Energy availability influences the dynamics of thermal phenotypic plasticity

Area of Science:

• Environmental physiology
• Marine biology
• Ecology

Background:

• Phenotypic plasticity is crucial for organisms adapting to environmental changes, particularly temperature fluctuations.
• Understanding the environmental factors limiting this plasticity is vital for predicting species' responses to climate change.

Purpose of the Study:

• To investigate the role of food availability in modulating phenotypic plasticity of thermal tolerance in the marine amphipod *Echinogammarus marinus*.
• To determine if food influences the rate and capacity of thermal tolerance adjustment.

Main Methods:

• Specimens of *Echinogammarus marinus* were acclimated to 20°C from a baseline of 10°C for varying durations.
• Two feeding treatments were applied: fed and unfed.
• Thermal tolerance was assessed by measuring the time to immobilization at 30°C.

Main Results:

• Thermal tolerance increased with acclimation duration in both fed and unfed groups.
• The enhancement of thermal tolerance with acclimation was approximately two times greater in fed individuals compared to unfed individuals.
• Food availability primarily affected the capacity component of thermal tolerance, rather than the rate of change.

Conclusions:

• Food availability is a critical factor limiting the phenotypic plasticity of thermal tolerance in *Echinogammarus marinus*.
• Laboratory studies conducted under optimal feeding conditions may overestimate the adaptive capacity of organisms to thermal stress in natural environments.
• Ecological factors like food availability must be considered when assessing organismal resilience to climate change.