The metabolic rate of Xenopus laevis: Interactional influences of development and short term hypoxia
Amphibians undergo pronounced physiological and morphological adjustments during metamorphosis, due in large part to the change from water breathing to predominantly air breathing. A developmental change in the ability of the respiratory and cardiovascular systems to transport oxygen or a change in tissue demand for oxygen may be reflected in the aerobic metabolic rate (MO{dollar}\sb2{dollar}). This study focuses on how MO{dollar}\sb2{dollar} of the South African clawed frog (Xenopus laevis) is affected by short term hypoxia during development. MO{dollar}\sb2{dollar} of animals from Nieuwkoop and Faber stages 1-66, 1 month post-metamorphic froglets, and adult frogs were measured under conditions of normoxia and various degrees of hypoxia down to PO{dollar}\sb2 > 10{dollar} mmHg. Whole-body lactate contents were also assayed to assess anaerobic metabolic supplementation of aerobic metabolism. Larvae up to stage 57 were oxygen conformers. After stage 58, larvae were oxygen regulators. Anaerobic metabolism was used to supplement aerobic metabolism only by animals older than stage 52.
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