Concentrations of lactic acid in neotenic and transformed tiger salamanders (Ambystoma tigrinum) before and after activity

Summary Concentrations of lactic acid in bodies of inactive neotenic tiger salamanders were similar to those recorded for inactive transformed animals. Transformed salamanders swimming against a water current for 5 min accumulated significantly more lactate in their body fluids than did neotenic salamanders, but subsequently metabolized the lactate at higher rates than characterized neotenic animals. Total body lactate in both morphs decreased rapidly in the first 1–1/2 h after activity, and within 6 h had returned to the level (common to both morphs) observed prior to activity. Whereas neotenic animals apparently swim with greater efficiency than transformed salamanders (4.26 mole ATP/gvs. 6.06 mole ATP/g expended by neotenic and transformed animals, respectively, during 5 min of continuous swimming), the transformed animals exhibit a metabolic adaptation to aquatic existence enabling them rapidly to recover from a lactacid debt.