HAMMOND, K.A.*; KRISTAN, D.M.; CHAPPELL, M.A.: Aerobic performance in deer mice (Peromyscus maniculatus)
Limits to whole-animal performance may be a result of peripheral effectors, central supportive organs, or both (“symmorphosis”). We examined these concepts using aerobic performance in deer mice (Peromyscus maniculatus). We correlated the masses of peripheral (foreleg and hind leg muscles) and central organs (liver, kidney, spleen, heart, lung and gut) with basal metabolic rate and maximal aerobic metabolism during tread-mill running (BMR and VO2max, respectively). We found that, with the exception of the small intestine, female mice had consistently larger guts than those of male mice. Male mice had larger combined leg muscle masses than female mice, but neither fore- nor hind-leg muscle alone was different between the sexes. We also found positive correlations between foreleg muscle mass and heart mass in both sexes. Despite the large variation in organ and muscle mass, and metabolic rates, we found no correlations between organ or muscle mass and VO2max although there was a positive correlation between BMR and hindleg muscle mass in both sexes. These data indicate that increased aerobic performance is not necessarily predicated upon possession of increased central or peripheral organs. Because deer mice have high aerobic performance at high altitudes, it will be interesting to determine if deer mice reared and tested at high altitude have stronger or different correlations than mice reared and tested at low altitudes.