterior traveling wave of muscle activation which traveled faster than the kinematic wave. Muscle activation intensity increased as the animal swam deeper into the material but was insensitive to undulation frequency. These findings were in accord with empirical force measurements, which showed that resistance force increased with depth but was independent of speed. The change in EMG intensity with depth indicates that the sandfish targets a kinematic waveform (a template) that models predict maximizes swimming speed and minimizes the mechanical cost of transport as the animal descends into granular media. The differences in the EMG pattern compared with EMG of undulatory swimmers in fluids can be attributed to the friction-dominated intrusion forces of granular media. Supplementary material available online at

“…This constancy of  bend with variable Gap max suggests  bend may be the primary limiting factor for performance over a wide range of conditions. Such a limit may result from the maximum muscular force that can be exerted (Jayne and Riley, 2007) by the semispinalis-spinalis (SSP) and multifidus (M) muscles, which are the primary dorsal flexors in snakes (Jayne, 1988). Three observations suggest that  pitch does not play a dominant role in determining maximum performance: (1) for orientations where torques were greatest, 50% or more of the total length of the body remained on the supporting perch to act as a counterweight, (2) snakes used their body or tail to wrap the perch or pegs, offsetting any tendency to pitch, and (3) all observed failures were the result of localized bending of the body rather than rigid-body pitching off the end of the perch.…”

Section: Limits To Gap-bridging Performancementioning

confidence: 99%

The effects of three-dimensional gap orientation on bridging performance and behavior of brown tree snakes (Boiga irregularis)

Byrnes

Jayne

2012

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SUMMARY Traversing gaps with different orientations within arboreal environments has ecological relevance and mechanical consequences for animals. For example, the orientation of the animal while crossing gaps determines whether the torques acting on the body tend to cause it to pitch or roll from the supporting perch or fail as a result of localized bending. The elongate bodies of snakes seem well suited for crossing gaps, but a long unsupported portion of the body can create large torques that make gap bridging demanding. We tested whether the three-dimensional orientation of substrates across a gap affected the performance and behavior of an arboreal snake (Boiga irregularis). The snakes crossed gaps 65% larger for vertical than for horizontal trajectories and 13% greater for straight trajectories than for those with a 90 deg turn within the horizontal plane. Our results suggest that failure due to the inability to keep the body rigid at the edge of the gap may be the primary constraint on performance for gaps with a large horizontal component. In addition, the decreased performance when the destination perch was oriented at an angle to the long axis of the initial perch was probably a result of the inability of snakes to maintain balance due to the large rolling torque. For some very large gaps the snakes enhanced their performance by using rapid lunges to cross otherwise impassable gaps. Perhaps such dynamic movements preceded the aerial behavior observed in other species of arboreal snakes.