Thermotaxis

Definition

Directed locomotion of an organism along a temperature gradient, typically toward or away from a preferred thermal zone. In ectothermic arthropods, thermotaxis enables behavioral thermoregulation: positive thermotaxis (movement toward warmth) accelerates metabolic processes and development, while negative thermotaxis (movement toward cool) prevents desiccation or thermal damage. The response may involve klinotaxis (sequential sampling) or tropotaxis (simultaneous bilateral comparison) and is often modulated by internal physiological state, prior thermal experience, or circadian rhythms.

Etymology

Greek thermē (heat) + taxis (arrangement, movement)

Example

Larvae of the fly Drosophila melanogaster navigate thermal gradients using peripheral thermosensory neurons in the dorsal organ; when placed on a 15–35°C gradient, healthy larvae exhibit robust negative thermotaxis, crawling toward cooler regions to avoid temperatures above their preferred ~24°C, whereas mutants lacking the TRPA1 ion channel show impaired gradient tracking and aggregate at harmful temperatures.

Synonyms

• thermal taxis

Related Terms

• Thermoregulation
• klinotaxis
• tropotaxis
• thermosensation
• behavioral fever
• ectothermy
• Chemotaxis
• Phototaxis

Usage Notes

Distinguish from thermotropism, which refers to growth curvature in sessile organisms (e.g., plant shoots). Positive and negative thermotaxis are defined relative to the organism's preferred body temperature, not absolute values; a desert ant may show positive thermotaxis toward 45°C surfaces while a springtail flees the same temperature. The term implies active orientation, not passive drift with convection currents.