Chemotaxis

Definition

Directed movement of an organism or cell toward (positive chemotaxis) or away from (negative chemotaxis) a chemical gradient. In arthropods, this mechanism mediates critical behaviors including host location by parasitoids and blood-feeding insects, trail following in social insects, predator avoidance, and mate finding via pheromone detection. Chemotaxis operates through chemoreceptor activation that triggers orientation responses, with integration of temporal or spatial sampling of concentration differences guiding the trajectory.

Etymology

From chemo- (chemical) + -taxis (ordered movement)

Example

Female mosquitoes exhibit positive chemotaxis toward carbon dioxide and lactic acid gradients emitted by vertebrate hosts, while gravid females show negative chemotaxis away from repellent compounds when selecting oviposition sites.

Related Terms

• chemoreceptor
• Olfaction
• Gustation
• Klinotaxis
• Tropotaxis
• Anemotaxis
• pheromone
• kairomone
• allomone

Usage Notes

Distinguish from chemokinesis, which is non-directional change in movement speed or frequency in response to chemicals. Chemotaxis requires a spatial gradient and results in oriented movement; chemokinesis does not require gradient detection and yields random or undirected movement changes. In insect behavior literature, 'chemotaxis' is sometimes used loosely for any chemically guided orientation; strict usage reserves it for direct movement along a gradient, with anemotaxis (wind-oriented) or klinotaxis (successive sampling) describing specific mechanisms.