Terrestrial locomotion 4037035 225706479 2008-07-15T00:25:22Z Jwinius 141528 /* Type of movement */ Edit to boa wlink. [[Image:Muybridge race horse animated.gif|right|thumb|250px|An example of terrestrial locomotion. A [[horse]] - an erect-stanced [[unguligrade]] [[quadruped]] - moving by a [[Horse_gait#Gallop|gallop]]ing [[Horse gait|gait]]. An animation of photos by [[Eadweard Muybridge]]]] '''Terrestrial locomotion''' has [[evolved]] many times as [[animal]]s moved onto the [[terrestrial environment|land]] from the [[water]]. [[animal locomotion|Locomotion]] on land raises different problems than that on water, with reduced [[friction]] being replaced by the effects of [[gravity]]. There are three basic forms of locomotion found among terrestrial animals *[[#Legged locomotion|Legged]] - Moving by using [[appendage]]s *[[#Slithering|Slithering]] - moving using the bottom surface of the body *[[#Rolling|Rolling]] - rotating the body over the substrate ==Legged locomotion== Movement on appendages is the most common form of terrestrial locomotion, it is the basic form of locomotion of two major groups with many terrestrial members, the [[vertebrate]]s and the [[arthropod]]s. Important aspects of legged locomotion are [[stance]] (the way the body is supported by the legs), the number of legs, and the functional structure of the [[leg]] and [[foot]]. There are also many [[gait]]s, ways of moving the legs in order to locomote, such as [[walking]], [[running]], or [[hopping]]. ===Stance=== [[Image:Sprawling and erect hip joints - horiz.png| thumb | right | 300px | Hip joints and hindlimb postures.]] Appendages can be used for movement in a number of ways. The [[stance]], the way the body is supported by the legs, is an important aspect. Charig 1972 identified three main ways in which vertebrates support themselves with their legs - the [[sprawling stance]], the [[semi-erect stance]], and the [[fully erect stance]]. Some animals may use different stances in different circumstances, depending on the stance's mechanical and energetic advantages. The most basic is the [[sprawling stance]]. Here the legs are used to drag the body over the land. This is the earliest form of use of legs on land. [[Amphibious fish]] such as the [[mudskipper]] drag themselves across land on their sturdy fins. Many [[reptiles]] and [[amphibians]], some or all of the time, use this method of locomotion. Among [[invertebrate]]s there is anecdotal evidence that some [[octopus]] species (such as the ''[[Pinnoctopus]]'' genus), sometimes to pursue prey between rockpools, can also drag themselves across land a short distance by hauling its body along by it tentacles, see [http://www.tonmo.com/forums/archive/index.php?t-102.html]. There may be video evidence of this [http://www.pbs.org/wnet/nature/octopus/index.html]. The second form of stance found among legged terrestrial animals is the [[semi-erect stance]]. Here the legs are to the side, but the body is held above the substrate. This mode of locomotion is found among some [[reptile]]s and [[amphibian]]s. It is also the main stance of the [[crocodilian]]s. A few mammals, such as the [[platypus]] also use this stance. Among the [[invertebrate]]s most [[arthropod]]s, which includes the most diverse group of animals - the [[insect]]s, many have a stance which might best be described as semi-erect. Finally there is the main form of stance of [[mammal]] and [[bird]]s, the [[fully erect stance]]. In these groups the legs are placed beneath the body. This is often linked with the evolution of [[endothermy]], as it avoids [[Carrier's constraint]] and thus allows prolonged periods of activity.(Bakker 1988). The fully erect stance is not necessarily the "most-evolved" stance, evidence suggests that crocodilians evolved a semi-erect stance from ancestors with fully erect stance as a result of adapting to a mostly aquatic lifestyle (Reilly & Elias 1998). For example, the [[mesozoic]] prehistoric crocodilian ''[[Erpetosuchus]]'' is believed to have had a fully erect stance and been terrestrial [http://www.dinoruss.com/jdp/misc/croc.htm]. ===Number of legs=== [[Image:31-Velvet Worm.JPG|right|thumb|The velvet worm.]] The number of locomotory appendages varies much between animals, and sometimes the same animal may use different numbers of its legs in different circumstances. The best contender for [[unipedal]] movement is the [[springtail]], which while typically [[hexapedal]], hurls itself away from danger using its [[furcula (Collembola)|furcula]], a [[tail]]-like forked