Energy Metabolism of Dormant Spadefoot Toads (Scaphiopus)

Rates of oxygen consumption of Scaphiopus couchii and S. hammondii during dormancy beneath the soil averaged approximately 1/5 those of awake toads resting on the surface during the same season. Oxygen consumption decreased gradually when S. couchii entered dormancy in autumn and stabilized after two to three weeks. In contrast, oxygen consumption leveled off after a few days in toads which were temporarily aroused and allowed to become dormant again in winter. Oxygen consumption of awake animals resting on the surface were similar during the seasons of activity (July-August) and dormancy (September-June) in both species. However, awake S. hammondii showed a decrease in Qlo of oxygen consumption during the seasons of dormancy. Most spadefoots had minute fat bodies and diminished total body lipid when they emerged in the summer. Feeding during July and August led to rapid fat deposition and egg development. Large increases in oxygen consumption following feeding of recently emerged S. hammondii suggested that food was rapidly converted into non-protein products. The ovarian eggs of both species were well developed by September and continued to enlarge during dormancy. About half of the energy required during dormancy came from the fat bodies. Changes in total body lipid from September to July correlated with rates of oxygen consumption of buried dormant toads at field temperatures. That at least some toads could survive two or more years of starvation is indicated by the presence of large fat bodies in a few individuals emerging in the summer, the ability to reabsorb gametes if reproduction is prevented, the potential utilization of body parts containing protein and low metabolic rates during dormancy.