Age and aerobic performance in deer mice

Area of Science:

• Gerontology
• Comparative Physiology
• Animal Science

Background:

• Aging affects phenotypes across species, but lifetime physiological changes remain poorly understood.
• Deer mice (Peromyscus maniculatus) offer a unique model due to their extended captive lifespan and well-studied aerobic physiology.

Purpose of the Study:

• To investigate age-related effects on body composition, aerobic performance, and ventilation in deer mice.
• To identify specific physiological traits that decline with age and their potential impact on the animals' phenotype.

Main Methods:

• A cross-sectional study design was employed to assess deer mice of various ages.
• Key physiological parameters including basal metabolic rate, maximal oxygen consumption, thermogenesis, breathing frequency, tidal volume, and body composition were measured.

Main Results:

• Basal metabolic rate was unaffected by age, but growth rate, maximal oxygen consumption ((VO2max)), and thermogenesis ((VO2sum)) decreased abruptly around 485 days.
• Mass-adjusted aerobic performance declined by 20-35% in old mice (5 years) compared to young ones.
• Breathing frequency and oxygen extraction decreased with age, while tidal volume and minute volume showed no consistent age-related changes after accounting for mass and VO2sum.

Conclusions:

• Age-related declines in aerobic performance in deer mice are not solely explained by changes in body composition, suggesting a decrease in mass-specific oxidative capacity.
• These performance decrements likely reduce mobility and thermal tolerance in older deer mice.
• Given the limited survival of wild mice to these ages, these declines may not be under strong natural selection.