rod that can be rapidly unfurled from the underside of its body. A fair number of species move and stand on two legs, that is, are [[bipedal]]. The group that is exclusively bipedal is the [[bird]]s, which have an alternating gait. There are also a number of bipedal mammals. Most bipedal mammals move by hopping - the [[macropod]]s and various jumping [[rodent]]s. Only a few mammals such as [[human]]s and the [[giant pangolin]] commonly show an alternating bipedal gait. Also [[cockroach]]es and some [[lizard]]s may run on their two hind legs. [[Macropod]]s such as [[kangaroo]]s are the only example of [[tripedal]] movement. They have thick muscular tails and when moving slowly may alternate between resting their weight on their tails and their two hind legs. With the exception of the [[bird]]s, all terrestrial vertebrate groups are mostly [[quadrupedal]] - the [[mammal]]s, the [[reptile]]s, and the [[amphibian]]s usually move on four legs. There are many quadrupedal gaits. The most diverse group of animals on earth, the [[insect]]s, are included in a larger [[taxon]] known as [[Hexapoda|hexapods]], most of which are [[hexapedal]], walking and standing on six legs. Exceptions among the insects include praying mantises which are quadrapeds, their front two legs having been modified for grasping, and some kinds of insect [[larva]] who may have no legs (e.g. [[maggot]]s) or additional [[proleg]]s (e.g. [[caterpillar]]s). [[Spider]]s and many of their relatives move on eight legs - are [[octopedal]]. However, some creatures move on many more legs. Terrestrial [[crustacean]]s may have a fair number - [[woodlice]] having fourteen legs. Also, as previously mentioned, some insect larvae such as [[caterpillar]]s have up to six additional fleshy [[proleg]]s in addition to the six legs standard to insects. Some species of invertebrate have even more legs, the unusual [[velvet worm]] having stubby legs under the length of its body, with around several dozen pairs of legs. [[Centipedes]] have one pair of legs per body segment, with typically around 50 legs, but some species having over 200. The terrestrial animals with the most legs are the [[millipede]]s, relatives of the [[centipede]]s. They have two pairs of legs per body segment, with common species having between 80 and 400 legs overall. However, the rare species [[Illacme plenipes]] can have up to 750 legs. Animals with many legs typically move by waves of motion travelling over their legs. ===Leg and foot structure=== The [[leg]]s of [[tetrapod]]s, the main group of terrestrial [[vertebrate]]s, have internal bones, with externally attached muscles for movement, and the basic form has three key [[joint]]s: the [[shoulder]] joint, the [[knee]] joint, and the [[ankle]] joint, at which the [[foot]] is attached. Within this theme there is much variation in form. An alternative form of vertebrate 'leg' to the tetrapod leg is the fins found on [[amphibious fish]]. Also a few [[tetrapod]]s, such as the [[macropod]]s, have adapted their [[tail]]s as additional locomotory appendages. The basic form of the vertebrate [[foot]] has five [[toe]]s, however some animals will have evolved fewer than this, and some early [[tetrapod]]s had more; [[Acanthostega]] had eight toes. Feet have evolved many forms depending on the animal's needs. One key variation is where on the foot the animal's weight is placed. Most vertebrates&mdash;the amphibians, the reptiles, and some mammals such as [[human]]s and [[bear]]s&mdash;are [[plantigrade]], walking on the whole of the underside of the foot. Many mammals, such as [[cat]]s and [[dog]]s are [[digitigrade]], walking on their toes, the greater stride length allowing more speed. Digitigrade mammals are also often adept at quiet movement. Birds are also digitigrade [http://www.geocities.com/Yosemite/Forest/5238/Jill/Avian_Skeleton/leg.htm]. Some animals such as [[horse]]s are [[unguligrade]], walking on the tips of their toes. This even further increases their stride length and thus their speed. A few mammals are also known to walk on their [[knuckle]]s, at least for their front legs. [[knuckle-walking|Knuckle-walking]] allows the foot (hand) to specialise for food gathering and/or climbing, as with the [[great ape]]s and the extinct [[chalicothere]]s, or for swimming, as with the [[platypus]]. In animals where feet have evolved into functional [[hand]]s, [[hand walking]] is also possible. Among terrestrial [[invertebrate]]s there are a number of leg forms. The [[arthropod leg]]s are jointed and supported