Behavior and muscle performance in heterothermic bats

Area of Science:

• Zoology
• Physiology
• Biophysics

Background:

• Heterothermic bats exhibit significant seasonal body temperature fluctuations.
• Understanding the interplay between body temperature, motor performance, and muscle physiology is crucial for bat survival.

Purpose of the Study:

• To investigate the impact of varying body temperatures on the whole-organism performance and flight muscle contractile properties of the Korean bat, Murina leucogaster ognevi.
• To determine the temperature-dependence of specific behaviors and muscle functions across seasons.

Main Methods:

• Measured lowest body temperature limits for behaviors like biting, crawling, shivering, wing flapping, and aerial flight.
• Assessed the temperature-dependence of contractile properties, including maximum isometric tetanic tension and rate of tension production, in isolated biceps brachii muscle.
• Compared seasonal differences in muscle physiology and behavioral temperature thresholds.

Main Results:

• Behavioral temperature thresholds varied seasonally, with flight requiring higher temperatures in summer than winter.
• Muscle contractile properties showed temperature sensitivity, particularly in tension production rate and shortening velocity.
• Maximum isometric tetanic tension was largely insensitive to temperature, while rate-dependent properties were sensitive, aligning with behavioral observations.

Conclusions:

• The motor system of Murina leucogaster ognevi possesses functional capacity across its annual body temperature range.
• Behavioral temperature limits are consistent with muscle physiology, with temperature-independent tension supporting low-temperature defensive actions and temperature-sensitive rates enabling high-temperature flight.
• Some muscle rate processes may be more temperature-sensitive in summer than in winter.