Why are 'suboptimal' temperatures preferred in a tropical intertidal ectotherm?

Area of Science:

• Ecology
• Environmental Physiology
• Animal Behavior

Background:

• Organisms in thermally extreme environments face challenges in maximizing performance due to temperature variability.
• Minimizing exposure to thermal risk over evolutionary time can lead to preferences for suboptimal temperatures.
• Intertidal snails on tropical shores experience increasing temperature variability over time.

Purpose of the Study:

• To test the hypothesis that organisms prefer suboptimal temperatures to minimize risk in variable thermal environments.
• To investigate the relationship between physiological thermal tolerance and behavioral thermal preference in intertidal snails.
• To understand how temporal variation in temperature influences thermal performance and decision-making.

Main Methods:

• Measured thermal performance curves for heart rate and locomotion in intertidal snails.
• Compared physiological thermal maxima with behavioral thermal preferences in field and laboratory settings.
• Simulated snail performance over multiple timescales incorporating thermal performance curves and carryover effects.

Main Results:

• A significant mismatch exists between physiological (higher) and behavioral (lower) thermal maxima, with snails selecting temperatures 7-14°C cooler than their physiological limit.
• Snails' risk-averse strategy is explained by predicted performances, suggesting decisions should be based on time periods of ≥5 hours to account for temporal variation.
• A 'cooler is better' approach, favoring suboptimal body temperatures, provides a buffer against mortality risk from heat stress in stochastic environments.

Conclusions:

• Intertidal snails exhibit risk-averse behavior by selecting suboptimal temperatures, demonstrating a strategy to mitigate mortality from thermal stress.
• Behavioral thermoregulation in variable environments is influenced by the need to buffer against long-term temporal variations, not just instantaneous conditions.
• The findings highlight the importance of considering temporal dynamics and risk-averse strategies in understanding organismal responses to extreme and stochastic environments.