by hard external armor, with the muscles attached to the internal surface of this [[exoskeleton]]. The other group of legged terrestrial invertebrates, the [[velvet worms]], have soft stumpy legs supported by a [[hydrostatic skeleton]]. The [[proleg]]s that some caterpillars have in addition to their six more-standard arthropod legs have a similar form to those of velvet worms, and suggest a distant shared ancestry. ===Gaits=== [[Image:Kangaroo-in-flight.jpg|thumb|200px|A jumping kangaroo.]] Animals show a vast range of [[gait]]s, the order that they place and lift their appendages in locomotion. Gaits can be grouped into categories according to their patterns of support sequence. For [[quadrupeds]], there are three main categories: walking gaits, running gaits, and [[leaping gaits]]. In one system,<ref name="Roberts1995">Tristan David Martin Roberts (1995) ''Understanding Balance: The Mechanics of Posture and Locomotion'', Nelson Thornes, ISBN 0412601605.</ref> there are 60 discrete patterns: 37 walking gaits, 14 running gaits, and 9 [[leaping gaits]]. [[Walking]] is the most common gait, where some feet are on the ground at any given time, and found in almost all legged animals. In an informal sense, [[running]] is considered to occur when at some points in the stride all feet are off the ground in a '''moment of suspension'''. Technically, however, moments of suspension occur in both running gaits (such as trot) and leaping gaits (such as canter and gallop). Gaits involving one or more moments of suspension can be found in many animals, and compared to walking they are faster but more energetically costly forms of locomotion. Animals will use different gaits for different speeds, terrain, and situations. For example horses show four natural gaits, the slowest [[horse gait]] is the [[Horse gait#walk|walk]], then there are three faster gaits which, from slowest to fastest, are the [[Trot (horse gait)|trot]], the [[canter]], and the [[Horse gait#gallop|gallop]]. Animals may also have unusual gaits that are used occasionally, such as for moving sideways or backwards. For example, the main [[gait (human)|human gaits]] are bipedal [[walking]] and [[running]], but they employ many other gaits occasionally, including a four-legged [[crawl]] in tight spaces. In walking, and for many animals running, the motion of legs on either side of the body alternates, i.e. is out of phase. Other animals, such as a horse when galloping, or an [[inchworm]], alternate between their front and back legs. An alternative to a gait which alternates between legs is hopping or saltation, where all legs move together. As a main means of locomotion, this is usually found in bipeds or semi-bipeds. Among the mammals saltation is commonly used among [[macropod]]s ([[kangaroo]]s and their relatives), [[jerboa]]s, [[springhare]]s, [[kangaroo rat]]s, [[hopping mice]], [[gerbil]]s, and [[sportive lemur]]s. Certain tendons in kangaroo hind legs are very [[Elasticity (physics)|elastic]], allowing kangaroos to effectively bounce along conserving energy from hop to hop, making hopping a very energy efficient way to move around in their nutrient poor environment. Saltation is also used by many small birds. [[Frog]]s and [[flea]]s also hop. Most animals move in the direction of their head. However there are some exceptions. [[Crab]]s move sideways, and [[naked mole rat]]s which live in tight tunnels underground can move backward or forward with equal facility. [[Crayfish]] can move backward much faster than they can move forward. [[Gait analysis]] is the study of gait in humans and other animals. This may involve videoing subjects with markers on particular anatomical landmarks and measuring the forces of their footfall using floor [[transducer]]s ([[strain gauge]]s). Skin [[electrode]]s may also be used to measure [[muscle]] activity. ==Slithering== [[Image:Aegista tokyoensis 01.JPG|right|thumb|A [[snail]] moves by slithering.]] There are a number of terrestrial and amphibious [[limbless vertebrates]] and invertebrates. These animals, due to lacking appendages, move by '''slithering''' on their underside. Slithering is also known as '''crawling''', although this is also used for some animals moving on all four limbs. All limbless animals come from [[cold-blooded]] groups, there are no [[endothermic]] limbless animals, i.e. there are no limbless birds or mammals. ===Lower body surface=== Where the foot is important to the legged mammal, for animals that slither the underside of the body is important. Some animals