Axolotl Metabolism: Measuring Metabolic Rate.

Deciphering how metabolic processes contribute to control of stem cell proliferation and differentiation is essential for understanding the mechanisms of regeneration. However, much is still unknown about axolotls' metabolism, which has not been studied in detail over their lifespan or under varied experimental conditions. We summarize the theoretical underpinnings of metabolism and respirometry, and describe a closed respirometry system to investigate metabolic energetics in axolotls as a specific aspect of metabolism. Placement of post-absorptive, fairly inactive animals in the multiple-probe respirometer for 24-48 h allows us to measure changes in concentrations of respiratory gases: oxygen (atmospheric and dissolved) and carbon dioxide, while monitoring the temperature and salinity (conductivity) of the chamber's water. Respirometry data are used to calculate oxygen intake and carbon dioxide output to estimate animal's metabolic energy dynamics during the observation periods. This method creates opportunities for study of potential fluctuations in axolotls' metabolic rate as it pertains to respiratory gases' dynamics during 24-h circadian cycle, as well as examination of changes in metabolic energy management during aging, under varied environmental temperatures, during post-amputation regeneration and many other circumstances.