Motility

For the Steve Kuhn album, see Motility (album).

"Motile" redirects here. For the independent British record label, see Motile (record label).

In biology, motility is the ability to move spontaneously and actively, consuming energy in the process. Motility is genetically determined but may be affected by environmental factors. For instance, muscles give animals motility but the consumption of hydrogen cyanide (the environmental factor in this case) would adversely affect muscle physiology causing them to stiffen leading to rigor mortis. Most animals are motile but the term applies to unicellular and simple multicellular organisms, as well as to some mechanisms of fluid flow in multicellular organs, in addition to animal locomotion. Motile marine animals are commonly called free-swimming.

Motility may also refer to an organism's ability to move food through its digestive tract, i.e., peristaltics (gut motility, intestinal motility, etc.).

Motility should not be confused with mobility which is the ability to be physically moved. For instance, a kipper can be moved from the sea to a fish market, making the fish mobile. A kipper can also swim in the sea on its own, making it motile. Organisms are both motile and mobile however their mobility is dependant on external influence. As a result, an organism's mobility is not considered to be one of the organism's phenotypic traits whereas an organism's motility (or lack of motility - sessility (zoology)) is considered to be a trait.

Cellular-level motility

At the cellular level, different modes of motility exist:

• flagellar motility, a swimming-like motion (observed for example in spermatozoa, propelled by the regular beat of their flagellum, or E. coli, which swims by rotating a helical prokaryotic flagellum)
• amoeboid movement, a crawling-like movement, which also makes swimming possible
• gliding motility
• Swarming motility

Many cells are not motile, for example Klebsiella pneumoniae and Shigella, or under specific circumstances such as Yersinia pestis at 37 °C.

Movements

See also: Taxis

The events that are perceived as movements can be directed:

• along a chemical gradient (see chemotaxis)
• along a temperature gradient (see thermotaxis)
• along a light gradient (see phototaxis)
• along a magnetic field line (see magnetotaxis)
• along an electric field (see galvanotaxis)
• along the direction of the gravitational force (see gravitaxis)
• along a rigidity gradient (see durotaxis)
• along a gradient of cell adhesion sites (see haptotaxis)
• along other cells or biopolymers

See also

• Cell migration