klinokinesis

Klinokinesis, also spelled clinokinesis, is a non-directional movement response observed in many microorganisms and small invertebrates. In klinokinesis, the organism does not orient toward or away from a stimulus; instead, the intensity of the stimulus modulates how often the organism changes direction (the turning rate) or its angular velocity. Thus, the movement pattern is a random walk whose properties depend on stimulus level.

By increasing or decreasing turning frequency in stronger gradients, klinokinesis can bias the distribution of individuals across an environment without producing a consistent bearing toward the stimulus. This distinguishes klinokinesis from taxis, in which movement has a persistent, directed trajectory toward (positive taxis) or away from (negative taxis) the stimulus, and from orthokinesis, where the speed of movement is altered with stimulus intensity while turning frequency remains constant.

Mechanistically, klinokinesis relies on sensory detection of stimulus intensity and a local neural or signaling response that adjusts locomotor activity. It is observed in various taxa, including some ciliates and aquatic invertebrates, and has been studied mainly with light, chemical, or thermal gradients. Experimental results typically report a correlation between stimulus strength and the frequency of reorientation events, such as sudden changes in swimming direction.

Interpretation and relevance: klinokinesis can facilitate exploration and avoidance of unfavorable zones when directional cues are weak or unreliable. It contributes to the diversity of behavioral strategies that organisms use to cope with heterogeneous environments.