Eurythermy

Eurythermy refers to the physiological ability of an organism to tolerate a wide range of environmental temperatures. It is used to describe species that can perform or survive across broad thermal conditions, in contrast to stenothermic species that have a narrow temperature tolerance. Eurythermy is observed in various groups, including some ectotherms, endotherms, plants, and microbes.

Thermal tolerance is typically quantified by measuring the limits of performance or survival at low and high temperatures, such as critical thermal minima and maxima (CTmin and CTmax) or lethal temperature thresholds. Many organisms exhibit acclimation or acclimatization, where their thermal tolerance shifts in response to prior exposure, seasonal changes, or developmental stage. Thermal breadth is influenced by physiology, behavior, and ecological context.

Mechanisms underlying eurythermy are diverse. They include adjustments in membrane lipid composition to preserve membrane fluidity, changes in enzyme kinetics and metabolic pathways, the expression of protective proteins such as heat shock proteins, antioxidant defenses, and other cellular stress responses. Behavioral strategies, like seeking shade, burrowing, or altering activity patterns, can also expand the effective thermal range.

Ecological and evolutionary implications include broader geographic distributions and greater resilience to fluctuating climates, though maintaining wide tolerance can involve energetic trade-offs. Eurythermy is a useful concept in studies of climate adaptation, species distributions, and responses to environmental change, complementing the related concept of stenothermy.