Oxygen consumption and carbon dioxide production in male prairie deermice (Peromyscus maniculatus bairdii) in different reproductive conditions and group densities.
Natural and laboratory populations of Peromyscus exhibit a profound but reversible reproductive inhibition related to population density. Our earlier studies described the endocrine physiology of inhibited animals which resembles a condition of delayed puberty, but they did not reveal a primary mechanism for the induction and maintenance of the inhibition. These studies indicated that reproductive inhibition could be associated with an overall change in general metabolism. To test this hypothesis, oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured in three groups of Peromyscus maniculatus males that were: 1) reproductively-proven, 2) reproductively-inhibited, or 3) recovered from inhibition. We found that the mean of the 2-hr period with the lowest VO2 (the Resting Metabolic Rate, or RMR) was significantly lower, and the mean Respiratory Exchange Ratio (RER) was significantly higher in reproductively-inhibited males compared with reproductively-proven males. In addition, previously inhibited males allowed to recover reproductive function had a significantly higher mean VO2, while the mean RER was not different from reproductively-proven males. Moreover, and contrary to some studies with other species, increasing the ambient carbon dioxide concentration or the caging densities to as high as six animals did not significantly affect oxygen consumption when compared with the corresponding values for individuals. Taken together, these findings indicate that the reproductive inhibition observed in P. maniculatus laboratory populations is causally associated with a significant reduction in general metabolism and that this metabolic reduction which is associated with reproductive-inhibition is not induced by a CO2 signal or induced by absolute density, per se.
Biomedical Science, School of Medicine, University of California, San Diego 92093, USA.
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Staubs
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Bradley
D000818:Animals; D001835:Body Weight; D002245:Carbon Dioxide / Q000502:physiology*; D005837:Genitalia, Male / Q000033:anatomy & histology; D008297:Male; D009929:Organ Size; D010101:Oxygen Consumption / Q000502:physiology*; D010542:Peromyscus / Q000033:anatomy & histology / Q000502:physiology*; D011156:Population Density; D011659:Pulmonary Gas Exchange; D012098:Reproduction / Q000502:physiology*
D002245:Carbon Dioxide