Concertina movement

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Concertina movement is the movement occurring in snakes and other legless organisms that consists of gripping or anchoring with portions of the body while pulling or pushing other sections in the direction of movement. [1]

Contents

Mechanism

Each point on the snake's body goes through alternating cycles of static contact and movement, with regions propagating posteriorly (i.e. any point on the snake will change from movement to stasis or vice versa shortly after the change occurs in the point anterior to it). This movement is quite strenuous and slow compared to other methods of locomotion. [2] Energetic studies show that it takes more calories per meter to use concertina locomotion than either sidewinding or lateral undulation. [3]

Modes

In snakes, there are two currently recognized modes of concertina locomotion.

Tunnel

Tunnel concertina locomotion is often employed in unobstructed tunnels, where the snake lacks both sufficient contact points to perform lateral undulation and sufficient lateral room to perform sidewinding. [2] During tunnel concertina locomotion, the snake anchors itself by flexing its body in a series on alternating bends which press against the walls of the tunnel. The snake extends the anterior portion of its body by straightening these bends, then flexes the anterior portion of the body to form anterior anchor points while pulling the posterior portion forward. This mode of concertina, while still slower than lateral undulation or sidewinding, is still fairly fast, with snakes moving approximately 10% of their length per second. [2] However, because the snake is straightening and re-forming bends, it requires the entire space of the tunnel to move, and any obstruction will disrupt locomotion. In the presence of either of these, snakes will switch from concertina to another mode (as both of the above are faster and more economical), though in the case of extreme lateral constraint (tunnel width less than 3x body width), snakes will ignore the contact points that could be used in lateral undulation and perform concertina.

Arboreal

Arboreal concertina locomotion is employed on bare branches on trees, when secondary branches are not available (when they are, snakes perform lateral undulation, using these branches as contact points). [4] In this mode of concertina locomotion, snakes likely grip the branch by ventrally flexing the body at the points where the alternation bends cross the perch, with the bends themselves sometimes extending beyond the edge of the branch. The snake extends the anterior portion of its body, but as it does so, the body follows a constant path (like lateral undulation, but unlike tunnel concertina locomotion). It then forms anterior grips and pulls the body forward, again demonstrating the 'path following' characteristic. Unlike tunnel concertina locomotion, this mode avoids any obstacle which falls between the bends of the snake's body. [4] However, it is exceptionally slow, with snakes rarely moving faster than 2% of their length per second. [4]

Some snakes, such as the brown tree snake, use a "lasso-climbing" or "lasso locomotion" technique to climb vertically by wrapping around the vertical object, including poles intended to stop predators. [5] [6]

Related Research Articles

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<span class="mw-page-title-main">Snake</span> Limbless, scaly, elongate reptile

Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes. Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads. To accommodate their narrow bodies, snakes' paired organs appear one in front of the other instead of side by side, and most have only one functional lung. Some species retain a pelvic girdle with a pair of vestigial claws on either side of the cloaca. Lizards have independently evolved elongate bodies without limbs or with greatly reduced limbs at least twenty-five times via convergent evolution, leading to many lineages of legless lizards. These resemble snakes, but several common groups of legless lizards have eyelids and external ears, which snakes lack, although this rule is not universal.

<span class="mw-page-title-main">Human leg</span> Lower extremity or limb of the human body (foot, lower leg, thigh and hip)

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<span class="mw-page-title-main">Undulatory locomotion</span>

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<span class="mw-page-title-main">Bio-inspired robotics</span>

Bio-inspired robotic locomotion is a fairly new subcategory of bio-inspired design. It is about learning concepts from nature and applying them to the design of real-world engineered systems. More specifically, this field is about making robots that are inspired by biological systems, including Biomimicry. Biomimicry is copying from nature while bio-inspired design is learning from nature and making a mechanism that is simpler and more effective than the system observed in nature. Biomimicry has led to the development of a different branch of robotics called soft robotics. The biological systems have been optimized for specific tasks according to their habitat. However, they are multifunctional and are not designed for only one specific functionality. Bio-inspired robotics is about studying biological systems, and looking for the mechanisms that may solve a problem in the engineering field. The designer should then try to simplify and enhance that mechanism for the specific task of interest. Bio-inspired roboticists are usually interested in biosensors, bioactuators, or biomaterials. Most of the robots have some type of locomotion system. Thus, in this article different modes of animal locomotion and few examples of the corresponding bio-inspired robots are introduced.

References

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  4. 1 2 3 Astley, H.C.; Jayne, B.C. (2007), "Effects of perch diameter and incline on the kinematics, performance and modes of arboreal locomotion of corn snakes (Elaphe guttata)", Journal of Experimental Biology, 210 (Pt 21): 3862–3872, doi: 10.1242/jeb.009050 , PMID   17951427
  5. Machemer, Theresa (11 January 2021). "Invasive Brown Tree Snakes Stun Scientists With Amazing New Climbing Tactic". Smithsonian . Retrieved 11 January 2021.
  6. Savidge, Julie A.; Seibert, Thomas F.; Kastner, Martin; Jayne, Bruce C. (11 January 2021). "Lasso locomotion expands the climbing repertoire of snakes". Current Biology. Retrieved 2 August 2023.