such as [[snake]]s or [[legless lizard]]s move on their smooth dry underside. Other animals have various features that aid movement. [[Mollusc]]s such as [[slug]]s and [[snail]]s move on a layer of [[mucus]] that is secreted from their underside, reducing friction and protecting from injury when moving over sharp objects. [[Earthworm]]s have small bristles ([[setae]]) that hook into the substrate and help them move. Some animals such as [[leeches]] have suction cups on either end of the body allowing [[two anchor movement]]. ===Type of movement=== Some limbless animals, such as leeches, have suction cups on either end of their body, which allow them to move by anchoring the rear end and then moving forward the front end, which is then anchored and then the back end is pulled in, and so on. This is know as [[two-anchor movement]]. A legged animal, the [[inchworm]], also moves like this, clasping with appendages at either end of its body. Limbless animals can also move using [[pedal locomotary wave]]s, rippling the underside of the body. This is the main method used by [[mollusc]]s such as slugs and snails, and also large flatworms, and some other worms. The waves may move in the opposite direction to motion, known as [[retrograde wave]]s, or in the same direction as motion, known as [[direct wave]]s. Earthworms move by retrograde waves alternatively swelling and contracting down the length of their body, the swollen sections being held in place using [[setae]]. Aquatic molluscs such as [[limpet]]s, which are sometimes out of the water, tend to move using retrograde waves. However terrestrial molluscs such as slugs and snails tend to use direct waves. [[Lugworm]]s also use direct waves. Most snakes move using [[lateral undulation]] where a lateral wave travels down the snake's body in the opposite direction to the snake's motion and pushes the snake off irregularities in the ground. This mode of locomotion requires these irregularities to function. Another form of locomotion, [[rectilinear locomotion]], is used at times by some snakes, especially large ones such as [[Pythonidae|python]]s and [[Boidae|boa]]. Here large scales on the underside of the body, known as [[scute]]s are used to push backwards and downwards. This is effective on a flat surface and is used for slow, silent movement, such as when stalking prey. Snakes use [[concertina movement|concertina locomotion]] for moving slowly in tunnels, here the snake alternates in bracing parts of its body on it surrounds. Finally the [[caenophidian]] snakes use the fast and unusual method of movement known as [[sidewinding]] on sand or loose soil, where the snake moves sideways. The snake cycles through throwing the front part of its body sideways in the direction of motion and bringing the back part of it body into line. ==Rolling==<!-- This section is linked from [[Wheel]] --> [[Image:Steppenschuppentier1a.jpg|right|thumb|The pangolin ''[[Manis temminckii]]'' in defensive position.]] Although animals have never evolved [[wheel]]s for locomotion (as [[bacteria]] have for their [[flagella]])[http://www.simonyi.ox.ac.uk/dawkins/WorldOfDawkins-archive/Dawkins/Work/Articles/1996-11-24wheels.shtml], a small number of animals will move at times by '''rolling''' their whole body. '''Rolling animals''' can be divided into those which roll under the force of gravity and those which roll using their own power. ===Gravity assisted=== [[Web-toed salamander]]. This 10cm long salamander lives on steep hills in the [[Sierra Nevada (U.S.)|Sierra Nevada]] mountains. When it's disturbed or startled it coils itself up into a little ball often causing it to roll down hill (García-París & Deban 1995). See [http://www.abc.net.au/science/k2/moments/s42510.htm]. [[Namib wheeling spiders]] (''[[Carparachne]] spp.''), found in the [[Namib]] desert, will actively roll down sand dunes. This action can be used to successfully escape predators such as the ''[[Pompilidae]]'' [[tarantula wasps]] which lays its eggs in a paralyzed spider so the larvae have enough food when they hatch. The spiders flip their body sideways and then cartwheel over their bent legs. The rotation is fast, with the [[golden wheel Spider]] (''[[Carparachne aureoflava]]'') moving up to 20 revolutions per second, moving the spider at 1 metre per second. At this speed the spider appears only as a blurred ball. A video of a wheeling spider in the Namib can be found at [http://www.bbc.co.uk/nature/programmes/tv/wildafrica/diary_jan.shtml]. More videos of Namib wheeling spiders, showing