Kinesis and Taxis
Nearly all animals are mobile at some point in their life. For some lower animals, movement is undirected and random, such as a Paramecium blundering about its environment. Such undirected orientation is called kinesis. In contrast to kinesis, taxis is the term for movement in response to some stimulus. Taxis involves more complex behavior than kinesis, and is generally what we think of when we think of movement.
Different taxes (plural of taxis) result in response to different types of stimuli. Each of these forms of taxis can be described by simply adding a prefix to the word taxis. The table below shows the most common forms of taxis.
From these terms we can describe almost any directed movement. For instance, phototaxis would be movement in response to light. Chemotaxis means movement in response to a chemical. Any combination of these words can be used. Movements toward a stimulus are positive taxes, while movements away from the stimulus are negative taxes.
Important Examples of Taxis
makes clear the variety of types of taxis. Below we will provide some examples.
- Menotaxis refers to an animal maintaining a constant angle to a stimulus. The Silkworm moth, for instance, flies at an angle perpendicular to the direction of the wind in order to pick up a scent trail. Once the moth detects the trail, it turns upwind to find the chemical gradient of the trail. Another type of menotaxis is sun compass orientation. Many animals use the position of the sun to orient themselves. These animals can compensate for the sun moving across the sky over the course of the day. Honeybees for instance, imprint on the arc of the sun. They can utilize polarized light, and so they can locate the position of the sun even on an overcast day.
- Tropotaxis refers to taking signal samples simultaneously from paired receptors. From , we can see tropotaxis literally means "turned movement." Animals taking samples from paired receptors often zigzag about the trail. An experiment by Martin and Lindauer revealed that crossing the antennae in honeybees results in the bees traveling in the opposite direction from where the trail would lead them.
- Magnetotaxis is orientation in response to magnetic cues. Wide varieties of animals use magnetic cues to navigate. Aquaspirillum bacteria burrow in the mud, and use the magnetic field of the earth to determine position. In the Northern Hemisphere, they direct themselves to the northern magnetic pole, which is actually the geographical South Pole, and so burrow down into the mud. In the Southern Hemisphere, they orient towards the geographical North Pole, which is a magnetic south pole.
- Telotaxis, or goal-directed movement, describes the motion of visual predators who can see a distant visual signal and move to attack.
- Klinotaxis refers to movement through a gradient while taking successive samples of the environment.
- Mnemotaxis, literally "memory movement", describes navigation through the use of landmarks. Many birds navigate using landmarks, as do salmon. Humans also use mnemotaxis when navigating through the use of street signs and familiar buildings.