Kinesis (biology)

Kinesis, like a taxis or tropism, is a movement or activity of a cell or an organism in response to a stimulus. However, unlike taxis, the response to the stimulus provided (such as gas exposure, light intensity or ambient temperature) is non-directional.

Kinesis is an animal's non-directional response to a stimulus, for example humidity. The animal does not move toward or away from the stimulus but moves at either a slow or fast rate depending on its "comfort zone." In this case a fast movement (non-random) means that the animal is searching for its comfort zone but a slow movement indicates that it has found it.

Types

The two main types of kineses are orthokinesis and klinokinesis. Both orthokinesis and klinokineses result in aggregations. However, the stimulus does not act to attract or repel individuals.

Orthokinesis: in which the speed of movement of the individual is dependent upon the intensity of the stimulus. Take, for example, the locomotion of a woodlice in relation to humidity. With increased humidity there is an increase in the percentage time that the woodlice will remain stationary.

Klinokinesis: in which the frequency or rate of turning is proportional to stimulus intensity. An example involves the behaviour of the flatworm (Dendrocoelum lacteum) which turns more frequently in response to increasing light thus ensuring that it spends more time in dark areas.