Development partly determines the aerobic performance of adult deer mice, Peromyscus maniculatus.

Previous studies suggest that genetic factors and acclimation can account for differences in aerobic performance (V(O(2)max)) between high and low altitude populations of small mammals. However, it remains unclear to what extent development at different oxygen partial pressures (P(O(2))) can affect aerobic performance during adulthood. Here we compared the effects of development at contrasting altitudes versus effects of acclimation during adulthood on V(O(2)max). Two groups of deer mice were born and raised for 5 weeks at one of two altitudes (340 and 3800 m above sea level). Then, a subset of each group was acclimated to the opposite altitude for 8 weeks. We measured V(O(2)max) for each individual in hypoxia (P(O(2))=13.5 kPa, 14% O(2) at 3800 m) and normoxia (P(O(2))=20.4 kPa, 21% O(2) at 340 m) to control for P(O(2)) effects. At 5 weeks of age, high altitude born mice attained significantly higher V(O(2)max) than low altitude born mice (37.1% higher in hypoxia and 72.1% higher in normoxia). Subsequently, deer mice acclimated for 8 weeks to high altitude had significantly higher V(O(2)max) regardless of their birth site (21.0% and 72.9% difference in hypoxia and normoxia, respectively). A significant development x acclimation site interaction comparing V(O(2)max) in hypoxia and normoxia at 13 weeks of age suggests that acclimation effects depend on development altitude. Thus, reversible plasticity during adulthood cannot fully compensate for developmental effects on aerobic performance. We also found that differences in aerobic performance in previous studies may have been underestimated if animals from contrasting altitudes were measured at different P(O(2)).

Deer mouse aerobic performance across altitudes: effects of developmental history and temperature acclimation.

Aerobic physiology at high altitudes has been studied in many animals. Prior work on laboratory-bred deer mice (a species with a wide altitudinal range) showed depression of aerobic capacity at high altitude, even after acclimation. However, wild deer mice show no reduction in thermogenic performance at high altitude, and performance limits seem to be due to physiological and anatomical adjustments to environmental temperature and not to oxygen availability. We asked whether across-altitude performance differences exist in deer mice after accounting for temperature acclimation (approximately 5 degrees and 20 degrees -25 degrees C) and prenatal and neonatal development altitude (340 vs. 3,800 m). We measured maximal thermogenic oxygen consumption (VO2sum) in cold exposure and ran mice on a treadmill to elicit maximal exercise oxygen consumption (VO2max). We found a 10% reduction in VO2max at 3,800 m compared with that at 340 m; thus, the mice were able to compensate for most of the 37% reduction in oxygen availability at the higher altitude. Development altitude did not affect VO2max. There was no effect of test altitude or development altitude on VO2sum in warm-acclimated animals, but both test and development altitude strongly affected VO2sum in cold-acclimated mice, and compensation for hypoxia at 3,800 m was considerably less than that for exercise.