wheeling and wasp/spider interactions can be found at [http://www.bbcmotiongallery.com/Customer/SearchDetails.aspx?itemId=7cd567f0-d8bc-4a53-8fd4-a9c417c5d9ce&page=4]. This spider was studied by Dr Joh Henschel of the Gobabeb Training & Research Centre. See [http://66.249.93.104/search?q=cache:rAAJe9bsbzMJ:www.gobabeb.org/Gobabeb%2520Times%2520I.pdf+Carparachne+aureoflava&hl=en&gl=uk&ct=clnk&cd=4]. [[Pangolin]]s, a type of mammal covered in thick scales rolls into a tight ball when threatened. Pangolins has been reported to roll away from danger, by both gravity and self-powered methods. A pangolin in hill country in [[Sumatra]], in order to flee from the researcher, was observed to run to the edge of a slope and then curl into a ball and roll down the slope, crashing through the vegetation, and covering an estimated 30 metres or more in 10 seconds (Tenaza 1975). ===Self-powered=== [[Caterpillar]] of the [[Mother-Of-Pearl Moth]], [[Pleurotya ruralis]]. This research was done by John Brackenbury at University of Cambridge in the United Kingdom. When attacked, this caterpillar will touch its head to its tail and roll backwards, up to 5 revolutions at about 40 cm per second, which is about 40 times its normal speed. See [http://www.abc.net.au/science/k2/moments/s42510.htm]. [[Nannosquilla decemspinosa]], a species of long-bodied, short-legged [[stomatopod|Mantis Shrimp]], lives in shallow sandy areas along the Pacific coast of Central and South America. When stranded a low tide the 3cm stomatopod lies on its back and performs backwards somersaults over and over. The animal moves up to 2 meters at a time by rolling 20-40 times, with speeds of around 72 revolutions per minute. That is 1.5 body lengths per second (3.5 cm/s). Researchers estimate that the stomatopod acts as a true wheel around 40% of the time during this series of rolls. The remaining 60% of the time it has to "jumpstart" a roll by using its body to thrust itself upwards and forwards. See [http://www.nwf.org/nationalwildlife/article.cfm?issueID=77&articleID=1114] and [http://www.abc.net.au/science/k2/moments/s42510.htm]. Discovered in 1979 by Roy Caldwell, an animal behaviourist at the University of California at Berkeley [[Pangolin]]s have also been reported to roll away from danger by self-powered methods. Witnessed by a lion researcher [http://www.serengeti.org/nightlife_animals.html] in the [[Serengeti]] in Africa, a group of lions surrounded a pangolin, but could not get purchase on it when it rolled into a ball, and so the lions sat around it waiting and dozing. Surrounded by lions, it would unroll itself slightly and give itself a push to roll some distance, until by doing this multiple times it could get far enough away from the lions to be safe. Moving like this would allow a pangolin to cover distance while still remaining in a protective armoured ball . ==References== <references/> *Charig, A.J. (1972) The evolution of the archosaur pelvis and hind-limb: an explanation in functional terms. In Studies in Vertebrate Evolution (eds K.A.Joysey and T.S.Kemp). Oliver & Boyd, Edinburgh, pp.121-55. *Reilly, Stephen M. and Elias, Jason A. 1998, Locomotion in alligator mississippiensis: kinematic effects of speed and posture and their relevance to the sprawling-to-erect paradigm, J. exp. Biol 201,2559-2574. [http://jeb.biologists.org/cgi/reprint/201/18/2559?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&andorexacttitle=and&andorexacttitleabs=and&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&volume=201&firstpage=2559&resourcetype=HWCIT pdf] *García-París, M. & Deban, S. M. 1995. A novel antipredator mechanism in salamanders: rolling escape in Hydromantes platycephalus. Journal of Herpetology 29, 149-151. *Tenaza, R. R. 1975. Pangolins rolling away from predation risks. Journal of Mammalogy 56, 257. ==See also== *[[Walking fish]] ==External links== *[http://animaldiversity.ummz.umich.edu/site/topics/mammal_anatomy/running_fast.html Adaptations of running animals] *[http://reptilis.net/crocodylia/bodyplan.html#Erect Crocodile stance] *[http://palaeo.gly.bris.ac.uk/Palaeofiles/Tracks/Report5/Stance.html Tetrapod stance] *[http://66.249.93.104/search?q=cache:rsRCLTTvr80J:polypedal.berkeley.edu/ib32/Lectures/Crawl.pdf+slug+locomotion+rectilinear&hl=en&gl=uk&ct=clnk&cd=3 Lecture on crawling (slithering) at Berkeley] *[http://www.maschinenbau.tu-ilmenau.de/pademis/html/Projects/Locomotion.htm Animation of earthworm movement by a propagating retrograde wave] [[Category:Zoology]] [[Category:Locomotion]]