Rectilinear locomotion or rectilinear progression is a mode of

locomotion Locomotion means the act or ability of something to transport or move itself from place to place. Locomotion may refer to: Motion * Motion (physics) * Robot locomotion, of man-made devices By environment * Aquatic locomotion * Flight * Locomo ...

most often associated with

snake 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 ...

s. In particular, it is associated with heavy-bodied species such as terrestrial pythons and boas; however, most snakes are capable of it. It is one of at least five forms of locomotion used by snakes, the others being lateral undulation,

sidewinding Sidewinding is a type of locomotion unique to snakes, used to move across loose or slippery substrates. It is most often used by the Saharan horned viper, '' Cerastes cerastes'', the Mojave sidewinder rattlesnake, '' Crotalus cerastes'', and th ...

, concertina movement, and slide-pushing. Unlike all other modes of snake locomotion, which include the snake bending its body, the snake flexes its body only when turning in rectilinear locomotion.

Biomechanics of rectilinear locomotion

Rectilinear locomotion relies upon two opposing

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of mus ...

s, the costocutaneous inferior and superior, which are present on every

rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ches ...

and connect the ribs to the

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

. Although it was originally believed that the ribs moved in a "walking" pattern during rectilinear movement, studies have shown that the ribs themselves do not move, only the muscles and the skin move to produce forward motion. First, the costocutaneous superior lifts a section of the snake's belly from the ground and places it ahead of its former position. Then the costocutaneous inferior pulls backwards while the belly scales are on the ground, propelling the snake forwards. These sections of contact propagate posteriorly, which results in the ventral surface, or belly, moving in discrete sections akin to "steps" while the overall body of the snake moves continuously forward at a relatively constant speed.

Uses of rectilinear locomotion

This method of locomotion is extremely slow (between ), but is also almost noiseless and very hard to detect, making it the mode of choice for many species when stalking prey. It is primarily used when the space being traversed is too constricting to allow for other forms of movement. When climbing, snakes will often use rectilinear locomotion in conjunction with concertina movements to exploit terrain features such as interstices in the surfaces they are climbing. Rectilinear locomotion may also be useful after snakes eat. Snakes have more difficulty bending their spines after consuming large prey, and rectilinear movement requires less flexing of the spine than other locomotion types.

In robotics

The development of rectilinear movement in

robotics Robotics is an interdisciplinary branch of computer science and engineering. Robotics involves design, construction, operation, and use of robots. The goal of robotics is to design machines that can help and assist humans. Robotics integrat ...

is centered around the development of snakelike

robot A robot is a machine—especially one programmable by a computer—capable of carrying out a complex series of actions automatically. A robot can be guided by an external control device, or the control may be embedded within. Robots may be ...

s, which have significant advantages over robots with wheeled or bipedal locomotion. The primary advantage in the creation of a serpentine robot is that the robot is often capable of traversing rough, muddy, and complex terrain that is often prohibitive to wheeled

robots "\n\n\n\n\nThe robots exclusion standard, also known as the robots exclusion protocol or simply robots.txt, is a standard used by websites to indicate to visiting web crawlers and other web robots which portions of the site they are allowed to visi ...

. Secondly, due to the mechanisms responsible for rectilinear and other forms of serpentine locomotion, the robots tend to have repetitive motor elements, which makes the entire robot relatively robust to

mechanical failure Structural integrity and failure is an aspect of engineering that deals with the ability of a structure to support a designed structural load (weight, force, etc.) without breaking and includes the study of past structural failures in order to ...

References

Snakes Terrestrial locomotion {{snake-stub

Biomechanics of rectilinear locomotion

Uses of rectilinear locomotion

In robotics

See also

References