Homeostasis

Definition

The active maintenance of stable internal physiological conditions despite external environmental fluctuations. In arthropods, homeostasis encompasses regulation of hemolymph osmolarity, ion concentrations, pH, and temperature through behavioral, morphological, and physiological mechanisms.

Etymology

Greek homoios (similar, alike) + stasis (standing still)

Example

Desert tenebrionid beetles maintain water homeostasis by producing highly concentrated urine, absorbing water from metabolic processes, and restricting activity to nocturnal periods when evaporative water loss is minimized.

Synonyms

• steady-state regulation
• physiological equilibrium

Related Terms

• Osmoregulation
• Thermoregulation
• Hemolymph
• metabolic water
• acclimation
• poikilothermy

Usage Notes

Contrast with poikilothermy (variable body temperature), though the two are not mutually exclusive—many arthropods are poikilothermic yet maintain chemical homeostasis. Specialists distinguish homeostasis (active regulation) from simple passive buffering. In ecological contexts, the term is sometimes extended metaphorically to population or ecosystem stability, though physiologists typically restrict it to organism-level processes.